Steven Teitelbaum - Academia.edu (original) (raw)

Papers by Steven Teitelbaum

Journal of Biological Chemistry, 2013

Background: PI(4,5)P 2 , mainly synthesized by PIP5KI␥, is essential for normal cell function. Re... more Background: PI(4,5)P 2 , mainly synthesized by PIP5KI␥, is essential for normal cell function. Results: Deficiency or overexpression of PIP5KI␥, which results in decrease or increase of PI(4,5)P 2 , respectively, impairs osteoclast differentiation and function. Conclusion: Optimal PIP5KI␥ and PI(4,5)P 2 expression are important for osteoclast function. Significance: This is the first demonstration that PIP5KI␥ regulates cells in a bifunctional manner.

Medicine, 1985

Gaucher disease is a collection of related disorders of sphingolipid catabolism caused by the def... more Gaucher disease is a collection of related disorders of sphingolipid catabolism caused by the deficiency of a specific beta-glucosidase. The inefficiency of this enzyme, glucocerebrosidase, to degrade its natural substrate leads to the accumulation of the complex lipid glucocerebroside in tissue macrophages. The pathogenesis of the disease is, as yet, poorly understood. The manifestations of the disease are protean with hepatosplenomegaly and bone deterioration frequently the predominating signs. The disease most frequently causes disability because of its effects on the skeleton. This review seeks to summarize the current clinical understanding of these complications. Experience with 327 patients reveals that the bone disease in this disorder is extremely variable. The severity of the problems range from asymptomatic persons with neither radiographic, scintigraphic, nor histologic evidence of bone involvement to those whose skeleton is completely devastated by a process of osteopenia, osteonecrosis, and osteosclerosis. These severely affected individuals show the most bizarre deformities in their bones and are subject to pathologic fracture. Most patients fortunately, are less profoundly affected, but many are plagued by bone pain of an arthritic nature or by an acute prostrating bone crisis probably best described as a bone infarction. The accepted etiology that these crises are a result of vascular compromise produced by occlusion of vessels by Gaucher cells is not supported by scintigraphic or histologic studies. Moreover, the vascular hypothesis does not explain the variety of lesions of the skeleton seen in this multifocal bone disease. Preliminary metabolic and endocrinologic studies suggest that this is not a systemic disorder of metabolism which affects bone uniformly. On the contrary, the lesions are multiple and localized, and sometimes much of the skeleton is preserved. These observations suggest that bone is affected because of collections of Gaucher cells scattered throughout its substance and may be the result of a toxic process around these foci. Alternatively, the storage of glucocerebroside in tissue macrophages may disturb the generation of competent osteoclasts and thus result in a failure to maintain a healthy skeleton. Further research is needed to delineate the pathogenesis of this disorder before any effective therapy can be developed.

Journal of Biological Chemistry, 2003

Mineral and electrolyte metabolism, 1995

The osteopetroses occur as both natural and induced mutations in a variety of species. They produ... more The osteopetroses occur as both natural and induced mutations in a variety of species. They produce a skeleton of increased mass due to reduced bone resorption, the result of reduced development and/or activation of osteoclasts. Each mutation appears to be distinct, with no known overlap within or across species. Like the osteoporoses they exhibit a superficially common pheonotype of heterogenous pathophysiology. Natural mutations in the mouse (mi; 9; and oc) , rat (ia; toothless, fl and s) and rabbit (@ have been studied most intensively.

Bollettino della Società italiana di biologia sperimentale, 1989

In this study the effect of high extracellular calcium concentration has been evaluated, by immun... more In this study the effect of high extracellular calcium concentration has been evaluated, by immunofluorescence, on podosome expression in chicken osteoclasts. Cells were cultured in presence of 0.2 and 4 mM calcium for 90 minutes and microfilaments were detected, after fixation and permeabilization, by decoration with rodhamine conjugated phalloidin. Results showed that increased extracellular calcium concentration induces the inhibition of podosome expression indicating that these close-contact areas are capable of calcium-mediated regulation.

Proceedings of the National Academy of Sciences of the United States of America, Jan 17, 2009

c-Src kinase is a rate-limiting activator of osteoclast (OC) function and Src inhibitors are ther... more c-Src kinase is a rate-limiting activator of osteoclast (OC) function and Src inhibitors are therefore candidate antiosteoporosis drugs. By affecting alphavbeta3 and macrophage-colony stimulating factor (M-CSF)-induced signaling, c-Src is central to osteoclast activity, but not differentiation. We find Lyn, another member of Src family kinases (SFK) is, in contrast, a negative regulator of osteoclastic bone resorption. The absence of Lyn enhances receptor activator of NF-kappaB ligand (RANKL)-mediated differentiation of osteoclast precursors without affecting proliferation and survival, while its overexpression decreases osteoclast formation. In further contrast to c-Src, Lyn deficiency does not impact the activity of the mature cell. Reflecting increased osteoclast development in vitro, Lyn-/- mice undergo accelerated osteoclastogenesis and bone loss, in vivo, in response to RANKL. Mechanistically, Lyn forms a complex with receptor activator of NF-kappaB (RANK), the tyrosine phosph...

Advances in Experimental Medicine and Biology, 2007

Journal of Clinical Investigation, 1978

Chronic administration of high doses of anticonvulsant drugs frequently produces classic osteomal... more Chronic administration of high doses of anticonvulsant drugs frequently produces classic osteomalacia with bone histologic changes characteristic of increased parathyroid hormone (PTH) effect in man. However, several reports have documented defects in calcified tissue metabolism suggestive of an end-organ resistance to PTH after chronic anticonvulsant drug therapy. To examine the direct action of anticonvulsant drugs on bone resorption, we investigated the effects of diphenylhydantoin (phenytoin) (DPH) (100-200 mug/ml) and phenobarbital (10-400 mug/ml) on basal and hormonally mediated resorption 5-day cultures of fetal rat forelimb rudiments. In this system both drugs significantly inhibited basal and PTH-stimulated (45)Ca and [(3)H]hydroxyproline release, as well as 1,25-dihydroxyvitamin D(3)-stimulated (45)Ca release. The effects of DPH and phenobarbital were additive, with DPH exhibiting a several-fold more potent inhibitory effect than phenobarbital. Whereas DPH exhibited a striking synergism with the inhibitory effects of human calcitonin (HCT) on PTH-induced resorption, the effect of phenobarbital was merely additive to that of HCT. PTH and PTH plus HCT-induced increases in bone cyclic AMP (cAMP) content were significantly inhibited by DPH but not by phenobarbital. However, in contrast to effects on (45)Ca release, DPH inhibition of cAMP generation was not accentuated in the presence of HCT. It is concluded that: (a) both DPH and phenobarbital can directly inhibit basal and hormonally stimulated bone resorption, with DPH being much more potent in this regard; (b) DPH appears to inhibit bone resorption via a cAMP-independent mechanism and has an additional suppressive effect on PTH-induced cAMP generation; and (c) the synergistic interaction of DPH and HCT in inhibiting (45)Ca release occurs at a site independent of cAMP generation.

Structure, 2012

Osteoprotegerin (OPG) and receptor activator of nuclear factor κB (RANK) are members of the tumor... more Osteoprotegerin (OPG) and receptor activator of nuclear factor κB (RANK) are members of the tumor necrosis factor receptor (TNFR) superfamily that regulate osteoclast formation and function by competing for RANK ligand (RANKL). RANKL promotes osteoclast development through RANK activation, while OPG inhibits this process by sequestering RANKL. For comparison, we solved crystal structures of RANKL with RANK and RANKL with OPG. Complementary biochemical and functional studies reveal that the monomeric cytokine-binding region of OPG binds RANKL with ∼500-fold higher affinity than RANK and inhibits RANKL-stimulated osteoclastogenesis ∼150 times more effectively, in part because the binding cleft of RANKL makes unique contacts with OPG. Several side chains as well as the C-D and D-E loops of RANKL occupy different orientations when bound to OPG versus RANK. High affinity OPG binding requires a 90s loop Phe residue that is mutated in juvenile Paget's disease. These results suggest cytokine plasticity may help to fine-tune specific tumor necrosis factor (TNF)-family cytokine/receptor pair selectivity.

Journal of Biological Chemistry

Osteoclast precursors selectively attach to bone and differentiate into multinucleated cells that... more Osteoclast precursors selectively attach to bone and differentiate into multinucleated cells that function to remodel and resorb it. We have shown previously that attachment of osteoclasts to bone and subsequent resorption are mediated by the integrin a&. la,25-Dihydroxyvitamin Ds ( 1,25-(OH)zD3) enhances osteoclast precursor differentiation in vivo by mechanisms that are still not clearly understood but entail enhanced attachment of cells to bone. This observation raises the possibility that at least one component of vitamin Dinduced osteoclast precursor differentiation involves modulation of integrin expression. To test if the steroid modulates the osteoclast integrin a d s (the vitronectin receptor), we examined the effects of 1,25-(OH)zD~ on transcription of the a,. gene as well as surface expression and function of aV& in chicken osteoclast precursors. Treatment of the cells with 1,25-(OH)zDs led to a progressive dose-dependent increase in steady state av mRNA levels with enhanced expression evident within 24 h. The effect was receptor-mediated as indicated by the effects of other vitamin D analogs. The increase in aV mRNA levels did not reflect decreased message degradation but, as demonstrated by nuclear run-on experiments, was due to accelerated rates of transcription. Most importantly, induction of ay mRNA by 1,25-(OH)2Ds was mirrored by higher levels of expression of a& on the cell surface, as well enhanced attachment to its substrate, vitronectin.

Journal of the American Geriatrics Society, 2014

To examine the association between depression, antidepressant use, and bone health in older adult... more To examine the association between depression, antidepressant use, and bone health in older adults and the implications for treatment. Systematic review. All studies that measured depression or antidepressant exposure and bone mineral density (BMD). Adults aged 60 and older. Age, site of BMD measurement using dual-energy X-ray absorptiometry (DXA), measure of depression or depressive symptoms, association between BMD changes, and depression or antidepressant use. Nineteen observational studies met the final inclusion criteria; no experimental studies were found. Several cross-sectional and longitudinal studies found that depression or depressive symptoms were associated with a decrease in BMD. Few studies and only two longitudinal studies addressed the association between serotonin reuptake inhibitor (SRI) antidepressant use and a decrease in BMD and they had conflicting results. Depression and depressive symptoms are associated with low bone mass and accelerated bone loss in older ...

Molecular Endocrinology, 1998

The integrins avb5 and avb3 are expressed recip- rocally during murine osteoclastogenesis in vitr... more The integrins avb5 and avb3 are expressed recip- rocally during murine osteoclastogenesis in vitro. Specifically, immature osteoclast precursors, in the form of bone marrow macrophages, contain exclusively avb5, surface expression of which de- clines with commitment to the osteoclast pheno- type, while levels of avb3 increase concomitantly. The distinct functional significance of avb5 is un- derscored by the integrin's capacity,

Journal of Clinical Investigation, 1979

Hypocalcemia during magnesium (Mg) depletion has been well described, but the precise mechanism(s... more Hypocalcemia during magnesium (Mg) depletion has been well described, but the precise mechanism(s) responsible for its occurrence is not yet fully understood. The hypocalcemia has been ascribed to decreased parathyroid hormone (PTH) secretion as well as skeletal resistance to PTH. Whereas the former is well established, controversy exists as to whether or not Mg depletion results in skeletal resistance to PTH. These studies examine the skeletal response to PTH in normal dogs and dogs fed a Mg-free diet for 4-6 mo. Isolated tibia from normal (serum Mg 1.83+/-0.1 mg/100 ml) and experimental dogs (serum Mg 1.34+/-0.15 mg/100 ml) were perfused with Krebs-Henseleit buffer during a constant infusion of 3 ng/ml of synthetic bovine PTH 1-34 (syn b-PTH 1-34). The arteriovenous (A-V) difference for immunoreactive PTH (iPTH) across seven normal bones was 37.5+/-3%. In contrast, the A-V difference for iPTH was markedly depressed to 10.1+/-1% across seven bones from Mg-depleted dogs. These findings correlated well with a biological effect (cyclic AMP [cAMP] production) of syn b-PTH 1-34 on bone. In control bones, cAMP production rose from a basal level of 5.8+/-0.2 to 17.5+/-0.7 pmol/min after syn b-PTH 1-34 infusion. In experimental bones, basal cAMP production was significantly lower than in controls, 4.5+/-0.1 pmol/min, and increased to only 7.1+/-0.4 pmol/min after syn b-PTH 1-34 infusion. Even when PTH concentrations were increased to 20 ng/ml, cAMP production by experimental bones was lower than in control bones perfused with 3 ng/ml. Histological examination of bones from Mg-deficient dogs showed a picture compatible with skeletal inactivity. These studies demonstrate decreased uptake of iPTH and diminished cAMP production by bone, which indicates skeletal resistance to PTH in chronic Mg deficiency.

Journal of cellular biochemistry, Jan 10, 2015

The interaction between Receptor Activator of NF-κB Ligand (RANKL) and its receptor RANK is essen... more The interaction between Receptor Activator of NF-κB Ligand (RANKL) and its receptor RANK is essential for the differentiation and bone resorbing capacity of the osteoclast. Osteoprotegerin (OPG), a soluble homodimer, acts as a decoy receptor for RANKL and thus inhibits osteoclastogenesis. An imbalance in the RANKL/RANK/OPG axis, with decreased OPG and/or increased RANKL, is associated with diseases that favor bone loss, including osteoporosis. Recently, we established a yeast surface display system and screened libraries of randomly mutated RANKL proteins to identify mutations that abolish binding to OPG while preserving recognition of RANK. These efforts yielded several RANKL variants possessing substantially higher affinity for RANK compared to their wild-type (WT) counterpart. Using recombinant RANKL mutant proteins, we find those with increased affinity for RANK produce more robust signaling in osteoclast lineage cells and have greater osteoclastogenic potential. Our results are...

The World Journal of Biological Psychiatry, 2013

Studies have reported an association between serotonin reuptake inhibitors (SRIs) and accelerated... more Studies have reported an association between serotonin reuptake inhibitors (SRIs) and accelerated bone loss. Genetic variation in the serotonin system might modulate bone metabolism changes during SRI treatment. In a clinical trial we examined functional genetic polymorphisms of serotonin transporter and receptors involved in bone metabolism to determine whether they predict changes in bone metabolism during SRI treatment. In 69 adults (age ≥ 60) participating in a 12-week, open-label trial of the SRI venlafaxine for major depression, serum markers of bone formation (P1NP) and resorption (β-CTX) were assayed before and after treatment. Participants were genotyped for putative high- versus low-expressing polymorphisms in the serotonin transporter (5HTTLPR) and 1B receptor (HTR1B) genes. Bone formation was significantly reduced with administration of venlafaxine in participants with the high-expressing 5HTTLPR genotype and those with the low-expressing HTR1B genotype. This primarily occurred in individuals with the combination of the high-expressing 5HTTLPR genotype and the low-expressing HTR1B genotype. These preliminary findings indicate that genetic variation in the serotonin receptors predicts changes in bone metabolism during SRI use. If these results are replicated and clinically confirmed, we will have identified a genetic subgroup at high risk for deleterious bone outcomes with the use of SRIs.

The Journal of cell biology, Jan 5, 2015

In vitro, ligand occupancy of αvβ3 integrin induces phosphorylation of Dap12, which is essential ... more In vitro, ligand occupancy of αvβ3 integrin induces phosphorylation of Dap12, which is essential for osteoclast function. Like mice deleted of only αvβ3, Dap12(-/-) mice exhibited a slight increase in bone mass, but Dap12(-/-) mice, lacking another ITAM protein, FcRγ, were severely osteopetrotic. The mechanism by which FcRγ compensates for Dap12 deficiency is unknown. We find that co-deletion of FcRγ did not exacerbate the skeletal phenotype of β3(-/-) mice. In contrast, β3/Dap12 double-deficient (DAP/β3(-/-)) mice (but not β1/Dap12 double-deficient mice) were profoundly osteopetrotic, reflecting severe osteoclast dysfunction relative to those lacking αvβ3 or Dap12 alone. Activation of OSCAR, the FcRγ co-receptor, rescued Dap12(-/-) but not DAP/β3(-/-)osteoclasts. Thus, the absence of αvβ3 precluded compensation for Dap12 deficiency by FcRγ. In keeping with this, Syk phosphorylation did not occur in OSCAR-activated DAP/β3(-/-) osteoclasts. Thus, FcRγ requires the osteoclast αvβ3 int...

The Journal of Cell Biology, 1982

The osteoclast, the multinucleated giant cell of bone, is derived from circulating blood cells, m... more The osteoclast, the multinucleated giant cell of bone, is derived from circulating blood cells, most likely monocytes. Evidence has accrued that is consistent with the hypothesis that the recruitment of monocytes for osteoclast development occurs by chemotaxis . In the present study, we have examined the chemotactic response of human peripheral blood monocytes and related polymorphonuclear leucocytes to three constituents of bone matrix : peptides from Type I collagen, a2 HS glycoprotein, and osteocalcin (bone gla protein) . The latter two substances are among the major noncollagenous proteins of bone and are uniquely associated with calcified connective tissue .

Science signaling, Jan 19, 2014

Signaling by receptor activator of nuclear factor κB (RANK) in response to its ligand RANKL, whic... more Signaling by receptor activator of nuclear factor κB (RANK) in response to its ligand RANKL, which is a member of the tumor necrosis factor (TNF) superfamily of cytokines, stimulates osteoclast formation and bone resorption. Thus, this ligand-receptor pair is a therapeutic target for various disorders, such as osteoporosis and metastasis of cancer to bone. RANKL exists as a physiological homotrimer, with each monomer recognizing a single molecule of RANK or the decoy receptor osteoprotegerin (OPG), which inhibits osteoclastogenesis. We engineered a RANKL protein in which all three monomers of RANKL were encoded as a single polypeptide chain, which enabled us to independently control receptor binding at each binding interface. To generate an effective RANK inhibitor, we used an unbiased forward genetic approach to identify mutations in RANKL that had a 500-fold increased affinity for RANK but had decreased affinity for the decoy receptor OPG. Incorporating mutations that blocked rece...

The Journal of Cell Biology, 2003

Annals of the rheumatic diseases, 2002

Journal of Biological Chemistry, 2013

Background: PI(4,5)P 2 , mainly synthesized by PIP5KI␥, is essential for normal cell function. Re... more Background: PI(4,5)P 2 , mainly synthesized by PIP5KI␥, is essential for normal cell function. Results: Deficiency or overexpression of PIP5KI␥, which results in decrease or increase of PI(4,5)P 2 , respectively, impairs osteoclast differentiation and function. Conclusion: Optimal PIP5KI␥ and PI(4,5)P 2 expression are important for osteoclast function. Significance: This is the first demonstration that PIP5KI␥ regulates cells in a bifunctional manner.

Medicine, 1985

Gaucher disease is a collection of related disorders of sphingolipid catabolism caused by the def... more Gaucher disease is a collection of related disorders of sphingolipid catabolism caused by the deficiency of a specific beta-glucosidase. The inefficiency of this enzyme, glucocerebrosidase, to degrade its natural substrate leads to the accumulation of the complex lipid glucocerebroside in tissue macrophages. The pathogenesis of the disease is, as yet, poorly understood. The manifestations of the disease are protean with hepatosplenomegaly and bone deterioration frequently the predominating signs. The disease most frequently causes disability because of its effects on the skeleton. This review seeks to summarize the current clinical understanding of these complications. Experience with 327 patients reveals that the bone disease in this disorder is extremely variable. The severity of the problems range from asymptomatic persons with neither radiographic, scintigraphic, nor histologic evidence of bone involvement to those whose skeleton is completely devastated by a process of osteopenia, osteonecrosis, and osteosclerosis. These severely affected individuals show the most bizarre deformities in their bones and are subject to pathologic fracture. Most patients fortunately, are less profoundly affected, but many are plagued by bone pain of an arthritic nature or by an acute prostrating bone crisis probably best described as a bone infarction. The accepted etiology that these crises are a result of vascular compromise produced by occlusion of vessels by Gaucher cells is not supported by scintigraphic or histologic studies. Moreover, the vascular hypothesis does not explain the variety of lesions of the skeleton seen in this multifocal bone disease. Preliminary metabolic and endocrinologic studies suggest that this is not a systemic disorder of metabolism which affects bone uniformly. On the contrary, the lesions are multiple and localized, and sometimes much of the skeleton is preserved. These observations suggest that bone is affected because of collections of Gaucher cells scattered throughout its substance and may be the result of a toxic process around these foci. Alternatively, the storage of glucocerebroside in tissue macrophages may disturb the generation of competent osteoclasts and thus result in a failure to maintain a healthy skeleton. Further research is needed to delineate the pathogenesis of this disorder before any effective therapy can be developed.

Journal of Biological Chemistry, 2003

Mineral and electrolyte metabolism, 1995

The osteopetroses occur as both natural and induced mutations in a variety of species. They produ... more The osteopetroses occur as both natural and induced mutations in a variety of species. They produce a skeleton of increased mass due to reduced bone resorption, the result of reduced development and/or activation of osteoclasts. Each mutation appears to be distinct, with no known overlap within or across species. Like the osteoporoses they exhibit a superficially common pheonotype of heterogenous pathophysiology. Natural mutations in the mouse (mi; 9; and oc) , rat (ia; toothless, fl and s) and rabbit (@ have been studied most intensively.

Bollettino della Società italiana di biologia sperimentale, 1989

In this study the effect of high extracellular calcium concentration has been evaluated, by immun... more In this study the effect of high extracellular calcium concentration has been evaluated, by immunofluorescence, on podosome expression in chicken osteoclasts. Cells were cultured in presence of 0.2 and 4 mM calcium for 90 minutes and microfilaments were detected, after fixation and permeabilization, by decoration with rodhamine conjugated phalloidin. Results showed that increased extracellular calcium concentration induces the inhibition of podosome expression indicating that these close-contact areas are capable of calcium-mediated regulation.

Proceedings of the National Academy of Sciences of the United States of America, Jan 17, 2009

c-Src kinase is a rate-limiting activator of osteoclast (OC) function and Src inhibitors are ther... more c-Src kinase is a rate-limiting activator of osteoclast (OC) function and Src inhibitors are therefore candidate antiosteoporosis drugs. By affecting alphavbeta3 and macrophage-colony stimulating factor (M-CSF)-induced signaling, c-Src is central to osteoclast activity, but not differentiation. We find Lyn, another member of Src family kinases (SFK) is, in contrast, a negative regulator of osteoclastic bone resorption. The absence of Lyn enhances receptor activator of NF-kappaB ligand (RANKL)-mediated differentiation of osteoclast precursors without affecting proliferation and survival, while its overexpression decreases osteoclast formation. In further contrast to c-Src, Lyn deficiency does not impact the activity of the mature cell. Reflecting increased osteoclast development in vitro, Lyn-/- mice undergo accelerated osteoclastogenesis and bone loss, in vivo, in response to RANKL. Mechanistically, Lyn forms a complex with receptor activator of NF-kappaB (RANK), the tyrosine phosph...

Advances in Experimental Medicine and Biology, 2007

Journal of Clinical Investigation, 1978

Chronic administration of high doses of anticonvulsant drugs frequently produces classic osteomal... more Chronic administration of high doses of anticonvulsant drugs frequently produces classic osteomalacia with bone histologic changes characteristic of increased parathyroid hormone (PTH) effect in man. However, several reports have documented defects in calcified tissue metabolism suggestive of an end-organ resistance to PTH after chronic anticonvulsant drug therapy. To examine the direct action of anticonvulsant drugs on bone resorption, we investigated the effects of diphenylhydantoin (phenytoin) (DPH) (100-200 mug/ml) and phenobarbital (10-400 mug/ml) on basal and hormonally mediated resorption 5-day cultures of fetal rat forelimb rudiments. In this system both drugs significantly inhibited basal and PTH-stimulated (45)Ca and [(3)H]hydroxyproline release, as well as 1,25-dihydroxyvitamin D(3)-stimulated (45)Ca release. The effects of DPH and phenobarbital were additive, with DPH exhibiting a several-fold more potent inhibitory effect than phenobarbital. Whereas DPH exhibited a striking synergism with the inhibitory effects of human calcitonin (HCT) on PTH-induced resorption, the effect of phenobarbital was merely additive to that of HCT. PTH and PTH plus HCT-induced increases in bone cyclic AMP (cAMP) content were significantly inhibited by DPH but not by phenobarbital. However, in contrast to effects on (45)Ca release, DPH inhibition of cAMP generation was not accentuated in the presence of HCT. It is concluded that: (a) both DPH and phenobarbital can directly inhibit basal and hormonally stimulated bone resorption, with DPH being much more potent in this regard; (b) DPH appears to inhibit bone resorption via a cAMP-independent mechanism and has an additional suppressive effect on PTH-induced cAMP generation; and (c) the synergistic interaction of DPH and HCT in inhibiting (45)Ca release occurs at a site independent of cAMP generation.

Structure, 2012

Osteoprotegerin (OPG) and receptor activator of nuclear factor κB (RANK) are members of the tumor... more Osteoprotegerin (OPG) and receptor activator of nuclear factor κB (RANK) are members of the tumor necrosis factor receptor (TNFR) superfamily that regulate osteoclast formation and function by competing for RANK ligand (RANKL). RANKL promotes osteoclast development through RANK activation, while OPG inhibits this process by sequestering RANKL. For comparison, we solved crystal structures of RANKL with RANK and RANKL with OPG. Complementary biochemical and functional studies reveal that the monomeric cytokine-binding region of OPG binds RANKL with ∼500-fold higher affinity than RANK and inhibits RANKL-stimulated osteoclastogenesis ∼150 times more effectively, in part because the binding cleft of RANKL makes unique contacts with OPG. Several side chains as well as the C-D and D-E loops of RANKL occupy different orientations when bound to OPG versus RANK. High affinity OPG binding requires a 90s loop Phe residue that is mutated in juvenile Paget's disease. These results suggest cytokine plasticity may help to fine-tune specific tumor necrosis factor (TNF)-family cytokine/receptor pair selectivity.

Journal of Biological Chemistry

Osteoclast precursors selectively attach to bone and differentiate into multinucleated cells that... more Osteoclast precursors selectively attach to bone and differentiate into multinucleated cells that function to remodel and resorb it. We have shown previously that attachment of osteoclasts to bone and subsequent resorption are mediated by the integrin a&. la,25-Dihydroxyvitamin Ds ( 1,25-(OH)zD3) enhances osteoclast precursor differentiation in vivo by mechanisms that are still not clearly understood but entail enhanced attachment of cells to bone. This observation raises the possibility that at least one component of vitamin Dinduced osteoclast precursor differentiation involves modulation of integrin expression. To test if the steroid modulates the osteoclast integrin a d s (the vitronectin receptor), we examined the effects of 1,25-(OH)zD~ on transcription of the a,. gene as well as surface expression and function of aV& in chicken osteoclast precursors. Treatment of the cells with 1,25-(OH)zDs led to a progressive dose-dependent increase in steady state av mRNA levels with enhanced expression evident within 24 h. The effect was receptor-mediated as indicated by the effects of other vitamin D analogs. The increase in aV mRNA levels did not reflect decreased message degradation but, as demonstrated by nuclear run-on experiments, was due to accelerated rates of transcription. Most importantly, induction of ay mRNA by 1,25-(OH)2Ds was mirrored by higher levels of expression of a& on the cell surface, as well enhanced attachment to its substrate, vitronectin.

Journal of the American Geriatrics Society, 2014

To examine the association between depression, antidepressant use, and bone health in older adult... more To examine the association between depression, antidepressant use, and bone health in older adults and the implications for treatment. Systematic review. All studies that measured depression or antidepressant exposure and bone mineral density (BMD). Adults aged 60 and older. Age, site of BMD measurement using dual-energy X-ray absorptiometry (DXA), measure of depression or depressive symptoms, association between BMD changes, and depression or antidepressant use. Nineteen observational studies met the final inclusion criteria; no experimental studies were found. Several cross-sectional and longitudinal studies found that depression or depressive symptoms were associated with a decrease in BMD. Few studies and only two longitudinal studies addressed the association between serotonin reuptake inhibitor (SRI) antidepressant use and a decrease in BMD and they had conflicting results. Depression and depressive symptoms are associated with low bone mass and accelerated bone loss in older ...

Molecular Endocrinology, 1998

The integrins avb5 and avb3 are expressed recip- rocally during murine osteoclastogenesis in vitr... more The integrins avb5 and avb3 are expressed recip- rocally during murine osteoclastogenesis in vitro. Specifically, immature osteoclast precursors, in the form of bone marrow macrophages, contain exclusively avb5, surface expression of which de- clines with commitment to the osteoclast pheno- type, while levels of avb3 increase concomitantly. The distinct functional significance of avb5 is un- derscored by the integrin's capacity,

Journal of Clinical Investigation, 1979

Hypocalcemia during magnesium (Mg) depletion has been well described, but the precise mechanism(s... more Hypocalcemia during magnesium (Mg) depletion has been well described, but the precise mechanism(s) responsible for its occurrence is not yet fully understood. The hypocalcemia has been ascribed to decreased parathyroid hormone (PTH) secretion as well as skeletal resistance to PTH. Whereas the former is well established, controversy exists as to whether or not Mg depletion results in skeletal resistance to PTH. These studies examine the skeletal response to PTH in normal dogs and dogs fed a Mg-free diet for 4-6 mo. Isolated tibia from normal (serum Mg 1.83+/-0.1 mg/100 ml) and experimental dogs (serum Mg 1.34+/-0.15 mg/100 ml) were perfused with Krebs-Henseleit buffer during a constant infusion of 3 ng/ml of synthetic bovine PTH 1-34 (syn b-PTH 1-34). The arteriovenous (A-V) difference for immunoreactive PTH (iPTH) across seven normal bones was 37.5+/-3%. In contrast, the A-V difference for iPTH was markedly depressed to 10.1+/-1% across seven bones from Mg-depleted dogs. These findings correlated well with a biological effect (cyclic AMP [cAMP] production) of syn b-PTH 1-34 on bone. In control bones, cAMP production rose from a basal level of 5.8+/-0.2 to 17.5+/-0.7 pmol/min after syn b-PTH 1-34 infusion. In experimental bones, basal cAMP production was significantly lower than in controls, 4.5+/-0.1 pmol/min, and increased to only 7.1+/-0.4 pmol/min after syn b-PTH 1-34 infusion. Even when PTH concentrations were increased to 20 ng/ml, cAMP production by experimental bones was lower than in control bones perfused with 3 ng/ml. Histological examination of bones from Mg-deficient dogs showed a picture compatible with skeletal inactivity. These studies demonstrate decreased uptake of iPTH and diminished cAMP production by bone, which indicates skeletal resistance to PTH in chronic Mg deficiency.

Journal of cellular biochemistry, Jan 10, 2015

The interaction between Receptor Activator of NF-κB Ligand (RANKL) and its receptor RANK is essen... more The interaction between Receptor Activator of NF-κB Ligand (RANKL) and its receptor RANK is essential for the differentiation and bone resorbing capacity of the osteoclast. Osteoprotegerin (OPG), a soluble homodimer, acts as a decoy receptor for RANKL and thus inhibits osteoclastogenesis. An imbalance in the RANKL/RANK/OPG axis, with decreased OPG and/or increased RANKL, is associated with diseases that favor bone loss, including osteoporosis. Recently, we established a yeast surface display system and screened libraries of randomly mutated RANKL proteins to identify mutations that abolish binding to OPG while preserving recognition of RANK. These efforts yielded several RANKL variants possessing substantially higher affinity for RANK compared to their wild-type (WT) counterpart. Using recombinant RANKL mutant proteins, we find those with increased affinity for RANK produce more robust signaling in osteoclast lineage cells and have greater osteoclastogenic potential. Our results are...

The World Journal of Biological Psychiatry, 2013

Studies have reported an association between serotonin reuptake inhibitors (SRIs) and accelerated... more Studies have reported an association between serotonin reuptake inhibitors (SRIs) and accelerated bone loss. Genetic variation in the serotonin system might modulate bone metabolism changes during SRI treatment. In a clinical trial we examined functional genetic polymorphisms of serotonin transporter and receptors involved in bone metabolism to determine whether they predict changes in bone metabolism during SRI treatment. In 69 adults (age ≥ 60) participating in a 12-week, open-label trial of the SRI venlafaxine for major depression, serum markers of bone formation (P1NP) and resorption (β-CTX) were assayed before and after treatment. Participants were genotyped for putative high- versus low-expressing polymorphisms in the serotonin transporter (5HTTLPR) and 1B receptor (HTR1B) genes. Bone formation was significantly reduced with administration of venlafaxine in participants with the high-expressing 5HTTLPR genotype and those with the low-expressing HTR1B genotype. This primarily occurred in individuals with the combination of the high-expressing 5HTTLPR genotype and the low-expressing HTR1B genotype. These preliminary findings indicate that genetic variation in the serotonin receptors predicts changes in bone metabolism during SRI use. If these results are replicated and clinically confirmed, we will have identified a genetic subgroup at high risk for deleterious bone outcomes with the use of SRIs.

The Journal of cell biology, Jan 5, 2015

In vitro, ligand occupancy of αvβ3 integrin induces phosphorylation of Dap12, which is essential ... more In vitro, ligand occupancy of αvβ3 integrin induces phosphorylation of Dap12, which is essential for osteoclast function. Like mice deleted of only αvβ3, Dap12(-/-) mice exhibited a slight increase in bone mass, but Dap12(-/-) mice, lacking another ITAM protein, FcRγ, were severely osteopetrotic. The mechanism by which FcRγ compensates for Dap12 deficiency is unknown. We find that co-deletion of FcRγ did not exacerbate the skeletal phenotype of β3(-/-) mice. In contrast, β3/Dap12 double-deficient (DAP/β3(-/-)) mice (but not β1/Dap12 double-deficient mice) were profoundly osteopetrotic, reflecting severe osteoclast dysfunction relative to those lacking αvβ3 or Dap12 alone. Activation of OSCAR, the FcRγ co-receptor, rescued Dap12(-/-) but not DAP/β3(-/-)osteoclasts. Thus, the absence of αvβ3 precluded compensation for Dap12 deficiency by FcRγ. In keeping with this, Syk phosphorylation did not occur in OSCAR-activated DAP/β3(-/-) osteoclasts. Thus, FcRγ requires the osteoclast αvβ3 int...

The Journal of Cell Biology, 1982

The osteoclast, the multinucleated giant cell of bone, is derived from circulating blood cells, m... more The osteoclast, the multinucleated giant cell of bone, is derived from circulating blood cells, most likely monocytes. Evidence has accrued that is consistent with the hypothesis that the recruitment of monocytes for osteoclast development occurs by chemotaxis . In the present study, we have examined the chemotactic response of human peripheral blood monocytes and related polymorphonuclear leucocytes to three constituents of bone matrix : peptides from Type I collagen, a2 HS glycoprotein, and osteocalcin (bone gla protein) . The latter two substances are among the major noncollagenous proteins of bone and are uniquely associated with calcified connective tissue .

Science signaling, Jan 19, 2014

Signaling by receptor activator of nuclear factor κB (RANK) in response to its ligand RANKL, whic... more Signaling by receptor activator of nuclear factor κB (RANK) in response to its ligand RANKL, which is a member of the tumor necrosis factor (TNF) superfamily of cytokines, stimulates osteoclast formation and bone resorption. Thus, this ligand-receptor pair is a therapeutic target for various disorders, such as osteoporosis and metastasis of cancer to bone. RANKL exists as a physiological homotrimer, with each monomer recognizing a single molecule of RANK or the decoy receptor osteoprotegerin (OPG), which inhibits osteoclastogenesis. We engineered a RANKL protein in which all three monomers of RANKL were encoded as a single polypeptide chain, which enabled us to independently control receptor binding at each binding interface. To generate an effective RANK inhibitor, we used an unbiased forward genetic approach to identify mutations in RANKL that had a 500-fold increased affinity for RANK but had decreased affinity for the decoy receptor OPG. Incorporating mutations that blocked rece...

The Journal of Cell Biology, 2003

Annals of the rheumatic diseases, 2002