Hadassah Tamir - Academia.edu (original) (raw)

Papers by Hadassah Tamir

The Journal of Cell Biology, 1988

Secretory granules of sheep thyroid parafollicular cells contain serotonin, a serotonin-binding p... more Secretory granules of sheep thyroid parafollicular cells contain serotonin, a serotonin-binding protein, and calcitonin. Parafollicular cells, isolated by affinity chromatography, were found to secrete serotonin when activated by thyrotropin (TSH) or elevated [Ca2÷]~. TSH also induced a rise in [Ca2÷]~. We studied the effect of these secretogogues on the pH difference (ApH) across the membranes of the secretory granules of isolated parafollicular cells. The trapping of the weak bases, acridine orange or 3-(2,4 dinitro anilino)-Y-amino-N-methyl dipropylamine (DAMP), within the granules was used to evaluate ApH. In contrast to lysosomes, which served as an internal control, the secretory granules of resting parafollicular cells displayed a limited and variable ability to trap either acridine orange or 3-(2,4 dinitro anilino)-3'-amino-N-methyldipropylamine; however, when parafollicular cells were stimulated with TSH or elevated [Ca2+],, the granules acidified. Weak base trapping was also used to evaluate the ATP-driven H ÷ translocation into isolated parafollicular granules. The isolated parafollicular granules did not acidify in response to addition of ATP unless their transmembrane potential was collapsed by the K ÷ ionophore, valinomycin. Secretory granules isolated from TSH-treated parafollicular cells had a high chloride conductance than did granules isolated similarly from untreated cells. Furthermore, ATP-driven H + translocation into parafollicular granules isolated from TSH-stimulated parafollicular cells occurred even in the absence of valinomycin. These results demonstrate that secretogogues can regulate the internal pH of the serotonin-storing secretory granules of parafollicular cells by opening a chloride channel associated with the granule membrane. This is the first demonstration that the pH of secretory vesicles may be modified by altering the conductance of a counterion for the H ÷ translocating ATPase.

Life Sciences, 1974

A soluble protein with high binding affinity for serotonin was detected in synaptosomes and cytos... more A soluble protein with high binding affinity for serotonin was detected in synaptosomes and cytosol of cortex and stem of rat brain. Both serotonin and dopamine inhibited the binding of labeled serotonin. 5, 7-dihydroxytryptamine was a very effective inhibitor whereas other indole ...

Endocrinology

Thyroid parafollicular (PF) cells are neural crest-derived endocrine cells that secrete serotonin... more Thyroid parafollicular (PF) cells are neural crest-derived endocrine cells that secrete serotonin and calcitonin. The secretory vesicles of PF cells acidify when secretion is induced by increased extracellular Ca2+ or TSH. We tested the hypothesis that acidification is regulated by secretogogue-gated Cl- channels in vesicular membranes. Cl- channel (p64) immunoreactivity was enriched in purified PF vesicles. X-Ray microanalysis showed a change in chlorine level in PF vesicles in response to secretogogue-stimulation of isolated cells. Secretogogue stimulation also altered the degree of p64 channel phosphorylation. Protein kinase and phosphatase inhibitors antagonized secretogogue-induced vesicle acidification and secretion; however, secretion could occur even when acidification was blocked. We conclude that acidification of PF vesicles is regulated by a gatable Cl- channel in vesicle membranes and that protein phosphorylation and dephosphorylation are involved in channel activation. Acidification of vesicles is not required for exocytosis.

Development

The possible involvement of the neurotransmitter serotonin (5-HT) in morphogenesis of the craniof... more The possible involvement of the neurotransmitter serotonin (5-HT) in morphogenesis of the craniofacial region in the mouse embryo has been investigated using the method of whole-embryo culture. Day-12 embryos were incubated for 3-4 h in the presence of 5-HT or its precursors L-tryptophan (L-TRP) or 5-hydroxytryptophan (5-HTP), followed by fixation, sectioning and staining with a specific antiserum to 5-HT. Sites of 5-HT immunoreactivity were found in a variety of locations in tissues of the head and neck, which are either epithelia derived from the non-neural ectoderm or are non-neuronal midline brain structures. These sites include the surface epithelia of the head, face, nasal prominences, branchial arches, oral cavity and associated parts of the nasal epithelium, the epithelium covering the eye, parts of the otic vesicle, the epiphysis and roof of the diencephalon. With the exception of the oral cavity, sites of immunoreactivity for serotonin-binding protein were identified in th...

Anatomy and embryology, 1993

Advances in Neurochemistry, 1978

Proceedings of the National Academy of Sciences, 1990

Guanine nucleotide-binding regulatory proteins (G proteins) are heterotrimeric proteins that tran... more Guanine nucleotide-binding regulatory proteins (G proteins) are heterotrimeric proteins that transduce extracellular signals into intracellular changes. Functionally different G proteins have been identified by their different a subunits. The 13 and ysubunits have been assumed to constitute a common pool shared among various G protein heterotrimers.

Journal of Neurochemistry, 1981

A protein fraction that binds serotonin was obtained from astrocytes in primary cultures. It was ... more A protein fraction that binds serotonin was obtained from astrocytes in primary cultures. It was found to differ in some of its physical, chemical, and pharmacological properties from neuronal serotonin binding protein.

Journal of Neurochemistry, 1990

Serotonin binding protein (SBP) is a vesicular protein found in neurectoderm-derived cells that s... more Serotonin binding protein (SBP) is a vesicular protein found in neurectoderm-derived cells that store 5-hydroxytryptamine (5-HT, serotonin), such as central and peripheral serotonergic neurons and paraneurons (parafollicular cells of the thyroid). 5-HT is stored as a complex with SBP in vivo. Two forms of the protein are found. These differ in molecular mass: one is 45 kDa and the other 56 kDa. It has been suggested that the 56-kDa form of SBP may be the precursor of the 45-kDa form. To study the relationship between these two proteins, we have used a covalently bound radiolabeled probe to analyze their binding domains. A photoaffinity reagent, N-(4-azido-2-nitrophenyl)-5-hydroxytryptamine (NAP-5-HT), was synthesized and characterized by nuclear magnetic resonance spectroscopy, mass spectra, and UV-visible absorption spectra. A 1 M excess of NAP-5-HT inhibited the binding of [3H]5-HT to SBP by 50%. NAPI3H]S-HT was also synthesized and attached to both high-and lowaffinity binding sites on both forms of SBP. The high-affinity binding constants for 45-kDa and 56-kDa proteins were 0.8 nM and 0.02 nM, respectively, whereas the low-affinity constants were 0.3 pM and 0.15 pM. When the high-affinity site of partially purified SBP was photoaffinity-labeled with the reagent, two covalently labeled proteins (45 kDa and 56 kDa) were found by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Inhibition of the labeling of both proteins by 50% was observed in the presence of a 15fold molar excess of 5-HT. Drugs and reagents affected to the same degree the binding of [3H]5-HT to SBP (45 kDa and 56 kDa) and the binding of NAP['H]S-HT to the two proteins. The 45-kDa SBP and 56-kDa SBP covalently labeled with NAP[3H]5-HT were analyzed by partial proteolytic digestion with either Staphylococcus aureus V8 protease or proteinase K. The generated radiolabeled peptides, separated on SDS-PAGE from both forms of the labeled SBP, exhibited a similar pattern, suggesting their close structural similarity. Structure-binding requirements suggest that this probe will be also useful in studying other proteins that bind 5-HT, such as carriers of 5-HT in the plasma membrane and vesicles, as well as some serotonergic receptors 5-HT1,). Key Words: Serotonin-Serotonin binding protein-Photoaffinity probe-N-( 4-Azido-2-nitrophenyl)-5-hydroxytryptamine-Peptide mapping-Photoactivation-Serotonin receptors. Liu K.-P. et al. Photoaffinity labeling of the two forms of serotonin binding protein: peptide mapping of the binding sites.

Journal of Neurochemistry, 1972

The subcellular distribution of pyruvate kinase (EC 2.7.1.40) in the cerebral cortex of the rat w... more The subcellular distribution of pyruvate kinase (EC 2.7.1.40) in the cerebral cortex of the rat was studied. The enzyme, which had been previously reported in the cytoplasm, was found to be present in synaptosomal, microsomal and mitochondria1 fractions as well. The activity of the enzyme in the synaptosomal fraction was localized predominantly in the synaptosomal membrane and was not dissociated by repeated washing or recentrifuging in a sucrose gradient. Some kinetic parameters of the membrane-associated pyruvate kinase were measured.

Journal of Neurochemistry, 1979

ABSTRACT Abstract—Several analogues of 5-hydroxytryptophan were tested for their ability to inhib... more ABSTRACT Abstract—Several analogues of 5-hydroxytryptophan were tested for their ability to inhibit the binding of serotonin to serotonin-binding protein (SBP), a protein found within serotonergic neurons which has a high affinity for serotonin. An N-substituted dipeptide, N-acetyl-5-hydroxytryptophan-5-hydroxytryptophan amide, was found to be an inhibitor of this binding. The inhibition (50% at 1.0 μM) was specific, since it did not affect other known sites of serotonin binding. The binding of serotonin to its membrane receptor was not affected by the dipeptide (up to 10 μM). Uptake of serotonin by synaptosomes was only slightly affected (9% at 10 μM), and aromatic-L-amino-acid carboxy-lyase(EC 4.1.1.28) and amine: oxygen oxidoreductase (deaminating) (flavin-containing) (EC 1.4.3.4) were not inhibited (10 μM and 5 mM respectively), The peptide was not hydrolyzed by honiogenates of brain or myenteric plexus. The 14C-labelled dipeptide was shown to be taken up by synaptosomes. However, the uptake of the peptide was not affected either by drugs that inhibit serotonin uptake or by serotonin itself although the uptake was abolished by excess 5-hydroxytryptophan. Intraventricular injection of N-acetyl dipeptide caused a biphasic effect depending on dose. Lower doses (10nmol) induced a decrease in serotonin brain levels (40%). Higher doses (300 nmol) caused a 95% increase in serotonin levels.It is suggested that 5-hydroxytryptophyl peptides may be used as potent specific inhibitors of SBP, a storage compartment of serotonin.

Journal of Neurochemistry, 1976

The binding of serotonin to a soluble, high affinity binding protein, present in synaptosomes and... more The binding of serotonin to a soluble, high affinity binding protein, present in synaptosomes and associated with serotonergic tracts, has now been studied for the effects of metallic ions and various drugs. At optimal concentration ( 1 0 -4~) of Fez'. the enhancement of binding was close to 20-fold. A much smaller effect was noted with Cu2+. With other ions (Fe3+, Mn2+, Coz+, Ni2+, Cr3+, Mg2+, Caz') little or no effect was seen. For the effect with Fez*. preincubation was required (10 min, 25°C) and concentrations higher than M were inhibitory. Studies based on equilibrium dialysis show that the effect of Fez+ was on the affinity of the binding of serotonin to the protein, rather than on the binding capacity. In polydcrylamide gels at pH 8.6 the migratory properties of thc serotonin-protein complex formed in the presence of Fez+ differ from those of the complex formed without Fe2+. Nucleotides (ATP, GTP, ADP, AMP) inhibited thc binding. The effects of several classes of drugs (inhibitors of biogenic amine storage and uptake, psychotomimetics, M A 0 inhibitors and drugs binding to contractile proteins) were also studied. The only effective inhibitors of serotonin binding were reserpine, vinblastine and CZ-74, which caused 50% inhibition at 2 x 1 0 -6~, 7.5 x lo-" M and 0.2 x M respectively.

Journal of Neurochemistry, 1982

Rat brain serotonin binding protein (SBP) was found to have essential -S-S and -SH groups. Both r... more Rat brain serotonin binding protein (SBP) was found to have essential -S-S and -SH groups. Both reduction of the disulfide bond by dithiothreitol or mercaptoethanol and modification of -SH group(s) by Ellman reagent or alkylating agents caused loss of binding capacity. In contrast, formation of a mixed disulfide bond with sodium metabisulfite did not affect the binding capacity. Serotonin in the presence of Fez' and phosphate was found to bind to either an -SH group or to a site in very close proximity. Addition of serotonin protected -SH groups from modification b y Ellman reagent and from denaturation of protein upon storage. Lipids that enhance binding of serotonin to S B P also protected -SH groups from modification. Nucleotides were found to be strong inhibitors of the binding of serotonin to SBP. The inhibitory effect of nucleotides was due to their chelating properties and not to their ability to phosphorylate the protein or to bind directly to it. Inhibition by nucleotides and other chelators was reversible. Binding capacity was fully restored after removal of the chelator by molecular sieve chromatography and addition of Fez+. The ionic environment had a marked effect on the binding: intracellular ions such as K' were found to enhance the binding, and extracellular ions such as Na' and Ca2+ inhibited the binding. Based on these data and our previous studies, we suggest that S B P is an intracellular protein that acts as a storage protein. Consistent with our data is formation of a complex of SBP-S-Fe-S that in a hydrophobic surrounding could bind up to four molecules of serotonin in coordination bond with Fez+ and thereby reduce the osmotic pressure within a storage vesicle. Extracellular ionic conditions that favor the dissociation of the complex would free the amine to interact with its receptor or the presynaptic reuptake carrier. Key Words: Serotonin-Serotonin binding protein-Nucleotides-Sulfhydryl groups-Iron-Storage.

Journal of Cellular Biochemistry, 2011

Recently, we discovered oxytocin receptor (OTR) expression in the developing gut villus epitheliu... more Recently, we discovered oxytocin receptor (OTR) expression in the developing gut villus epithelium that emerges in villus-crypt junctions after weaning. Oxytocin (OT) and OTR regulate many physiological functions in various tissues; however, their function in gut epithelium is unknown. We explored responses of PI3K and Akt phosphoisoforms to OT stimuli in the Caco2BB human gut cell line. In Caco2BB cells, PI3K and pAkt levels peaked at 62.5 nM OT. At higher concentrations, PI3K decreased more gradually than pAkt(S473) suggesting that the pAkt(S473) response is separate from PI3K. At ≤7.8 nM OT, pAkt(T308) increased while pAkt(S473) decreased. Using a specific OTR antagonist, we demonstrated that responses of pAkt(T308) to OT depend on OTR in contrast to the partial OTR-dependence of the pAkt(S473) response. Differential pAkt phosphoisoform responses included pAkt phosphoserine 473 persistently free of phosphothreonine 308. The reduction in PI3K after 62.5 nM OT for 30 min coincided with OTR internalization. The PI3K/Akt activation profile was somewhat different in other cell lines (MCF-7 breast cancer cells, HT29 gut cells), which have PI3K activating mutations, that were examined to establish experimental parameters. In Caco2BB cells, the divergent effects of OT upon pAkt phosphoisoforms suggests separate sub-pathways; pAkt (T308) activation depends on OTR via the PI3K pathway and pAkt(S473) presumably results from its specific kinase mTORC2 (mammalian target of rapamycin complex 2). Thus, OT may modulate gut cell functions downstream of mTOR complexes (e.g., translation control as suggested by others in uterine cells). We will next explore OT-stimulated kinase activities downstream of mTOR related to pAkt phosphoisoforms.

Glia, 1996

Intracellular calcium responses of cultured rat Schwann cells to 5-hydroxytryptamine (5-HT) were ... more Intracellular calcium responses of cultured rat Schwann cells to 5-hydroxytryptamine (5-HT) were examined using the calcium indicator dye fluo-3. Consistent changes in [Ca2+]i were observed with bath application of 5-HT and the basis of these responses was characterized. Application of 5-HT elicited a transient increase in intracellular calcium in a subpopulation of cultured Schwann cells. In many responding cells, the response recurred at approximately regular intervals following the initial transient. In some cases, these oscillations lasted for hours following removal of 5-HT from the bath. The increase in intracellular calcium evoked by 5-HT still occurred in the absence of extracellular calcium, suggesting that 5-HT induces calcium release from intracellular stores. Consistent with this hypothesis, the response to 5-HT was prevented by depletion of inositol trisphosphate-sensitive intracellular calcium stores with thapsigargin. Bath application of caffeine, known to activate Ca2+ release from ryanodine receptor-mediated stores, did not elicit an increase in [Ca2+]i. These results also suggested that 5-HT acted by stimulating a member of the 5-HT2 receptor family since this family employs inositol trisphosphate as a second messenger. In agreement with this interpretation, it was found that the 5-HT-induced intracellular calcium transients could be reversibly blocked by both ketanserin and spiperone, suggesting that the transients are mediated by 5-HT2A receptors. Additional support for this conclusion was obtained by immunocytochemistry using an anti-idiotypic antibody that recognizes a subset of 5-HT receptors.

Experimental Neurology, 1987

The antinociceptive properties of a new synthetic dipeptide (N-hexanoyl-5-hydroxytryptophyl-5-hyd... more The antinociceptive properties of a new synthetic dipeptide (N-hexanoyl-5-hydroxytryptophyl-5-hydroxytryptophan amide, or 5-HTP-DP-hex) were studied in rats by an electrophysiological method. After an i.p. injection of alpha-chloralose and urethane, the animals were prepared for stereotaxic approach to the nucleus ventralis posterolateralis of the thalamus. With tungsten microelectrodes, individual nociceptive neurons in the nucleus were identified by the sequence of spikes emitted in response to single-pulse stimulation of the sciatic nerve. In addition to the usual short-latency spikes, a nociceptive neuron fired late spikes at regular intervals within 500 ms following each stimulus. When the spikes were accumulated in poststimulus time histograms, the short-latency spikes compiled an intensity-related (I) peak. The late spikes formed modality-related (M) peaks with spacing characteristic of nociception. Intracarotid infusion of 5-HTP-DP-hex (1 mg/kg) elevated the delayed portion of the I peak and the first M peak. This effect was followed in 25 min by suppression of all M peaks. The control record could be reinstated at any time by 5-hydroxytryptophan (3.5 mg/kg), or by natural recovery in 2.5 h. Responses evoked from a thalamic nociceptive neuron by single-pulse stimulation of the spinothalamic tract were modified by 5-HTP-DP-hex in a similar manner, except that no elevation of the activity peaks was observed. As shown previously, elevation of the delayed I peak and M1 indicated an increased input of A-delta and C fibers, respectively. The increased input lowers the response threshold and may represent hyperalgesia. Suppression of the M peaks may result from altered function of the positive feedback loop in the nociceptive system at the thalamic level, and may represent analgesia. Naloxone, methysergide, as well as ketanserin had no significant effect on the response histograms. These findings suggested that 5-HTP-DP-hex, a known serotonin receptor antagonist, targeted its action on very specific receptors, and thus interfered with particular synaptic activity within the spinal cord and on the thalamic level.

Experimental Neurology, 1989

Anatomy and Embryology, 1993

This study describes the timecourse of expression of low-affinity serotonin uptake sites in the d... more This study describes the timecourse of expression of low-affinity serotonin uptake sites in the developing craniofacial region of the mouse embryo. Whole mouse embryos were incubated in the presence of various serotonergic compounds followed by immunocytochemical localization of serotonin (5-HT) and its binding protein. In the gestational day 9 embryo (3 5 somites), 5-HT uptake was observed in the myocardium of the heart, the visceral yolk sac and foregut. A specific and transient pattern of 5-HT uptake was observed in the hindbrain neuroepithelium from day 9.5-11, where it was localized in rhombomeres 2-5 in the day 9.5 embryo. By day 10, when rhombomeres were no longer evident, uptake was present in the dorso-lateral neuroepithelium surrounding the fourth ventricle (rhombic lip; cerebellar anlage). Uptake of 5-HT was initially observed in the surface epithelium of the craniofacial region at day 10 (20-25 somites) and was greatly increased at day 11. The invaginating lens, nasal placode epithelium and otocyst also took up 5-HT at day 11. During these stages a 45 kD serotonin-binding protein (SBP) was expressed in craniofacial mesenchyme, and became progressively restricted to regions subjacent to epithelial uptake sites. These staining patterns were shown to be specific for 5-HT and SBP by their absence in embryos stained using preabsorbed antisera. The timecourse of these patterns are correlated with critical events in craniofacial morphogenesis including (1) onset of inductive epithelialmesenchymal interactions, (2) invagination and fusion of placodal structures, (3) presence of rhombomeres, and (4) regions of low proliferative activity.

Brain Research, 1981

Key words: thiamine deficiency --serotonin --serotonin binding protein --rat hypothalamus Thiamin... more Key words: thiamine deficiency --serotonin --serotonin binding protein --rat hypothalamus Thiamine deficiency (TD) selectively impairs the accumulation of serotonin by rat brain synaptosomes 4. 5-Hydroxyindole acetic acid (5-HIAA) levels and serotonin turnover rates increase in the brain of the deficient animals and there is a close correlation between these biochemical changes and neurological manifestations resulting from TD 5,11. It has been hypothesized ~ that these changes may be related to alternations in vesicular transport or storage of serotonin that is induced by TD.