David Strick | Stanford University (original) (raw)

Papers by David Strick

Research paper thumbnail of Identification and characterization of effectors/binding molecules for the small GTPase Rab15

UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive collection of dissert... more UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive collection of dissertations and theses. Learn more... ProQuest, Identification and characterization of effectors/binding molecules for the small GTPase Rab15. ...

Research paper thumbnail of Focus on molecules: MERTK

Experimental Eye Research, 2010

Research paper thumbnail of MEMBRANE TRANSPORT, STRUCTURE, FUNCTION, AND BIOGENESIS-Mammalian Suppressor of Sec4 Modulates the Inhibitory Effect of Rab15 …

Journal of Biological …, 2002

Research paper thumbnail of Functional properties of rab15 effector protein in endocytic recycling

Methods in Enzymology, 2005

Receptor recycling has emerged as an important regulatory mechanism for cell surface composition,... more Receptor recycling has emerged as an important regulatory mechanism for cell surface composition, pathogen invasion, and for control over the intensity and duration of receptor signaling in multiple cell types. In the case of the transferrin receptor, receptor recycling is an important step for facilitating iron uptake into the cell, by regulating the availability of the receptor at the cell surface. Following internalization into clathrin-coated pits, the transferrin receptor first enters peripheral sorting endosomes. Here, internalized transferrin receptor is either sorted for recycling back to the cell surface directly, or targeted to a slower route of recycling through a perinuclear population of endosomes termed the endocytic recycling compartment. This chapter describes methodologies to examine the fast and slow modes of transferrin receptor recycling, with a particular emphasis on the function of the novel protein Rab15 effector protein.

Research paper thumbnail of Mammalian suppressor of Sec4 modulates the inhibitory effect of Rab15 during early endocytosis

Journal of Biological Chemistry, 2002

Rab15 is a novel endocytic Rab that counters the stimulatory effect of Rab5-GTP on early endocyti... more Rab15 is a novel endocytic Rab that counters the stimulatory effect of Rab5-GTP on early endocytic trafficking. Rab15 may interfere with Rab5 function directly by sequestering Rab5 effectors or indirectly through novel sets of effector interactions. To distinguish between these possibilities, we examined the effector binding properties of Rab15. Rab15 does not interact directly with the Rab5 effectors rabex-5 and rabaptin-5 in a yeast two-hybrid binding assay. Rather mammalian suppressor of Sec4 (Mss4) was identified as a binding partner for Rab15. Mss4 preferentially binds GDP-bound (T22N) and nucleotide-free (N121I) Rab15, consistent with the proposed role of Mss4 as a chaperone that stabilizes target Rabs in their nucleotide-free form. Mutational analysis of Rab15 indicates that lysine at position 48 (K48Q) is important for the binding of Rab15-GDP to Mss4. Moreover, the mutation K48Q counters the inhibitory phenotype of wild type Rab15 on receptor-mediated endocytosis in HeLa cells and homotypic endosome fusion in vitro without altering the relative amount of cell surface-associated transferrin receptor. Together, these data indicate a novel role for Mss4 as an effector for Rab15 in early endocytic trafficking.

Research paper thumbnail of Rab15 effector protein: a novel protein for receptor recycling from the endocytic recycling compartment

Molecular Biology of The Cell, 2005

Sorting endosomes and the endocytic recycling compartment are critical intracellular stores for t... more Sorting endosomes and the endocytic recycling compartment are critical intracellular stores for the rapid recycling of internalized membrane receptors to the cell surface in multiple cell types. However, the molecular mechanisms distinguishing fast receptor recycling from sorting endosomes and slow receptor recycling from the endocytic recycling compartment remain poorly understood. We previously reported that Rab15 differentially regulates transferrin receptor trafficking through sorting endosomes and the endocytic recycling compartment, suggesting a role for distinct Rab15effector interactions at these endocytic compartments. In this study, we identified the novel protein Rab15 effector protein (REP15) as a binding partner for Rab15-GTP. REP15 is compartment specific, colocalizing with Rab15 and Rab11 on the endocytic recycling compartment but not with Rab15, Rab4, or early endosome antigen 1 on sorting endosomes. REP15 interacts directly with Rab15-GTP but not with Rab5 or Rab11. Consistent with its localization, REP15 overexpression and small interfering RNA-mediated depletion inhibited transferrin receptor recycling from the endocytic recycling compartment, without affecting receptor entry into or recycling from sorting endosomes. Our data identify REP15 as a compartment-specific protein for receptor recycling from the endocytic recycling compartment, highlighting that the rapid and slow modes of transferrin receptor recycling are mechanistically distinct pathways.

Research paper thumbnail of Perspektive: Tissue engineering bei RPE-Transplantation in AMD

Spektrum Der Augenheilkunde, 2007

The Retinal pigment epithelium (RPE) incurs a lifelong damage, which is one mechanism leading to ... more The Retinal pigment epithelium (RPE) incurs a lifelong damage, which is one mechanism leading to agerelated macular degeneration (AMD), the most common cause of blindness over 55. Despite intense research, to date the majority of those affected have no effective therapy available. Cell based replacement strategies of the RPE represent, in contrast to current pharmacologic interventions, a curative treatment. This article describes potential future perspectives of current autologous clinical RPE transplantation protocols. Intermittent culturing could potentially rejuvenate aged RPE. Age related changes of the RPE are reflected in culture, yet our findings suggest that they can be overcome with modern artificial substrates and defined culture media. Degenerations and surgical damage in Bruch's membrane may potentially compromise survival or function of transplanted RPE. Hence, an important adjunct to RPE replacement is Bruch's membrane prosthesis, for which we dedicated a significant proportion of this manuscript. Results of our in vitro and in vivo studies with amniotic membrane, porous polyester membranes and electrospun nanofibers are briefly summarized. We conclude with an outlook on future research on the use of tissue engineering for replacement of the entire RPE/Choriocapillaris Complex, and on promising results from stem cell derived RPE-like cells.

Research paper thumbnail of Mertk drives myosin II redistribution during retinal pigment epithelial phagocytosis

Investigative Ophthalmology & Visual Science, 2009

Mertk is a key phagocytic receptor in the immune, male reproductive, and visual systems. In the r... more Mertk is a key phagocytic receptor in the immune, male reproductive, and visual systems. In the retinal pigment epithelium, Mertk is required for the daily ingestion of photoreceptor outer segment (OS) tips. Loss of Mertk function causes retinal degeneration in rats, mice, and humans; however, little is known about the mechanism by which Mertk regulates the ingestion phase of retinal pigment epithelial (RPE) phagocytosis. To address this, the authors sought proteins that associated with Mertk during OS phagocytosis. Lysates of RPE-J cells challenged with OS for various times were immunoprecipitated with Mertk antibody. Potential interacting proteins were identified by mass spectrometry and characterized with confocal microscopy, pharmacologic inhibition, and siRNA knockdown coupled with an in vitro phagocytic assay in primary RPE cells. Myh9, the non-muscle myosin II-A heavy chain, was enriched in immunoprecipitates from OS-treated samples. Myosin II-A and II-B isoforms exhibited a striking redistribution in wild-type rat primary RPE cells challenged with OS, moving from the cell periphery to colocalize with ingested OS over time. In contrast, myosin II-A redistribution in response to OS was blunted in primary RPE cells from RCS rats, which lack functional Mertk. Wild-type rat primary RPE cells treated with the myosin II-specific inhibitor blebbistatin or myosin II siRNAs exhibited a significant phagocytic defect. Mertk mobilizes myosin II from the RPE cell periphery to sites of OS engulfment, where myosin II function is essential for the normal phagocytic ingestion of OS.

Research paper thumbnail of Identification and characterization of effectors/binding molecules for the small GTPase Rab15

UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive collection of dissert... more UMI, ProQuest ® Dissertations & Theses. The world's most comprehensive collection of dissertations and theses. Learn more... ProQuest, Identification and characterization of effectors/binding molecules for the small GTPase Rab15. ...

Research paper thumbnail of Focus on molecules: MERTK

Experimental Eye Research, 2010

Research paper thumbnail of MEMBRANE TRANSPORT, STRUCTURE, FUNCTION, AND BIOGENESIS-Mammalian Suppressor of Sec4 Modulates the Inhibitory Effect of Rab15 …

Journal of Biological …, 2002

Research paper thumbnail of Functional properties of rab15 effector protein in endocytic recycling

Methods in Enzymology, 2005

Receptor recycling has emerged as an important regulatory mechanism for cell surface composition,... more Receptor recycling has emerged as an important regulatory mechanism for cell surface composition, pathogen invasion, and for control over the intensity and duration of receptor signaling in multiple cell types. In the case of the transferrin receptor, receptor recycling is an important step for facilitating iron uptake into the cell, by regulating the availability of the receptor at the cell surface. Following internalization into clathrin-coated pits, the transferrin receptor first enters peripheral sorting endosomes. Here, internalized transferrin receptor is either sorted for recycling back to the cell surface directly, or targeted to a slower route of recycling through a perinuclear population of endosomes termed the endocytic recycling compartment. This chapter describes methodologies to examine the fast and slow modes of transferrin receptor recycling, with a particular emphasis on the function of the novel protein Rab15 effector protein.

Research paper thumbnail of Mammalian suppressor of Sec4 modulates the inhibitory effect of Rab15 during early endocytosis

Journal of Biological Chemistry, 2002

Rab15 is a novel endocytic Rab that counters the stimulatory effect of Rab5-GTP on early endocyti... more Rab15 is a novel endocytic Rab that counters the stimulatory effect of Rab5-GTP on early endocytic trafficking. Rab15 may interfere with Rab5 function directly by sequestering Rab5 effectors or indirectly through novel sets of effector interactions. To distinguish between these possibilities, we examined the effector binding properties of Rab15. Rab15 does not interact directly with the Rab5 effectors rabex-5 and rabaptin-5 in a yeast two-hybrid binding assay. Rather mammalian suppressor of Sec4 (Mss4) was identified as a binding partner for Rab15. Mss4 preferentially binds GDP-bound (T22N) and nucleotide-free (N121I) Rab15, consistent with the proposed role of Mss4 as a chaperone that stabilizes target Rabs in their nucleotide-free form. Mutational analysis of Rab15 indicates that lysine at position 48 (K48Q) is important for the binding of Rab15-GDP to Mss4. Moreover, the mutation K48Q counters the inhibitory phenotype of wild type Rab15 on receptor-mediated endocytosis in HeLa cells and homotypic endosome fusion in vitro without altering the relative amount of cell surface-associated transferrin receptor. Together, these data indicate a novel role for Mss4 as an effector for Rab15 in early endocytic trafficking.

Research paper thumbnail of Rab15 effector protein: a novel protein for receptor recycling from the endocytic recycling compartment

Molecular Biology of The Cell, 2005

Sorting endosomes and the endocytic recycling compartment are critical intracellular stores for t... more Sorting endosomes and the endocytic recycling compartment are critical intracellular stores for the rapid recycling of internalized membrane receptors to the cell surface in multiple cell types. However, the molecular mechanisms distinguishing fast receptor recycling from sorting endosomes and slow receptor recycling from the endocytic recycling compartment remain poorly understood. We previously reported that Rab15 differentially regulates transferrin receptor trafficking through sorting endosomes and the endocytic recycling compartment, suggesting a role for distinct Rab15effector interactions at these endocytic compartments. In this study, we identified the novel protein Rab15 effector protein (REP15) as a binding partner for Rab15-GTP. REP15 is compartment specific, colocalizing with Rab15 and Rab11 on the endocytic recycling compartment but not with Rab15, Rab4, or early endosome antigen 1 on sorting endosomes. REP15 interacts directly with Rab15-GTP but not with Rab5 or Rab11. Consistent with its localization, REP15 overexpression and small interfering RNA-mediated depletion inhibited transferrin receptor recycling from the endocytic recycling compartment, without affecting receptor entry into or recycling from sorting endosomes. Our data identify REP15 as a compartment-specific protein for receptor recycling from the endocytic recycling compartment, highlighting that the rapid and slow modes of transferrin receptor recycling are mechanistically distinct pathways.

Research paper thumbnail of Perspektive: Tissue engineering bei RPE-Transplantation in AMD

Spektrum Der Augenheilkunde, 2007

The Retinal pigment epithelium (RPE) incurs a lifelong damage, which is one mechanism leading to ... more The Retinal pigment epithelium (RPE) incurs a lifelong damage, which is one mechanism leading to agerelated macular degeneration (AMD), the most common cause of blindness over 55. Despite intense research, to date the majority of those affected have no effective therapy available. Cell based replacement strategies of the RPE represent, in contrast to current pharmacologic interventions, a curative treatment. This article describes potential future perspectives of current autologous clinical RPE transplantation protocols. Intermittent culturing could potentially rejuvenate aged RPE. Age related changes of the RPE are reflected in culture, yet our findings suggest that they can be overcome with modern artificial substrates and defined culture media. Degenerations and surgical damage in Bruch's membrane may potentially compromise survival or function of transplanted RPE. Hence, an important adjunct to RPE replacement is Bruch's membrane prosthesis, for which we dedicated a significant proportion of this manuscript. Results of our in vitro and in vivo studies with amniotic membrane, porous polyester membranes and electrospun nanofibers are briefly summarized. We conclude with an outlook on future research on the use of tissue engineering for replacement of the entire RPE/Choriocapillaris Complex, and on promising results from stem cell derived RPE-like cells.

Research paper thumbnail of Mertk drives myosin II redistribution during retinal pigment epithelial phagocytosis

Investigative Ophthalmology & Visual Science, 2009

Mertk is a key phagocytic receptor in the immune, male reproductive, and visual systems. In the r... more Mertk is a key phagocytic receptor in the immune, male reproductive, and visual systems. In the retinal pigment epithelium, Mertk is required for the daily ingestion of photoreceptor outer segment (OS) tips. Loss of Mertk function causes retinal degeneration in rats, mice, and humans; however, little is known about the mechanism by which Mertk regulates the ingestion phase of retinal pigment epithelial (RPE) phagocytosis. To address this, the authors sought proteins that associated with Mertk during OS phagocytosis. Lysates of RPE-J cells challenged with OS for various times were immunoprecipitated with Mertk antibody. Potential interacting proteins were identified by mass spectrometry and characterized with confocal microscopy, pharmacologic inhibition, and siRNA knockdown coupled with an in vitro phagocytic assay in primary RPE cells. Myh9, the non-muscle myosin II-A heavy chain, was enriched in immunoprecipitates from OS-treated samples. Myosin II-A and II-B isoforms exhibited a striking redistribution in wild-type rat primary RPE cells challenged with OS, moving from the cell periphery to colocalize with ingested OS over time. In contrast, myosin II-A redistribution in response to OS was blunted in primary RPE cells from RCS rats, which lack functional Mertk. Wild-type rat primary RPE cells treated with the myosin II-specific inhibitor blebbistatin or myosin II siRNAs exhibited a significant phagocytic defect. Mertk mobilizes myosin II from the RPE cell periphery to sites of OS engulfment, where myosin II function is essential for the normal phagocytic ingestion of OS.