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APEX2-mediated RAB proximity labeling identifies a role for RAB21 in clathrin-independent cargo sorting

ABSTRACT: RAB GTPases are central modulators of membrane trafficking. They are under the dynamic regulation of activating guanine exchange factors (GEFs) and inactivating GTPase activating proteins (GAPs). Once activated, RABs recruit a large spectrum of effectors to control trafficking functions of eukaryotic cells. Multiple proteomic studies, using pull-down or yeast two-hybrid approaches, have identified a number of RAB interactors. However, due to the in vitro nature of these and to inherent limitations of each technique, a comprehensive definition of RAB interactors is still lacking. By comparing quantitative affinity purifications of GFP:RAB21 with APEX2-mediated proximity labeling of RAB4a, RAB5a, RAB7a and RAB21, we find that APEX2 proximity labeling allows for the comprehensive identification of RAB regulators and interactors. Importantly, through biochemical and genetic approaches, we establish a novel link between RAB21 and the WASH and retromer complexes, with functional consequences on cargo sorting. Hence, APEX2-mediated proximity labeling of RAB neighboring proteins represents a new and efficient tool to define RAB functions.

SUBMITTER: Tomas Del Olmo

PROVIDER: S-SCDT-91748_2_1551690886_jats | biostudies-other |

REPOSITORIES: biostudies-other

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APEX2-mediated RAB proximity labeling identifies a role for RAB21 in clathrin-independent cargo sorting.

Project description:RAB GTPases are central modulators of membrane trafficking. They are under the dynamic regulation of activating guanine exchange factors (GEFs) and inactivating GTPase-activating proteins (GAPs). Once activated, RABs recruit a large spectrum of effectors to control trafficking functions of eukaryotic cells. Multiple proteomic studies, using pull-down or yeast two-hybrid approaches, have identified a number of RAB interactors. However, due to the in vitro nature of these approaches and inherent limitations of each technique, a comprehensive definition of RAB interactors is still lacking. By comparing quantitative affinity purifications of GFP:RAB21 with APEX2-mediated proximity labeling of RAB4a, RAB5a, RAB7a, and RAB21, we find that APEX2 proximity labeling allows for the comprehensive identification of RAB regulators and interactors. Importantly, through biochemical and genetic approaches, we establish a novel link between RAB21 and the WASH and retromer complexes, with functional consequences on cargo sorting. Hence, APEX2-mediated proximity labeling of RAB neighboring proteins represents a new and efficient tool to define RAB functions.

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4 RABs proxymity labelling - APEX2-mediated RAB proximity labeling identifies a role for RAB21 in clathrin-independent cargo sorting

Project description:APEX2-mediated proximity labeling was performed with 4 endosomal RABs allowed an efficient and comprehensive identification of their protein neighbors. APEX2-mediated proximity labeling was performed in triplicate. Protein enrichments obtained from all RABs were compared to APEX2-nude proximity labeling results. Finally, bioinformatic and biochemical approaches were used to confirm functional validity of RAB protein neighbor’s identification.

2019-01-07 | PXD010950 | Pride

Sorting of Clathrin-Independent Cargo Proteins Depends on Rab35 Delivered by Clathrin-Mediated Endocytosis.

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Microtubule-dependent endosomal sorting of clathrin-independent cargo by Hook1.

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SEC-10 and RAB-10 coordinate basolateral recycling of clathrin-independent cargo through endosomal tubules in Caenorhabditis elegans.

Project description:Despite the increasing number of regulatory proteins identified in clathrin-independent endocytic (CIE) pathways, our understanding of the exact functions of these proteins and the sequential manner in which they function remains limited. In this study, using the Caenorhabditis elegans intestine as a model, we observed a unique structure of interconnected endosomal tubules, which is required for the basolateral recycling of several CIE cargoes including hTAC, GLUT1, and DAF-4. SEC-10 is a subunit of the octameric protein complex exocyst. Depleting SEC-10 and several other exocyst components disrupted the endosomal tubules into various ring-like structures. An epistasis analysis further suggested that SEC-10 operates at the intermediate step between early endosomes and recycling endosomes. The endosomal tubules were also sensitive to inactivation of the Rab GTPase RAB-10 and disruption of microtubules. Taken together, our data suggest that SEC-10 coordinates with RAB-10 and microtubules to form the endosomal tubular network for efficient recycling of particular CIE cargoes.

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