Membrane fusion is an essential step during the trafficking of endosomes and vesicles throughout the cell. Membrane fusion events are facilitated by multisubunit tethering complexes (MTC) including CORVET and HOPS. These complexes interact with Rab GTPases and SNARE proteins to promote the fusion of endosomes and lysosomes (1). In yeast VPS41 is a component of the HOPS complex that is needed for transport of endosomes and Golgi-derived vesicles to the vacuole. The choice between these two substrates is facilitated by the phosphorylation of VPS1 by Yck3 (2). Carbrera et al. used VPS41 antibodies in western blots to examine phosphorylation status of VPS41 (2). Their study identified the importance of VPS41 phosphorylation in localization and in the regulation of either endosome or vesicle targeting (2). VPS41 also seems to play a role in the transport and fusion of autophagosomes. A group from the University of British Colombia characterized the role of VPS34, a PI3K, in delivering lysosomal proteins to the vacuole during autophagy (3). Through western blotting with the VPS41 antibody the authors showed HOPS complex assembly on autophagosomes (3). The known functions of VPS41 in cell biology have continued to expand beyond just lysosomal trafficking with tools provided by VPS41 antibodies. Wang et al. used immunoprecipitation experiments to identify a direct interaction of VPS41 with caspase-8 that is able to regulate apoptosis (4). Lin et al. used the VPS41 antibody to characterize the function of VPS41 in the HOPS complex during endocytic trafficking (5). In order to examine the localization of VPS41 they performed immunofluorescence with the VPS41 antibody (5). Their experiments showed RILP (Rab interacting lysosomal protein) interacts with the HOPS complex through VPS41 and this interaction is needed for membrane recruitment (5). Together these studies have clarified the functions of VPS41 in the HOPS complex and have pointed to new biological roles for VPS41 in autophagy and apoptosis.
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