Agef-1 Functions In Endocytosis Of C. Elegans

The endocytic pathway is a vesicle-mediated process required for various essential cellular functions, including processing fluid and macromolecules from the outside environment, and internalizing plasma membrane lipids and proteins. Although much is known about how some cellular proteins, such as Rab GTPases, regulate some steps of the endocytic pathway, the precise molecular mechanisms are not fully understood, which is especially true for lysosomal transport and dynamics.Because the endocytic machinery is highly conserved from yeast to mammals, several studies have utilized the worm Caenorhabditis elegans to reveal mechanisms associated with endocytosis in a multicellular organism. We analysed AGEF-1, which is thought to activate classâ… Arfs(ARF1-3, small G proteins with long lipid tails function on vecicle traffic and cytoskeleton), endocytic functions in Caenorhabditis elegans coelomocytes. Knockdown of AGEF-1 levels results in two apparent trafficking defects in coelomocytes of Caenorhabditis elegans. First, there is a delay in the uptake of solutes from the extracellular medium. Second, there is a dramatic enlargement of the sizes of lysosomes which is likely the products of homotypic lysosome fusion events, even though lysosomal acidification is normal and degradation still occurs. Our epistasis analysis showed that reduced ARL-8 function abrogates the lysosome defect due to reduced AGEF-1 function, but not the uptake defect. Indeed, early steps of endocytosis analysis showed that after reduced of AGEF-1 levels, the distribution of clathrin at plasma membrane was obviously changed, suggesting that AGEF-1 has a direct role in regulating uptake. Full-length and truncated AGEF-1 proteins overexpressed experiment indicates that AGEF-1 associates with distinct complexs at surface and in endosome/lysosomes.In conclusion, AGEF-1 is the first identified GTPase regulator that functions at lysosomes fusion/fission stage of the endocytic pathway. Our study sheds light on lysosomal dynamics and endocytosis regulation network. What's more, after reduced of AGEF-1 levels the distribution of clathrin at nervous system was obviously changed. Crawl speed was seriously suppressed, while swimming speed was increased, indicating these two types of locomotion were regulated by different neural circuits. It provides a good model in studing Clathrin-dependent endocytosis functions in maintenance of synaptic vesicle pools.