Caenorhabditis elegans intestinal cells are characterized by the presence of gut granules, lysosome-related organelles that contain autofluorescent and birefringent material. Gut granule formation requires the activity of evolutionarily conserved AP-3 subunits, HOPS complex, and GLO-1/Rab38, genes whose homologues function in trafficking to lysosomes and lysosome-related organelles. In addition, we have identified nematode specific factors, such as the gut granule associated GLO-3 protein, that function in gut granule biogenesis. Mutations in these genes result in the loss and/or mislocalization of birefringent material into the embryonic intestinal lumen (the glo phenotype). Here we present our phenotypic and molecular analysis of another nematode specific gene required for gut granule biogenesis,
glo-2.
glo-2 is defined by two alleles that exhibit maternal effect gut granule biogenesis defects.
glo-2 mutant adults and embryos lack multiple markers associated with gut granules, while other endolysosomal organelles do not appear to be similarly affected. Our genetic and cellular studies implicate
glo-2 function in gut granule biogenesis pathways distinct from those currently implicated in gut granule formation.
glo-2 encodes a small cytoplasmically localized protein that is not obviously conserved outside of nematodes.
glo-2(-) is partially suppressed by overexpression of RAB-7, which is not obviously required for gut granule formation, suggesting overlap in trafficking pathways to lysosome-related and conventional lysosomal organelles, which co-exist in C. elegans intestinal cells. To better understand the function of GLO-2 we are currently carrying out studies of intracellular trafficking pathways in
glo-2(-) animals and searching for GLO-2 interacting proteins.