RME-8, a conserved J-domain protein, is required for endocytosis in Caenorhabditis elegans.
By genetic analysis of Caenorhabditis elegans mutants defective in yolk uptake, we have identified new molecules functioning in the endocytosis pathway. Here we describe a novel J-domain-containing protein, RME-8, identified by such genetic analysis. RME-8 is required for receptor-mediated endocytosis and fluid-phase endocytosis in various cell types and is essential for C. elegans development and viability. In the macrophage-like coelomocytes, RME-8 localizes to the limiting membrane of large endosomes. Endocytosis markers taken up by the coelomocytes rapidly accumulate in these large RME-8-positive endosomes, concentrate in internal subendosomal structures, and later appear in RME-8-negative lysosomes. rme-8 mutant coelomocytes fail to accumulate visible quantities of endocytosis markers. These observations show that RME-8 functions in endosomal trafficking before the lysosome. RME-8 homologues are found in multicellular organisms from plants to humans but not in the yeast Saccharomyces cerevisiae. These sequence homologies suggest that RME-8 fulfills a conserved function in multicellular organisms.
Zhang
Y
Y
Department of Biochemistry and Molecular Biophysics, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA.
Grant
B
B
Hirsh
D
D
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins; D002455:Cell Division; D017124:Conserved Sequence; D018509:DNA, Helminth; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism; D015870:Gene Expression; D017238:Genes, Helminth / Q000502:physiology; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
D029742:Caenorhabditis elegans Proteins; D018509:DNA, Helminth; D015801:Helminth Proteins; D018832:Molecular Chaperones; C439316:RME-8 protein, C elegans