Caenorhabditis elegans num-1 negatively regulates endocytic recycling.
Much of the material taken into cells by endocytosis is rapidly returned to the plasma membrane by the endocytic recycling pathway. Although recycling is vital for the correct localization of cell membrane receptors and lipids, the molecular mechanisms that regulate recycling are only partially understood. Here we show that in Caenorhabditis elegans endocytic recycling is inhibited by NUM-1A, the nematode Numb homolog. NUM-1AGFP fusion protein is localized to the baso-lateral surfaces of many polarized epithelial cells, including the hypodermis and the intestine. We show that increased NUM-1A levels cause morphological defects in these cells similar to those caused by loss-of-function mutations in rme-1, a positive regulator of recycling in both C. elegans and mammals. We describe the isolation of worms lacking num-1A activity and show that, consistent with a model in which NUM-1A negatively regulates recycling in the intestine, loss of num-1A function bypasses the requirement for RME-1. Genetic epistasis analysis with rab-10, which is required at an early part of the recycling pathway, suggests that loss of num-1A function does not affect the uptake of material by endocytosis but rather inhibits baso-lateral recycling downstream of rab-10.
Nilsson
Lars
L
Umeå Center for Molecular Pathogenesis, Umeå University, SE-901 87 Umeå, Sweden.
Conradt
Barbara
B
Ruaud
Anne-Françoise
AF
Chen
Carlos Chih-Hsiung
CC
Hatzold
Julia
J
Bessereau
Jean-Louis
JL
Grant
Barth D
BD
Tuck
Simon
S
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004705:Endocytosis / Q000235:genetics / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D022161:Transport Vesicles / Q000502:physiology* / Q000648:ultrastructure
D048868:Adaptor Proteins, Signal Transducing; D029742:Caenorhabditis elegans Proteins; D017931:DNA Primers; C425313:num-1 protein, C elegans; D049452:Green Fluorescent Proteins