Cells internalize extracellular macromolecules, fluid, plasma membrane lipids and proteins by endocytosis. The reduced cell membrane is compensated by endocytic recycling pathway which could return much of the endocytosed proteins and lipids back to the plasma membrane. Moreover, internalized proteins can also be sent to lysosome for degradation.
tat-1, which encodes a C. elegans P4-ATPase, is required for maintaining plasma membrane PS asymmetry (1). In addition,
tat-1(lf) mutants accumulate big intestinal vacuoles and display various defects in endocytic transport (2 and our unpublished results). To understand how endocytic trafficking is regulated by TAT-1, we performed a genetic screen to search for mutants which can suppress the vacuolation phenotype in the intestine of
tat-1(lf) animals. From a screen of 12,000 hyploid genomes, we isolated the
qx49 mutant. We found that
qx49 completely suppressed the appearance of abnormal vacuoles in the
tat-1(
qx30) mutants. Moreover,
qx49 mutants suppress the endocytic recycling defect in
tat-1(
qx30) animals, but cargo degradation is still defective in the double mutants.
qx49 was mapped to linkage group III and we are in the process of cloning the gene affected in
qx49 mutants and performing further functional analyses to understand its function in endocytic transport. Identification and characterization of
tat-1 suppressors will help us to better understand how endocytic trafficking is regulated in C. elegans. We will report our progress in the meeting. References:1. Darland-Ransom, M., Wang X.., Sun, C. L., Mmapes, J., Gengyo-Ando, K., Mitani, S., and Xue, D., (2008) Role of C. elegans TAT-1 protein in maintaining plasma membrane phosphatidylserine asymmetry. Science 320, 528-531.2. Anne-Francoise Ruaud, Lars Nilssoon, Fabrice Richard, Morten Krog Larsen, Jen-Louis Bessereau and Simon Tuck, 2009. The C. elegans P4-ATPase TAT-1 regulates lysosome biogenesis and endocytosis. Traffic 10(1): 88-100.