Identification and characterization of Saccharomyces cerevisiae mutants defective in fluid-phase endocytosis

A mutant library generated by the European Functional Analysis Network (EUR OFAN) was screened for strains defective in fluid-phase endocytosis. Accumu lation of Lucifer yellow in the vacuole was used as a marker for efficient endocytosis. Fourteen mutants, including ede1 Delta, rcy1 Delta, sys1 Delta and tlg2 Delta, previously described to be involved in membrane traffickin g, were identified in this screen. alpha -Factor uptake, endocytosis of FM4 -64, carboxypeptidase Y secretion, vacuolar morphology, and a vma2 syntheti c growth defect were used as criteria to characterize the endocytic defect of the mutant strains obtained. Accordingly, eight mutant strains have endo cytic phenotypes in addition to their defect in Lucifer yellow accumulation . These fluid-phase endocytosis mutants are defective at different steps of the endocytic pathway, Interestingly, only two mutants were defective for internalization, two for vacuolar protein sorting and four mutants had aber rant vacuolar morphologies, Some of the mutants identified in this screen t hat sort carboxypeptidase Y correctly may affect endocytosis at an early po st-internalization step before the intersection of the endocytic with the v acuolar protein-sorting pathway. Copyright (C) 2001 John Wiley & Sons, Ltd.