End13p/Vps4p is required for efficient transport from early to late endosomes in Saccharomyces cerevisiae

end13-1 was isolated in a screen for endocytosis mutants and has been shown to have a post-internalisation defect in endocytic transport as well as a defect in vacuolar protein sorting (Vps(-) phenotype), leading to secretion of newly synthesised vacuolar proteins. Here we demonstrate that END13 is identical to VPS4, encoding an AAA (ATPase associated with a variety of cel lular activities)-family ATPase, We also report that the end13-1 mutation i s a serine 335 to phenylalanine substitution in the AAA-ATPase domain of En d13p/Vps4p. It has been reported that mutant cells lacking End13p/Vps4p (en d13(vps4)Delta) accumulate endocytosed marker dyes, plasma membrane recepto rs and newly synthesised vacuolar hydrolase precursors in an endosomal comp artment adjacent to the vacuole (prevacuolar compartment, or PVC). We find, however, that the end13 mutants have defects in transport of endocytosed f luorescent dyes, plasma membrane receptors and ligands from small periphera lly located early endosomes to larger late endosomes, which are often locat ed adjacent to the vacuole, Our results indicate that End13p/Vps4p may play an important role in multiple steps of membrane traffic through the endocy tic pathway.