Rvs161p and Rvs167p, the two yeast amphiphysin homologs, function togetherin vivo

Mutations in RVS161 and RVS167, the two yeast amphiphysin homologs, cause v ery similar growth phenotypes, a depolarized actin cytoskeleton, and a defe ct in the internalization step of endocytosis. Rvs161p and Rvs167p have bee n shown to interact in the two-hybrid system, but their localization in the cell may be different thus raising the question whether the interaction is physiologically relevant. Here we demonstrate that the two proteins functi on together in vivo. We find that the steady state level of Rvs167p is stro ngly reduced in an rvs161 Delta strain. Similarly the level of Rvs161p is s trongly reduced in an rvs167 Delta strain, We demonstrate that these reduce d protein levels at steady state are due to a decreased stability of either Rvs protein in the absence of the other protein. Furthermore, we find that the amount and ratio of Rvs161p and Rvs167p are critical parameters for re ceptor-mediated endocytosis. In addition, by using the two-hybrid system we show that the interaction of Rvs167p with actin is not abolished in an abp 1 Delta strain suggesting that Abp1p is not essential for this interaction.