Yeast lacking the amphiphysin family protein Rvs167 is sensitive to disruptions in sphingolipid levels

Rvs167 and Rvs161 in Saccharomyces cerevisiae are amphiphysin family proteins, which are involved in several important cellular events, such as invagination and scission of endocytic vesicles, and actin cytoskeleton organization. It has been reported that cellular dysfunctions caused by deletion of RVS167 or RVS161 are rescued by deletion of specific nonessential sphingolipid-metabolizing enzyme genes. Here, we found that yeast cells lacking RVS167 or RVS161 exhibit a decrease in sphingolipid levels. In rvs167∆ cells, the expression level of Orm2, a negative regulator of serine palmitoyltransferase (SPT) catalyzing the initial step of sphingolipid biosynthesis, was increased in a calcineurin-dependent manner, and the decrease in sphingolipid levels in rvs167∆ cells was reversed on deletion of ORM2. Moreover, repression of both ORM1 and ORM2 expression or overexpression of SPT caused a strong growth defect of rvs167∆ cells, indicating that enhancement of de novo sphingolipid biosynthesis is detrimental to rvs167∆ cells. In contrast, partial repression of LCB1-encoding SPT suppressed abnormal phenotypes caused by the deletion of RVS167, including supersensitivity to high temperature and salt stress, and impairment of endocytosis and actin cytoskeleton organization. In addition, the partial repression of SPT activity suppressed the temperature supersensitivity and abnormal vacuolar morphology caused by deletion of VPS1 encoding a dynamin-like GTPase, which is required for vesicle scission and is functionally closely related to Rvs167/Rvs161, whereas repression of both ORM1 and ORM2 expression in vps1∆ cells caused a growth defect. Thus, it was suggested that proper regulation of SPT activity is indispensable for amphiphysin-deficient cells.