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Sphingoid Base Synthesis Is Required for Oligomerization and Cell Surface Stability of the Yeast Plasma Membrane ATPase, Pma1
Qiongqing Wang and Amy Chang
Proceedings of the National Academy of Sciences of the United States of America
Vol. 99, No. 20 (Oct. 1, 2002), pp. 12853-12858
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/3073312
Page Count: 6
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The plasma membrane H+-ATPase, Pma1, is an essential and long-lived integral membrane protein. Previous work has demonstrated that the Pma1-D378N mutant is a substrate for endoplasmic reticulum (ER)-associated degradation and causes a dominant negative effect on cell growth by preventing ER export of wild-type Pma1. We now show that Pma1-D378N is ubiquitylated, and it heterooligomerizes with wild-type Pma1, resulting in ubiquitylation and ER-associated degradation of wild-type Pma1. In temperature-sensitive lcb1-100 cells, defective in sphingoid base synthesis, Pma1 fails to oligomerize. At 30°C, lcb1-100 is a suppressor of pma1-D378N because wild-type Pma1 fails to heterooligomerize with Pma1-D378N; wild-type Pma1 moves to the cell surface, indicating that oligomerization is not required for delivery to the plasma membrane. Even in the absence of Pma1-D378N, wild-type Pma1 is ubiquitylated and it undergoes internalization from the cell surface and vacuolar degradation at 30°C in lcb1-100 cells. At 37°C in lcb1-100 cells, a more severe defect occurs in sphingoid base synthesis, and targeting of newly synthesized Pma1 to the plasma membrane is impaired. These data indicate requirements for sphingolipids at three discrete stages: Pma1 oligomerization at the ER, targeting to the plasma membrane, and stability at the cell surface.
Proceedings of the National Academy of Sciences of the United States of America © 2002 National Academy of Sciences