| Title: | Elimination of defective alpha-factor pheromone receptors |
| Author(s): | Jenness DD; Li Y; Tipper C; Spatrick P; |
| Address: | "Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655-0122, USA. jennessd@ummed.edu" |
| ISSN/ISBN: | 0270-7306 (Print) 1098-5549 (Electronic) 0270-7306 (Linking) |
| Abstract: | "This report compares trafficking routes of a plasma membrane protein that was misfolded either during its synthesis or after it had reached the cell surface. A temperature-sensitive mutant form of the yeast alpha-factor pheromone receptor (ste2-3) was found to provide a model substrate for quality control of plasma membrane proteins. We show for the first time that a misfolded membrane protein is recognized at the cell surface and rapidly removed. When the ste2-3 mutant cells were cultured continuously at 34 degrees C, the mutant receptor protein (Ste2-3p) failed to accumulate at the plasma membrane and was degraded with a half-life of 4 min, compared with a half-life of 33 min for wild-type receptor protein (Ste2p). Degradation of both Ste2-3p and Ste2p required the vacuolar proteolytic activities controlled by the PEP4 gene. At 34 degrees C, Ste2-3p comigrated with glycosylated Ste2p on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating that Ste2-3p enters the secretory pathway. Degradation of Ste2-3p did not require delivery to the plasma membrane as the sec1 mutation failed to block rapid turnover. Truncation of the C-terminal cytoplasmic domain of the mutant receptors did not permit accumulation at the plasma membrane; thus, the endocytic signals contained in this domain are unnecessary for intracellular retention. In the pep4 mutant, Ste2-3p accumulated as series of high-molecular-weight species, suggesting a potential role for ubiquitin in the elimination process. When ste2-3 mutant cells were cultured continuously at 22 degrees C, Ste2-3p accumulated in the plasma membrane. When the 22 degrees C culture was shifted to 34 degrees C, Ste2-3p was removed from the plasma membrane and degraded by a PEP4-dependent mechanism with a 24-min half-life; the wild-type Ste2p displayed a 72-min half-life. Thus, structural defects in Ste2-3p synthesized at 34 degrees C are recognized in transit to the plasma membrane, leading to rapid degradation, and Ste2-3p that is preassembled at the plasma membrane is also removed and degraded following a shift to 34 degrees C" |
| Keywords: | "Biological Transport Cell Compartmentation Cell Membrane/metabolism Cloning, Molecular Fungal Proteins/chemistry/genetics/*metabolism Models, Molecular Mutation Protein Conformation Protein Folding Receptors, Mating Factor Receptors, Peptide/chemistry/gen;" |
| Notes: | "MedlineJenness, D D Li, Y Tipper, C Spatrick, P eng Research Support, Non-U.S. Gov't 1997/10/29 Mol Cell Biol. 1997 Nov; 17(11):6236-45. doi: 10.1128/MCB.17.11.6236" |
