Gaits F, Russell P
Departments of Molecular Biology and Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Mol Biol Cell. 1999 Aug;10(8):2647-54. doi: 10.1091/mbc.10.8.2647.
The gene ptc4+ encodes one of four type 2C protein phosphatases (PP2C) in the fission yeast Schizosaccharomyces pombe. Deletion of ptc4+ is not lethal; however, Deltaptc4 cells grow slowly in defined minimal medium and undergo premature growth arrest in response to nitrogen starvation. Interestingly, Deltaptc4 cells are unable to fuse vacuoles in response to hypotonic stress or nutrient starvation. Conversely, Ptc4 overexpression appears to induce vacuole fusion. These findings reveal a hitherto unrecognized function of type 2C protein phosphatases: regulation of vacuole fusion. Ptc4 localizes in vacuole membranes, which suggests that Ptc4 regulates vacuole fusion by dephosphorylation of one or more proteins in the vacuole membrane. Vacuole function is required for the process of autophagy that is induced by nutrient starvation; thus, the vacuole defect of Deltaptc4 cells might explain why these cells undergo premature growth arrest in response to nitrogen starvation.
基因ptc4+编码粟酒裂殖酵母中的四种2C型蛋白磷酸酶（PP2C）之一。ptc4+的缺失并非致死性的；然而，Δptc4细胞在限定的基本培养基中生长缓慢，并且在响应氮饥饿时会过早地停止生长。有趣的是，Δptc4细胞在响应低渗胁迫或营养饥饿时无法融合液泡。相反，Ptc4的过表达似乎会诱导液泡融合。这些发现揭示了2C型蛋白磷酸酶迄今为止未被认识的功能：调节液泡融合。Ptc4定位于液泡膜，这表明Ptc4通过使液泡膜中的一种或多种蛋白质去磷酸化来调节液泡融合。营养饥饿诱导的自噬过程需要液泡功能；因此，Δptc4细胞的液泡缺陷可能解释了为什么这些细胞在响应氮饥饿时会过早地停止生长。
