Nomoto S, Watanabe Y, Ninomiya-Tsuji J, Yang L X, Nagai Y, Kiuchi K, Hagiwara M, Hidaka H, Matsumoto K, Irie K
Laboratory for Genes of Motor Systems, Bio-Mimetic Control Research Program, RIKEN, Nagoya, Japan.
Genes Cells. 1997 Oct;2(10):601-14. doi: 10.1046/j.1365-2443.1997.1470346.x.
The PKC1 gene of Saccharomyces cerevisiae encodes a homologue of mammalian protein kinase C (PKC) that is required for yeast cell growth. Pkc1 has been proposed to regulate a protein kinase cascade which includes the Bck1, Mkk1/Mkk2 and Mpk1 kinases. The functional relationship between Pkc1 and mammalian PKCs is unknown. Another signal transduction in Saccharomyces cerevisiae, the mating pheromone signalling pathway, is mediated by a heterotrimeric G protein, and causes cell cycle arrest in the G1 interval. It is not clear whether PKC is involved in this pathway. The effects of overexpression of PKCs in mammalian cells have been widely studied to analyse the function of PKCs in vivo.
We isolated a human cDNA which encodes a protein kinase C type eta (PKC-eta) by complementation of pkc1 mutations in Saccharomyces cerevisiae. The human PKC-eta was able to complement the growth defect caused by the deletion of PKC1, whereas PKC-eta was unable to suppress the defect caused by deletion of BCK1. We also isolated human cDNAs that can suppress the adaptation defect of sst2. One of them encodes a protein kinase C type delta (PKC-delta). Expression of this gene in yeast stimulated an adaptation to the pheromone response. Human PKC-delta suppressed the adaptation defect of a pheromone receptor mutation lacking its C-terminal domain, but not that of a G protein beta-subunit mutation eliminating signal-induced phosphorylation, and not the lethality of the gpa1 null mutation. Moreover, overexpression of PKC-eta in NIH3T3 cells induced anchorage-independent growth.
PKC-eta has a biological activity which is closely related to Pkc1, and PKC-eta activates the Pkc1-mediated pathway through an activation of the Bck1 kinase that is a homologue of MAP kinase kinase kinase. PKC-eta appears to play a critical role in growth control of yeast and mammalian cells. Suppression experiments with PKC-delta suggest that PKC-delta desensitizes the pathway by regulating an aspect of G protein function.
酿酒酵母的PKC1基因编码一种哺乳动物蛋白激酶C（PKC）的同源物，它是酵母细胞生长所必需的。有人提出Pkc1可调节一个蛋白激酶级联反应，其中包括Bck1、Mkk1/Mkk2和Mpk1激酶。Pkc1与哺乳动物PKC之间的功能关系尚不清楚。酿酒酵母中的另一种信号转导，即交配信息素信号通路，由一个异源三聚体G蛋白介导，并导致细胞周期在G1期停滞。目前尚不清楚PKC是否参与该通路。人们广泛研究了PKC在哺乳动物细胞中的过表达效应，以分析PKC在体内的功能。
我们通过互补酿酒酵母中的pkc1突变，分离出了一个编码蛋白激酶C eta型（PKC-eta）的人cDNA。人PKC-eta能够互补因PKC1缺失而导致的生长缺陷，而PKC-eta无法抑制因BCK1缺失而导致的缺陷。我们还分离出了能够抑制sst2适应性缺陷的人cDNA。其中一个编码蛋白激酶C delta型（PKC-delta）。该基因在酵母中的表达刺激了对信息素反应的适应性。人PKC-delta抑制了缺乏C末端结构域的信息素受体突变的适应性缺陷，但不抑制消除信号诱导磷酸化的G蛋白β亚基突变的适应性缺陷，也不抑制gpa1缺失突变的致死性。此外，PKC-eta在NIH3T3细胞中的过表达诱导了不依赖贴壁的生长。
PKC-eta具有与Pkc1密切相关的生物学活性，并且PKC-eta通过激活作为丝裂原活化蛋白激酶激酶激酶同源物的Bck1激酶来激活Pkc1介导的通路。PKC-eta似乎在酵母和哺乳动物细胞的生长控制中起关键作用。用PKC-delta进行的抑制实验表明，PKC-delta通过调节G蛋白功能的一个方面使该通路脱敏。
