Yang Xiao-Xian, Maurer Kick C T, Molanus Michiel, Mager Willem H, Siderius Marco, van der Vies Saskia M
Department of Biochemistry and Molecular Biology, Faculty of Science, Vrije Universiteit, Amsterdam, The Netherlands.
FEMS Yeast Res. 2006 Mar;6(2):195-204. doi: 10.1111/j.1567-1364.2006.00026.x.
Exposure of Saccharomyces cerevisiae to high osmotic stress evokes a number of adaptive changes that are necessary for its survival. These adaptive responses are mediated via multiple mitogen-activated protein kinase pathways, of which the high-osmolarity glycerol (HOG) pathway has been studied most extensively. Yeast strains that bear the hsp82T22I or hsp82G81S mutant alleles are osmosensitive. Interestingly, the osmosensitive phenotype is not due to inappropriate functioning of the HOG pathway, as Hog1p phosphorylation and downstream responses including glycerol accumulation are not affected. Rather, the hsp82 mutants display features that are characteristic for cell-wall mutants, i.e. resistance to Zymolyase and sensitivity to Calcofluor White. The osmosensitivity of the hsp82T22I or hsp82G81S strains is suppressed by over-expression of the Hsp90 co-chaperone Cdc37p but not by other co-chaperones. Hsp90 is shown to be required for proper adaptation to high osmolarity via a novel signal transduction pathway that operates parallel to the HOG pathway and requires Cdc37p.
将酿酒酵母暴露于高渗胁迫下会引发许多适应性变化，这些变化对其生存至关重要。这些适应性反应是通过多种丝裂原活化蛋白激酶途径介导的，其中高渗甘油（HOG）途径研究最为广泛。携带hsp82T22I或hsp82G81S突变等位基因的酵母菌株对渗透压敏感。有趣的是，渗透压敏感表型并非由于HOG途径功能异常，因为Hog1p磷酸化以及包括甘油积累在内的下游反应并未受到影响。相反，hsp82突变体表现出细胞壁突变体的特征，即对溶菌酶有抗性且对荧光增白剂敏感。hsp82T22I或hsp82G81S菌株的渗透压敏感性可通过Hsp90共伴侣蛋白Cdc37p的过表达得到抑制，但其他共伴侣蛋白则无此作用。研究表明，Hsp90通过一条与HOG途径平行且需要Cdc37p的新型信号转导途径，对高渗环境的适当适应是必需的。
