Pak1 protein kinase regulates activation and nuclear localization of Snf1-Gal83 protein kinase
Pak1 protein kinase regulates activation and nuclear localization of Snf1-Gal83 protein kinase
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DOI：
10.1128/mcb.24.18.8255-8263.2004
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发表时间：
2004-09-01
影响因子：
5.3
通讯作者：
Carlson, M
中科院分区：
文献类型：
--
作者：
Hedbacker, K;Hong, SP;Carlson, M
在酿酒酵母中，三种激酶Pak1、Tos3和Elm1激活Snf1蛋白激酶。这一激酶级联在哺乳动物中是保守的，在哺乳动物中LKB1激活AMP激活的蛋白激酶。我们研究了激活激酶对包含β亚基异构体Gal83、Sip1和Sip2的三种形式的Snf1蛋白激酶的特异性。Pak1是在葡萄糖限制条件下激活Snf1 - Gal83的最重要激酶，但Elm1也起着重要作用；此外，Pak1和Elm1都会影响Snf1 - Sip2。这些发现排除了激活激酶与Snf1复合物之间一一对应的可能性。我们进一步发现了Pak1在调节Snf1 - Gal83方面的第二个意想不到的作用：Pak1的催化活性是Snf1 - Gal83在碳胁迫下核富集所必需的。与绿色荧光蛋白（GFP）融合的Snf1的核富集依赖于Gal83和Pak1，并且会因激活环苏氨酸的突变而消失；相比之下，Gal83 - GFP的核富集在snf1Δ突变体中发生，并且只有当Snf1存在时才依赖于Pak1。Snf1 - Gal83是唯一一种定位于细胞核的激酶形式。这些发现表明，Pak1既激活Snf1 - Gal83又控制其核定位，这意味着Pak1参与调节细胞核中的Snf1蛋白激酶活性。
Three kinases, Pak1, Tos3, and Elm1, activate Snf1 protein kinase in Saccharomyces cerevisiae. This cascade is conserved in mammals, where LKB1 activates AMP-activated protein kinase. We address the specificity of the activating kinases for the three forms of Snf1 protein kinase containing the beta-subunit isoforms Gal83, Sip1, and Sip2. Pak1 is the most important kinase for activating Snf1-Gal83 in response to glucose limitation, but Elm1 also has a significant role; moreover, both Pak1 and Elm1 affect Snf1-Sip2. These findings exclude the possibility of a one-to-one correspondence between the activating kinases and the Snf1 complexes. We further identify a second, unexpected role for Pak1 in regulating Snf1-Gal83: the catalytic activity of Pak1 is required for the nuclear enrichment of Snf1-Gal83 in response to carbon stress. The nuclear enrichment of Snf1 fused to green fluorescent protein (GFP) depends on both Gal83 and Pak1 and is abolished by a mutation of the activation loop threonine; in contrast, the nuclear enrichment of Gal83-GFP occurs in a snf1Delta mutant and depends on Pak1 only when Snf1 is present. Snf1-Gal83 is the only form of the kinase that localizes to the nucleus. These findings, that Pak1 both activates Snf1-Gal83 and controls its nuclear localization, implicate Pak1 in regulating nuclear Snf1 protein kinase activity.