Nutrient control of yeast PKA activity involves opposing effects on phosphorylation of the Bcy1 regulatory subunit.
Nutrient control of yeast PKA activity involves opposing effects on phosphorylation of the Bcy1 regulatory subunit.
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DOI：
10.1091/mbc.e10-05-0388
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发表时间：
2010-11-01
影响因子：
3.3
通讯作者：
Hirsch JP
中科院分区：
文献类型：
--
作者：
Budhwar R;Lu A;Hirsch JP
Kelch重复蛋白Gpb 1和Gpb 2通过刺激Bcy 1调节亚基的磷酸化来控制酵母PKA活性。Gpb 1和Gpb 2通过阻断PKA催化亚基对Bcy 1磷酸化的抑制而发挥功能。磷酸化Bcy 1更稳定，是PKA活性的更有效抑制剂。GPB 1和GPB 2编码含有Kelch重复序列的蛋白，其通过cAMP非依赖性过程调节酵母中的蛋白激酶A（PKA）。在这里，我们表明，GPB 1和GPB 2刺激磷酸化的PKA调节亚基Bcy 1在低葡萄糖浓度，从而促进抑制功能的Bcy 1时，营养物质是稀缺的，PKA活性预计将是低的。Gpb 1和Gpb 2刺激Bcy 1磷酸化在一个未知的网站，这种修饰稳定Bcy 1已被磷酸化的PKA催化亚基在丝氨酸-145。BCY 1 S145 A突变消除了gpb 1 Δ gpb 2 Δ对Bcy 1稳定性的影响，但保持了它们对磷酸化和信号传导的影响，表明Gpb 1和Gpb 2对PKA活性的调节不仅仅是由于Bcy 1水平的增加。抑制ATP类似物敏感的PKA催化亚基导致高糖下未知位点Bcy 1磷酸化增加。当PKA被抑制时，gpb 1 Δ gpb 2 Δ突变对Bcy 1磷酸化没有影响。因此，Gpb 1和Gpb 2通过阻断PKA抑制Bcy 1在丝氨酸145以外的位点磷酸化的能力来对抗PKA活性。通过Gpb 1和Gpb 2刺激Bcy 1磷酸化产生一种更稳定的Bcy 1形式，是一种更有效的PKA抑制剂。
Kelch repeat proteins Gpb1 and Gpb2 control yeast PKA activity in response to nutrients by stimulating phosphorylation of the Bcy1 regulatory subunit. Gpb1 and Gpb2 function by blocking inhibition of Bcy1 phosphorylation by PKA catalytic subunits. Phosphorylated Bcy1 is more stable and is a more effective inhibitor of PKA activity. GPB1 and GPB2 encode kelch repeat-containing proteins that regulate protein kinase A (PKA) in yeast by a cAMP-independent process. Here we show that Gpb1 and Gpb2 stimulate phosphorylation of PKA regulatory subunit Bcy1 in low glucose concentrations, thereby promoting the inhibitory function of Bcy1 when nutrients are scarce and PKA activity is expected to be low. Gpb1 and Gpb2 stimulate Bcy1 phosphorylation at an unknown site, and this modification stabilizes Bcy1 that has been phosphorylated by PKA catalytic subunits at serine-145. The BCY1S145A mutation eliminates the effect of gpb1Δ gpb2Δ on Bcy1 stability but maintains their effect on phosphorylation and signaling, indicating that modulation of PKA activity by Gpb1 and Gpb2 is not solely due to increased levels of Bcy1. Inhibition of PKA catalytic subunits that are ATP analog-sensitive causes increased Bcy1 phosphorylation at the unknown site in high glucose. When PKA is inhibited, gpb1Δ gpb2Δ mutations have no effect on Bcy1 phosphorylation. Therefore, Gpb1 and Gpb2 oppose PKA activity by blocking the ability of PKA to inhibit Bcy1 phosphorylation at a site other than serine-145. Stimulation of Bcy1 phosphorylation by Gpb1 and Gpb2 produces a form of Bcy1 that is more stable and is a more effective PKA inhibitor.