Protein kinase C phosphorylates G(12 alpha) and inhibits its interaction with G(beta gamma)
Protein kinase C phosphorylates G(12 alpha) and inhibits its interaction with G(beta gamma)
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DOI：
10.1074/jbc.271.21.12562
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发表时间：
1996-05-24
影响因子：
4.8
通讯作者：
Gilman, AG
中科院分区：
文献类型：
--
作者：
Kozasa, T;Gilman, AG
在9种G蛋白α亚基中，只有α（12）和α（z）在体外被各种蛋白激酶C亚型磷酸化。α（12）的一个密切同源物，α（13），没有磷酸化。将稳定表达α（12）的NIH 3 T3细胞暴露于佛波醇12-肉豆蔻酸酯13-乙酸酯也导致蛋白质的磷酸化。体外磷酸化发生在氨基末端附近（可能是Ser（38）），每摩尔α（12）约掺入1摩尔磷酸盐。虽然G蛋白异源三聚体含有α（12）或α（z）是磷酸化的不良底物，但分离的α亚基在其GDP或GTP γ S结合形式中同样被磷酸化。纯化的α（12）和α（z）的鸟嘌呤核苷酸结合特性未被磷酸化改变，α（z）抑制V型腺苷酸环化酶的能力也未改变。然而，这两种蛋白质的磷酸化大大降低了其对G蛋白β γ亚基的亲和力，这与新确定的G蛋白异源三聚体的晶体结构一致。我们认为蛋白激酶C通过阻止α（12）和α（z）介导的信号通路与β-γ的结合来调节它们。
Of nine G protein alpha subunits examined, only alpha(12) and alpha(z) served as substrates for phosphorylation by various iso forms of protein kinase C in vitro. A close homolog of alpha(12), alpha(13), was not phosphorylated. Exposure of NIH 3T3 cells that stably express alpha(12) to phorbol 12-myristate 13-acetate also resulted in phosphorylation of the protein. Phosphorylation in vitro occurred near the amino terminus (probably Ser(38)), and approximately 1 mol of phosphate was incorporated per mol of alpha(12). Although G protein heterotrimers containing either alpha(12) or alpha(z) were poor substrates for phosphorylation, the isolated a subunits were phosphorylated equally well in their GDP- or GTP gamma S bound forms. The guanine nucleotide binding properties of purified alpha(12) and alpha(z) were unaltered by phosphorylation, as was the capacity of alpha(z) to inhibit type V adenylyl cyclase. However, phosphorylation of either protein greatly reduced its affinity for G protein beta gamma subunits, consistent with the newly determined crystal structure of a G protein heterotrimer. We suggest that protein kinase C regulates alpha(12)- and alpha(z)-mediated signaling pathways by preventing their association with beta gamma.