Analysis of DrkA kinase's role in STATa activation
Analysis of DrkA kinase's role in STATa activation
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DrkA激酶在STATa激活中的作用分析
DOI：
10.1111/gtc.12686
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发表时间：
2019
期刊：
影响因子：
2.1
通讯作者：
Kawata T.
中科院分区：
文献类型：
--
作者：
Saga Y;Iwade Y;Araki T;Ishikawa M;Kawata T.
DictyosteliumSTATa是后生动物信号转导子和转录激活子（STAT）的同源物，对形态建成很重要。当细胞暴露于细胞外cAMP时，STATa通过Tyr 702上的磷酸化而活化。虽然两种酪氨酸激酶样（TKL）蛋白Pyk 2和Pyk 3已被确定为STATc激酶，但没有已知的激酶激活STATa。基于与先前鉴定的酪氨酸选择性TKL的同源性，我们鉴定了TKL家族和Dictyostelium受体样激酶（DRK）亚家族的成员DrkA作为候选STATa激酶。drkA基因几乎只在前茎A（pstA）细胞中表达，其中STATa被激活。DrkA的瞬时过表达增加了STATa磷酸化，尽管蛋白质的过表达导致严重的生长缺陷和细胞死亡。此外，重组DrkA蛋白在酪氨酸和苏氨酸残基上自磷酸化，并且体外激酶测定显示DrkA可以以STATa-SH 2（磷酸酪氨酸结合）结构域依赖性方式磷酸化Tyr 702上的STATa。这些观察结果强烈表明DrkA是STATa酪氨酸磷酸化的关键调节因子之一，并且与其作为直接激活STATa的激酶一致。
DictyosteliumSTATa is a homologue of metazoan signal transducers and activators of transcription (STATs) and is important for morphogenesis. STATa is activated by phosphorylation on Tyr702 when cells are exposed to extracellular cAMP. Although two tyrosine kinase‐like (TKL) proteins, Pyk2 and Pyk3, have been definitively identified as STATc kinases, no kinase is known for STATa activation. Based on homology to the previously identified tyrosine‐selective TKLs, we identified DrkA, a member of the TKL family and theDictyosteliumreceptor‐like kinase (DRK) subfamily, as a candidate STATa kinase. ThedrkAgene is almost exclusively expressed in prestalk A (pstA) cells, where STATa is activated. Transient over‐expression of DrkA increased STATa phosphorylation, although over‐expression of the protein causes a severe growth defect and cell death. Furthermore, recombinant DrkA protein is auto‐phosphorylated on tyrosine and threonine residues, and an in vitro kinase assay shows that DrkA can phosphorylate STATa on Tyr702 in a STATa‐SH2 (phosphotyrosine binding) domain‐dependent manner. These observations strongly suggest that DrkA is one of the key regulators of STATa tyrosine phosphorylation and is consistent with it being the kinase that directly activates STATa.