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Analysis of DrkA kinase’s role in STATa activation
Author(s) -
Saga Yukika,
Iwade Yumi,
Araki Tsuyoshi,
Ishikawa Megumi,
Kawata Takefumi
Publication year - 2019
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/gtc.12686
Subject(s) - biology , phosphorylation , kinase , receptor tyrosine kinase , tyrosine kinase , microbiology and biotechnology , tyrosine phosphorylation , protein tyrosine phosphatase , biochemistry , signal transduction
Dictyostelium STATa 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 the Dictyostelium receptor‐like kinase (DRK) subfamily, as a candidate STATa kinase. The drkA gene 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.