| First Author | Akizuki K | Year | 2019 |
| Journal | Arch Biochem Biophys | Volume | 668 |
| Pages | 29-38 | PubMed ID | 31071303 |
| Mgi Jnum | J:277422 | Mgi Id | MGI:6316784 |
| Doi | 10.1016/j.abb.2019.05.004 | Citation | Akizuki K, et al. (2019) Autoactivation of C-terminally truncated Ca(2+)/calmodulin-dependent protein kinase (CaMK) Idelta via CaMK kinase-independent autophosphorylation. Arch Biochem Biophys 668:29-38 |
| abstractText | Ca(2+)/calmodulin-dependent protein kinase I isoforms (CaMKIalpha, beta, gamma, and delta) play important roles in Ca(2+) signaling in eukaryotic cells by being activated by CaMK kinase (CaMKK) through phosphorylation at a Thr residue in the activation loop. However, we have recently found that, unlike rat CaMKIalpha (rCaMKIalpha), C-terminally truncated fragments of zebrafish and mouse CaMKIdelta [zCaMKIdelta(1-299) and mCaMKIdelta(1-297)] produced by Escherichia coli exhibit almost full activity in the absence of CaMKK. To address the CaMKK-independent activation mechanism of CaMKIdelta in E. coli cells, here we performed comparative analyses between recombinant zCaMKIdelta(1-299) and rCaMKIalpha(1-294) in vitro. By using a kinase-dead mutant of zCaMKIdelta(1-299) and lambda phosphatase coexpression method, we elucidated that zCaMKIdelta(1-299) was highly autophosphorylated and activated in E. coli during cell culture, but rCaMKIalpha(1-294) was not. The major autophosphorylation site leading to activation of the kinase was Ser(296), determined using mass spectrometry analysis in conjunction with site-directed mutagenesis. Furthermore, mimicking phosphorylation at Ser(296) in full-length zCaMKIdelta resulted in additional activation of the kinase compared with CaMKI fully activated by CaMKK. Our results provide the first evidence that CaMKIdelta is activated through CaMKK-independent phosphorylation at Ser(296), which might be a clue to understand the physiological regulation of CaMKIdelta isoform. |
