Phosphorylation and Activation of Ca-Calmodulin-dependent Protein Kinase IV by Ca-Calmodulin-dependent Protein Kinase Ia Kinase

• Published in: The Journal of biological chemistry Vol. 270; no. 29; p. 17616
• Main Authors: Michele A. Selbert, Kristin A. Anderson, Qi-Hui Huang, Elaine G. Goldstein, Anthony R. Means, Arthur M. Edelman
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 21-07-1995
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.270.29.17616

Purified pig brain Ca -calmodulin (CaM)-dependent protein kinase Ia kinase (Lee, J. C., and Edelman, A. M.(1994) J. Biol. Chem . 269, 2158-2164) enhances, by up to 24-fold, the activity of recombinant CaM kinase IV in a reaction also requiring Ca -CaM and MgATP. The addition of brain extract, although capable of activating CaM kinase IV by itself, provides no further
activation beyond that induced by purified CaM kinase Ia kinase, consistent with the lack of a requirement of additional components
for activation. Activation is accompanied by the development of significant (38%) Ca -CaM-independent CaM kinase IV activity. In parallel fashion to its activation, CaM kinase IV is phosphorylated in a CaM kinase
Ia kinase-, Ca -CaM-, and MgATP-dependent manner. Phosphorylation occurs on multiple serine and threonine residues with a Ser-P:Thr-P ratio
of 3:1. The identical requirements for phosphorylation and activation and a linear relationship between extent of phosphorylation
of CaM kinase IV and its activation state indicate that CaM kinase IV activation is induced by its phosphorylation. Replacement
of Thr-196 of CaM kinase IV with a nonphosphorylatable alanine by site-directed mutagenesis abolishes both the phosphorylation
and activation of CaM kinase IV, demonstrating that Thr-196 phosphorylation is essential for activation.