NO generation by β-AR stimulation to activate Ca MKII

摘要

Ca~(2+)-Calmodulin (CaM) kinase II (CaMKII) activation depends predominantly on modifications of amino acids within the regulatory domain on this multidomain kinase. A number of mechanisms of activation have been described since the original mode of activation, via Ca~(2+)-CaM binding and phosphorylation of athreonine residue in the regulatory domain of CaMKII, was demonstrated. Gutierrez et al. propose a mechanism of CaMKII activation by nitrosation.CaMKII serves as a linkbetween beta-adrenergic stimuli with subsequent changes in Ca~(2+) levels to the cellular response in cardiomyocytes. CaMKII phosphorylates dozens of substrates in many cell types. When activated by binding of Ca~(2+)-CaM, CaMKII subunits can autophosphor-ylate neighbouring subunits at Threonine-287 (Thr287) within the CaMKII holoenzyme. Autophosphorylation at Thr287 results in autonomous kinase activity, converting to an activation state independent ofCa~(2+)-CaM binding. A number of studies have shown that CaMKII can achieve sustained activity even in the absence of phosphorylation at Thr287. Mechanisms to attain CaMKII sustained include substrate binding, oxidation ofthe paired methionine residues (281/282) proximal to the Thr287, and now nitrosation of cysteine residues. Modifications that activate CaMKII occur primarily in the regulatory domain (figure 1)