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  • Ser-2030, but not Ser-2808, is the major phosphorylation site in cardiac ryanodine receptors responding to protein kinase A activation upon beta-adrenergic stimulation in normal and failing hearts.

Ser-2030, but not Ser-2808, is the major phosphorylation site in cardiac ryanodine receptors responding to protein kinase A activation upon beta-adrenergic stimulation in normal and failing hearts.

The Biochemical journal (2006-02-18)
Bailong Xiao, Guofeng Zhong, Masakazu Obayashi, Dongmei Yang, Keyun Chen, Michael P Walsh, Yakhin Shimoni, Heping Cheng, Henk Ter Keurs, S R Wayne Chen
ABSTRACT

We have recently shown that RyR2 (cardiac ryanodine receptor) is phosphorylated by PKA (protein kinase A/cAMP-dependent protein kinase) at two major sites, Ser-2030 and Ser-2808. In the present study, we examined the properties and physiological relevance of phosphorylation of these two sites. Using site- and phospho-specific antibodies, we demonstrated that Ser-2030 of both recombinant and native RyR2 from a number of species was phosphorylated by PKA, indicating that Ser-2030 is a highly conserved PKA site. Furthermore, we found that the phosphorylation of Ser-2030 responded to isoproterenol (isoprenaline) stimulation in rat cardiac myocytes in a concentration- and time-dependent manner, whereas Ser-2808 was already substantially phosphorylated before beta-adrenergic stimulation, and the extent of the increase in Ser-2808 phosphorylation after beta-adrenergic stimulation was much less than that for Ser-2030. Interestingly, the isoproterenol-induced phosphorylation of Ser-2030, but not of Ser-2808, was markedly inhibited by PKI, a specific inhibitor of PKA. The basal phosphorylation of Ser-2808 was also insensitive to PKA inhibition. Moreover, Ser-2808, but not Ser-2030, was stoichiometrically phosphorylated by PKG (protein kinase G). In addition, we found no significant phosphorylation of RyR2 at the Ser-2030 PKA site in failing rat hearts. Importantly, isoproterenol stimulation markedly increased the phosphorylation of Ser-2030, but not of Ser-2808, in failing rat hearts. Taken together, these observations indicate that Ser-2030, but not Ser-2808, is the major PKA phosphorylation site in RyR2 responding to PKA activation upon beta-adrenergic stimulation in both normal and failing hearts, and that RyR2 is not hyperphosphorylated by PKA in heart failure. Our results also suggest that phosphorylation of RyR2 at Ser-2030 may be an important event associated with altered Ca2+ handling and cardiac arrhythmia that is commonly observed in heart failure upon beta-adrenergic stimulation.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
KT 5823, ≥85% (HPLC), lyophilized powder
Sigma-Aldrich
KN-93, A cell-permeable, reversible and competitive inhibitor of rat brain CaM kinase II (Ki = 370 nM).
Sigma-Aldrich
PKA Inhibitor 14-22 Amide, Cell-Permeable, Myristoylated, PKA Inhibitor 14-22 Amide is myristoylated at the N-terminus that enhances its cell-permeability. The non-myristoylated version is shown to be a specific inhibitor of PKA (Ki = 36 nM).
Sigma-Aldrich
Staurosporine from Streptomyces sp., ≥98% (HPLC), film
Sigma-Aldrich
Calyculin A, Discodermia calyx, Calyculin A, CAS 101932-71-2, is a cell-permeable inhibitor of protein phosphatase 2A (IC₅₀ = 0.5-1 nM) and protein phosphatase 1 (PP1; IC₅₀ = 2 nM).
Sigma-Aldrich
H-89 dihydrochloride hydrate, ≥98% (HPLC), powder