Targeting of Protein Kinase A by Muscle A Kinase-anchoring Protein (mAKAP) Regulates Phosphorylation and Function of the Skeletal Muscle Ryanodine Receptor

• Published in: The Journal of biological chemistry Vol. 278; no. 27; pp. 24831 - 24836
• Main Authors: Ruehr, Mary L, Russell, Mary A, Ferguson, Donald G, Bhat, Manju, Ma, Jianjie, Damron, Derek S, Scott, John D, Bond, Meredith
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 04-07-2003
• Subjects: Animals; Calcium - metabolism; Carrier Proteins - metabolism; CHO Cells; Cricetinae; Muscle Proteins - metabolism; Muscle, Skeletal - metabolism; Phosphorylation; Rats; Ryanodine Receptor Calcium Release Channel - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M213279200

Protein kinase A anchoring proteins (AKAPs) tether cAMP-dependent protein kinase (PKA) to specific subcellular locations.
The muscle AKAP, mAKAP, co-localizes with the sarcoplasmic reticulum Ca 2 + release channel or ryanodine receptor (RyR). The purpose of this study was to determine whether anchoring of PKA by mAKAP
regulates RyR function. Either mAKAP or mAKAP-P, which is unable to anchor PKA, was expressed in CHO cells stably expressing
the skeletal muscle isoform of RyR (CHO-RyR1). Immunoelectron microscopy showed that mAKAP co-localized with RyR1 in disrupted
skeletal muscle. Following the addition of 10 μ m forskolin to activate adenylyl cyclase, RyR1 phosphorylation in CHO-RyR1 cells expressing mAKAP increased by 42.4 ± 6.6%
( n = 4) compared with cells expressing mAKAP-P. Forskolin treatment alone did not increase the amplitude of the cytosolic
Ca 2 + transient in CHO-RyR1 cells expressing mAKAP or mAKAP-P; however, forskolin plus 10 m m caffeine elicited a cytosolic Ca 2 + transient, the amplitude of which increased by 22% ( p < 0.05) in RyR1/mAKAP-expressing cells compared with RyR1/mAKAP-P-expressing cells. Therefore, localization of PKA by mAKAP
at RyR1 increases both PKA-dependent RyR phosphorylation as well as efflux of Ca 2 + through the RyR. Therefore, RyR1 function is regulated by mAKAP targeting of PKA, implying an important functional role
for PKA phosphorylation of RyR in skeletal muscle.