Strand M A, Louis C F, Mickelson J R
Department of Veterinary Pathobiology, University of Minnesota, St. Paul 55108.
Biochim Biophys Acta. 1993 Feb 17;1175(3):319-26. doi: 10.1016/0167-4889(93)90224-d.
Porcine skeletal and cardiac muscle sarcoplasmic reticulum (SR) vesicle fractions enriched in the ryanodine receptor were phosphorylated in the presence of [gamma-32P]MgATP and either exogenous cAMP-dependent protein kinase (cAMP-PK), or Ca2+ plus calmodulin. Phosphorylation of the cardiac muscle ryanodine receptor in the presence of either cAMP-PK or calmodulin (6.4 and 10.6 pmol Pi/mg SR respectively) was approximately equal to or twice the [3H]ryanodine binding activity of this preparation (5.2 pmol/mg). Furthermore, cardiac muscle ryanodine receptor Pi incorporation catalyzed by cAMP-PK and calmodulin was approximately additive. In skeletal muscle SR, however, the level of cAMP-PK or calmodulin catalyzed phosphorylation of the intact ryanodine receptor (0.2 or 2.9 pmol Pi/mg SR, respectively) was much less than the [3H]ryanodine binding activity of this fraction (11.6 pmol/mg). Furthermore, Pi incorporation into the intact skeletal muscle ryanodine receptor was 3-8-fold less than that incorporated into a component of slightly lower M(r). Although this latter component comigrated with an immunoreactive fragment of the ryanodine receptor on polyacrylamide gels, it did not appear to be derived from the ryanodine receptor. We conclude that the significant phosphorylation of the cardiac muscle SR ryanodine receptor indicates a likely physiological role for protein kinase-mediated regulation of this Ca(2+)-channel. In contrast, the minimal phosphorylation of the skeletal muscle SR ryanodine receptor indicates that such a role of protein kinases is unlikely in this tissue.
富含兰尼碱受体的猪骨骼肌和心肌肌浆网（SR）囊泡组分，在存在[γ-32P]MgATP以及外源性环磷酸腺苷依赖性蛋白激酶（cAMP-PK）或Ca2+加钙调蛋白的情况下会发生磷酸化。在存在cAMP-PK或钙调蛋白时，心肌兰尼碱受体的磷酸化（分别为6.4和10.6 pmol Pi/mg SR）约等于或为该制剂[3H]兰尼碱结合活性（5.2 pmol/mg）的两倍。此外，由cAMP-PK和钙调蛋白催化的心肌兰尼碱受体Pi掺入量大致呈加和性。然而，在骨骼肌SR中，cAMP-PK或钙调蛋白催化的完整兰尼碱受体磷酸化水平（分别为0.2或2.9 pmol Pi/mg SR）远低于该组分的[3H]兰尼碱结合活性（11.6 pmol/mg）。此外，完整骨骼肌兰尼碱受体中的Pi掺入量比掺入稍低分子量组分中的量少3 - 8倍。尽管后一组分在聚丙烯酰胺凝胶上与兰尼碱受体的免疫反应性片段迁移率相同，但它似乎并非源自兰尼碱受体。我们得出结论，心肌SR兰尼碱受体的显著磷酸化表明蛋白激酶介导的对该Ca(2+)通道的调节可能具有生理作用。相比之下，骨骼肌SR兰尼碱受体的最小磷酸化表明蛋白激酶在该组织中不太可能具有这样的作用。
