Kim S O, Hasham M I, Katz S, Pelech S L
Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada.
J Cell Biochem. 1998 Dec 1;71(3):328-39. doi: 10.1002/(sici)1097-4644(19981201)71:3<328::aid-jcb2>3.0.co;2-u.
The control of glucose uptake and glycogen metabolism by insulin in target organs is in part mediated through the regulation of protein-serine/threonine kinases. In this study, the expression and phosphotransferase activity levels of some of these kinases in rat heart ventricle were measured to investigate whether they might mediate the shift in the energy dependency of the developing heart from glycogen to fatty acids. Following tail-vein injection of overnight fasted adult rats with 2 U of insulin per kg body weight, protein kinase B (PKB), the 70-kDa ribosomal S6 kinase (S6K), and casein kinase 2 (CK2) were activated (30-600%), whereas the MAP/extracellular regulated kinases (ERK)1 and ERK2 were not stimulated under these conditions. When the expression levels of the insulin-activated kinases were probed with specific antibodies in ventricular extracts from 1-, 10-, 20-, 50-, and 365-day-old rats, phosphatidylinositol 3-kinase (PI3K), PKB, S6K, and CK2 were downregulated (40-60%) with age. By contrast, ventricular glycogen synthase kinase-3beta (GSK3beta) protein levels were maintained during postnatal development. Similar findings were obtained when the expression of these kinases was investigated in freshly isolated ventricular myocytes, where they were detected predominantly in the cytosolic fraction of the myocytes. Compared to other adult rat tissues such as brain and liver, the levels of PI3K, PKB, S6K, and GSK3beta were relatively low in the heart. Even though CK2 protein and activity levels were reduced by approximately 60% in 365 day as compared to 1-day-old rats, expression of CK2 in the adult heart was as high as detected in any of the other rat tissues. The high basal activities of CK2 in early neonatal heart may be associated with the proliferating state of myocytes.
胰岛素对靶器官中葡萄糖摄取和糖原代谢的控制部分是通过对蛋白质丝氨酸/苏氨酸激酶的调节来介导的。在本研究中，测定了大鼠心室中某些此类激酶的表达和磷酸转移酶活性水平，以研究它们是否可能介导发育中心脏的能量依赖性从糖原向脂肪酸的转变。在对过夜禁食的成年大鼠进行尾静脉注射每千克体重2单位胰岛素后，蛋白激酶B（PKB）、70 kDa核糖体S6激酶（S6K）和酪蛋白激酶2（CK2）被激活（30 - 600%），而在这些条件下，丝裂原活化蛋白激酶/细胞外调节激酶（ERK）1和ERK2未受到刺激。当用特异性抗体检测1日龄、10日龄、20日龄、50日龄和365日龄大鼠心室提取物中胰岛素激活激酶的表达水平时，磷脂酰肌醇3激酶（PI3K）、PKB、S6K和CK2随年龄下调（40 - 60%）。相比之下，心室糖原合酶激酶3β（GSK3β）蛋白水平在出生后发育过程中保持稳定。当在新鲜分离的心室肌细胞中研究这些激酶的表达时，也得到了类似的结果，在这些肌细胞中它们主要存在于胞质部分。与其他成年大鼠组织如脑和肝相比，心脏中PI3K、PKB、S6K和GSK3β的水平相对较低。尽管与1日龄大鼠相比，365日龄大鼠的CK2蛋白和活性水平降低了约60%，但成年心脏中CK2的表达与在任何其他大鼠组织中检测到的一样高。新生早期心脏中CK2的高基础活性可能与心肌细胞的增殖状态有关。
