Differentiated phenotype of smooth muscle cells depends on signaling pathways through insulin-like growth factors and phosphatidylinositol 3-kinase
Differentiated phenotype of smooth muscle cells depends on signaling pathways through insulin-like growth factors and phosphatidylinositol 3-kinase
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DOI：
10.1074/jbc.273.44.28860
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发表时间：
1998-10-30
影响因子：
4.8
通讯作者：
Sobue, K
中科院分区：
文献类型：
--
作者：
Hayashi, K;Saga, H;Sobue, K
在常规培养条件下，平滑肌细胞表现出从分化到去分化状态的表型调节。在这里，我们建立了平滑肌细胞的原代培养系统，维持分化的表型，其特征是平滑肌特异性标记基因（如h-caldesmon和calponin）的表达、细胞形态和配体诱导的收缩性。层粘连蛋白延缓了平滑肌细胞去分化的进程。胰岛素样生长因子（IGF-I和IGF-II）和胰岛素显著延长分化表型，其中IGF-I的作用更大。相反，血清、表皮生长因子、转化生长因子和血小板源性生长因子比血管紧张素II、精氨酸-血管加压素和碱性成纤维细胞生长因子更能诱导去分化。利用现有的培养系统，我们研究了调节平滑肌细胞表型的信号通路。在培养细胞中，igf - 1特异性激活磷脂酰肌醇3-激酶（pi3 -激酶）及其下游靶点蛋白激酶B，但不激活丝裂原激活的蛋白激酶。pis激酶特异性抑制剂（wortmannin和LY294002）诱导平滑肌细胞去分化，即使它们在igf - i刺激条件下在层粘连蛋白上培养。层粘连蛋白延缓去分化的唯一作用被抗IGF-I抗体完全阻断，层粘连蛋白促进培养细胞内源性IGF-I的表达。血小板源性生长因子BE诱导的caldesmon基因启动子活性降低被pi3 -激酶p110 α催化亚基的组成活性形式的强制表达所克服。这些发现表明，通过pi3激酶的IGF-I信号通路在维持平滑肌细胞分化表型中起关键作用。
Under conventional culture conditions, smooth muscle cells display their phenotypic modulation from a differentiated to a dedifferentiated state. Here, we established a primary culture system of smooth muscle cells maintaining a differentiated phenotype, as characterized by expression of smooth muscle-specific marker genes such as h-caldesmon and calponin, cell morphology, and ligand-induced contractility. Laminin retarded the progression of dedifferentiation of smooth muscle cells. Insulin-like growth factors (IGF-I and IGF-II) and insulin markedly prolonged the differentiated phenotype, with IGF-I being the more potent, In contrast, serum, epidermal growth factor, transforming growth factors, and platelet-derived growth factors potently induced dedifferentiation compared with angiotensin II, arginine-vasopressin, and basic fibroblast growth factor. Using the present culture system, we investigated signaling pathways regulating a phenotype of smooth muscle cells. In cultured cells, IGF-I specifically activated phosphatidylinositol 3-kinase (PI3-kinase) and its downstream target, protein kinase B, but not mitogen-activated protein kinases. Specific inhibitors of PIS-kinase (wortmannin and LY294002) induced dedifferentiation of smooth muscle cells even when they were cultured on laminin under IGF-I-stimulated conditions. The sole effect of laminin to retard the dedifferentiation was completely blocked by anti-IGF-I antibody, and laminin promoted the endogenous expression of IGF-I in cultured cells. The reduced promoter activity of the caldesmon gene induced by platelet-derived growth factor BE was overcome by the forced expression of the constitutive active form of PI3-kinase p110 alpha catalytic subunit. These findings suggest that an IGF-I signaling pathway through PI3-kinase plays a critical role in maintaining a differentiated phenotype of smooth muscle cells.