Signaling pathways regulating a phenotypic modulation of smooth muscle cells

在前期的研究中，我们发现IGF-I激活了培养的肌胃平滑肌细胞的磷脂酰肌醇3-激酶（PI 3-K）和蛋白激酶B（PKB（Akt）），该信号通路在维持平滑肌细胞分化表型中起着重要作用。在这里，我们研究了参与的信号转导通路的去分化的砂囊平滑肌细胞诱导的PDGF-BB，bFGF和EGF使用上述原代培养系统。与IGF-I触发的通路相反，PDGF-BB、bFGF和EGF协同激活ERK和p38 MAPK通路。此外，MEK 1和MKK 6（分别为ERK和p38 MAPK的上游激酶）的活性形式的强制表达诱导去分化，即使当SMC用IGF-I刺激时也是如此。在三种生长因子中，PDGF-BB除了触发ERK和p38 MAPK途径外，还仅触发PI 3-K/PKB（Akt）途径。当ERK和p38 MAPK通路同时被其特异性抑制剂阻断或PI 3-K或PKB的活性形式（Akt）被阻断时， ...更多信息 转染后，PDGF-BB又开始维持分化的SMC表型。我们将这些发现应用于血管SMC，并证明了相同的信号通路可能参与调节血管SMC表型的可能性。以上结果提示，PI 3-K/PKB（Akt）通路与ERK和p38 MAPK通路之间的平衡变化决定了内脏和血管平滑肌细胞的表型，并进一步用mRNA消减法揭示了平滑肌细胞表型调控的分子机制。用这种方法，我们发现，一个10 kb的mRNA编码的同型细胞粘附分子，钙粘蛋白6 B，强烈表达在分化的血管和内脏平滑肌细胞，但不是在去分化的平滑肌细胞来自他们。在体内，钙粘蛋白6 B表达在血管和内脏SMC，除了脑，脊髓，视网膜和肾脏，在鸡胚胎发育的后期阶段。这些结果表明，钙粘蛋白6 B是一个新的分子标记的SMC表型，并参与了SMC的晚期分化。少

In previous study, we found that IGF-I triggered the phosphoinositide 3-kinase (PI3-K) and protein kinase B (PKB(Akt)) in cultured gizzard SMCs and this signaling pathway played a vital role in maintaining a differentiated phenotype of SMCs. Here, we investigated the signaling pathways involved in dedifferentiation of gizzard SMCs induced by PDGF-BB, bFGF, and EGF using the primary culture system described above. In contrast to the IGF-I-triggered pathway, PDGF-BB, bFGF, and EGF coordinately activated ERK and p38MAPK pathways. Further, the forced expression of active forms of MEK1 and MKK6, which are the upstream kinases of ERK and p38MAPK, respectively, induced dedifferentiation even when SMCs were stimulated with IGF-I. Among three growth factors, PDGF-BB only triggered the PI3-K/PKB (Akt) pathway in addition to the ERK and p38MAPK pathways. When the ERK and p38MAPK pathways were simultaneously blocked by their specific inhibitors or an active form of either PI3-K or PKB (Akt) was tr … More ansfected, PDGF-BB in turn initiated to maintain the differentiated SMC phenotype. We applied these findings to vascular SMCs, and demonstrated the possibility that the same signaling pathways might be involved in regulating the vascular SMC phenotype. These results suggest that changes in the balance between the PI3-K/PKB (Akt) pathway and the ERK and p38MAPK pathways would determine phenotypes of visceral and vascular SMCs.Further, we used mRNA subtraction method to reveal the molecular mechanisms underlying the phenotypic modulation of SMCs. With this approach, we found that a 10 kb mRNA encoding a homotypic cell adhesion molecule, cadherin 6B, was strongly expressed in differentiated vascular and visceral SMCs, but not in the dedifferentiated SMCs derived from them. In vivo, cadherin 6B was expressed in vascular and visceral SMCs, in addition to brain, spinal cord, retina, and kidney, at a late stage of chicken embryonic development. These results suggest that cadherin 6B is a novel molecular marker for SMC phenotype and is involved in the late differentiation of SMCs. Less