Mutations in Smooth Muscle Contractile Proteins: Pathways to Vascular Diseases

血管平滑肌细胞在动脉中周向排列成多层，在大的弹性动脉中嵌入弹性蛋白层之间，或在较小的肌肉动脉中嵌入结缔组织基质中。对于收缩功能，SMC表达α-肌动蛋白和β-肌球蛋白的平滑肌特异性同种型，其多聚化以分别形成薄的和厚的细丝。我们已经确定，编码SMC α-肌动蛋白和β-肌球蛋白、ACTA 2和MYH 11以及控制SMC收缩的激酶肌球蛋白轻链激酶（MYLK）的基因突变使个体易患血管疾病，包括胸主动脉瘤和主动脉夹层以及闭塞性血管疾病，如早发性冠状动脉疾病和中风。计划项目资助（PPG）将检验ACTA 2、MYH 11和MYLK突变导致胸主动脉疾病和/或闭塞性血管疾病的假设，这是由于SMC对收缩单位功能障碍引起的生物力学应力的不同反应。我们假设这些基因的突变会导致功能丧失，特别是升主动脉中SMC收缩单位的调节丧失或力输出改变，导致生物力学应力增加和SMC通路激活，从而导致胸主动脉瘤和主动脉夹层。相反，我们假设与ACTA 2突变亚组相关的闭塞性血管疾病，以及可能的MYH 11变体，是由肌性动脉中的SMC "功能获得"引起的，特别是由于改变的局灶性粘连和PDGFR-β受体激活引起的SMC增殖，以响应异常的细胞力产生。为了验证这些假设。项目1和2将评估ACTA 2和MYH 11遗传变异体对体外动力学、运动性、调节和细丝形成的影响。项目3将评估特定信号传导模块的年龄依赖性紊乱，这些模块负责选择ACTA 2、MYH 11和MYLK突变的小鼠模型中血管SMC的血管反应性。项目4将在这些相同的小鼠模型中研究导致胸主动脉疾病和SMC增殖的SMC细胞通路。

Vascular SMCs are arranged circumferentially in arteries in multiple layers, either embedded between layers of elastin lamellae in large elastic arteries or in a matrix of connective tissue in smaller muscular arteries. For contractile function, SMCs express smooth muscle specific isoforms of alpha-actin and Beta-myosin, which multimerize to form thin and thick filaments, respectively. We have determined that mutations in the genes encoding SMC alpha-actin and Beta-myosin, ACTA2 and MYH11, along with the kinase that controls SMC contraction, myosin light chain kinase (MYLK), predispose individuals to vascular diseases, including thoracic aortic aneurysms and aortic dissections and occlusive vascular diseases, such as early onset coronary artery disease and stroke. The Program Project Grant (PPG) will test the hypothesis that the ACTA2, MYH11 and MYLK mutations lead to thoracic aortic and disease and/or occlusive vascular diseases due to a differential SMC response to biomechanical stresses resulting from dysfunction of the contractile unit. We hypothesize that mutations in these genes cause a ¿loss of function¿, specifically loss of regulation or altered force output of contractile unit in SMCs in ascending aorta, resulting in increased biomechanical stresses and activation of SMC pathways leading to thoracic aortic aneurysms and aortic dissections. In contrast, we hypothesize that the occlusive vascular diseases associated with a subset of ACTA2 mutations, and possibly MYH11 variants, result from a SMC "gain of function" in muscular arteries, specifically increased SMC proliferation as a consequence of altered focal adhesions and activation of PDGFR-Beta receptors in response to abnormal cellular force generation. To test these hypotheses. Project 1 and 2 will assess the Impact of ACTA2 and MYH11 genetic variants on kinetics, motility, regulation, and filament formation in vitro. Project 3 will assess age-dependent derangements in specific signaling modules responsible for vasomotor responsiveness in vascular SMCs in mouse models of select ACTA2, MYH11 and MYLK mutations. Project 4 will Investigate SMC cellular pathways leading to thoracic aortic disease and SMC proliferation in these same mouse models.