P49/STRAP与MYOCD相互作用协同调控血管平滑肌细胞表型转化的机制

Phenotypic switching of vascular smooth muscle cells (VSMCs) and subsequent proliferation contribute to various vascular proliferative diseases. MYOCD is a key co-transcriptional factor of serum response factor (SRF). The MYOCD-SRF complex, through interaction with CArG boxes in promoter regions, can directly transactivates contractile smooth muscle genes. Although MYOCD is considered as a critical component of the contractile “switch” in VSMCs, there are other cofactors needed. Up to now, it’s still not clear how MYOCD-SRF transactivation is activated by these cofactors. Our preliminary data indicated that P49/STRAP directly binds to MYOCD and acts synergistically with MYOCD to regulate the transcription of VSMCs-specific genes. However, the molecular mechanism remains elusive. In this project, we propose that P49/STRAP can increase MYOCD-SRF binding with CArG boxes elements because of their protein-protein interaction, and P49/STRAP binding with MYOCD and MYOCD-SRF complex binding with CArG boxes may be enhanced by the phosphorylation of P49/STRAP. Novel evidence will be provided to prove that P49/STRAP suppress the phenotypic switching of VSMCs in vitro and in vivo through a variety of cellular and molecular methods. These studies will provide new insights into the mechanisms controlling the phenotypic switch of VSMC by P49/STRAP and toward a better understanding of the pathogenesis of vascular proliferative diseases.

血管平滑肌细胞(VSMCs)由正常分化型转化为增殖型是血管增生性疾病的重要病理基础。血清反应因子(SRF)与辅助因子MYOCD结合形成复合物，与DNA序列CArG box结合激活VSMCs分化基因转录，对于抑制VSMCs表型转化至关重要，该过程仍需其它辅助因子参与。我们前期的研究发现P49/STRAP与MYOCD互作协同激活VSMCs分化基因转录，但机制尚不清楚。本研究拟将利用细胞和分子生物学手段，从P49/STRAP与MYOCD蛋白互作、SRF与CArG box的结合力、P49/STRAP磷酸化修饰等方面，探究P49/STRAP协同MYOCD激活VSMCs分化基因转录的调控机制，并在动物体内探究P49/STRAP和MYOCD互作对VSMCs表型转化与新生内膜形成的影响。本研究能提高对P49/STRAP调控功能机制的理解，并加深VSMCs表型转化及血管增生性疾病发病机理的认识。

血管平滑肌细胞(vascular smooth muscle cells, VSMCs)由正常分化型转化为增殖型是血管增生性疾病的重要病理基础。 血清反应因子(serum response factor, SRF)与辅助因子MYOCD (myocardin)结合形成复合物，与DNA序列CArG box结合激活VSMCs收缩基因转录，对于抑制VSMCs表型转化至关重要，该过程仍需其它辅助因子参与，但机制并不清楚。本研究利用报告基因方法证明了辅因子P49/STRAP（SRF binding protein 1, SRFBP1）与MYOCD蛋白互作，协同促进了SRF 对VSMCs 收缩基因的转录激活；小鼠Srfbp1基因敲除后导致胚胎在E9.5 左右可能因为心脏发育异常所致死亡；利用动脉粥样硬化动物模型Apolipoprotein e缺失小鼠在主动脉中敲低和过表达SRFBP1，证明了SRFBP1体内抑制动脉粥样硬化斑块内VSMCs的增殖且不依赖于血脂的影响发挥抗动脉粥样硬化的作用。本研究对于进一步认识VSMCs表型转换的机制具有一定的意义，为探究血管增生性疾病发病机制及治疗策略提供了一定的理论依据。