Functional Analysis of p53-Regulatory Protein CARP in Atherosclerosis

TGF-β在血管疾病的发展中起主要作用。尽管TGF-β对血管平滑肌细胞（VSMC）具有多效性作用，但只有少数基因被表征为VSMC中TGF-β的直接靶标。在这项研究中，我们发现CARP在球囊损伤后的新生内膜SMC中表达，并在培养的VSMC中对TGF-β做出反应。TGF-β在转录水平上增加CARP基因表达。转染编码Smads的表达载体显著激活CARP启动子/荧光素酶活性。用表达CARP的腺病毒载体转染的细胞显示DNA合成显著减少。CARP过表达增强了TGF-β介导的DNA合成抑制作用。这些数据表明CARP是VSMC中TGF-β/Smad信号传导的下游靶点，并提示其在介导TGF-β对VSMC增殖的抑制作用中的作用。我们还研究了CARP对多能性10 T1/2细胞和血管平滑肌细胞中SMC基因表达的影响。结果表明，TGF β 1通过增加SRF表达诱导CArG依赖的SM 22 α基因表达，酪氨酸激酶Src家族在此作用中起重要作用。此外，CARP过表达增强TGF-β1诱导的SM 22 α基因表达而不影响SRF表达。这些发现阐明了CARP在发育和血管疾病中调节SMC基因表达的作用。

TGF-β plays a major role in the development of vascular diseases. Despite the pleiotropic effects of TGF-b on vascular smooth muscle cells (VSMCs), only few genes have been characterized as direct targets of TGF-β in VSMCs. In this study we showed that CARP is expressed in neointimal SMCs after balloon injury and in cultured VSMCs in response to TGF-β. The CARP gene expression is increased by TGF-β at the transcriptional level. Transfection of expression vectors encoding Smads significantly activated the CARP promoter/luciferase activity. Cells transfected with adenovirus vector expressing CARP showed a significant decrease in DNA synthesis. Overexpression of CARP enhanced the TGF-β-mediated the inhibition of the DNA synthesis. These data indicate that CARP is a downstream target of TGF-β/Smad-signalings in VSMCs, and suggest a role for mediating the inhibitory effects of TGF-β on the proliferation of VSMCs. We also investigated the effects of CARP on the SMC gene expression in the pluripotent 10T1/2 cells and in vascular SMC. The results demonstrated that TGFb1 induces CArG-dependent SM22α gene expression via an increase in SRF expression, and Src-family of tyrosine kinase is important for this effect. Furthermore, CARP overexpression enhanced TGF-β1-induced SM22α gene expression without affecting SRF expression. These findings shed light on the role of CARP for modulating SMC gene expression during development and in vascular disease.