激活的固醇调节元件结合蛋白在内皮细胞移行中的作用

Activation of sterol regulatory element binding protein and its involvement in endothelial cell migration

目的探讨固醇调节元件结合蛋白（SREBP）在内皮细胞移行中的激活及其作用。方法培养牛主动脉内皮细胞，应用Western blot分析、即时定量PCR、细胞移行测定、Cdc42活性测定等方法，研究了SREBP的激活在内皮细胞移行中的作用，以及这个过程中涉及SREBP的潜在的信号转达。结果（1）内皮细胞移行组与非移行组相比，SREBP被显著激活（P〈0．05）；（2）内皮细胞移行组与非移行组相比，SREBP下游基因，低密度脂蛋白受体、羟甲基戊二酰辅酶A还原酶及脂肪酸合成酶的mRNA的表达显著增加（P〈0．05）；（3）SREBP裂解激活蛋白RNAi和SREBP抑制剂（25-羟化胆固醇）能够明显抑制内皮细胞的移行；（4）在各种模型中SREBP的抑制导致内皮细胞移行的减少；（5）SREBP裂解激活蛋白缺陷型、S2P缺陷型及SIP缺陷型细胞株，表现为内皮细胞移行损伤；（6）抑制内皮细胞SREBP活性后，Rho、Cdc42活性也被抑制。结论SREBP是内皮细胞移行中的关键调控分子，靶向干预SREBP将可能成为治疗异常内皮细胞移行相关疾病的一条新途径。

Objective To study the activation of sterol regulatory element binding protein （SREBP） and its critical role in endothelial cell migration. Methods Bovine aortic endothelial cells （ECs） were cultured. The expression of SREBP and Cdc42 were determined by Western blot and quantitative real-time PCR. Moreover, outward growth migration model and transwell chamber assay were used to detect ECs migration. Results （1） SREBP was activated during ECs migration. Western blot analysis demonstrated increased active form SREBP in migrating as compared to non-migrating ECs population. SREBP activation decreased as ECs migration slowed ; （2） Coincidental with SREBP activation, mRNA expression of its target genes such as low density lipoprotein receptor, HMG-CoA reductase, and fatty acid synthase also increased in migrating ECs population as detected by real-time PCR ; （3） Migration induced SREBP activation in ECs was inhibited by SREBP-acting protein RNAi and pharmacologically by 25-hydroxycholesterol ; （4） Inhibition of SREBP led to decreased ECs migration in various models; （5） Cells genetically deficient in SREBP-acting protein,SIP, or S2P,phenotypically exhibited impaired migration; （6） SREBP inhibition in ECs suppressed the activity of small GTPase Cdc42, a key molecule for ECs motility. Conclusions SREBP is activated during and plays a critical role in ECs migration. Targeting SREBP could become a novel approach in fighting diseases involving abnormal ECs migration.