热休克蛋白72肽结合区对肾小管上皮间质转分化的影响

Impact of peptide binding domain of heat shock protein 72 on epithelial to mesenchymal transition

目的探讨热休克蛋白72肽结合区在肾小管上皮间质转分化（EMT）过程中的作用和可能机制。方法应用质粒转染方法分别诱导热休克蛋白72（HSP72）野生型、肽结合区缺失型（HSP72-△PBD）和肽结合区（PBD）的表达。用转化生长因子β1（TGF-β1）刺激大鼠肾小管上皮细胞（NRK-52E）48h，Western印迹和免疫荧光染色检测细胞E-钙黏蛋白（cadherin），α-平滑肌肌动蛋白（SMA），HSP72和Smad3／磷酸化（P）-Smad3蛋白表达。结果TGF-β1（10μg／L）刺激NRK-52E细胞48h后上调α—SMA和下调E—cadherin蛋白表达水平。Western印迹及细胞免疫荧光显示，过表达HSP72和PBD能明显减轻TGF-β1诱导的NRK-52E细胞E-cadherin蛋白表达下调和α—SMA蛋白表达上调，而过表达HSP72-△PBD不能改变上述蛋白的表达。此外，过表达HSP72和PBD显著抑制Smad3的磷酸化。结论HSP72抑制Smad3活化和EMT的发生可能与PBD的功能有关。

Objective To investigate the effects of peptide-binding domain （PBD） of heat shock protein （HSP） 72 on epithelial to mesenchymal transition （EMT） in rat renal tubular epithelial cells. Methods The expressions of wild-type HSP72, mutant of HSP72 lacking peptide binding domain （HSP72 -APBD） and HSP72-PBD were induced by plasmid transfection. NRK-52E cells were stimulated by TGF-β1 for 48 h. The expressions of a-smooth muscle actin （a-SMA）, E-cadherin, HSP72 and Smad3/p-Smad3 were detected by Western blot and immunofluorescence. Results After NRK-52E cells were stimulated by TGF-β 1 （10 μg/L） for 48 h, the expression of a-SMA was increased and the protein level of E-cadhefin was decreased. Western blotting and immunofluorescence showed that over-expression of both HSP72 and PBD inhibited TGF-β1-indueed up-regulation of protein a-SMA expression, down-regulation of protein E-cadherin. However, over- expression of HSP72-APBD did not change the protein level of E-cadherin and et-SMA. In addition, over-expression of HSP72 and PBD significantly inhibited the phosphorylation of Smad3. Conclusion Inhibition of Smad3 activation and EMT by HSP72 is associated with the function of PBD.