Study On The Interaction Of Mutant P53 With HSP70 And HSP90

TP53 gene encodes a protein with a molecular weight of 53 kDa, named p53. Inactivation of TP53 gene plays an important role in tumor formation. This gene mutation occurs in more than 50% of malignant cancers. Most p53 mutations are missense mutation caused by a single amino acid substitution. Mutant p53 protein still retains the full length, but contributes to the change from oncogene to tumor suppressor gene.Heat shock proteins(HSPs) are induced by various environmental stimulations such as physical, chemical, biological or mental stress. Heat shock proteins are a kind of highly conserved proteins, widely exist in prokaryotes and eukaryotes. The HSP family exerts their role, mainly as a molecular chaperone, and can influence cell apoptosis, be involved in immune system and improve heat resistance.Firstly, we performed co-immunoprecipitation followed by mass spectrometry, and identified 59 proteins interacting with p53R273 H in breast cancer cell line MDA-MB-468 harboring p53R273 H mutant. Among these p53R273 H partners, nine are heat shock proteins, including HSP70 family members(HSP70A2、HSP70A5、HSP70A6、HSP70A7、HSP70A8、HSP70A1L) and HSP90 family members(HSP90AA1、HSP90AB1、HSP90B1).Then, we studied the effects of HSP70 and HSP90 on p53R273 H protein function. We co-transfected p53R273 H expression plasmid with HSP90-AB1 and HSP70-A5 expression plasmids into HEK293 cells, and then detected stability of p53R273 H protein. The results show that HSP70 and HSP90 can enhance the stability of the p53R273H; moreover, effect of co-transfection with HSP70 and HSP90 is better than that of transfection with only HSP70 or HSP90. Treatment with the HSP70 inhibitor pifithrin-μ and/or HSP90 inhibitor 17-AAG in MDA-MB-468 cells can promote p53R273 H protein degradation. Further studies show that interfering p53R273 H mutant in MDA-MB-468 cells inhibits cell proliferation. Treatment with HSP70 inhibitor pifithrin-μ and/or HSP90 inhibitor 17-AAG inhibit cell proliferation and migration, and promotes cell apoptosis. These results suggest that HSP70 and HSP90 may promote protein stability of p53R273 H through interacting with p53R273 H, and then affect cell proliferation and inhibit cell apoptosis...