Blood cellular mutant LXR-α protein stability governs initiation of coronary heart disease

摘要

AIM: To investigate the role of [breast and ovarian cancer susceptibility 1(BRCA1)-associated RING domain 1(BARD1)]/BRCA1 E3-ubiquitin ligase complex in governing the stability of mutant liver X receptor-(LXR-α) protein in coronary heart disease(CHD) subjects.METHODS: The expression analysis of various genes was carried out by quantitative real time polymerase chain reaction and western blotting within blood mononuclear cells of human CHD subjects at various stages of coronary occlusion and their corresponding normal healthy counterparts.Immunoprecipitation experiments were performed to establish protein interactions between LXR-αand BARD1.Peripheral blood mononuclear cells were cultured and exposed to Vitamin D_3 and Cisplatin to validate the degradation of mutant LXR-αprotein in CHD subjects by BARD1/BRCA1 complex.RESULTS: The expression of mutant LXR-αprotein in CHD subjects was found to decrease gradually with the severity of coronary occlusion exhibiting a strong negative correlation,r =-0.975 at P < 0.001.Further,the expression of BARD1 and BRCA1 also increased with the disease severity,r = 0.895 and 0.873 respectively(P < 0.001).Immunoprecipitation studies established that BARD1/BRCA1 complex degrades mutant LXR-αvia ubiquitination.The absence of functional LXR-αprotein resulted in increased expression of inflammatory cytokines such as interleukin(IL)-6,IL-8 and interferon-and decreased expression of ABCA1(ATP-binding cassette A1)(r = 0.932,0.949,0.918 and-0.902 with respect to Gensini score;P < 0.001).Additionally,cell culture experiments proved that Vitamin D_3 could prevent the degradation of mutant LXR-αand restore its functional activity to some extent.CONCLUSION: Mutant LXR-αprotein in CHD subjects is degraded by BARD1/BRCA1 complex and Vitamin D_3 can rescue and restore its function.