title: Blood cellular mutant LXR-α protein stability governs initiation of coronary heart disease.
abstract: OBJECTIVE
  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-α (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-α and BARD1. Peripheral blood mononuclear cells were cultured and exposed to Vitamin D3 and Cisplatin to validate the degradation of mutant LXR-α protein in CHD subjects by BARD1/BRCA1 complex.
  
  
  RESULTS
  The expression of mutant LXR-α protein 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-α via ubiquitination. The absence of functional LXR-α protein resulted in increased expression of inflammatory cytokines such as interleukin (IL)-6, IL-8 and interferon-γ 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 D3 could prevent the degradation of mutant LXR-α and restore its functional activity to some extent.
  
  
  CONCLUSIONS
  Mutant LXR-α protein in CHD subjects is degraded by BARD1/BRCA1 complex and Vitamin D3 can rescue and restore its function.
authors.affiliation: Mansi Arora, Deepak Kaul, Yash Paul Sharma, Department of Experimental Medicine, Biotechnology and Cardiology, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India.
authors.forename: Mansi
authors.initials: M
authors.lastname: Arora
authors.forename: Deepak
authors.initials: D
authors.lastname: Kaul
authors.forename: Yash Paul
authors.initials: YP
authors.lastname: Sharma
keywords: Breast and ovarian cancer susceptibility 1-associated RING domain 1/breast and ovarian cancer susceptibility 1; Coronary heart disease subjects; Mononuclear Cells; Mutant liver X receptor-α; Ubiquitination; Vitamin D3