Gu X.,Cleveland Clinic |
Wu Z.,Cleveland Clinic |
Huang Y.,Cleveland Clinic |
Wagner M.A.,Cleveland Clinic |
And 11 more authors.
Journal of Biological Chemistry | Year: 2016
The interaction of lecithin-cholesterol acyltransferase (LCAT) with apolipoprotein A-I (apoA-I) plays a critical role in highdensity lipoprotein (HDL) maturation.Wepreviously identified a highly solvent-exposed apoA-I loop domain (Leu159-Leu170) in nascent HDL, the so-called "solar flare" (SF) region, and proposed that it serves as an LCAT docking site (Wu, Z., Wagner, M. A., Zheng, L., Parks, J. S., Shy, J. M., 3rd, Smith, J. D., Gogonea, V., and Hazen, S. L. (2007) Nat. Struct. Mol. Biol. 14, 861-868). The stability and role of the SF domain of apoA-I in supporting HDL binding and activation of LCAT are debated. Here we show by site-directed mutagenesis that multiple residues within the SF region (Pro165, Tyr166, Ser167, and Asp168) of apoA-I are critical for both LCAT binding to HDL and LCAT catalytic efficiency. The critical role for possible hydrogen bond interaction at apoA-I Tyr166 was further supported using reconstituted HDL generated from apoA-I mutants (Tyr1663Glu or Asn), which showed preservation in both LCAT binding affinity and catalytic efficiency. Moreover, the in vivo functional significance ofNO2-Tyr166- ApoA-I, a specific post- Translational modification on apoA-I that is abundant within human atherosclerotic plaque, was further investigated by using the recombinant protein generated from E. coli containing a mutated orthogonal tRNA synthetase/tRNACUA pair enabling site-specific insertion. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc. Source
Weckerle A.,Sections on Molecular Medicine |
Cheng D.,Sections on Molecular Medicine |
Gebre A.K.,Sections on Molecular Medicine |
Reisz J.A.,Sections on Molecular Medicine |
And 4 more authors.
Journal of Lipid Research | Year: 2016
APOL1 gene renal-risk variants are associated with nephropathy and CVD in African Americans; however, little is known about the circulating APOL1 variant proteins which reportedly bind to HDL. We examined whether APOL1 G1 and G2 renal-risk variant serum concentrations or lipoprotein distributions differed from nonrisk G0 APOL1 in African Americans without nephropathy. Serum APOL1 protein concentrations were similar regardless of APOL1 genotype. In addition, serum APOL1 protein was bound to protein complexes in two nonoverlapping peaks, herein referred to as APOL1 complex A (12.2 nm diameter) and complex B (20.0 nm diameter). Neither of these protein complexes associated with HDL or LDL. Proteomic analysis revealed that complex A was composed of APOA1, haptoglobin-related protein (HPR), and complement C3, whereas complex B contained APOA1, HPR, IgM, and fibronectin. Serum HPR was less abundant on complex B in individuals with G1 and G2 renal-risk variant genotypes, relative to G0 (P = 0.0002-0.037). These circulating complexes may play roles in HDL metabolism and susceptibility to CVD. Copyright © 2016 by the American Society for Biochemistry and Molecular Biology, Inc. Source
Mims J.,Sections on Molecular Medicine |
Bansal N.,Sections on Molecular Medicine |
Bharadwaj M.S.,Gerontology and Geriatric Medicine |
Chen X.,Sections on Molecular Medicine |
And 3 more authors.
Radiation Research | Year: 2015
While radiation therapy is commonly used for treating cancer, radiation resistance can limit long-term control of the disease. In this study, we investigated the reprogramming of the energy metabolism in radiosensitive and radioresistant head and neck squamous cell carcinomas (HNSCC) using a preclinical matched model of radiation resistance. Our investigation found that radioresistant rSCC-61 cells: 1. They display increased glucose uptake and decreased fatty acid uptake; 2. They deviate from the classical Warburg effect by diverting the glycolytic flux into the pentose phosphate pathway; 3. They are more dependent on glucose than glutamine metabolism to support growth; 4. They have decreased mitochondrial oxidative phosphorylation; 5. They have enhanced fatty acid biosynthesis by increasing the expression of fatty acid synthase; and 6. They utilize endogenous fatty acids to meet the energy demands for proliferation. Inhibition of fatty acid synthase with orlistat or FASN siRNA resulted in increased cytotoxicity and sensitivity to radiation in rSCC-61 cells. These results demonstrate the potential of combination therapy using radiation and orlistat or other inhibitors of lipid and energy metabolism for treating radiation resistance in HNSCC. © 2015 by Radiation Research Society. Source