Ubiquinone (coenzyme Q or Q) functions in cells as a redox-active coenzyme of mitochondrial and plasma membrane electron transport, as well as an essential lipid soluble antioxidant. Human dietary supplementation with Q appears to have beneficial effects in slowing the progression of neuro- and muscle- degenerative diseases. Cells are capable of synthesizing Q, but much remains to be learned about the sites of its synthesis, mechanisms of inter- and intra-cellular transport, and the regulation and enzymology of its biosynthesis. The goals of the proposed research are to characterize the polypeptides of the Q biosynthetic pathway and to define the enzymology of Q biosynthesis. The experimental system takes advantage of nine complementation groups of Q-deficient (coq) mutants in the yeast Saccharomyces cerevisiae. The coq mutants provide the basis for the characterization of the Coq polypeptides in both yeast and mammals. Synthetic analogs of Q-intermediates provide reagents that serve both as standards in the isolation and identification of Q intermediates, and as substrates for assays of enzyme activities. Genetic and biochemical evidence indicate that synthesis of Q in yeast requires a mitochondrial Coq multienzyme complex. We propose to identify the polypeptide components, and to determine whether Q-intermediates constitute important lipid components of these complexes. A potentially important function of the Coq biosynthetic complex is to regulate the flux of Q and Q-intermediates through the pathway, a process that potentially impacts performance of the respiratory electron transport chain. We will also characterize a tenth complementation group of yeast mutants. The yeast coqIO mutant defines a unique respiratory deficiency because mitochondria exhibit the characteristic phenotype of Q-defiency, yet have normal levels of Q. This class of mutants has a defect in a Q binding protein that shares homology with START domain proteins. We will determine whether this Q binding protein functions as a chaperone in the delivery of Q from its site of synthesis to its proper location for respiratory electron transport. The experimental approach employs a combination of lipid chemistry, yeast genetics, and biochemistry to delineate the biosynthetic steps responsible for the production of Q in yeast and human cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM045952-17
Application #
7529887
Study Section
Biochemistry and Biophysics of Membranes Study Section (BBM)
Program Officer
Anderson, Vernon
Project Start
1991-04-01
Project End
2011-11-30
Budget Start
2008-12-01
Budget End
2011-11-30
Support Year
17
Fiscal Year
2009
Total Cost
$348,851
Indirect Cost
Name
University of California Los Angeles
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
He, Cuiwen H; Xie, Letian X; Allan, Christopher M et al. (2014) Coenzyme Q supplementation or over-expression of the yeast Coq8 putative kinase stabilizes multi-subunit Coq polypeptide complexes in yeast coq null mutants. Biochim Biophys Acta 1841:630-44
Gasser, David L; Winkler, Cheryl A; Peng, Min et al. (2013) Focal segmental glomerulosclerosis is associated with a PDSS2 haplotype and, independently, with a decreased content of coenzyme Q10. Am J Physiol Renal Physiol 305:F1228-38
Allan, Christopher M; Hill, Shauna; Morvaridi, Susan et al. (2013) A conserved START domain coenzyme Q-binding polypeptide is required for efficient Q biosynthesis, respiratory electron transport, and antioxidant function in Saccharomyces cerevisiae. Biochim Biophys Acta 1831:776-791
Hill, Shauna; Lamberson, Connor R; Xu, Libin et al. (2012) Small amounts of isotope-reinforced polyunsaturated fatty acids suppress lipid autoxidation. Free Radic Biol Med 53:893-906
Xie, Letian X; Ozeir, Mohammad; Tang, Jeniffer Y et al. (2012) Overexpression of the Coq8 kinase in Saccharomyces cerevisiae coq null mutants allows for accumulation of diagnostic intermediates of the coenzyme Q6 biosynthetic pathway. J Biol Chem 287:23571-81
Rahman, Shamima; Clarke, Catherine F; Hirano, Michio (2012) 176th ENMC International Workshop: diagnosis and treatment of coenzyme Q?? deficiency. Neuromuscul Disord 22:76-86
Falk, Marni J; Polyak, Erzsebet; Zhang, Zhe et al. (2011) Probucol ameliorates renal and metabolic sequelae of primary CoQ deficiency in Pdss2 mutant mice. EMBO Mol Med 3:410-27
Clarke, Catherine F (2011) Coq6 hydroxylase: unmasked and bypassed. Chem Biol 18:1069-70
Heeringa, Saskia F; Chernin, Gil; Chaki, Moumita et al. (2011) COQ6 mutations in human patients produce nephrotic syndrome with sensorineural deafness. J Clin Invest 121:2013-24
Xie, Letian X; Hsieh, Edward J; Watanabe, Shota et al. (2011) Expression of the human atypical kinase ADCK3 rescues coenzyme Q biosynthesis and phosphorylation of Coq polypeptides in yeast coq8 mutants. Biochim Biophys Acta 1811:348-60

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