Catherine Clarke Summary

Introduction
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. However, at least in lower animal species, such as the nematode Caenorhabditis elegans, dietary Q can also contribute to a shortened lifespan. These apparently disparate effects may reflect the potential of Q to contribute to the generation of reactive oxygen species. 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 my research are to characterize the Coq polypeptides responsible for production of Q and to determine how their activity can be modulated for optimal health.

Research Overview
My research focuses on understanding the physiological roles of Q at the molecular level. Our studies have centered on elucidating the gene-enzyme relationships of Q biosynthesis, characterizing the polypeptide components responsible for the production of Q, and investigating the in vivo functions of Q/QH₂. Recently we have turned to the nematode Caenorhabditis elegans as an excellent model for genetic studies of the aging process. Gene mutations that increase life span have been identified in C. elegans that have homologs in vertebrates and appear to act by highly conserved mechanisms, and in pathways that parallel those present in humans.

Elucidating Q biosynthesis
Our research takes advantage of the availability of respiratory defective coq mutants of the yeast Saccharomyces cerevisiae auxotrophic for Q. The yeast coq mutants provide for the isolation and characterization of the COQ genes and their products from both yeast and animals. Yeast is an ideal organism for these studies because mutants completely lacking Q can remain viable through their ability to grow by fermentation. Synthetic analogs of Q intermediates provide reagents that serve both as standards in the isolation and characterization of Q intermediates, and as substrates for in vitro assays of enzyme activities. Thus, the experimental approach employs a combination of molecular genetics, chemistry and biochemistry to delineate the eukaryotic biosynthetic steps responsible for the production of Q, as well as to investigate the function of Q/QH₂ as an antioxidant. We now have isolated ten yeast COQ genes that complement the corresponding coq respiratory defective mutants. We have thus defined a minimal cohort of the potential polypeptide components in Q biosynthesis. My laboratory has contributed a large part of this information. Nine of the Coq polypeptides are matrix proteins peripherally associated with the mitochondrial inner membrane. A growing body of genetic evidence indicates that certain of these Coq polypeptides, together with Q and/or Q intermediates, interact to form a mitochondrial Q biosynthetic complex.

Q and aging
Mutations in the C. elegans clk-1 gene result in an extended life span, slowed development and sluggish behavior. Homology of nematode clk-1 and yeast COQ7 genes suggested that the long-lived C. elegans clk-1 mutants are defective in Q biosynthesis. Normally nematodes are provided a diet of Q-replete E. coli. In the absence of dietary Q, the clk-1 mutants display their true phenotype – growth arrest in early development and sterility when emerging from the dauer stage. Our studies show that the rescue by dietary Q₈ depends upon the uptake and transport of dietary Q₈ to mitochondria within the nematode. Our recent work shows that the rescue is mediated by Q₈, Q₉ or Q₁₀ isoforms

These results suggest that clk-1 is essential for Q biosynthesis, and that the aging and developmental phenotypes previously described may be attributed to Q levels. Our recent studies indicate that both mean and maximum life span of wild-type nematodes fed Q-less diets is extended 60%. This life span extension is quite robust and is observed in all Age mutants tested so far, when transferred to the Q-less diet as adults. Our current studies are aimed towards defining the metabolic alterations resulting from dietary Q, and should help determine how diet/environment and genotype interact to change longevity. Based on the strong conservation of Q biosynthesis and function, our findings should be very relevant to aging in other organisms.

Researchers
Dr. Grigory Belogrudov	Department of Physiology, UCLA School of Medicine
Dr. Deborah Berthold	Research Associate, University of Illinois Champagne-Urbana
Dr. Jenna Hutton	Research Associate, University of Rutgers
Dr. Pam Larsen	University of Texas Health Sciences Center at San Antonio, Dept. of Cellular and Structural Biology
Postdoctoral Fellows
Dr. Susan Morvaridi	B.S. & Ph.D., Lund University
Dr. Ryoichi Saiki	B.A., M.S., & Ph.D. University of Shimane, Research Scientist, Funakoshi, Tokyo, Japan
Ph.D. Students
Dr. Thai Do	B.S., Ph.D.,UCLA, Project Scientist, Molecular Express, Rancho Dominguez, CA
Dr. Peter Gin	B.S., Ph.D. 2005, UCLA - Postdoc. Researcher - Dr. Stephen Young, Dept. of Medicne, UCLA
Dr. Melissa Gulmezian	B.A., University of California, Irvine; Ph.D., University of California, Los Angeles 2006; Scientist, Allergan, Irvine, CA
Dr. Edward Hsieh	Ph.D. 2006, UCLA - Research Faculty, Univ. of Washington, Seattle
Dr. Tanya Kruse	B.S., Ph.D., UCLA - Project Scientist, Baxter, Los Angeles, CA
Dr. Adam Lunceford	B.S., Brigham Young University; Ph.D., University of California, Los Angeles 2008; J.D., UC Davis, Patent Attorney, Cooley LLP, Washington, D.C.
Dr. Wayne Poon	B.S., Ph.D. UCLA - Research Faculty, University of California, Irvine
Dr. UyenPhuong C. Tran	B.S., UCLA, Ph.D., University of California, Los Angeles 2007; Postdoctoral Fellow, UC San Diego
Master Students
Suzie Ward Baba
Diana Davis	B.S., North Carolina State University
Edouard Debonneuil	M.S., Computational Biology, University of California, Los Angeles
Shota Watanabe	B.S., University of California, Los Angeles, currently at the University of Hawaii Medical School
Undergraduate Students
Jia Yan Chen	Class of 2011 - UCLA Biochemistry
Samuel Choi	Class of 2010 - UCLA Biochemistry
Peter Dang	Class of 2006 - UCLA Biochemistry, currently a Masters student at the UCLA School of Dentistry
Jason Dinoso	Class of 2001 - UCLA Biochemistry, currently a postdoc at the University of Washington, Seattle
Shauna Hill	B.S., Biochemistry, University of California, Los Angeles, currently a graduate student at The University of Texas Health Science Center at San Antonio
Kathleen Hirano	Class of 2009 - UCLA Biochemistry, currently a graduate student at UC Berkeley
Kyle Hyman	Class of 2008 - UCLA Biochemistry
Ziming Ji	Class of 2010 - BS Biophysics, University of California, Los Angeles
Bradley Kay	Class of 2011 - UCLA Biochemistry
Laura Lee	Class of 2010 - California State University, Fullerton
Nico Lee	B.S., M.S., UCLA Biochemistry
Amjad Nazzal	Current Biochemistry major, University of California, Los Angeles
Tin Mai	Class of 2009 - UCLA Biochemistry
Sabine Paterson	Class of 2001 - UCLA Biochemistry
An Pham	Class of 2010 - UCLA Biochemistry
Yuchen Shi	Class of 2008 - UCLA Biochemistry
Aye Win Tin	Class of 2011 - UCLA Biochemistry
Ruiwen Wang	Class of 2010 - UCLA Biochemistry
Summer Interns
Jonathan Fine	Pali High 2011
Eva Morozko	Class of 2012 - Seton Hall University, B.S. in Biochemistry
Jeffery Roth	Class of 2010 - Beverly Hills High