Stephen Barnes, PhD

MCLM 452

I have three major research areas. Firstly, since 1972 I have had a longstanding interest in the biochemistry, chemistry and analysis of bile acids. This has included the enzymes catalyzing the formation of bile acid sulfate esters (1980-1989) and those that form the bile acid glycine and taurine amino acid conjugates (1987-present). In the latter case, two enzymes are involved - bile acid CoA ligase (BAL) and bile acid CoA: amino acid N-acyltransferase (BAT). Initially, in collaboration with Dr. Robert Diasio's group, hBAT was purified from human liver. Subsequently, in collaboration with Dr. Charles Falany, a cDNA encoding hBAT was cloned from a human liver cDNA library, sequenced and expressed. These experiments revealed that a single enzyme in human liver was responsible for both glycine and taurine conjugation. Further work with Dr. Falany resulted in the isolation of mBAT cDNA from a mouse liver cDNA library - interestingly, it was an obligate taurine conjugator. Currently, experiments are underway to determine the critical amino acids necessary for BAT activity. BAL was isolated from rat liver by Dr. James Wheeler, a graduate student in my laboratory (now in the Department of Pharmacology, Vanderbilt University) and its cDNA has been recently isolated from a rat liver library.

Future studies on this NIH-funded project include the generation of BAAT and BAAL gene knockout mice to examine the importance of bile acid amino acid conjugation in mammalian physiology. The second major research area is in role of soy isoflavonoids in the prevention of chronic disases (atherosclerosis, breast and prostate cancer, inflammatory disease and osteoporosis). Experiments on the chemopreventive effects of soy isoflavones on the appearance of mammary tumors have been carried out in collaboration with Dr. Coral Lamartiniere and Dr. Clinton Grubbs. Additional research to determine the mechanism(s) of action of isoflavones has been carried out in tissue culture experiments and involved former graduate student Greg Peterson (recently graduated from the University of Virginia Law School), current graduate student Brenda Boersma, postdoctoral fellow Dr. Rakesh Patel (Pathology) and faculty colleagues Dr. Helen Kim and Dr. Victor Darley-Usmar (Pathology).

Our current focus is on the effects of genistein on TGF beta signalling pathways and the formation of and biological properties of the products of the reaction of isoflavones and the oxidants HOCI and peroynitrite. I also contribute to the research being carried out on the role of soy isoflavones in prevention of neurodegenerative diseases by Dr. Kim and osteoporosis by Dr. Harry Blair (Pathology). In 1997, I was a co-organizer (with Dr. Ken Setchel, Children's Hospital Medical Center, Cincinnati) of an International Symposium on Phytoestrogen Research Methods in Tucson, AZ. The papers from that symposium will be published this fall in the Journal of Medicinal Food. Those interested in research on soy should be aware of the upcoming Third International Symposium on the role of Soy in the Prevention and Treatment of Chronic Disease in Washington, DC, October 31 - November 3. The third major area in the application of mass spectrometry to biomedical research. Since 1993, I have been the Director of the Mass Spectrometry Shared Facility in the UAB Comprehensive Cancer Center.

During this time, the NIH/NCRR has awarded grants for the purchase of a PE-Sciex API triple quadrupole instrument (1993), a Perseptive Biosystems MALDI-TOF instrument (1996), and recently, a hybrid quadrupole orthogonal-time-of-flight instrument (1999). Further support for the development of mass spectrometry has come from the Howard Hughes Medical Institute and the UAB-HSF General Endowment Fund. These technologies have been used for each of my other funded projects on bile acid and isoflavone metabolism. In addition, experimental methods have been developed for the study of chemical modification of proteins in collaboration with Dr. Ahmad Safavy (Radiation Biology) and Dr. Joseph Beckman (Anesthesiology), high sensitivity peptide sequencing, and the dynamics of protein folding using hydrogen-deuterium exchange in collaboration with Dr. Peter Prevelige (Microbiology).