Kai Xu, Ph.D. Associate Professor      108 N. Greene St.      Baltimore, MD 21201      Phone: 410-706-1615      Fax: 410-706-8297      email: kxu002@umaryland.edu EDUCATION 1985     M.S., Department of Chemistry, University of California, San Diego,              Chemistry 1988     Ph.D., Department of Chemistry, University of California, San              Diego,  Biochemistry POST GRADUATE EDUCATION Postdoctoral: 1988-1990    Harvard University School of Medicine and Massachusetts                    General Hospital,  Biomedical Sciences. 1990-1992    Yale University School of Medicine, Molecular Biology Instructor:  1992-1995    Johns Hopkins University School of Medicine, Department of                    Medicine, Division of Cardiology, Biomedical Sciences

RESEARCH DESCRIPTION
Enzymes catalyze essential chemical reactions needed for living processes. (Na⁺+K⁺)-ATPase (NKA) is one of the key enzymes that controls intracellular ion homeostasis and regulates cardiac function. For half a century, scientists have only known that inhibition of NKA induces a positive inotropic effect. Recently, we have discovered that activation of NKA markedly augments intracellular Ca²⁺ transient and cardiac contraction. The finding changes our traditional thinking about NKA and opens a new chapter of investigation. The current research concentrates on the molecular pathways, mechanisms, and regulations of activation of NKA medicated biological processes. We attempt to reveal the atomic basis of activation of NKA and to characterize the functional links between activation of NKA and the positive inotropy induced by it to advance our understanding of NKA in health and disease. Congestive heart failure is a major cause of death both in the United States and abroad. Understanding of the molecular regulation of NKA in cardiac function will help to develop new therapies to benefit heart failure patients.

SELECTED PUBLICATIONS
Xu KY, Takimoto E, Juang GJ, Zhang Q, Rohde H, Myers AC. Evidence that the H1-H2 Domain of α1 Subunit of (Na++K+)-ATPase Participates in the Regulation of Cardiac Contraction, FASEB J (2005)19:53-61.

Xu KY, Kuppusamy P. Dual Effects of Copper-Zinc Superoxide Dismutase. Biochem. Biophys. Res. Commun.  (2005) 336:1190-1193

Xu KY. Activation of (Na++K+)-ATPase J. Gen. Physiol. (2005) 126:78-79. 

Xu KY. Activation of Na,K-ATPase Biochem. Biophys. Res. Commun.  (2005)338:1669-1677

Xu KY, Kuppusamy SP, Wang JQ, Li H, Cui, H, Dawson TM, Huang PL, Burnett AL, Kuppusamy P, Becker, LC. Nitric Oxide Protects Cardiac Sarcolemmal Membrane Enzyme Function and Ion Active Transport Against Ischemia Induced Inactivation. J. Biol. Chem. (2003)278: 41798-41803.

Xu KY, Huso DL, Dawson TM, Bredt DS, Becker LC. Nitric Oxide Synthase in Cardiac Sarcoplasmic Reticulum. Proc. Natl. Acad. Sci. (1999)96:657-662.

Xu KY, Zweier JL, Becker LC. Hydroxyl Radical Inhibits Sarcoplasmic Reticulum Ca-ATPase Function by Direct Attack on the ATP Binding Site. Circ. Res. (1997)80:76-81.

Xu KY, Zweier JL, Becker LC. Functional Coupling Between Glycolysis and Sarcoplasmic Reticulum Ca²⁺ Transport. Circ. Res. (1995)77:88-97.