department of pharmacology

George Dubyak, Ph.D.

dubyak

Professor University Co-Director, CWRU Medical Scientist Training Program

School of Medicine, Robbins Building, 5th Floor
Labs E-550 G, H, I, J
2109 Adelbert Rd.
Case Western Reserve University

Mailing Address:
10900 Euclid Ave.
Cleveland, Ohio 44106-4970

Phone:  (216) 368-5523
Fax: (216) 368-5586
E-mail: gxd3@case.edu

Research

General Description: Diverse types of stress, including mechanical shear, changes in extracellular osmolarity, and hypoxia/ ischemia can induce the release of adenine nucleotides from cells. In turn, locally released adenine nucleotides or their nucleoside metabolites stimulate cell surface receptors in nearby cells, or the releasing cell itself, with the consequent activation of adaptive responses to the particular cellular stress. These responses include cell volume control, vasodilation/ relaxation, hemostasis, secretion of hormones and neurotransmitters, and proinflammatory activation. Fourteen distinct nucleotide receptors, 4 adenosine receptors, and 9 different ecto-nucleotidases have been identified in the human genome. The nucleotide receptors include both G-protein coupled receptors (P2Y class) and ionotropic ATP-gated channel receptors (P2X class). My research group focuses on two fundamental aspects of nucleotide-based signal transduction: 1) the physiological and pathophysiological roles of extracellular ATP in various proinflammatory cascades; and 2) the mechanisms by which ATP and other nucleotides are released into, and metabolized within, extracellular compartments.

Specific Projects

1. We are investigating multiple aspects of nucleotide-based signaling during inflammation with a particular emphasis on the P2X7 receptor, an ATP-gated ion channel that is predominantly expressed in the lymphocytes and macrophages that mediate local proinflammatory responses. We study natively expressed P2X7 receptors, recombinant P2X7 receptors ectopically expressed in various model cell types, and the inflammatory cells derived from P2X7-knockout mice. A current focus is analysis of the signaling mechanisms and proteins that couple P2X7 receptors to the activation of caspase-family proteases involved in either the maturation of inflammatory cytokines (IL-1 β and IL-18) or induction of regulated cell death.

2. We are analyzing how cardiac myocytes, endothelial cells, and astrocytes release and metabolize adenine nucleotides under basal conditions and during stimulation by neurotransmitters, vasoactive hormones, or hypoxic stress. We developing novel protocols that permit quantitative analysis of the nucleotide release and extracellular metabolism with high temporal resolution, and spatial localization. Some of these latter protocols involve optical methods that use engineered luciferase constructs as a highly sensitive on-line sensor of extracellular ATP in particular microenvironments. Another focus is characterization of the particular ecto-nucleotidase genes that are expressed in cardiac, vascular, and inflammatory cell types.

SELECTED REFERENCES:


B.D. Humphreys, J. Rice , S.B. Kertesy, and G.R. Dubyak. SAPK/JNK activation and apoptotic induction by the macrophage P2X7 nucleotide receptor. J. Biol. Chem. 275: 26792-26798, 2000.

R. Beigi and G.R. Dubyak. Endotoxin activation of macrophages does not induce ATP release and autocrine stimulation of P2 nucleotide receptors. J. Immunol. 165: 7189-7198. 2000.

L. Gudipaty, B.D. Humphreys, G. Buell, and G.R. Dubyak. Regulation of P2X7 nucleotide receptor function in human monocytes by extracellular ions and receptor density. Am J. Physiol. Cell. 280: C943-C953. 2001.

L.C. Denlinger, P.L. Fisette, J.A. Sommer, J.J. Watters, U. Prabhu, R.A. Proctor, G.R. Dubyak and P.J. Bertics. Cutting Edge: The nucleotide receptor P2X7 contains multiple protein- and lipid-interaction motifs including a potential binding site for bacterial lipopolysaccharide. J. Immunol. 167; 1871-1876. 2001.

R.G. Ravi. S.B. Kertesy, G.R. Dubyak, and K.A. Jacobson. Potent P2X7 receptor antagonists: Tyrosyl derivatives synthesized using a sequential parallel synthetic approach. Drug Dev. Res. 54: 75-87. 2001.

D.H. Canaday, R. Beigi, R.F. Silver, C.V. Harding, W.H. Boom, and G.R. Dubyak. ATP and control of intracellular growth of Mycobacteria by T cells. Infection and Immunity. 70: 6456-6459 2002.

G..R. Dubyak. Perspective: Knock-out mice reveal tissue-specific roles of P2Y receptor subtypes in different epithelia. Mol. Pharmacol. 63: 773-776. 2003

P.A. Verhoef, M. Estacion, W. Schilling, and G.R. Dubyak. P2X7 Receptor-Dependent Blebbing and the Activation of Rho-effector Kinases, Caspases, and IL-1? Release. J. Immunol. 170: 5728-5738. 2003

S.M. Joseph, M.R. Buchakjian, and G.R. Dubyak. Colocalization of ATP release sites and ecto-ATPase activity at the extracellular surface of human astrocytes. J. Biol. Chem. 278: 23331-23342. 2003.

L. Gudipaty, J. Munetz, P.A. Verhoef, and G.R. Dubyak. Essential role for Ca2+ in the regulation of IL-1? secretion by the P2X7 nucleotide receptor in monocytes, macrophages, and HEK293 fibroblasts. Am J. Physiol. Cell. 285:C286-299. 2003.

L.C. Denlinger, J.A. Sommer, K. Parker, L. Gudipaty, P.L. Fisette, J.J. Watters, R.A. Proctor, G.R. Dubyak and P.J. Bertics. Mutation of a dibasic amino acid motif within the C-terminus of the P2X7 nucleotide receptor results in trafficking defects and impaired function. J. Immunol. 171: 1304-1311. 2003.

R.D. Beigi, S.B. Kertesy, G. Aquilina, and G.R. Dubyak. Oxidized ATP (oATP) attenuates proinflammatory signaling via P2 receptor-independent mechanisms. Br. J. Pharmacol. 140: 507-519. 2003.