Download Joshua Berlin, Ph.D. Department of Pharmacology and Physiology

Joshua Berlin, Ph.D.
Department of Pharmacology and Physiology
UMDNJ - New Jersey Medical School
Medical Sciences Building, I621/I623/I625
185 S. Orange Avenue
Newark, NJ 07103
(973) 972-1618/1490 Office/Lab
(973) 972-7950 Fax
[email protected]
Electrogenic Ion Transport and Muscle Excitation-Contraction Coupling
Research projects in my laboratory are directed at answering fundamental questions that
have broad implications for cell function. We are currently
studying mechanisms of active electrogenic ion transport and
muscle excitation-contraction coupling using biophysical,
biochemical and molecular biological techniques.
Our goal is to determine which amino acid residues of the
enzyme are responsible for ion coordination and voltagedependent ion binding reactions and, in doing so, identify the
changes in enzyme conformations that underlie ion transport
reaction steps. Voltage-dependent reactions steps involved in
active ion transport are studied by measuring steady state
and transient kinetics of Na+ and K+ transport by the Na,K-ATPase. These experiments
utilize patch-clamp techniques with single cardiac myocytes and HeLa cells expressing
Na,K-ATPase enzymes that contain mutations in membrane spanning regions of the
protein. This project should allow us to pinpoint the molecular mechanism of ion transport
by the Na,K-ATPase and will also serve as a guide for studying transport by other ion
pumps. Our second area of investigation is cardiac muscle excitation-contraction
coupling, the process by which the cardiac action potential triggers muscle contraction.
We are studying how Ca2+ influx controls sarcoplasmic reticulum Ca 2+ release and the
role of positive feedback mechanisms in amplifying sarcoplasmic reticulum Ca2+ release
under normal and pathologic conditions. In these studies, whole-cell patch-clamp
techniques are combined with confocal microscopy and microfluorimetry to
simultaneously measure membrane currents, subcellular changes in intracellular ion
(Ca2+, Mg2+, H+, Na+) concentration and cell contraction. The resulting data are
incorporated into computer models that calculate cellular Ca2+ movements so that we
can understand how individual Ca2+-dependent mechanism contribute to the excitation-
contraction coupling process. This combination of experimental and analytical
approaches allows us to carefully characterize the kinetically complex changes of
intracellular Ca2+ that underlie muscle contraction.
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Peluffo RD, Arguello JM, Lingrel JB, Berlin JR. Electrogenic sodium-sodium
exchange carried out by NaK-ATPase containing the amino acid substitution
Glu779Ala. J. Gen. Physiol. 116: 61-73, 2000.
Link: http://www.jgp.org/cgi/reprint/116/1/61.pdf
Yasukochi M, Uehara A, Kobayashi S, Berlin JR. Ca2+ and voltage dependence
of cardiac ryanodine receptor channel block by sphingosylphosphorylcholine.
Pflügers Archiv. 445: 665-73m 2003.
Link: http://www.springerlink.com/app/home/content
Peluffo RD, Berlin JR. Na,K-pump reaction kinetics at the tip of a patch electrode:
Derivation of reactions kinetics for electrogenic and electrically-silent reactions
during ion transport by the Na,K-ATPase. Ann NY Acad. Sci. 986: 141-49, 2003.