|
Pharmacology & Physiology |
|
Research Interest |
|
Joshua R. Berlin, PhD |
|
Contact Info: Office Phone: (973) 972-1618 — Lab Phone (973) 972-1490 Dr. Berlin’s Biosketch |
|
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 manisms 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 voltage-dependent 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. |
