1986 — 1990 |
Liang, Bruce T |
K11Activity Code Description: Undocumented code - click on the grant title for more information. |
Role of Protein Phosphorylation in Cultured Heart Cells @ University of Pennsylvania
The main objective is to investigate the role of cardiac phosphoproteins in the modulation of cardiac function and excitability. These studies are proposed to test the hypotheses that cardiac phosphoproteins modulate cardiac function by mediating changes in calcium and potassium permeability as well as in the force and rate of contraction and that the phosphoproteins serve as the locus of interaction between beta-adrenergic and muscarinic cholinergic inputs to the heart. The proposed studies will use monolayer heart cells cultured from embryonic chick heart, which provide the advantage of permitting measurement at intervals as short as five seconds and hence the ability to obtain accurate time course analysis. The specific goals of these studies are to determine whether: 1) a subunit of the cardiac calcium channel becomes phosphorylated in response to isoproterenol and mediates the increase in calcium influx (measured as 45Ca++ influx rate) and contractility; 2) a close correlation exists between the time course of appearance of the phosphorylation of calcium channel subunit and other phosphoproteins (protein C and phospholamban) and that of development of the respective physiologic responses and whether a close correlation also exists between the time course of reversal of the phosphorylation of these proteins and that of reversal of the respective physiologic responses; 3) the muscarinic agonist carbachol antagonizes isoproterenol-stimulated physiologic responses by dephosphorylating the calcium channel subunit, phospholamban and protein C; 4) the coupling of muscarinic receptor to the inhibition of cAMP accumulation and the inhibition of calcium channel phosphorylation differs between the atria and the ventricle and whether the physiologic effects caused by the inhibition of cAMP formation differ between the atria and the ventricle; 5) one of the cardiac physiologic functions of protein kinase C is to modulate the physiologic responses to beta-adrenergic and muscarinic cholinergic agonists by phosphorylating its respective receptors or its respective GTP-binding proteins. These studies should enhance our understanding of the molecular basis of cholinergic-adrenergic interaction in modulating the inotropic and chronotropic state in the heart and should provide insights into the events important in predisposing to brady-and tachyarrhythmia.
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0.951 |
1989 — 1993 |
Liang, Bruce T |
R29Activity Code Description: Undocumented code - click on the grant title for more information. |
Ai Adenosine Receptor in Cultured Heart Cells @ University of Pennsylvania
The main objectives of the present study are to study the process and mechanism of desensitization and sensitization of the cardiac A1 adenosine receptor (A1AR)-mediated physiologic response, to determine whether changes in the levels of A1AR and/or the high-affinity form of the A1AR regulate physiologic responsiveness of the heart to A1AR agonist stimulation, and to determine the molecular mechanism(s) by which activation of A1AR causes the A1AR-mediated contractile response. Monolayer atrial cells cultured from 14 day chick embryo will be used as a model system. Specifically, we will: a) characterize the functional responses elicited by A1AR agonist stimulation; b) carry out biochemical studies of the binding of radioligand antagonist and agonist to the A1AR in membranes of these cultures cells. We will further determine whether 1) A1AR are coupled to the various potential effectors such as the adenylate cyclase, phosphodiesterase, guanylate cyclase or the potassium channel, and we will study the role of these potential effectors in mediating the contractile effects of A1AR agonist; 2) pertussis toxin-sensitive GTP-binding protein(s) is involved in the coupling between A1AR and the various effectors; 3) chronic exposure of cultured atrial cells to A1AR agonist causes attenuation of the A1AR- mediated functional responses and whether such decreased responsiveness is associated with a conversion of the high-affinity A1AR to a low-affinity form, a downregulation of the A1AR, or both; 4) chronic treatment of the culture with an adenosine receptor antagonist or adenosine deaminase induces sensitization of the A1AR-mediated functional response by causing the conversion of low-affinity A1AR to a high-affinity form, an upregulation of the receptor or by both mechanisms; 5) desensitization of A1AR is accompanied by a compensatory increase in the level of stimulatory G protein (Gs) or beta-adrenergic receptors (beta AR) with a concomitant increase in responsiveness to beta-adrenergic stimulation; 6) on the other hand, sensitization of these inhibitory receptors is associated with a compensatory decrease in the level of Gs or beta AR with concomitant decrease in beta-adrenergic responsiveness. These studies should help elucidate the mechanism of sensitization and desensitization of the A1AR system as well as the role of the regulation of A1AR and its high-affinity form in modulating the sensitivity of atrial myocytes to A1AR agonist stimulation. They should also provide insights into the mechanisms responsible for the cellular action of adenosine.
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0.951 |
1993 — 2005 |
Liang, Bruce T |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Purinergic Signaling in Cultured Heart Cells @ University of Connecticut Sch of Med/Dnt
[unreadable] DESCRIPTION (provided by applicant): The overall objectives of the present study are to elucidate basic signaling mechanisms in the adenosine A1 and A3 receptor pathways, to define the interaction between A1R, A3R and A2AR on the myocyte, and to delineate the mechanisms underlying these potentially important interactions. Pharmacological, functional and cellular approaches as well as novel cardiac models based on transfected chick cardiac cells and intact mouse heart preparations will be used. Specifically, the study will 1) test the hypothesis that the A3R signals via Ga12 or Ga13 to activate RhoA, which in turn stimulates phospholipase D (PLD, likely PLD1) and causes cardioprotection, 2) determine the function of ADP-ribosylation factor (ARF) and its potential interaction with RhoA in mediating these A3 responses in intact cardiac myocytes, 3) test the role of Rho kinase, PIP2 level and cytoskeleton as well as that of a direct RhoA-PLD1 interaction in mediating the A3 responses, 4) characterize the role of A2AR in modulating the protective effects mediated via A1 and A3 receptors and determine the mechanism by which this modulation occurs, 5) investigate the mechanistic basis of the synergistic interaction between the A1 and A3 receptors, 6) determine whether activation of the A1R enhances the signaling in the A3R pathway or whether the synergism arises from a facilitating effect of activated A3R on the A1R signaling, 7) test the hypotheses that the phosphatidylinositol-derived diacylglycerol (from the A1R coupled phospholipase C) and its subsequent activation of PKC play an important role in enhancing the A3R -RhoA-PLD signaling and that a diacylglycerol-initiated positive PKC-KATP channel feedback Ioop is also an important mechanism in mediating the synergism between the two receptors. The cDNAs encoding constitutively active and dominant negative mutants of the various signaling molecules as well as selective activators and inhibitors at these molecules will be used in delineating the signaling cascades in the intact myocyte. Phospholipase CBeta2-, Beta3 and Beta2/Beta3-null mice, in conjunction with pharmacological inhibitors of PLD and adenosine receptor-selective agents, will be used to further delineate the signaling role of phospholipase C in mediating the cardioprotective effect of A1 and A3 receptors. The studies should provide novel insights into the cardiac actions of adenosine as well as the basic signaling mechanism(s). They should also contribute to our understanding of the signaling pathway and the mechanism by which cardioprotection and ischemic preconditioning occur.
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0.978 |
2004 |
Liang, Bruce T |
M01Activity Code Description: An award made to an institution solely for the support of a General Clinical Research Center where scientists conduct studies on a wide range of human diseases using the full spectrum of the biomedical sciences. Costs underwritten by these grants include those for renovation, for operational expenses such as staff salaries, equipment, and supplies, and for hospitalization. A General Clinical Research Center is a discrete unit of research beds separated from the general care wards. |
Feasibility Study - Adenosine Transporter Function @ University of Connecticut Sch of Med/Dnt
neurotransmitter transport; adenosine; membrane transport proteins; protein structure function; cardiovascular pharmacology; coronary vasodilator; dipyridamole; clinical research; human subject;
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0.978 |