Many known and unknown ligands for G protein coupled receptors, released in the heart in response to stress, converge on RhoA activation, making it a nodal point in determining cardiomyocyte responses. The overall goal of this proposal is to demonstrate that activation of RhoA signaling provides cardioprotection against ischemic injury and to elucidate the molecular mechanisms by which this occurs. The specific focus is on the cardiomyocyte and an early time window, distinct from later effects of RhoA signaling pathways on fibroblasts and leukocytes, which may in fact be deleterious. The proposal examines direct RhoA targets, early genetic responses and mitochondrial involvement in cardioprotection by RhoA. The proposed work is divided into three Specific Aims.
Aim #1 characterizes several lines of transgenic mice expressing constitutively active RhoA in an inducible cardiac specific manner, comparing the ability of RhoA expression to provide protection against ischemia/reperfusion (I/R) injury in the ex vivo perfused heart, and extending this work to examine contractile function and susceptibility to I/R injury, inflammation and apoptotic gene expression in vivo. Studies using mice in which the upstream regulator of RhoA, G112, is deleted, are also proposed as are studies using RhoA knockout mice.
Aim #2 examines mediators of RhoA induced cardioprotection. One pathway examined is the activation of FAK and Akt through Rho kinase (ROCK). Two novel RhoA targets, the matricellular protein CCN1, which works through integrin signaling, and PLC epsilon which activates PKC epsilon and PKD, are also examined for their role as downstream effectors of RhoA signaling and mediators of protection in the heart. Finally three RhoA regulated transcription factors (cJun, NFKB, MRTF-A) are considered as targets of RhoA in the heart. Experiments are designed to determine if these pathways are differentially activated in tTA control vs. RhoA TG mice, and during ex vivo or in vivo I/R, and to examine the protective roles of these pathways using pharmacological inhibitors or, for PLC epsilon and CCN1, knockout mice.
Aim #3 considers a unique aspect of RhoA function in the heart i.e. its localization at mitochondria, as demonstrated by its presence in the mitochondrial heart proteome and by subcellular fractionation studies. Questions addressed include whether activation of RhoA alters its appearance at mitochondria, whether RhoA affects mitochondrial permeability transition (MPT) and associates with MPT components, whether mitochondrial structure and localization, as detected by electron microscopy, differ when RhoA at mitochondria is increased, whether RhoA associates with mitochondrial fission/fusion proteins or motility regulators, and whether RhoA affects mitochondrial metabolism. The significance of this research is that it could provide evidence that activation of RhoA and its novel effectors, at early times following ischemia reperfusion, are therapeutic target for preventing ischemic damage and improving contractile recovery of the heart.

Public Health Relevance

Ischemic heart disease, characterized by loss of blood flow and oxygenation, is a major cause of death worldwide. Current treatment of heart attacks involve restoration of blood flow and this reperfusion provides both protective and damaging signals. We are exploring a novel protective signal, the activation of RhoA and its downstream targets, which has the potential to be used as a therapeutic strategy to diminish loss of cardiac tissue and contractile function during reperfusion.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
2R37HL028143-26
Application #
7921891
Study Section
Myocardial Ischemia and Metabolism Study Section (MIM)
Program Officer
Schwartz, Lisa
Project Start
1982-08-01
Project End
2015-03-31
Budget Start
2010-04-02
Budget End
2011-03-31
Support Year
26
Fiscal Year
2010
Total Cost
$386,250
Indirect Cost
Name
University of California San Diego
Department
Pharmacology
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Suetomi, Takeshi; Willeford, Andrew; Brand, Cameron S et al. (2018) Inflammation and NLRP3 Inflammasome Activation Initiated in Response to Pressure Overload by Ca2+/Calmodulin-Dependent Protein Kinase II ? Signaling in Cardiomyocytes Are Essential for Adverse Cardiac Remodeling. Circulation 138:2530-2544
Willeford, Andrew; Suetomi, Takeshi; Nickle, Audrey et al. (2018) CaMKII?-mediated inflammatory gene expression and inflammasome activation in cardiomyocytes initiate inflammation and induce fibrosis. JCI Insight 3:
Yu, Olivia M; Benitez, Jorge A; Plouffe, Steven W et al. (2018) YAP and MRTF-A, transcriptional co-activators of RhoA-mediated gene expression, are critical for glioblastoma tumorigenicity. Oncogene 37:5492-5507
Brand, Cameron S; Tan, Valerie P; Brown, Joan Heller et al. (2018) RhoA regulates Drp1 mediated mitochondrial fission through ROCK to protect cardiomyocytes. Cell Signal 50:48-57
Dusaban, Stephanie S; Chun, Jerold; Rosen, Hugh et al. (2017) Sphingosine 1-phosphate receptor 3 and RhoA signaling mediate inflammatory gene expression in astrocytes. J Neuroinflammation 14:111
Yung, Bryan S; Brand, Cameron S; Xiang, Sunny Y et al. (2017) Selective coupling of the S1P3 receptor subtype to S1P-mediated RhoA activation and cardioprotection. J Mol Cell Cardiol 103:1-10
Sanna, M Germana; Vincent, Kevin P; Repetto, Emanuela et al. (2016) Bitopic Sphingosine 1-Phosphate Receptor 3 (S1P3) Antagonist Rescue from Complete Heart Block: Pharmacological and Genetic Evidence for Direct S1P3 Regulation of Mouse Cardiac Conduction. Mol Pharmacol 89:176-86
Yu, Olivia M; Miyamoto, Shigeki; Brown, Joan Heller (2016) Myocardin-Related Transcription Factor A and Yes-Associated Protein Exert Dual Control in G Protein-Coupled Receptor- and RhoA-Mediated Transcriptional Regulation and Cell Proliferation. Mol Cell Biol 36:39-49
Castaldi, Alessandra; Chesini, Gino P; Taylor, Amy E et al. (2016) Sphingosine 1-phosphate elicits RhoA-dependent proliferation and MRTF-A mediated gene induction in CPCs. Cell Signal 28:871-9
Miyamoto, Shigeki; Brown, Joan Heller (2016) Drp1 and Mitochondrial Autophagy Lend a Helping Hand in Adaptation to Pressure Overload. Circulation 133:1225-7

Showing the most recent 10 out of 34 publications