Signaling pathways that control rho kinase activity maintain the embryonic epicardial progenitor state.
This study identifies signaling pathways that play key roles in the formation and maintenance of epicardial cells, a source of progenitors for coronary smooth muscle cells (SMCs). After epithelial to mesenchymal transition (EMT), mesenchymal cells invade the myocardium to form coronary SMCs. RhoA/Rho kinase activity is required for EMT and for differentiation into coronary SMCs, whereas cAMP activity is known to inhibit EMT in epithelial cells by an unknown mechanism. We use outgrowth of epicardial cells from E9.5 isolated mouse proepicardium (PE) explants, wild type and Epac1 null E12.5 mouse heart explants, adult rat epicardial cells, and immortalized mouse embryonic epicardial cells as model systems to identify signaling pathways that regulate RhoA activity to maintain the epicardial progenitor state. We demonstrate that RhoA activity is suppressed in the epicardial progenitor state, that the cAMP-dependent Rap1 GTP exchange factor (GEF), Epac, known to down-regulate RhoA activity through activation of Rap1 GTPase activity increased, that Rap1 activity increased, and that expression of the RhoA antagonistic Rnd proteins known to activate p190RhoGAP increased and associated with p190RhoGAP. Finally, EMT is associated with increased p63RhoGEF and RhoGEF-H1 protein expression, increased GEF-H1 activity, with a trend in increased p63RhoGEF activity. EMT is suppressed by partial silencing of p63RhoGEF and GEF-H1. In conclusion, we have identified new signaling molecules that act together to control RhoA activity and play critical roles in the maintenance of coronary smooth muscle progenitor cells in the embryonic epicardium. We suggest that their eventual manipulation could promote revascularization after myocardial injury.
From the Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908 and.
Mykhaylo V
MV
Artamonov
From the Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908 and.
Li
L
Jin
From the Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908 and.
Aaron S
AS
Franke
From the Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908 and.
Ko
K
Momotani
From the Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908 and.
Ruoya
R
Ho
Seattle Children's Research Institute, Seattle, Washington 98101.
Xiu Rong
XR
Dong
Seattle Children's Research Institute, Seattle, Washington 98101.
Mark W
MW
Majesky
From the Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908 and avs5u@virginia.edu.
Avril V
AV
Somlyo
D000818:Animals; D002454:Cell Differentiation; D004622:Embryo, Mammalian; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D010496:Pericardium / Q000166:cytology / Q000378:metabolism*; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D046509:Tissue Culture Techniques; D020741:rho GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D020742:rhoA GTP-Binding Protein
C513041:Arhgap35 protein, mouse; C577402:Arhgef2 protein, mouse; C482601:Epac protein, mouse; C577427:GEFT protein, mouse; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; C526380:RhoA protein, mouse; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein
Cardiovascular; Epac; Epicardial Cells; Epithelial to Mesenchymal Transformation; Guanine Nucleotide Exchange Factor (GEF); Ras Homolog Gene Family, Member A (RhoA); Rnds; Signal Transduction; Transformation; p190RhoGAP