TY - JOUR
T1 - Adenylyl cyclase type 6 overexpression selectively enhances β-adrenergic and prostacyclin receptor-mediated inhibition of cardiac fibroblast function because of colocalization in lipid rafts
AU - Liu, Xiaoqiu
AU - Thangavel, Muthusamy
AU - Sun, Shu Qiang
AU - Kaminsky, Joseph
AU - Mahautmr, Penden
AU - Stitham, Jeremiah
AU - Hwa, John
AU - Ostrom, Rennolds S.
N1 - Funding Information:
Acknowledgments The authors would like to thank Ms. Fengying Li for her technical assistance. This work was supported by grant number HL071781 from the National Institutes of Health (RSO).
PY - 2008/6
Y1 - 2008/6
N2 - Cardiac fibroblasts produce and degrade extracellular matrix and are critical in regulating cardiac remodeling and hypertrophy. Fibroblasts are activated by factors such as transforming growth factor β and inhibited by agents that elevate 3′,5′-cyclic adenosine monophosphate (cAMP) levels. cAMP signal generation and response is known to be compartmentalized in many cell types in part through the colocalization of receptors and specific adenylyl cyclase isoforms in lipid rafts and caveolae. The present study sought to define the localization of key G protein-coupled receptors with adenylyl cyclase type 6 (AC6) in lipid rafts of rat cardiac fibroblasts and to determine if this colocalization was functionally relevant. We found that cardiac fibroblasts produce cAMP in response to agonists for β-adrenergic (isoproterenol), prostaglandin EP2 (butaprost), adenosine (adenosine-5′-N-ethylcarboxamide, NECA), and prostacyclin (beraprost) receptors. Overexpression of AC6 increased cAMP production stimulated by isoproterenol and beraprost but not by butaprost or NECA. A key function of fibroblasts is the production of collagen. Isoproterenol- and beraprostmediated inhibition of collagen synthesis was also enhanced by AC6 overexpression, while inhibition by butaprost and NECA were unaltered. Lipid raft fractions from cardiac fibroblasts contain the preponderance of β-adrenergic receptors and AC6 but exclude EP2 receptors. While we could not determine the localization of native prostacyclin receptors, we were able to determine that epitope-tagged prostanoid IP receptors (IPR) expressed in COS7 cells did localize, in part, in lipid raft fractions. These findings indicate that IP receptors are expressed in lipid rafts and can activate raft-localized AC isoforms. AC6 is completely compartmentized in lipid raft domains where it is activated solely by coresident G protein-coupled receptors to regulate cardiac fibroblast function.
AB - Cardiac fibroblasts produce and degrade extracellular matrix and are critical in regulating cardiac remodeling and hypertrophy. Fibroblasts are activated by factors such as transforming growth factor β and inhibited by agents that elevate 3′,5′-cyclic adenosine monophosphate (cAMP) levels. cAMP signal generation and response is known to be compartmentalized in many cell types in part through the colocalization of receptors and specific adenylyl cyclase isoforms in lipid rafts and caveolae. The present study sought to define the localization of key G protein-coupled receptors with adenylyl cyclase type 6 (AC6) in lipid rafts of rat cardiac fibroblasts and to determine if this colocalization was functionally relevant. We found that cardiac fibroblasts produce cAMP in response to agonists for β-adrenergic (isoproterenol), prostaglandin EP2 (butaprost), adenosine (adenosine-5′-N-ethylcarboxamide, NECA), and prostacyclin (beraprost) receptors. Overexpression of AC6 increased cAMP production stimulated by isoproterenol and beraprost but not by butaprost or NECA. A key function of fibroblasts is the production of collagen. Isoproterenol- and beraprostmediated inhibition of collagen synthesis was also enhanced by AC6 overexpression, while inhibition by butaprost and NECA were unaltered. Lipid raft fractions from cardiac fibroblasts contain the preponderance of β-adrenergic receptors and AC6 but exclude EP2 receptors. While we could not determine the localization of native prostacyclin receptors, we were able to determine that epitope-tagged prostanoid IP receptors (IPR) expressed in COS7 cells did localize, in part, in lipid raft fractions. These findings indicate that IP receptors are expressed in lipid rafts and can activate raft-localized AC isoforms. AC6 is completely compartmentized in lipid raft domains where it is activated solely by coresident G protein-coupled receptors to regulate cardiac fibroblast function.
KW - Caveolae
KW - Collagen
KW - Fibrosis
KW - PGE
KW - PGI
UR - http://www.scopus.com/inward/record.url?scp=45749129007&partnerID=8YFLogxK
U2 - 10.1007/s00210-007-0196-0
DO - 10.1007/s00210-007-0196-0
M3 - Article
C2 - 17934720
AN - SCOPUS:45749129007
SN - 0028-1298
VL - 377
SP - 359
EP - 369
JO - Naunyn-Schmiedeberg's Archives of Pharmacology
JF - Naunyn-Schmiedeberg's Archives of Pharmacology
IS - 4-6
ER -