Published online before print August 25, 2005, doi: 10.1161/01.RES.0000183880.49270.f9
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
© 2005 American Heart Association, Inc.
Cellular Biology |
Enhanced Functional Gap Junction Neoformation by Protein Kinase A–Dependent and Epac-Dependent Signals Downstream of cAMP in Cardiac Myocytes
From the Department of Structural Analysis (S.F., Y.N., H.F., N.M.), National Cardiovascular Center Research Institute, Suita, Osaka; the First Department of Internal Medicine (S.S., Y.S.), Nara Medical University, Kashihara, Nara, Japan.
Correspondence to Naoki Mochizuki, Department of Structural Analysis, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka 565-8565, Japan. E-mail nmochizu{at}ri.ncvc.go.jp
Gap junctions (GJs) constituted by neighboring cardiac myocytes are essential for gating ions and small molecules to coordinate cardiac contractions. cAMP is suggested to be a potent stimulus for enhancement of GJ function. However, it remains elusive how cAMP potentiates the GJ of cardiomyocytes. Here we demonstrated that the gating function of GJ is enhanced by the protein kinase A (PKA)–dependent signal, and that the accumulation of connexin43 (Cx43), the most abundant Cx in myocytes, is enhanced by an exchange protein directly activated by cAMP (Epac) (Rap1 activator)–dependent signal. The gating function of GJs was analyzed by microinjected dye transfer method. The accumulation of Cx43 was analyzed by quantitative immunostaining. Using the PKA-specific activator N6-benzoyladenosine-3',5'-cyclic monophosphate (6Bnz) and Epac-specific activator 8-(4-chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8CPT), we could delineate the two important downstream signals of cAMP for enhanced GJ neoformation. Whereas 6Bnz potentiated gating function of GJs with slight accumulation of Cx43 at cell–cell contacts, 8CPT remarkably enhanced the accumulation of Cx43 with a slight effect on gating. We further noticed that adherens junctions (AJs) were maturated by 8CPT, as marked by increased neural-cadherin immunostaining. Because AJ formation precedes the GJ formation, AJ formation accelerated by Epac-Rap1 signal may result in enhanced GJ formation. The involvement of Epac-Rap1 signal in GJ neoformation was further confirmed by evidence that inactivation of Rap1 by overexpression of Rap1GAP1b perturbed the accumulation of Cx43 at cell–cell contacts. Collectively, PKA and Epac cooperatively enhance functional GJ neoformation in cardiomyocytes.
Key Words: gap junction • connexin43 • myocardial structure • cardiac gap junction connexins
This article has been cited by other articles:
 |
|
 |
|
  R. Hanstein, J. Trotter, C. Behl, and A. B. Clement Increased Connexin 43 Expression as a Potential Mediator of the Neuroprotective Activity of the Corticotropin-Releasing Hormone Mol. Endocrinol., September 1, 2009; 23(9): 1479 - 1493. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 O. Cazorla, A. Lucas, F. Poirier, A. Lacampagne, and F. Lezoualc'h The cAMP binding protein Epac regulates cardiac myofilament function PNAS, August 18, 2009; 106(33): 14144 - 14149. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Ponsioen, M. Gloerich, L. Ritsma, H. Rehmann, J. L. Bos, and K. Jalink Direct Spatial Control of Epac1 by Cyclic AMP Mol. Cell. Biol., May 15, 2009; 29(10): 2521 - 2531. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.-C. Lissitzky, D. Parriaux, E. Ristorcelli, A. Verine, D. Lombardo, and P. Verrando Cyclic AMP Signaling as a Mediator of Vasculogenic Mimicry in Aggressive Human Melanoma Cells In vitro Cancer Res., February 1, 2009; 69(3): 802 - 809. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Li, I. B. M. Konings, J. Zhao, L. S. Price, E. de Heer, and P. M. T. Deen Renal expression of exchange protein directly activated by cAMP (Epac) 1 and 2 Am J Physiol Renal Physiol, August 1, 2008; 295(2): F525 - F533. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Metrich, A. Lucas, M. Gastineau, J.-L. Samuel, C. Heymes, E. Morel, and F. Lezoualc'h Epac Mediates {beta}-Adrenergic Receptor-Induced Cardiomyocyte Hypertrophy Circ. Res., April 25, 2008; 102(8): 959 - 965. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Dremier, M. Milenkovic, S. Blancquaert, J. E. Dumont, S. O. Doskeland, C. Maenhaut, and P. P. Roger Cyclic Adenosine 3',5'-Monophosphate (cAMP)-Dependent Protein Kinases, But Not Exchange Proteins Directly Activated by cAMP (Epac), Mediate Thyrotropin/cAMP-Dependent Regulation of Thyroid Cells Endocrinology, October 1, 2007; 148(10): 4612 - 4622. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Pereira, M. Metrich, M. Fernandez-Velasco, A. Lucas, J. Leroy, R. Perrier, E. Morel, R. Fischmeister, S. Richard, J.-P. Benitah, et al. The cAMP binding protein Epac modulates Ca2+ sparks by a Ca2+/calmodulin kinase signalling pathway in rat cardiac myocytes J. Physiol., September 1, 2007; 583(2): 685 - 694. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Ulucan, X. Wang, E. Baljinnyam, Y. Bai, S. Okumura, M. Sato, S. Minamisawa, S. Hirotani, and Y. Ishikawa Developmental changes in gene expression of Epac and its upregulation in myocardial hypertrophy Am J Physiol Heart Circ Physiol, September 1, 2007; 293(3): H1662 - H1672. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. R. H. Kooistra, N. Dube, and J. L. Bos Rap1: a key regulator in cell-cell junction formation J. Cell Sci., January 1, 2007; 120(1): 17 - 22. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. G. Holz, G. Kang, M. Harbeck, M. W. Roe, and O. G. Chepurny Cell physiology of cAMP sensor Epac J. Physiol., November 15, 2006; 577(1): 5 - 15. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Kang, O. G. Chepurny, B. Malester, M. J. Rindler, H. Rehmann, J. L. Bos, F. Schwede, W. A. Coetzee, and G. G. Holz cAMP sensor Epac as a determinant of ATP-sensitive potassium channel activity in human pancreatic {beta} cells and rat INS-1 cells J. Physiol., June 15, 2006; 573(3): 595 - 609. [Abstract] [Full Text] [PDF]
|
|