Mechanisms underlying the activation of L-type calcium channels by urocortin in rat ventricular myocytes.
OBJECTIVE
The aim of this study was to elucidate the signalling pathways implicated in the modulation of cardiac L-type Ca(2+) channels by urocortin (Ucn) in ventricular myocytes.


RESULTS
Adult rat ventricular myocytes were stimulated in vitro with Ucn for 20-40 min. L-type calcium currents (I(CaL)) were measured with the patch-clamp technique, whereas quantification of activation of extracellular signal-regulated kinases 1/2 (ERK1/2) was assessed by sandwich-ELISA. Ucn induced a significant increase in I(CaL) density that was not prevented by the protein kinase A (PKA) inhibitor KT-5720 or the non-selective antagonist of guanine nucleotide exchange factor brefeldin A. The Ucn effect was antagonized by astressin, a corticotropin-releasing factor receptor-2 (CRF-R2) antagonist, and significantly reduced by protein kinase C (PKC) and ERK1/2 inhibitors. The cyclic AMP (cAMP) analogue 8-pCPT-2'OMe-cAMP, which selectively activates the exchange protein activated by cAMP (Epac), was ineffective in modifying I(CaL). Analysis of phospho-ERK1/2 showed that Ucn induced a significant activation of the ERK1/2 pathway in ventricular myocytes and this effect was prevented by pre-incubation with PKC inhibitors.


CONCLUSIONS
The present study provides evidence of new mechanisms involved in the modulation of L-type Ca(2+) channels by Ucn in adult ventricular myocytes. We propose that the marked increase in I(CaL) density induced by Ucn is mediated through CRF-R2 and involves PKC-dependent activation of the ERK1/2 pathway, whereas PKA and Epac signalling are not implicated.
Smani
Tarik
T
Laboratorio de Investigación Cardiovascular, Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Sevilla 41013, Spain.
Calderón-Sanchez
Eva
E
Gómez-Hurtado
Nieves
N
Fernández-Velasco
María
M
Cachofeiro
Victoria
V
Lahera
Vicente
V
Ordoñez
Antonio
A
Delgado
Carmen
C
D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism*; D006727:Hormone Antagonists / Q000494:pharmacology; D015640:Ion Channel Gating; D008297:Male; D008564:Membrane Potentials; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018019:Receptors, Corticotropin-Releasing Hormone / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D054832:Urocortins / Q000378:metabolism*
C101531:CRF receptor type 2; D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D006727:Hormone Antagonists; D018019:Receptors, Corticotropin-Releasing Hormone; D054832:Urocortins; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3