Membrane association of nitric oxide-sensitive guanylyl cyclase in cardiomyocytes.
OBJECTIVE
Although the importance of the cyclic GMP (cGMP) signaling pathway in cardiac myocytes is well established, little is known about its regulation. Ca2+-dependent translocation of nitric oxide (NO) sensitive guanylyl cyclase (GCNO) to the cell membrane has been recently proposed to play a role. The aim of this study was to determine the possible functional relevance of GCNO bound to the cardiomyocyte membrane.


METHODS
Cytosolic and particulate fractions of adult rat cardiomyocytes were isolated and blotted, and their GCNO activity was assayed in parallel experiments.


RESULTS
In untreated cardiomyocytes, approximately 30% of beta1-and alpha1-subunits of GCNO and a similar proportion of GCNO activity were found in the particulate fraction. The dependence of GCNO activity on pH, Ca2+, GTP and NO donor concentrations was similar in particulate and cytosolic fractions. Treatment of cardiomyocytes with the ionophore A23187 caused GCNO to translocate to the sarcolemma, increased GCNO activity in this fraction, and potentiated NO-mediated cGMP synthesis. These effects appeared to be mediated by Ca2+-dependent changes on the phosphorylation status of GCNO, since they were enhanced by the non-selective inhibitor staurosporine and by the selective inhibitor of Ca2+/calmodulin-dependent protein kinase KN-93. The effect of drugs increasing intracellular Ca2+ on cGMP synthesis was clearly correlated with their effects on membrane-associated GCNO activity but not with their effects on cytosol-associated GCNO.


CONCLUSIONS
These results are the first evidence that 1) GCNO is associated with the cell membrane in cardiomyocytes, 2) the regulation of membrane-associated GCNO differs from that of cytosolic GCNO, and 3) membrane association may have a crucial role in determining the response of cells to NO.
Agulló
Luis
L
Servicio de Cardiología, Hospital Universitari Vall d'Hebron, Pg Vall d'Hebron 129, 08035 Barcelona, Spain.
Garcia-Dorado
David
D
Escalona
Noelia
N
Ruiz-Meana
Marisol
M
Mirabet
Maribel
M
Inserte
Javier
J
Soler-Soler
Jordi
J
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D001596:Benzylamines / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism; D015153:Blotting, Western / Q000379:methods; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D006162:Guanylate Cyclase / Q000032:analysis / Q000378:metabolism*; D007150:Immunohistochemistry / Q000379:methods; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D000096926:Benzenesulfonamides
D015056:1-Methyl-3-isobutylxanthine; D001596:Benzylamines; D002118:Calcium; D006152:Cyclic GMP; D006162:Guanylate Cyclase; D009569:Nitric Oxide; D020030:Nitric Oxide Donors; D010396:Penicillamine; D010726:Phosphodiesterase Inhibitors; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D019311:Staurosporine; D013449:Sulfonamides; C110881:S-nitro-N-acetylpenicillamine; C072105:KN 93; D000096926:Benzenesulfonamides