title: Inhibition of SERCA pumps induces desynchronized RyR activation in overloaded internal Ca2+ stores in smooth muscle cells.
abstract: We have previously shown that rapid inhibition of sarcoplasmic reticulum (SR) ATPase (SERCA pumps) decreases the amplitude and rate of rise (synchronization) of caffeine induced-Ca(2+) release without producing a reduction of free luminal SR Ca(2+) level in smooth muscle cells (Gómez-Viquez L, Guerrero-Serna G, García U, Guerrero-Hernández A. Biophys J 85: 370-380, 2003). Our aim was to investigate the role of luminal SR Ca(2+) content in the communication between ryanodine receptors (RyRs) and SERCA pumps. To this end, we studied the effect of SERCA pump inhibition on RyR-mediated Ca(2+) release in smooth muscle cells with overloaded SR Ca(2+) stores. Under this condition, the amplitude of RyR-mediated Ca(2+) release was not affected but the rate of rise was still decreased. In addition, the caffeine-induced Ca(2+)-dependent K(+) outward currents revealed individual events, suggesting that SERCA pump inhibition reduces the coordinated activation of RyRs. Collectively, our results indicate that SERCA pumps facilitate the activation of RyRs by a mechanism that does not involve the regulation of SR Ca(2+) content. Importantly, SERCA pumps and RyRs colocalize in smooth muscle cells, suggesting a possible local communication between these two proteins.
authors.affiliation: Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados-Instituto Politécnico Nacional, Mexico City, Mexico.
authors.forename: Norma Leticia
authors.initials: NL
authors.lastname: Gómez-Viquez
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Guerrero-Serna
authors.forename: Fernando
authors.initials: F
authors.lastname: Arvizu
authors.forename: Ubaldo
authors.initials: U
authors.lastname: García
authors.forename: Agustín
authors.initials: A
authors.lastname: Guerrero-Hernández
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D006168:Guinea Pigs; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D002120:Calcium Channel Agonists; D004791:Enzyme Inhibitors; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D019284:Thapsigargin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium