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Simvastatin improves vascular endothelial functions via calmodulin‐dependent activities
Author(s) -
TRAN KIM,
GILES JENNIFER
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.lb526
Subject(s) - simvastatin , enos , calmodulin , hek 293 cells , mutant , transfection , microbiology and biotechnology , chemistry , phosphorylation , cerivastatin , pharmacology , biochemistry , biology , enzyme , reductase , receptor , nitric oxide synthase , gene
Calmodulin is required for the activity of many cellular proteins. We hypothesized that HMG‐CoA reductase inhibitors improve endothelial functions partly via CaM‐dependent activities. At therapeutic doses, simvastatin upregulates CaM expression in primary endothelial cells up to 250%. This effect is produced by both active and inactive simvastatin, and is also observed with atorvastatin, suggesting that it is general for statins, but independent of a cholesterol‐lowering effect. The increased CaM expression is associated with an increase in the interaction between CaM and the plasma membrane Ca 2+ ‐ATPase as well as dynamic PMCA activity. Simvastatin phosphorylates the dominant CaM target eNOS at Ser‐617, Ser‐635 and Ser‐1179. Simvastatin upregulates total CaM expression in HEK 293 cells stably expressing eNOS, but to a negligible extent in non‐transfected cells, suggesting that the increased CaM expression in endothelial cells is mediated by the effect of simvastatin on eNOS. At similar free Ca 2+ concentrations, HEK 293 cells expressing an S617D/S635D/S1179DeNOS mutant produce higher free Ca 2+ ‐CaM levels than cells expressing the S617A/S635A/S1179AeNOS mutant. In‐vitro competitive binding assays revealed that the S617D/S635D/S1179DeNOS mutant displays a 3‐fold increase in the Ca 2+ sensitivity for complex formation with CaM compared to WTeNOS, lowering the EC50(Ca 2+ ) to a value well within the basal Ca 2+ level in cells. Our data strongly indicate that via phosphorylation‐dependent increases Ca 2+ ‐CaM sensitivity of the dominant CaM binding protein eNOS, simvastatin increases CaM expression and CaM‐dependent functions in endothelial cells. We suggest a general mechanism that cellular CaM expression is governed partly by its requirement at basal Ca 2+ concentrations.