Insulin-like growth factor-1 and PTEN deletion enhance cardiac L-type Ca2+ currents via increased PI3Kalpha/PKB signaling.
Ca2+ influx through the L-type Ca2+ channel (I(Ca,L)) is a key determinant of cardiac contractility and is modulated by multiple signaling pathways. Because the regulation of I(Ca,L) by phosphoinositide-3-kinases (PI3Ks) and phosphoinositide-3-phosphatase (PTEN) is unknown, despite their involvement in the regulation of myocardial growth and contractility, I(Ca,L) was recorded in myocytes isolated from mice overexpressing a dominant-negative p110alpha mutant (DN-p110alpha) in the heart, lacking the PI3Kgamma gene (PI3Kgamma(-/-)) or with muscle-specific ablation of PTEN (PTEN(-/-)). Combinations of these genetically altered mice were also examined. Although there were no differences in the expression level of CaV1.2 proteins, basal I(Ca,L) densities were larger (P<0.01) in PTEN(-/-) myocytes compared with littermate controls, PI3Kgamma(-/-), or DN-p110alpha myocytes and showed negative shifts in voltage dependence of current activation. The I(Ca,L) differences seen in PTEN(-/-) mice were eliminated by pharmacological inhibition of either PI3Ks or protein kinase B (PKB) as well as in PTEN(-/-)/DN-p110alpha double mutant mice but not in PTEN(-/-)/PI3Kgamma(-/-) mice. On the other hand, application of insulin-like growth factor-1 (IGF-1), an activator of PKB, increased I(Ca,L) in control and PI3Kgamma(-/-), while having no effects on I(Ca,L) in DN-p110alpha or PTEN(-/-) mice. The I(Ca,L) increases induced by IGF-1 were abolished by PKB inhibition. Our results demonstrate that IGF-1 treatment or inactivation of PTEN enhances I(Ca,L) via PI3Kalpha-dependent increase in PKB activation.
Sun
Hui
H
Department of Physiology, University Health Network, University of Toronto, Canada.
Kerfant
Benoit-Gilles
BG
Zhao
Dongling
D
Trivieri
Maria G
MG
Oudit
Gavin Y
GY
Penninger
Josef M
JM
Backx
Peter H
PH
D000818:Animals; D020746:Calcium Channels, L-Type / Q000502:physiology*; D058534:Class I Phosphatidylinositol 3-Kinases; D004553:Electric Conductivity; D017353:Gene Deletion; D005799:Genes, Dominant; D007334:Insulin-Like Growth Factor I / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009206:Myocardium / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000172:deficiency* / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
D020746:Calcium Channels, L-Type; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; C509622:1-phosphatidylinositol 3-kinase p110 subunit, mouse; D058534:Class I Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse