Abstract 16307: Connexin-43 Contributes to Transmission of MitoKATP Channel-Derived Redox Signal to Akt-GSK-3β Pathway in Cardiomyocyte Protection Afforded by G-protein Coupled Receptors
Background: Connexin-43 (Cx43) in mitochondria reportedly plays a crucial role in activation of the mitochondrial ATP-sensitive K+ channel (mKATP), which triggers reactive oxygen species (ROS)-mediated signaling. Here we examined the hypothesis that roles of non-gap junctional Cx43 and the mKATP differ between protection afforded by G-protein coupled receptors (GPCRs) and that afforded by cytokine receptors.
Methods and Results: In H9c2 cardiomyocytes, treatment with endothelin-1 (ET-1, 10 nM), [D-Ala2,D-Leu5]-enkephalin acetate (DADLE, 300 nM) or insulin-like growth factor-1 (IGF-1, 10 nM) induced phosphorylation of Akt at Ser473 and phosphorylation of glycogen synthase kinase-3β (GSK-3β) at Ser9. Cell necrosis after hypoxia-reoxygenation and that after incubation with antimycin A were significantly suppressed to approximately 30∼40% by ET-1, DALDE or IGF-1. Knockdown of Cx43 expression by siRNA abrogated phosphorylation of Akt and GSK-3β and cytoprotection by ET-1 and by DADLE, though responses of the kinases to IGF-1 and cytoprotection by IGF-1 were preserved. ET-1 and DADLE induced ROS production by activated mKATP, which was monitored by MitoTracker Red, though such ROS production was not induced by IGF-1. In contrast to our assumption, Cx43 knockdown did not eliminate ROS production by ET-1 or DADLE. Cx43 knockdown did not abolish ET-1-induced phosphorylation of PKC-ε and ERK1/2.
Conclusion: The findings suggest that non-gap junctional Cx43 molecules play a significant role in transmission of signal from PKC-ε activated by mKATP-derived ROS to Akt-GSK-3β pathway, leading to cell tolerance against necrosis. This role of Cx43 is specific to GPCR-triggered cytoprotection and is not required for the IGF-1 receptor to afford the protection.
- © 2010 by American Heart Association, Inc.