Stress response protein GJA1-20k promotes mitochondrial biogenesis, metabolic quiescence, and cardioprotection against ischemia/reperfusion injury
Wassim A. Basheer, … , TingTing Hong, Robin M. Shaw
Wassim A. Basheer, … , TingTing Hong, Robin M. Shaw
Published October 18, 2018
Citation Information: JCI Insight. 2018;3(20):e121900. https://doi.org/10.1172/jci.insight.121900.
View: Text | PDF
Research Article Metabolism Muscle biology

Stress response protein GJA1-20k promotes mitochondrial biogenesis, metabolic quiescence, and cardioprotection against ischemia/reperfusion injury

Abstract

Connexin 43 (Cx43), a product of the GJA1 gene, is a gap junction protein facilitating intercellular communication between cardiomyocytes. Cx43 protects the heart from ischemic injury by mechanisms that are not well understood. GJA1 mRNA can undergo alternative translation, generating smaller isoforms in the heart, with GJA1-20k being the most abundant. Here, we report that ischemic and ischemia/reperfusion (I/R) injuries upregulate endogenous GJA1-20k protein in the heart, which targets to cardiac mitochondria and associates with the outer mitochondrial membrane. Exploring the functional consequence of increased GJA1-20k, we found that AAV9-mediated gene transfer of GJA1-20k in mouse hearts increases mitochondrial biogenesis while reducing mitochondrial membrane potential, respiration, and ROS production. By doing so, GJA1-20k promotes a protective mitochondrial phenotype, as seen with ischemic preconditioning (IPC), which also increases endogenous GJA1-20k in heart lysates and mitochondrial fractions. As a result, AAV9-GJA1-20k pretreatment reduces myocardial infarct size in mouse hearts subjected to in vivo ischemic injury or ex vivo I/R injury, similar to an IPC-induced cardioprotective effect. In conclusion, GJA1-20k is an endogenous stress response protein that induces mitochondrial biogenesis and metabolic hibernation, preconditioning the heart against I/R insults. Introduction of exogenous GJA1-20k is a putative therapeutic strategy for patients undergoing anticipated ischemic injury.

Authors

Wassim A. Basheer, Ying Fu, Daisuke Shimura, Shaohua Xiao, Sosse Agvanian, Diana M. Hernandez, Tara C. Hitzeman, TingTing Hong, Robin M. Shaw

×

Figure 10

GJA1-20k mimics the IPC protective phenotype seen in heart ex vivo I/R injury.

Options: View larger image (or click on image) Download as PowerPoint
GJA1-20k mimics the IPC protective phenotype seen in heart ex vivo I/R i...
(A) Representative transverse slices of TTC-stained cardiac sections from Langendorff-perfused hearts isolated from AAV9-GST– or AAV9-GJA1-20k–expressing mice and subjected to ex vivo I/R injury alone (30-minute ischemia and 60-minute reperfusion) or to IPC stimulus prior to the prolonged I/R injury. (B) Infarct size is quantified as a percentage of total slice area, corrected by slice weight (number of hearts quantified per group in shown on the graph). Data are shown as mean ± SEM. *P < 0.05, ***P < 0.001, Kruskal-Wallis test. (C) Left ventricular end diastolic pressure (LVEDP) and (D) left ventricular developed pressure (LVDP) measurements during I/R in Langendorff-perfused hearts isolated from AAV9-GST– or AAV9-GJA1-20k–expressing mice. The hearts were subjected to ex vivo I/R injury alone or to 4 cycles of IPC followed by I/R. GST+IR compared with 20k+IR is indicated by either * or **, and GST+IR compared with GST+IPC+IR is indicated by either # or ##. *P < 0.05, #P < 0.05, **P < 0.01, ##P < 0.01, 2-way ANOVA. Data are mean ± SEM (GST+I/R, n = 6 hearts; GST+IPC+IR, n = 4 hearts; 20k+IR, n = 5 hearts).