Integrins protect cardiomyocytes from ischemia/reperfusion injury
Hideshi Okada, N. Chin Lai, Yoshitaka Kawaraguchi, Peter Liao, Jeffrey Copps, Yasuo Sugano, Sunaho Okada-Maeda, Indroneal Banerjee, Jan M. Schilling, Alexandre R. Gingras, Elizabeth K. Asfaw, Jorge Suarez, Seok-Min Kang, Guy A. Perkins, Carol G. Au, Sharon Israeli-Rosenberg, Ana Maria Manso, Zheng Liu, Derek J. Milner, Stephen J. Kaufman, Hemal H. Patel, David M. Roth, H. Kirk Hammond, Susan S. Taylor, Wolfgang H. Dillmann, Joshua I. Goldhaber, Robert S. Ross
Hideshi Okada, N. Chin Lai, Yoshitaka Kawaraguchi, Peter Liao, Jeffrey Copps, Yasuo Sugano, Sunaho Okada-Maeda, Indroneal Banerjee, Jan M. Schilling, Alexandre R. Gingras, Elizabeth K. Asfaw, Jorge Suarez, Seok-Min Kang, Guy A. Perkins, Carol G. Au, Sharon Israeli-Rosenberg, Ana Maria Manso, Zheng Liu, Derek J. Milner, Stephen J. Kaufman, Hemal H. Patel, David M. Roth, H. Kirk Hammond, Susan S. Taylor, Wolfgang H. Dillmann, Joshua I. Goldhaber, Robert S. Ross
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Research Article Cardiology

Integrins protect cardiomyocytes from ischemia/reperfusion injury

Abstract

Ischemic damage is recognized to cause cardiomyocyte (CM) death and myocardial dysfunction, but the role of cell-matrix interactions and integrins in this process has not been extensively studied. Expression of α7β1D integrin, the dominant integrin in normal adult CMs, increases during ischemia/reperfusion (I/R), while deficiency of β1 integrins increases ischemic damage. We hypothesized that the forced overexpression of integrins on the CM would offer protection from I/R injury. Tg mice with CM-specific overexpression of integrin α7β1D exposed to I/R had a substantial reduction in infarct size compared with that of α5β1D-overexpressing mice and WT littermate controls. Using isolated CMs, we found that α7β1D preserved mitochondrial membrane potential during hypoxia/reoxygenation (H/R) injury via inhibition of mitochondrial Ca2+ overload but did not alter H/R effects on oxidative stress. Therefore, we assessed Ca2+ handling proteins in the CM and found that β1D integrin colocalized with ryanodine receptor 2 (RyR2) in CM T-tubules, complexed with RyR2 in human and rat heart, and specifically bound to RyR2 amino acids 165–175. Integrins stabilized the RyR2 interdomain interaction, and this stabilization required integrin receptor binding to its ECM ligand. These data suggest that α7β1D integrin modifies Ca2+ regulatory pathways and offers a means to protect the myocardium from ischemic injury.

Authors

Hideshi Okada, N. Chin Lai, Yoshitaka Kawaraguchi, Peter Liao, Jeffrey Copps, Yasuo Sugano, Sunaho Okada-Maeda, Indroneal Banerjee, Jan M. Schilling, Alexandre R. Gingras, Elizabeth K. Asfaw, Jorge Suarez, Seok-Min Kang, Guy A. Perkins, Carol G. Au, Sharon Israeli-Rosenberg, Ana Maria Manso, Zheng Liu, Derek J. Milner, Stephen J. Kaufman, Hemal H. Patel, David M. Roth, H. Kirk Hammond, Susan S. Taylor, Wolfgang H. Dillmann, Joshua I. Goldhaber, Robert S. Ross

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Figure 11

The β1D cytoplasmic domain stabilizes RyR2; integrin heterodimers require ECM binding for RyR2 stabilization.

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The β1D cytoplasmic domain stabilizes RyR2; integrin heterodimers requir...
(A) FRET image of RyR2S437-YFP/S2367-CFP expressed alone or with α7, β1A, or β1D integrin (original magnification, ×63). (B) Graphic FRET ratio. Relative signal detected in the RyR2-transfected cells was set as 1. FRET signal detected in other samples is displayed relative to control. The RyR2 sensor FRET ratio was increased by dantrolene, an RyR2 stabilizer. β1D integrin cotransfected with the sensor increased the FRET ratio, indicating increased RyR2 stability. No change was seen with α7 or β1A integrin (*P < 0.05 vs. RyR2-transfected cells, n = 20 cells per group). (C) Western blots of control and β1D integrin stably transfected OE cells (OE). β1D integrin precursor (P) was substantially increased in OE cells, but the higher MW mature (M) form increased minimally. No β1D integrin was detected in untransfected cells. GAPDH was used as a loading control. (D) Graphic FRET ratio. FRET ratio in β1D OE cells transiently transfected with RyR2 alone and plated without ECM was set as 1. FRET detected in other samples is displayed relative to this amount. Cells expressing β1D integrin alone showed no change in FRET signal regardless of ECM coating, indicating that there was no stabilization of RyR2. With OE of the FN-binding integrin α5β1D and plating on FN matrix, a stronger FRET signal was found compared with cells plated on LN or no substrate. Cells expressing the LN-binding α7β1D integrin had the most robust FRET signal when plated on LN (*P < 0.05 vs. β1D OE cells transfected with RyR2 alone).