BIN1 is reduced and Cav1.2 trafficking is impaired in human failing cardiomyocytes

Hong, Ting-Ting; Smyth, James W.; Chu, Kevin Y.; Vogan, Jacob M.; Fong, Tina S.; Jensen, Brian C.; Fang, Kun; Halushka, Marc K.; Russell, Stuart D.; Colecraft, Henry; Hoopes, Charles W.; Ocorr, Karen; Chi, Neil C.; Shaw, Robin M.

doi:10.1016/j.hrthm.2011.11.055

« Previous Next »Heart Rhythm
Volume 9, Issue 5 , Pages 812-820, May 2012

BIN1 is reduced and Cav1.2 trafficking is impaired in human failing cardiomyocytes

Ting-Ting Hong, MD, PhD
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California
James W. Smyth, PhD
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California
Kevin Y. Chu, BS
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California
Jacob M. Vogan, BS
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California
Tina S. Fong, BA
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California
Brian C. Jensen, MD
- Department of Medicine, University of California, San Francisco, San Francisco, California
Kun Fang, PhD
- Department of Physiology, Columbia University, New York, New York
Marc K. Halushka, MD, PhD
- Department of Pathology, Johns Hopkins University, Baltimore, Maryland
Stuart D. Russell, MD
- Department of Medicine, Johns Hopkins University, Baltimore, Maryland
Henry Colecraft, PhD
- Department of Physiology, Columbia University, New York, New York
Charles W. Hoopes, MD
- Department of Surgery, University of California, San Francisco, San Francisco, California
Karen Ocorr, PhD
- Sanford-Burnham Medical Research Institute, La Jolla, California
Neil C. Chi, MD, PhD
- Department of Medicine, University of California San Diego, La Jolla, California
Robin M. Shaw, MD, PhD
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California
- Department of Medicine, University of California, San Francisco, San Francisco, California
- Address reprint requests and correspondence: Dr Robin M. Shaw, MD, PhD, Cardiovascular Research Institute, University of California, San Francisco, 555 Mission Bay Blvd. South, Room 352T, San Francisco, CA 94158

published online 05 December 2011.

Background

Heart failure is a growing epidemic, and a typical aspect of heart failure pathophysiology is altered calcium transients. Normal cardiac calcium transients are initiated by Cav1.2 channels at cardiac T tubules. Bridging integrator 1 (BIN1) is a membrane scaffolding protein that causes Cav1.2 to traffic to T tubules in healthy hearts. The mechanisms of Cav1.2 trafficking in heart failure are not known.

Objective

To study BIN1 expression and its effect on Cav1.2 trafficking in failing hearts.

Methods

Intact myocardium and freshly isolated cardiomyocytes from nonfailing and end-stage failing human hearts were used to study BIN1 expression and Cav1.2 localization. To confirm Cav1.2 surface expression dependence on BIN1, patch-clamp recordings were performed of Cav1.2 current in cell lines with and without trafficking-competent BIN1. Also, in adult mouse cardiomyocytes, surface Cav1.2 and calcium transients were studied after small hairpin RNA–mediated knockdown of BIN1. For a functional readout in intact heart, calcium transients and cardiac contractility were analyzed in a zebrafish model with morpholino-mediated knockdown of BIN1.

Results

BIN1 expression is significantly decreased in failing cardiomyocytes at both mRNA (30% down) and protein (36% down) levels. Peripheral Cav1.2 is reduced to 42% by imaging, and a biochemical T-tubule fraction of Cav1.2 is reduced to 68%. The total calcium current is reduced to 41% in a cell line expressing a nontrafficking BIN1 mutant. In mouse cardiomyocytes, BIN1 knockdown decreases surface Cav1.2 and impairs calcium transients. In zebrafish hearts, BIN1 knockdown causes a 75% reduction in calcium transients and severe ventricular contractile dysfunction.

Conclusions

The data indicate that BIN1 is significantly reduced in human heart failure, and this reduction impairs Cav1.2 trafficking, calcium transients, and contractility.

Keywords: Calcium , L-type calcium channel , Trafficking , Cardiomyopathy , Heart failure , Ion channels , Calcium transient