Over-expression of FK506-binding protein FKBP12.6 alters excitation-contraction coupling in adult rabbit cardiomyocytes

Loughrey, C.M. , Seidler, T., Miller, S.L.W., Prestle, J., MacEachern, K.E., Reynolds, D.F., Hasenfuss, G. and Smith, G.L. (2004) Over-expression of FK506-binding protein FKBP12.6 alters excitation-contraction coupling in adult rabbit cardiomyocytes. Journal of Physiology, 556(3), pp. 919-934. (doi:10.1113/jphysiol.2003.057166)

Loughrey, C.M. , Seidler, T., Miller, S.L.W., Prestle, J., MacEachern, K.E., Reynolds, D.F., Hasenfuss, G. and Smith, G.L. (2004) Over-expression of FK506-binding protein FKBP12.6 alters excitation-contraction coupling in adult rabbit cardiomyocytes. Journal of Physiology, 556(3), pp. 919-934. (doi:10.1113/jphysiol.2003.057166)

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Publisher's URL: http://dx.doi.org/10.1113/jphysiol.2003.057166

Abstract

This study investigated the function of FK506-binding protein (FKBP12.6) using adenoviral-mediated gene transfer to over-express FKBP12.6 (Ad-FKBP12.6) in adult rabbit ventricular cardiomyocytes. Infection with a β-galactosidase-expressing adenovirus (Ad-LacZ) was used as a control. Peak-systolic intracellular [Ca<sup>2+</sup>] (measured with Fura-2) was higher in the Ad-FKBP12.6 group compared to Ad-LacZ (1 Hz field stimulation at 37°C). The amplitude of caffeine-induced Ca<sup>2+</sup> release was also greater, indicating a higher SR Ca<sup>2+</sup> content in the Ad-FKBP12.6 group. Voltage clamp experiments indicated that FKBP 12.6 over-expression did not change L-type Ca<sup>2+</sup> current amplitude or Ca<sup>2+</sup> efflux rates via the Na+-Ca<sup>2+</sup> exchanger. Ca<sup>2+</sup> transients comparable to those after Ad-FKBP12.6 transfection could be obtained by enhancing SR Ca<sup>2+</sup> content of Ad-LacZ infected cells with periods of high frequency stimulation. Line-scan confocal microscopy (Fluo-3 fluorescence) of intact cardiomyocytes stimulated at 0.5 Hz (20-21degreesC) revealed a higher degree of synchronicity of SR Ca<sup>2+</sup> release and fewer non-responsive Ca<sup>2+</sup> release sites in the Ad-FKBP12.6 group compared to control. Ca<sup>2+</sup> spark morphology was measured in β-escin-permeabilized cardiomyocytes at a free [Ca<sup>2+</sup>](i) of 150 nm. The average values of the spark parameters (amplitude, duration, width and frequency) were reduced in the Ad-FKBP12.6 group. Increasing [Ca<sup>2+</sup>](i) to 400 nm caused coherent propagating Ca<sup>2+</sup> waves in the Ad-FKBP12.6 group but only limited Ca<sup>2+</sup> release events were recorded in the control group. These data indicate that FKBP12.6 over-expression enhances Ca<sup>2+</sup> transient amplitude predominately by increasing SR Ca<sup>2+</sup> content. Moreover, there is also evidence that FKBP 12.6 can enhance the coupling between SR Ca<sup>2+</sup> release sites independently of SR content.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Smith, Professor Godfrey and Miller, Dr Steven and MacEachern, Dr Karen and Loughrey, Dr Christopher
Authors: Loughrey, C.M., Seidler, T., Miller, S.L.W., Prestle, J., MacEachern, K.E., Reynolds, D.F., Hasenfuss, G., and Smith, G.L.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Medical Veterinary and Life Sciences > School of Veterinary Medicine
Journal Name:Journal of Physiology
ISSN:0022-3751
ISSN (Online):1469-7793
Published Online:13 February 2004

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