Overexpression of FK-506-binding protein 12.0 modulates excitation-contraction coupling in adult rabbit ventricular cardiomyocytes

Seidler, T., Loughrey, C. , Zibrova, D., Kettlewell, S., Teucher, N., Kogler, H., Hasenfuss, G. and Smith, G. (2007) Overexpression of FK-506-binding protein 12.0 modulates excitation-contraction coupling in adult rabbit ventricular cardiomyocytes. Circulation Research, 101(10), pp. 1020-1029. (doi:10.1161/CIRCRESAHA.107.154609)

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Abstract

The effect of the 12-kDa isoform of FK-506-binding protein (FKBP)12.0 on cardiac excitation contraction coupling was studied in adult rabbit ventricular myocytes after transfection with a recombinant adenovirus coding for human FKBP12.0 (Ad-FKBP12.0). Western blots confirmed overexpression (by 2.6 +/- 0.4 fold, n = 5). FKBP12.0 association with rabbit cardiac ryanodine receptor (RyR2) was not detected by immunoprecipitation. However, glutathione S-transferase pull-down experiments indicated FKBP12.0-RyR2 binding to proteins isolated from human and rabbit but not dog myocardium. Voltage-clamp experiments indicated no effects of FKBP12.0 overexpression on L-type Ca2+ current (I-Ca,I-L) or Ca2+ efflux rates via the Na+/Ca2+ exchanger. Ca2+ transient amplitude was also not significantly different. However, sarcoplasmic reticulum Ca2+ load was approximate to 25% higher in myocytes in the Ad-FKBP12.0 group. The reduced ability of ICa, L to initiate sarcoplasmic reticulum Ca2+ release was observed over a range of values of sarcoplasmic reticulum Ca2+ content, indicating that overexpression of FKBP12.0 reduces the sensitivity of RyR2 to Ca2+. Ca2+ spark morphology was measured in beta-escin-permeabilized cardiomyocytes. Ca2+ spark amplitude and duration were significantly increased, whereas frequency was decreased in cells overexpressing FKBP12.0. These changes were accompanied by an increased sarcoplasmic reticulum Ca2+ content. In summary, the effects of FKBP12.0 overexpression on intact and permeabilized cells were similar to those of tetracaine, a drug known to reduce RyR2 Ca2+ sensitivity and distinctly different from the effects of overexpression of the FKBP12.6 isomer. In conclusion, FKBP12.0-RyR2 interaction can regulate the gain of excitation-contraction coupling.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Smith, Professor Godfrey and Kettlewell, Dr Sarah and Loughrey, Professor Christopher
Authors: Seidler, T., Loughrey, C., Zibrova, D., Kettlewell, S., Teucher, N., Kogler, H., Hasenfuss, G., and Smith, G.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
College of Medical Veterinary and Life Sciences
Journal Name:Circulation Research
ISSN:0009-7330

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