Overexpression of FKBP12.6 in adult rabbit cardiomyocytes significantly increased fractional shortening compared with control cells (4.8% vs 4.0%, P=0.001) and reduced SR-Ca2+ leak.
Does adenovirus-mediated overexpression of FKBP12.6 increase contractility and reduce SR-Ca2+ leak in adult rabbit cardiomyocytes?
Overexpression of FKBP12.6 in cardiomyocytes reduces SR-Ca2+ leak and increases contractility, highlighting its role in stabilizing the closed conformation of the RyR2 channel.
Absolute Event Rate: 4.8% vs 4%
p-value: p=0.001
The FK506-binding protein FKBP12.6 is tightly associated with the cardiac sarcoplasmic reticulum (SR) Ca(2+)-release channel (ryanodine receptor type 2 RyR2), but the physiological function of FKBP12.6 is unclear. We used adenovirus (Ad)-mediated gene transfer to overexpress FKBP12.6 in adult rabbit cardiomyocytes. Western immunoblot and reverse transcriptase-polymerase chain reaction analysis revealed specific overexpression of FKBP12.6, with unchanged expression of endogenous FKBP12. FKBP12.6-transfected myocytes displayed a significantly higher (21%) fractional shortening (FS) at 48 hours after transfection compared with Ad-GFP-infected control cells (4.8+/-0.2% FS versus 4+/-0.2% FS, respectively; n=79 each; P:=0.001). SR-Ca(2+) uptake rates were monitored in beta-escin-permeabilized myocytes using Fura-2. Ad-FKBP12.6-infected cells showed a statistically significant higher rate of Ca(2+) uptake of 0.8+/-0.09 nmol/s(-)(1)/10(6) cells (n=8, P:<0.05) compared with 0.52+/-0.1 nmol/s(-)(1)/10(6) cells in sham-infected cells (n=8) at a Ca(2+) of 1 micromol/L. In the presence of 5 micromol/L ruthenium red to block Ca(2+) efflux via RyR2, SR-Ca(2+) uptake rates were not significantly different between groups. From these measurements, we calculate that SR-Ca(2+) leak through RyR2 is reduced by 53% in FKBP12.6-overexpressing cells. Caffeine-induced contractures were significantly larger in Ad-FKBP12.6-infected myocytes compared with Ad-GFP-infected control cells, indicating a higher SR-Ca(2+) load. Taken together, these data suggest that FKBP12.6 stabilizes the closed conformation state of RyR2. This may reduce diastolic SR-Ca(2+) leak and consequently increase SR-Ca(2+) release and myocyte shortening.
Prestle et al. (Fri,) reported a other. Adenovirus-mediated gene transfer to overexpress FKBP12.6 vs. Ad-GFP-infected control cells was evaluated on Fractional shortening (FS) at 48 hours after transfection (p=0.001). Overexpression of FKBP12.6 in adult rabbit cardiomyocytes significantly increased fractional shortening compared with control cells (4.8% vs 4.0%, P=0.001) and reduced SR-Ca2+ leak.