title: Overexpression of FK-506 binding protein 12.0 modulates excitation contraction coupling in adult rabbit ventricular cardiomyocytes.
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,L)) or Ca2+ efflux rates via the Na+/Ca2+ exchanger. Ca2+ transient amplitude was also not significantly different. However, sarcoplasmic reticulum Ca2+ load was approximately 25% higher in myocytes in the Ad-FKBP12.0 group. The reduced ability of I(Ca,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.
authors.affiliation: Department of Cardiology and Pneumology, Georg-August-University Goettingen, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Seidler
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Loughrey
authors.forename: Darya
authors.initials: D
authors.lastname: Zibrova
authors.forename: Sarah
authors.initials: S
authors.lastname: Kettlewell
authors.forename: Nils
authors.initials: N
authors.lastname: Teucher
authors.forename: Harald
authors.initials: H
authors.lastname: Kögler
authors.forename: Gerd
authors.initials: G
authors.lastname: Hasenfuss
authors.forename: Godfrey L
authors.initials: GL
authors.lastname: Smith
mesh_terms: D000367:Age Factors; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D006352:Heart Ventricles / Q000166:cytology; D006801:Humans; D009200:Myocardial Contraction / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D022061:Tacrolimus Binding Protein 1A / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection
chemical_list: D010726:Phosphodiesterase Inhibitors; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D022061:Tacrolimus Binding Protein 1A; D002118:Calcium