Mitochondrial affinity for ADP is twofold lower in creatine kinase knock-out muscles. Possible role in rescuing cellular energy homeostasis.
Adaptations of the kinetic properties of mitochondria in striated muscle lacking cytosolic (M) and/or mitochondrial (Mi) creatine kinase (CK) isoforms in comparison to wild-type (WT) were investigated in vitro. Intact mitochondria were isolated from heart and gastrocnemius muscle of WT and single- and double CK-knock-out mice strains (cytosolic (M-CK-/-), mitochondrial (Mi-CK-/-) and double knock-out (MiM-CK-/-), respectively). Maximal ADP-stimulated oxygen consumption flux (State3 Vmax; nmol O2 x mg mitochondrial protein(-1) x min(-1)) and ADP affinity (K50ADP; microM) were determined by respirometry. State 3 Vmax and of M-CK-/- and MiM-CK-/- gastrocnemius mitochondria were twofold higher than those of WT, but were unchanged for Mi-CK-/-. For mutant cardiac mitochondria, only the of mitochondria isolated from the MiM-CK-/- phenotype was different (i.e. twofold higher) than that of WT. The implications of these adaptations for striated muscle function were explored by constructing force-flow relations of skeletal muscle respiration. It was found that the identified shift in affinity towards higher ADP concentrations in MiM-CK-/- muscle genotypes may contribute to linear mitochondrial control of the reduced cytosolic ATP free energy potentials in these phenotypes.
ter Veld
Frank
F
Department of Experimental In Vivo NMR, Image Sciences Institute, University Medical Center, Utrecht, the Netherlands. frank.terveld@mpi-dortmund.mpg.de
Jeneson
Jeroen A L
JA
Nicolay
Klaas
K
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000818:Animals; D019069:Cell Respiration / Q000235:genetics; D003402:Creatine Kinase / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008931:Mitochondria, Muscle / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*
D000244:Adenosine Diphosphate; D003402:Creatine Kinase