title: Resistance to Ca2+-induced opening of the permeability transition pore differs in mitochondria from glycolytic and oxidative muscles.
abstract: This study determined whether susceptibility to opening of the permeability transition pore (PTP) varies according to muscle phenotype represented by the slow oxidative soleus (Sol) and superficial white gastrocnemius (WG). Threshold for Ca2+-induced mitochondrial Ca2+ release following PTP opening was determined with a novel approach using permeabilized ghost myofibers. Threshold values for PTP opening were approximately threefold higher in fibers from WG compared with those from Sol (124+/-47 vs. 30.4+/-6.8 pmol Ca2+/mU citrate synthase). A similar phenomenon was also observed in isolated mitochondria (threshold: 121+/-60 vs. 40+/-10 nmol Ca2+/mg protein in WG and Sol), indicating that this was linked to differences in mitochondrial factors between the two muscles. The resistance of WG fibers to PTP opening was not related to the expression of putative protein modulators (cyclophilin D, adenylate nucleotide translocator-1, and voltage-dependent anion channels) or to difference in respiratory properties and occurred despite the fact that production of reactive oxygen species, which promote pore opening, was higher than in the Sol. However, endogenous matrix Ca2+ measured in mitochondria isolated under resting baseline conditions was approximately twofold lower in the WG than in the Sol (56+/-4 vs. 111+/-11 nmol/mg protein), which significantly accounted for the resistance of WG. Together, these results reveal fiber type differences in the sensitivity to Ca2+-induced PTP opening, which may constitute a physiological mechanism to adapt mitochondria to the differences in Ca2+ dynamics between fiber types.
authors.affiliation: Université de Montréal, Department of Kinesiology, PO Box 6128 Centre-Ville, Montreal, Quebec, Canada, H3C 3J7.
authors.forename: Martin
authors.initials: M
authors.lastname: Picard
authors.forename: Kristina
authors.initials: K
authors.lastname: Csukly
authors.forename: Marie-Eve
authors.initials: ME
authors.lastname: Robillard
authors.forename: Richard
authors.initials: R
authors.lastname: Godin
authors.forename: Alexis
authors.initials: A
authors.lastname: Ascah
authors.forename: Céline
authors.initials: C
authors.lastname: Bourcier-Lucas
authors.forename: Yan
authors.initials: Y
authors.lastname: Burelle
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D019069:Cell Respiration; D006019:Glycolysis; D066298:In Vitro Techniques; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D024101:Mitochondrial Proteins / Q000378:metabolism; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010641:Phenotype; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species