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8. Variants in Mitochondrial ATP Synthase Cause Variable Neurologic Phenotypes

Author

Zech, M., Kopajtich, R., Steinbrücker, K., Bris, C., Gueguen, N., Feichtinger, R.G., Achleitner, M.T., Duzkale, N., Périvier, M., Koch, J., Engelhardt, H., Freisinger, P., Wagner, M., Brunet, T., Berutti, R., Smirnov, D., Navaratnarajah, T., Rodenburg, R.J.T., Pais, L.S., Austin-Tse, C., O'Leary, M., Boesch, S., Jech, R., Bakhtiari, S., Jin, S.C., Wilbert, F., Kruer, M.C., Wortmann, S.B., Eckenweiler, M., Mayr, J.A., Distelmaier, F., Steinfeld, R., Winkelmann, J., Prokisch, H., Zech, M., Kopajtich, R., Steinbrücker, K., Bris, C., Gueguen, N., Feichtinger, R.G., Achleitner, M.T., Duzkale, N., Périvier, M., Koch, J., Engelhardt, H., Freisinger, P., Wagner, M., Brunet, T., Berutti, R., Smirnov, D., Navaratnarajah, T., Rodenburg, R.J.T., Pais, L.S., Austin-Tse, C., O'Leary, M., Boesch, S., Jech, R., Bakhtiari, S., Jin, S.C., Wilbert, F., Kruer, M.C., Wortmann, S.B., Eckenweiler, M., Mayr, J.A., Distelmaier, F., Steinfeld, R., Winkelmann, J., and Prokisch, H.

Abstract

Item does not contain fulltext, OBJECTIVE: ATP synthase (ATPase) is responsible for the majority of ATP production. Nevertheless, disease phenotypes associated with mutations in ATPase subunits are extremely rare. We aimed at expanding the spectrum of ATPase-related diseases. METHODS: Whole-exome sequencing in cohorts with 2,962 patients diagnosed with mitochondrial disease and/or dystonia and international collaboration were used to identify deleterious variants in ATPase-encoding genes. Findings were complemented by transcriptional and proteomic profiling of patient fibroblasts. ATPase integrity and activity were assayed using cells and tissues from 5 patients. RESULTS: We present 10 total individuals with biallelic or de novo monoallelic variants in nuclear ATPase subunit genes. Three unrelated patients showed the same homozygous missense ATP5F1E mutation (including one published case). An intronic splice-disrupting alteration in compound heterozygosity with a nonsense variant in ATP5PO was found in one patient. Three patients had de novo heterozygous missense variants in ATP5F1A, whereas another 3 were heterozygous for ATP5MC3 de novo missense changes. Bioinformatics methods and populational data supported the variants' pathogenicity. Immunohistochemistry, proteomics, and/or immunoblotting revealed significantly reduced ATPase amounts in association to ATP5F1E and ATP5PO mutations. Diminished activity and/or defective assembly of ATPase was demonstrated by enzymatic assays and/or immunoblotting in patient samples bearing ATP5F1A-p.Arg207His, ATP5MC3-p.Gly79Val, and ATP5MC3-p.Asn106Lys. The associated clinical profiles were heterogeneous, ranging from hypotonia with spontaneous resolution (1/10) to epilepsy with early death (1/10) or variable persistent abnormalities, including movement disorders, developmental delay, intellectual disability, hyperlactatemia, and other neurologic and systemic features. Although potentially reflecting an ascertainment bias, dystonia was common (7/10). INTERPRETA

Published
2022

21. Mitochondrial respiratory states and rate

Author

Gnaiger, E., Aasander Frostner, E., Abdul Karim, N., Abumrad, NA., Acuna-Castroviejo, D., Adiele, RC., Ahn, B., Ali, SS., Alton, L., Alves, MG., Amati, F., Amoedo, ND., Andreadou, I., Arago, M., Aral, C., Arandarcikaite, O., Armand, AS., Arnould, T., Avram, VF., Bailey, DM., Bajpeyi, S., Bajzikova, M., Bakker, BM., Barlow, J., Bastos Sant'Anna Silva, AC., Batterson, P., Battino, M., Bazil, J., Beard, DA., Bednarczyk, P., Bello, F., Ben-Shachar, D., Bergdahl, A., Berge, RK., Bergmeister, L., Bernardi, P., Berridge, MV., Bettinazzi, S., Bishop, D., Blier, PU., Blindheim, DF., Boardman, NT., Boetker, HE., Borchard, S., Boros, M., Borsheim, E., Borutaite, V., Botella, J., Bouillaud, F., Bouitbir, J., Boushel, RC., Bovard, J., Breton, S., Brown, DA., Brown, GC., Brown, RA., Brozinick, JT., Buettner, GR., Burtscher, J., Calabria, E., Calbet, JA., Calzia, E., Cannon, DT., Cano Sanchez, M., Canto, AC., Cardoso, LHD., Carvalho, E., Casado Pinna, M., Cassar, S., Cassina, AM., Castelo, MP., Castro, L., Cavalcanti-de-Albuquerque, JP., Cervinkova, Z., Chabi, B., Chakrabarti, L., Chakrabarti, S., Chaurasia, B., Chen, Q., Chicco, AJ., Chinopoulos, C., Chowdhury, SK., Cizmarova, B., Clementi, E., Coen, PM., Cohen, BH., Coker, RH., Collin, A., Crisostomo, L., Dahdah, N., Dalgaard, LT., Dambrova, M., Danhelovska, T., Darveau, CA., Das, AM., Dash, RK., Davidova, E., Davis, MS., De Goede, P., De Palma, C., Dembinska-Kiec, A., Detraux, D., Devaux, Y., Di Marcello, M., Dias, TR., Distefano, G., Doermann, N., Doerrier, C., Dong, L., Donnelly, C., Drahota, Z., Duarte, FV., Dubouchaud, H., Duchen, MR., Dumas, JF., Durham, WJ., Dymkowska, D., Dyrstad, SE., Dyson, A., Dzialowski, EM., Eaton, S., Ehinger, J., Elmer, E., Endlicher, R., Engin, AB., Escames, G., Ezrova, Z., Falk, MJ., Fell, DA., Ferdinandy, P., Ferko, M., Ferreira, JCB., Ferreira, R., Ferri, A., Fessel, JP., Filipovska, A., Fisar, Z., Fischer, C., Fischer, M., Fisher, G., Fisher, JJ., Ford, E., Fornaro, M., Galina, A., Galkin, A., Gallee, L., Galli, GL., Gama Perez, P., Gan, Z., Ganetzky, R., Garcia-Rivas, G., Garcia-Roves, PM., Garcia-Souza, LF., Garipi, E., Garlid, KD., Garrabou, G., Garten, A., Gastaldelli, A., Gayen, J., Genders, AJ., Genova, ML., Giovarelli, M., Goncalo Teixeira da Silva, R., Goncalves, DF., Gonzalez-Armenta, JL., Gonzalez-Freire, M., Gonzalo, H., Goodpaster, BH., Gorr, TA., Gourlay, CW., Granata, C., Grefte, S., Guarch, ME., Gueguen, N., Gumeni, S., Haas, CB., Haavik, J., Haendeler, J., Haider, M., Hamann, A., Han, J., Han, WH., Hancock, CR., Hand, SC., Handl, J., Hargreaves, IP., Harper, ME., Harrison, DK., Hassan, H., Hausenloy, DJ., Heales, SJR., Heiestad, C., Hellgren, KT., Hepple, RT., Hernansanz-Agustin, P., Hewakapuge, S., Hickey, AJ., Ho, DH., Hoehn, KL., Hoel, F., Holland, OJ., Holloway, GP., Hoppel, CL., Hoppel, F., Houstek, J., Huete-Ortega, M., Hyrossova, P., Iglesias-Gonzalez, J., Irving, BA., Isola, R., Iyer, S., Jackson, CB., Jadiya, P., Jana, PF., Jang, DH., Jang, YC., Janowska, J., Jansen, K., Jansen-Duerr, P., Jansone, B., Jarmuszkiewicz, W., Jaskiewicz, A., Jedlicka, J., Jespersen, NR., Jha, RK., Jurczak, MJ., Jurk, D., Kaambre, T., Kaczor, JJ., Kainulainen, H., Kampa, RP., Kandel, SM., Kane, DA., Kapferer, W., Kappler, L., Karabatsiakis, A., Karavaeva, I., Karkucinska-Wieckowska, A., Kaur, S., Keijer, J., Keller, MA., Keppner, G., Khamoui, AV., Kidere, D., Kilbaugh, T., Kim, HK., Kim, JKS., Klepinin, A., Klepinina, L., Klingenspor, M., Klocker, H., Komlodi, T., Koopman, WJH., Kopitar-Jerala, N., Kowaltowski, AJ., Kozlov, AV., Krajcova, A., Krako Jakovljevic, N., Kristal, BS., Krycer, JR., Kuang, J., Kucera, O., Kuka, J., Kwak, HB., Kwast, K., Laasmaa, M., Labieniec-Watala, M., Lagarrigue, S., Lai, N., Land, JM., Lane, N., Laner, V., Lanza, IR., Laranjinha, J., Larsen, TS., Lavery, GG., Lazou, A., Lee, HK., Leeuwenburgh, C., Lehti, M., Lemieux, H., Lenaz, G., Lerfall, J., Li, PA., Li Puma, L., Liepins, E., Liu, J., Lopez, LC., Lucchinetti, E., Ma, T., Macedo, MP., Maciej, S., MacMillan-Crow, LA., Majtnerova, P., Makarova, E., Makrecka-Kuka, M., Malik, AN., Markova, M., Martin, DS., Martins, AD., Martins, JD., Maseko, TE., Maull, F., Mazat, JP., McKenna, HT., McKenzie, M., Menze, MA., Merz, T., Meszaros, AT., Methner, A., Michalak, S., Moellering, DR., Moisoi, N., Molina, AJA., Montaigne, D., Moore, AL., Moreau, K., Moreira, BP., Moreno-Sanchez, R., Mracek, T., Muccini, AM., Munro, D., Muntane, J., Muntean, DM., Murray, AJ., Musiol, E., Nabben, M., Nair, KS., Nehlin, JO., Nemec, M., Neufer, PD., Neuzil, J., Neviere, R., Newsom, SA., Nozickova, K., O'Brien, KA., O'Gorman, D., Olgar, Y., Oliveira, B., Oliveira, MF., Oliveira, MT., Oliveira, PF., Oliveira, PJ., Orynbayeva, Z., Osiewacz, HD., Pak, YK., Pallotta, ML., Palmeira, CM., Parajuli, N., Passos, JF., Passrugger, M., Patel, HH., Pavlova, N., Pecina, P., Pedersen, TM., Pereira da Silva Grilo da Silva, F., Pereira, SP., Perez Valencia, JA., Perks, KL., Pesta, D., Petit, PX., Pettersen, IKN., Pichaud, N., Pichler, I., Piel, S., Pietka, TA., Pino, MF., Pirkmajer, S., Plangger, M., Porter, C., Porter, RK., Procaccio, V., Prochownik, EV., Prola, A., Pulinilkunnil, T., Puskarich, MA., Puurand, M., Radenkovic, F., Ramzan, R., Rattan, SIS., Reboredo, P., Renner-Sattler, K., Rial, E., Robinson, MM., Roden, M., Rodriguez, E., Rodriguez-Enriquez, S., Roesland, GV., Rohlena, J., Rolo, AP., Ropelle, ER., Rossignol, R., Rossiter, HB., Rubelj, I., Rybacka-Mossakowska, J., Saada, A., Safaei, Z., Saharnaz, S., Salin, K., Salvadego, D., Sandi, C., Saner, N., Sanz, A., Sazanov, LA., Scatena, R., Schartner, M., Scheibye-Knudsen, M., Schilling, JM., Schlattner, U., Schoenfeld, P., Schots, PC., Schulz, R., Schwarzer, C., Scott, GR., Selman, C., Shabalina, IG., Sharma, P., Sharma, V., Shevchuk, I., Shirazi, R., Shiroma, JG., Siewiera, K., Silber, AM., Silva, AM., Sims, CA., Singer, D., Singh, BK., Skolik, R., Smenes, BT., Smith, J., Soares, FAA., Sobotka, O., Sokolova, I., Sonkar, VK., Sowton, AP., Sparagna, GC., Sparks, LM., Spinazzi, M., Stankova, P., Starr, J., Stary, C., Stelfa, G., Stepto, NK., Stiban, J., Stier, A., Stocker, R., Storder, J., Sumbalova, Z., Suomalainen, A., Suravajhala, P., Svalbe, B., Swerdlow, RH., Swiniuch, D., Szabo, I., Szewczyk, A., Szibor, M., Tanaka, M., Tandler, B., Tarnopolsky, MA., Tausan, D., Tavernarakis, N., Tepp, K., Thakkar, H., Thapa, M., Thyfault, JP., Tomar, D., Ton, R., Torp, MK., Towheed, A., Tretter, L., Trewin, AJ., Trifunovic, A., Trivigno, C., Tronstad, KJ., Trougakos, IP., Truu, L., Tuncay, E., Turan, B., Tyrrell, DJ., Urban, T., Valentine, JM., Van Bergen, NJ., Van Hove, J., Varricchio, F., Vella, J., Vendelin, M., Vercesi, AE., Victor, VM., Vieira Ligo Teixeira, C., Vidimce, J., Viel, C., Vieyra, A., Vilks, K., Villena, JA., Vincent, V., Vinogradov, AD., Viscomi, C., Vitorino, RMP., Vogt, S., Volani, C., Volska, K., Votion, DM., Vujacic-Mirski, K., Wagner, BA., Ward, ML., Warnsmann, V., Wasserman, DH., Watala, C., Wei, YH., Whitfield, J., Wickert, A., Wieckowski, MR., Wiesner, RJ., Williams, CM., Winwood-Smith, H., Wohlgemuth, SE., Wohlwend, M., Wolff, JN., Wrutniak-Cabello, C., Wuest, RCI., Yokota, T., Zablocki, K., Zanon, A., Zanou, N., Zaugg, K., Zaugg, M., Zdrazilova, L., Zhang, Y., Zhang, YZ., Zikova, A., Zischka, H., Zorzano, A., and Zvejniece, L.

Subjects
Mitochondrial respiratory control, coupling control, mitochondrial preparations, protonmotive force, uncoupling, oxidative phosphorylation, OXPHOS, efficiency, electron transfer, ET, proton leak, LEAK, residual oxygen consumption, ROX, State 2, State 3, State 4, normalization, flow, flux, O2
Abstract

As the knowledge base and importance of mitochondrial physiology to human health expands, the necessity for harmonizing the terminologyconcerning mitochondrial respiratory states and rates has become increasingly apparent. Thechemiosmotic theoryestablishes the mechanism of energy transformationandcoupling in oxidative phosphorylation. Theunifying concept of the protonmotive force providestheframeworkfordeveloping a consistent theoretical foundation ofmitochondrial physiology and bioenergetics.We followguidelines of the International Union of Pure and Applied Chemistry(IUPAC)onterminology inphysical chemistry, extended by considerationsofopen systems and thermodynamicsof irreversible processes.Theconcept-driven constructive terminology incorporates the meaning of each quantity and alignsconcepts and symbols withthe nomenclature of classicalbioenergetics. We endeavour to provide a balanced view ofmitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes.Uniform standards for evaluation of respiratory states and rates will ultimatelycontribute to reproducibility between laboratories and thussupport the development of databases of mitochondrial respiratory function in species, tissues, and cells.Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery.

Published
2019

24. Sensori-motor adaptation to knee osteoarthritis during stepping-down before and after total knee replacement

Author

Viton J-M, Gimet G, Boulay C, Blanchard C, Gueguen N, Mouchnino L, Franceschi J-P, and Delarque A

Subjects
Diseases of the musculoskeletal system, RC925-935
Abstract

Abstract Background Stepping-down is preceded by a shift of the center of mass towards the supporting side and forward. The ability to control both balance and lower limb movement was investigated in knee osteoarthritis patients before and after surgery. It was hypothesized that pain rather than knee joint mobility affects the coordination between balance and movement control. Methods The experiment was performed with 25 adult individuals. Eleven were osteoarthritic patients with damage restricted to one lower limb (8 right leg and 3 left leg). Subjects were recruited within two weeks before total knee replacement by the same orthopedic surgeon using the same prosthesis and technics of surgery. Osteoarthritic patients were tested before total knee replacement (pre-surgery session) and then, 9 of the 11 patients were tested one year after the surgery when re-educative training was completed (post-surgery session). 14 adult individuals (men: n = 7 and women: n = 7) were tested as the control group. Results The way in which the center of mass shift forward and toward the supporting side is initiated (timing and amplitude) did not vary within patients before and after surgery. In addition knee joint range of motion of the leading leg remained close to normal before and after surgery. However, the relative timing between both postural and movement phases was modified for the osteoarthritis supporting leg (unusual strategy for stepping-down) before surgery. The "coordinated" control of balance and movement turned to be a "sequential" mode of control; once the body weight transfer has been completed, the movement onset is triggered. This strategy could be aimed at shortening the duration-time supporting on the painful limb. However no such compensatory response was observed. Conclusion The change in the strategy used when supporting on the arthritis and painful limb could result from the action of nociceptors that lead to increased proprioceptor thresholds, thus gating the proprioceptive inputs that may be the critical afferents in controlling the timing of the coordination between balance and movement initiation control.

Published
2005
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26. Loss of function of Ywhah in mice induces deafness and cochlear outer hair cells' degeneration

Author

Buret, L, primary, Rebillard, G, additional, Brun, E, additional, Angebault, C, additional, Pequignot, M, additional, Lenoir, M, additional, Do-cruzeiro, M, additional, Tournier, E, additional, Cornille, K, additional, Saleur, A, additional, Gueguen, N, additional, Reynier, P, additional, Amati-Bonneau, P, additional, Barakat, A, additional, Blanchet, C, additional, Chinnery, P, additional, Yu-Wai-Man, P, additional, Kaplan, J, additional, Roux, A-F, additional, Van Camp, G, additional, Wissinger, B, additional, Boespflug-Tanguy, O, additional, Giraudet, F, additional, Puel, J-L, additional, Lenaers, G, additional, Hamel, C, additional, Delprat, B, additional, and Delettre, C, additional

Published
2016
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28. AK2 deficiency compromises the mitochondrial energy metabolism required for differentiation of human neutrophil and lymphoid lineages

Author

Six, E, primary, Lagresle-Peyrou, C, additional, Susini, S, additional, De Chappedelaine, C, additional, Sigrist, N, additional, Sadek, H, additional, Chouteau, M, additional, Cagnard, N, additional, Fontenay, M, additional, Hermine, O, additional, Chomienne, C, additional, Reynier, P, additional, Fischer, A, additional, André-Schmutz, I, additional, Gueguen, N, additional, and Cavazzana, M, additional

Published
2015
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30. Ca2+- activated myosin- ATPases, creatine and adenylate kinases regulate mitochondrial function according to myofibre type in rabbit

Author

Gueguen, N, Lefaucheur, L, Ecolan, P, Fillaut, M, and Herpin, P

Subjects
Cell Physiology
Abstract

Mitochondrial respiration rates and their regulation by ADP, AMP and creatine, were studied at different free Ca2+ concentrations (0.1 versus 0.4 μm) on permeabilized fibre bundles of rabbit skeletal muscles differing in their myosin heavy chain profiles. Four fibre bundle types were obtained: pure types I and IIx, and mixed types IIax (approximately 50% IIa and 50% IIx fibres) and IIb+ (60% IIb fibres, plus IIx and IIa). At rest, pure type I fibres displayed a much higher apparent Km for ADP (212 μm) than IIx fibres (8 μm). Within the IIax and IIb+ mixed fibre bundle types, two KADPm values were observed (70 μm and 5 μm). Comparison between pure IIx and mixed types indicates that the intermediate Km of 70 μm most probably corresponds to the mitochondrial affinity for ADP in IIa fibres, the lowest Km for ADP (5 μm) corresponding to IIx and IIb types. Activation of mitochondrial creatine and adenylate kinase reactions stimulated mitochondrial respiration only in type I and IIax fibre bundles, indicating an efficient coupling between both kinases and ADP rephosphorylation in type I and, likely, IIa fibres, since no effect was observed in pure IIx fibres. Following Ca2+-induced activation of myosin-ATPase, an increase in mitochondrial sensitivity to ADP of 45% and 250% was observed in type IIax and I bundles, respectively, an effect mostly prevented by addition of vanadate, an inhibitor of myosin-ATPase. Ca2+-induced activation of myosin-ATPase also prevented the stimulation of respiration rates by creatine and AMP in I and IIax bundles. In addition to differential regulation of mitochondrial respiration and energy transfer systems at rest in I and IIa versus IIx and IIb muscle fibres, our results indicate a regulation of phosphotransfer systems by Ca2+ via the stimulation of myosin-ATPases in type I and IIa fibres of rabbit muscles.

Published
2005

32. Reversible optic neuropathy with OPA1 exon 5b mutation

Author

Cornille, K., Milea, D., Amati-Bonneau, P., Procaccio, V., Zazoun, L., Guillet, V., Achouri, G. El, Delettre, C., Gueguen, N., Loiseau, D., Muller, A., Ferre, M., Chevrollier, A., Wallace, D.C., Bonneau, D., Hamel, C., Reynier, P., Lenaers, G., Cornille, K., Milea, D., Amati-Bonneau, P., Procaccio, V., Zazoun, L., Guillet, V., Achouri, G. El, Delettre, C., Gueguen, N., Loiseau, D., Muller, A., Ferre, M., Chevrollier, A., Wallace, D.C., Bonneau, D., Hamel, C., Reynier, P., and Lenaers, G.

Abstract

A new c.740G>A (R247H) mutation in OPA1 alternate spliced exon 5b was found in a patient presenting with bilateral optic neuropathy followed by partial, spontaneous visual recovery. R247H fibroblasts from the patient and his unaffected father presented unusual highly tubular mitochondrial network, significant increased susceptibility to apoptosis, oxidative phosphorylation uncoupling, and altered OPA1 protein profile, supporting the pathogenicity of this mutation. These results suggest that the clinical spectrum of the OPA1-associated optic neuropathies may be larger than previously described, and that spontaneous recovery may occur in cases harboring an exon 5b mutation Udgivelsesdato: 2008/5

Published
2008

49. Tactile precision in right‐handed archery experts with visual disabilities: A pseudoneglect effect?

Author

Coudereau, J. P., Gueguen, N., Pratte, M., and Sampaio, E.

Subjects
*VISION disorders, *HANDEDNESS, *ARCHERS, *LATERAL dominance, *PSYCHOPHYSIOLOGY
Abstract

Space perception was investigated in two groups of participants with severe visual deficiencies performing a tactile bisection task: the participants in the first group (Archers) regularly practised a high-precision sport, whereas those in the second group (Non-Archers) had never practised this activity. Experiments were carried out to determine whether practising this sport might affect the pseudoneglect (resulting in a deviation to the left of the perceived midpoint with respect to the actual physical midpoint) occurring in sighted persons (Bowers & Heilman, 1980) as well as in completely blind children (Sampaio, Gouarir, & Mvondo Mvondo, 1995). No particular deviation was observed in the group of Non-Archers, whereas pseudoneglect was present in the Archers' group. A significant hand effect (left/right), and a significant effect of starting point of tactile exploration were observed across groups. This confirms the existence of a relationship between hemisphere–hands and hemisphere–hemispace mechanisms. The results obtained here show that practising archery affects pseudoneglect. [ABSTRACT FROM AUTHOR]

Published
2006
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50. Ca2+-activated myosin-ATPases, creatine and adenylate kinases regulate mitochondrial function according to myofibre type in rabbit.

Author

Gueguen, N., Lefaucher, Louis, Ecolan, P., Fillaut, M., and Herpin, P.

Subjects
*RESPIRATION, *CREATINE, *PHOSPHORYLATION, *ENERGY transfer, *ADENOSINE triphosphate
Abstract

Mitochondrial respiration rates and their regulation by ADP, AMP and creatine, were studied at different free Ca2+ concentrations (0.1versus0.4μm) on permeabilized fibre bundles of rabbit skeletal muscles differing in their myosin heavy chain profiles. Four fibre bundle types were obtained: pure types I and IIx, and mixed types IIax (approximately 50% IIa and 50% IIx fibres) and IIb+ (60% IIb fibres, plus IIx and IIa). At rest, pure type I fibres displayed a much higher apparentKm for ADP (212μm) than IIx fibres (8μm). Within the IIax and IIb+ mixed fibre bundle types, twoKADPm values were observed (70μmand 5μm). Comparison between pure IIx and mixed types indicates that the intermediateKm of 70μmmost probably corresponds to the mitochondrial affinity for ADP in IIa fibres, the lowestKm for ADP (5μm) corresponding to IIx and IIb types. Activation of mitochondrial creatine and adenylate kinase reactions stimulated mitochondrial respiration only in type I and IIax fibre bundles, indicating an efficient coupling between both kinases and ADP rephosphorylation in type I and, likely, IIa fibres, since no effect was observed in pure IIx fibres. Following Ca2+-induced activation of myosin-ATPase, an increase in mitochondrial sensitivity to ADP of 45% and 250% was observed in type IIax and I bundles, respectively, an effect mostly prevented by addition of vanadate, an inhibitor of myosin-ATPase. Ca2+-induced activation of myosin-ATPase also prevented the stimulation of respiration rates by creatine and AMP in I and IIax bundles. In addition to differential regulation of mitochondrial respiration and energy transfer systems at rest in I and IIaversusIIx and IIb muscle fibres, our results indicate a regulation of phosphotransfer systems by Ca2+ via the stimulation of myosin-ATPases in type I and IIa fibres of rabbit muscles. [ABSTRACT FROM AUTHOR]

Published
2005
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