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. 1994 Oct 1;480(Pt 1):45–60. doi: 10.1113/jphysiol.1994.sp020339

The role of troponin C in modulating the Ca2+ sensitivity of mammalian skinned cardiac and skeletal muscle fibres.

S Palmer 1, J C Kentish 1
PMCID: PMC1155776  PMID: 7853225

Abstract

1. We investigated the effects of acidosis, inorganic phosphate (Pi) and caffeine on the Ca2+ affinity of isolated fast-twitch skeletal and cardiac troponin C (TnC), labelled with fluorescent probes to report Ca2+ binding to the regulatory sites. We also measured the effects of these interventions on the maximum force development and the Ca2+ sensitivity of skinned fibres from fast-twitch skeletal muscle and cardiac muscle, as has been done previously. The two types of experiment were carried out under similar solution conditions, so that we could assess the contribution of any direct actions on TnC to the modulation of Ca2+ sensitivity in the skinned muscle fibres. 2. In skinned fibres, acidosis (decreasing pH from 7.0 to 6.2) and Pi (20 mM) suppressed maximum force to the same extent within a given muscle type, but had greater effects on cardiac fibres compared with skeletal fibres. Caffeine (20 mM) depressed maximum force equally in cardiac and skeletal muscle. Thus, the fall of force induced by acidosis or Pi may involve a different mechanism from that induced by caffeine. 3. Skinned skeletal fibres were more Ca2+ sensitive than cardiac fibres by 0.29 pCa units (pCa = -log10[Ca2+]). Isolated skeletal TnC also had a greater Ca2+ affinity than cardiac TnC, by 0.20 pCa units. These results suggest that the Ca2+ sensitivity of skinned fibres is at least partly determined by the type of TnC present. 4. Acidosis reduced the Ca2+ sensitivity of force in skinned fibres profoundly and had a 2-fold greater effect in cardiac muscle than skeletal muscle (falls in pCa for 50% activation, pCa50, were 1.09 and 0.55, respectively). Acidosis also reduced the Ca2+ affinity of TnC, again having double the effect on the pCa50 for cardiac TnC (0.58) as on that for skeletal TnC (0.28). The greater effect of acidosis on cardiac skinned fibres, compared with skeletal, may be partly explained, therefore, by the type of TnC present, and one-half of the effect on fibres may be attributed to the direct effect of H+ on TnC. 5. Pi reduced the Ca2+ sensitivity of force in skeletal and cardiac skinned fibres by 0.30 and 0.19 pCa units, respectively. However, the Ca2+ affinity of isolated cardiac and skeletal TnC was unaffected by Pi, indicating that the decrease in muscle Ca2+ sensitivity is not mediated by a direct action of Pi on TnC. 6. Caffeine increased the Ca2+ sensitivity of cardiac skinned fibres by 0.31 pCa units, which was 3 times greater than for the skeletal fibres (0.09 pCa units).(ABSTRACT TRUNCATED AT 400 WORDS)

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Selected References

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  1. Blanchard E. M., Pan B. S., Solaro R. J. The effect of acidic pH on the ATPase activity and troponin Ca2+ binding of rabbit skeletal myofilaments. J Biol Chem. 1984 Mar 10;259(5):3181–3186. [PubMed] [Google Scholar]
  2. Blanchard E. M., Solaro R. J. Inhibition of the activation and troponin calcium binding of dog cardiac myofibrils by acidic pH. Circ Res. 1984 Sep;55(3):382–391. doi: 10.1161/01.res.55.3.382. [DOI] [PubMed] [Google Scholar]
  3. Brandt P. W., Diamond M. S., Schachat F. H. The thin filament of vertebrate skeletal muscle co-operatively activates as a unit. J Mol Biol. 1984 Dec 5;180(2):379–384. doi: 10.1016/s0022-2836(84)80010-8. [DOI] [PubMed] [Google Scholar]
  4. Bremel R. D., Weber A. Cooperation within actin filament in vertebrate skeletal muscle. Nat New Biol. 1972 Jul 26;238(82):97–101. doi: 10.1038/newbio238097a0. [DOI] [PubMed] [Google Scholar]
  5. Chalovich J. M., Chock P. B., Eisenberg E. Mechanism of action of troponin . tropomyosin. Inhibition of actomyosin ATPase activity without inhibition of myosin binding to actin. J Biol Chem. 1981 Jan 25;256(2):575–578. [PMC free article] [PubMed] [Google Scholar]
  6. Cooke R., Pate E. The effects of ADP and phosphate on the contraction of muscle fibers. Biophys J. 1985 Nov;48(5):789–798. doi: 10.1016/S0006-3495(85)83837-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Fabiato A., Fabiato F. Effects of pH on the myofilaments and the sarcoplasmic reticulum of skinned cells from cardiace and skeletal muscles. J Physiol. 1978 Mar;276:233–255. doi: 10.1113/jphysiol.1978.sp012231. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Ferenczi M. A., Homsher E., Trentham D. R. The kinetics of magnesium adenosine triphosphate cleavage in skinned muscle fibres of the rabbit. J Physiol. 1984 Jul;352:575–599. doi: 10.1113/jphysiol.1984.sp015311. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Godt R. E., Nosek T. M. Changes of intracellular milieu with fatigue or hypoxia depress contraction of skinned rabbit skeletal and cardiac muscle. J Physiol. 1989 May;412:155–180. doi: 10.1113/jphysiol.1989.sp017609. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Grabarek Z., Grabarek J., Leavis P. C., Gergely J. Cooperative binding to the Ca2+-specific sites of troponin C in regulated actin and actomyosin. J Biol Chem. 1983 Dec 10;258(23):14098–14102. [PubMed] [Google Scholar]
  11. Greaser M. L., Gergely J. Reconstitution of troponin activity from three protein components. J Biol Chem. 1971 Jul 10;246(13):4226–4233. [PubMed] [Google Scholar]
  12. Güth K., Potter J. D. Effect of rigor and cycling cross-bridges on the structure of troponin C and on the Ca2+ affinity of the Ca2+-specific regulatory sites in skinned rabbit psoas fibers. J Biol Chem. 1987 Oct 5;262(28):13627–13635. [PubMed] [Google Scholar]
  13. Hibberd M. G., Dantzig J. A., Trentham D. R., Goldman Y. E. Phosphate release and force generation in skeletal muscle fibers. Science. 1985 Jun 14;228(4705):1317–1319. doi: 10.1126/science.3159090. [DOI] [PubMed] [Google Scholar]
  14. Holroyde M. J., Robertson S. P., Johnson J. D., Solaro R. J., Potter J. D. The calcium and magnesium binding sites on cardiac troponin and their role in the regulation of myofibrillar adenosine triphosphatase. J Biol Chem. 1980 Dec 25;255(24):11688–11693. [PubMed] [Google Scholar]
  15. Ingraham R. H., Swenson C. A. Stability of the Ca2+-specific and Ca2+-Mg2+ domains of troponin C. Effect of pH. Eur J Biochem. 1983 Apr 15;132(1):85–88. doi: 10.1111/j.1432-1033.1983.tb07328.x. [DOI] [PubMed] [Google Scholar]
  16. Johnson J. D., Charlton S. C., Potter J. D. A fluorescence stopped flow analysis of Ca2+ exchange with troponin C. J Biol Chem. 1979 May 10;254(9):3497–3502. [PubMed] [Google Scholar]
  17. Johnson J. D., Collins J. H., Potter J. D. Dansylaziridine-labeled troponin C. A fluorescent probe of Ca2+ binding to the Ca2+-specific regulatory sites. J Biol Chem. 1978 Sep 25;253(18):6451–6458. [PubMed] [Google Scholar]
  18. Johnson J. D., Collins J. H., Robertson S. P., Potter J. D. A fluorescent probe study of Ca2+ binding to the Ca2+-specific sites of cardiac troponin and troponin C. J Biol Chem. 1980 Oct 25;255(20):9635–9640. [PubMed] [Google Scholar]
  19. Kawai M., Saeki Y., Zhao Y. Crossbridge scheme and the kinetic constants of elementary steps deduced from chemically skinned papillary and trabecular muscles of the ferret. Circ Res. 1993 Jul;73(1):35–50. doi: 10.1161/01.res.73.1.35. [DOI] [PubMed] [Google Scholar]
  20. Kentish J. C. Combined inhibitory actions of acidosis and phosphate on maximum force production in rat skinned cardiac muscle. Pflugers Arch. 1991 Oct;419(3-4):310–318. doi: 10.1007/BF00371112. [DOI] [PubMed] [Google Scholar]
  21. Kentish J. C., Stienen G. J. Differential effects of length on maximum force production and myofibrillar ATPase activity in rat skinned cardiac muscle. J Physiol. 1994 Feb 15;475(1):175–184. doi: 10.1113/jphysiol.1994.sp020059. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Kentish J. C. The effects of inorganic phosphate and creatine phosphate on force production in skinned muscles from rat ventricle. J Physiol. 1986 Jan;370:585–604. doi: 10.1113/jphysiol.1986.sp015952. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Kerrick W. G., Malencik D. A., Hoar P. E., Potter J. D., Coby R. L., Pocinwong S., Fischer E. H. Ca2+ and Sr2+ activation: comparison of cardiac and skeletal muscle contraction models. Pflugers Arch. 1980 Aug;386(3):207–213. doi: 10.1007/BF00587470. [DOI] [PubMed] [Google Scholar]
  24. Kobayashi T., Takagi T., Konishi K., Morimoto S., Ohtsuki I. Amino acid sequence of porcine cardiac muscle troponin C. J Biochem. 1989 Jul;106(1):55–59. doi: 10.1093/oxfordjournals.jbchem.a122819. [DOI] [PubMed] [Google Scholar]
  25. Lamont C., Miller D. J. Calcium sensitizing action of carnosine and other endogenous imidazoles in chemically skinned striated muscle. J Physiol. 1992 Aug;454:421–434. doi: 10.1113/jphysiol.1992.sp019271. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Lehrer S. S., Leavis P. C. Fluorescence and conformational changes caused by proton binding to troponin C. Biochem Biophys Res Commun. 1974 May 7;58(1):159–165. doi: 10.1016/0006-291x(74)90905-x. [DOI] [PubMed] [Google Scholar]
  27. Metzger J. M., Parmacek M. S., Barr E., Pasyk K., Lin W. I., Cochrane K. L., Field L. J., Leiden J. M. Skeletal troponin C reduces contractile sensitivity to acidosis in cardiac myocytes from transgenic mice. Proc Natl Acad Sci U S A. 1993 Oct 1;90(19):9036–9040. doi: 10.1073/pnas.90.19.9036. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Morano I., Rüegg J. C. What does TnCDANZ fluorescence reveal about the thin filament state? Pflugers Arch. 1991 May;418(4):333–337. doi: 10.1007/BF00550870. [DOI] [PubMed] [Google Scholar]
  29. Moss R. L., Lauer M. R., Giulian G. G., Greaser M. L. Altered Ca2+ dependence of tension development in skinned skeletal muscle fibers following modification of troponin by partial substitution with cardiac troponin C. J Biol Chem. 1986 May 5;261(13):6096–6099. [PubMed] [Google Scholar]
  30. Ogawa Y. Calcium binding to troponin C and troponin: effects of Mg2+, ionic strength and pH. J Biochem. 1985 Apr;97(4):1011–1023. doi: 10.1093/oxfordjournals.jbchem.a135143. [DOI] [PubMed] [Google Scholar]
  31. Pate E., Cooke R. Addition of phosphate to active muscle fibers probes actomyosin states within the powerstroke. Pflugers Arch. 1989 May;414(1):73–81. doi: 10.1007/BF00585629. [DOI] [PubMed] [Google Scholar]
  32. Potter J. D., Gergely J. The calcium and magnesium binding sites on troponin and their role in the regulation of myofibrillar adenosine triphosphatase. J Biol Chem. 1975 Jun 25;250(12):4628–4633. [PubMed] [Google Scholar]
  33. Seow C. Y., Ford L. E. High ionic strength and low pH detain activated skinned rabbit skeletal muscle crossbridges in a low force state. J Gen Physiol. 1993 Apr;101(4):487–511. doi: 10.1085/jgp.101.4.487. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Shiner J. S., Solaro R. J. The hill coefficient for the Ca2+-activation of striated muscle contraction. Biophys J. 1984 Oct;46(4):541–543. doi: 10.1016/S0006-3495(84)84051-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Solaro R. J., Lee J. A., Kentish J. C., Allen D. G. Effects of acidosis on ventricular muscle from adult and neonatal rats. Circ Res. 1988 Oct;63(4):779–787. doi: 10.1161/01.res.63.4.779. [DOI] [PubMed] [Google Scholar]
  36. Stull J. T., Buss J. E. Calcium binding properties of beef cardiac troponin. J Biol Chem. 1978 Sep 10;253(17):5932–5938. [PubMed] [Google Scholar]
  37. Tsukui R., Ebashi S. Cardiac troponin. J Biochem. 1973 May;73(5):1119–1121. doi: 10.1093/oxfordjournals.jbchem.a130168. [DOI] [PubMed] [Google Scholar]
  38. Walker J. W., Lu Z., Moss R. L. Effects of Ca2+ on the kinetics of phosphate release in skeletal muscle. J Biol Chem. 1992 Feb 5;267(4):2459–2466. [PubMed] [Google Scholar]
  39. Wendt I. R., Stephenson D. G. Effects of caffeine on Ca-activated force production in skinned cardiac and skeletal muscle fibres of the rat. Pflugers Arch. 1983 Aug;398(3):210–216. doi: 10.1007/BF00657153. [DOI] [PubMed] [Google Scholar]
  40. Zot H. G., Güth K., Potter J. D. Fast skeletal muscle skinned fibers and myofibrils reconstituted with N-terminal fluorescent analogues of troponin C. J Biol Chem. 1986 Dec 5;261(34):15883–15890. [PubMed] [Google Scholar]
  41. de Beer E. L., Gründeman R. L., Wilhelm A. J., Caljouw C. J., Klepper D., Schiereck P. Caffeine suppresses length dependency of Ca2+ sensitivity of skinned striated muscle. Am J Physiol. 1988 Apr;254(4 Pt 1):C491–C497. doi: 10.1152/ajpcell.1988.254.4.C491. [DOI] [PubMed] [Google Scholar]
  42. el-Saleh S. C., Solaro R. J. Troponin I enhances acidic pH-induced depression of Ca2+ binding to the regulatory sites in skeletal troponin C. J Biol Chem. 1988 Mar 5;263(7):3274–3278. [PubMed] [Google Scholar]

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