Fast-twitch skeletal muscle

Parvalbumin (Fig 1) is a cytosolic protein expressed in fast-twitch skeletal muscles and in the nervous system. In muscles, parvalbumin controls the relaxation process. In the CNS, parvalbumin, expressed in a subpopulation of GABAergic neurons, is correlated with their firing rates, protecting the cells from Ca2+ overload. 

SERCA la denotes the Ca -ATPase of adult fast-twitch skeletal muscle with glycine at its C-terminus in the rabbit [53,58], and alanine at the C-terminus in the chicken [59,60]. The C-terminus of the lobster enzyme is apparently blocked [59]. 

SERCAlb Neonatal fast-twitch skeletal muscle Rabbit 1001 110331 MEAA EDPEDERRK 8, 53... 

The first Ca -ATPase clones were isolated by probing cDNA libraries with radiolabeled synthetic oligonucleotides [42] that represented an established amino acid sequence ((Trp-) Phe Met Tyr Ala) in the fast-twitch skeletal muscle... 

The cDNA clone for the neonatal rabbit fast-twitch skeletal muscle Ca -ATPase encodes for 1001 amino acids giving a product with an estimated molecular weight of 110 331 Da [8], The clone for the Ca -ATPase of slow-twitch skeletal muscle sarcoplasmic reticulum (S-Ca -ATPase) encoded for 997 amino acids with a relative molecular mass (Mr) of 109 529 kDa [42],... 

The smooth endoplasmic reticulum calcium pumps (SERCA) found in brain were first identified in sarcoplasmic reticulum. The three isoforms of SERCA are products of separate genes SERCA-1 is expressed in fast-twitch skeletal muscle SERCA-2a in cardiac/slow-twitch muscle SERCA-2b, an alternatively spliced form, is expressed in smooth muscle and non-muscle tissues SERCA-3 is... 

Odermatt, A., Taschner, P. E., Khanna, V. K. etal. Mutations in the gene-encoding SERCA1, the fast-twitch skeletal muscle sarcoplasmic reticulum Ca2+ ATPase, are associated with Brody disease. Nat. Genet.lA. 191-194,1996. 

Odermatt A, Barton K, Khanna VK et al 2000 The mutation of Pro789 to Leu reduces the activity of the fast-twitch skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA1) and is associated with Brody disease. Hum Genet 106 482-491... 

ATP2A1 16pl2.1 SERCAla (adult) SERCAlb (neonate) Fast twitch skeletal muscle (type 2) fibers Brody s myopathy (recessive)... 

In muscle cells, the contraction is induced by Ca2+ release from the sarcoplasmic reticulum, as a result of membrane depolarization and activation of RyRl receptors located at the surface of the SR. The subsequent transport of cytoplasmic Ca2+ back into the lumen of the sarcoplasmic reticulum restores low resting calcium levels and allows muscle relaxation. In fast-twitch skeletal muscle fibers, Ca2+ uptake is mediated by the sarco(endo)plasmic reticulum Ca2+ ATPase SERCA1 which represents more than 99% of SERCA isoforms in these muscle fibers. 

In Brody disease, as a result of loss of function mutations in ATP2A1, Ca2+ is not transported back into the SR after its release from the stores and accumulates in the myoplasm, resulting in delayed relaxation and muscle cramping. It is of interest that patients with Brody disease are still able to relax their fast-twitch skeletal muscles, even though relaxation is significantly reduced. This suggest that SERCA2... 

Zhang, Y., Fujii, J., Phillips, M. S., Chen, H. S., Karpati, G., Yee, W. C., Schrank, B., Cornblath, D. R., Boylan, K. B., and MacLennan, D. H., 1995, Characterization of cDNA and genomic DNA encoding SERCA 1, the Ca(2+)-ATPase of human fast-twitch skeletal muscle sarcoplasmic reticulum, and its elimination as a candidate gene for Brody disease. Genomics, 30 415-24. 

Divet, A., and Huchet-Cadiou, C., 2002, Sarcoplasmic reticulum function in slow- and fast-twitch skeletal muscles from mdx mice, Pflugers Arch, 444, pp 634-643. 

The contractile proteins of the myofibril include three troponin regulatory proteins. The troponin complex includes three protein subunits, troponin C (the calcium-binding component), troponin I (the inhibitory component), and troponin T (the tropomyosin-binding component). The subunits exist in a number of isoforms. The distribution of these isoforms varies between cardiac muscle and slow- and fast-twitch skeletal muscle. Only two major isoforms of troponin C are found in human heart and skeletal muscle. These are characteristic of slow- and fast-twitch skeletal muscle. The heart isoform is identical with the slow-twitch skeletal muscle isoform. Isoforms of cardiac-specific troponin T (cTnT) and cTnl also have been identified and are the products of unique genes. All cardiac troponins are localized primarily in the myofibrils (94%-97%), with a smaller cytoplasm fraction (3%-6%). 

Ogut O, Granzier H, Jin JP. Acidic and basic troponin-T isoforms in mature fast-twitch skeletal muscle and effect on contractility. Am Physiol. 1999 276 C1162-C1170. 

Lewis SEM, Kelly FJ, Goldspink DF (1984) Pre- and post-natal growth and protein turnover in smooth muscle, heart and slow- and fast-twitch skeletal muscle of the rat. Biochem J 217 517-526... 

It is possible, of course, to use direct calorimetry, often in combination with the indirect approach (OUR) to investigate the properties of muscle under different physiological conditions and in the diseased state. Chinet s group [70] found that the slow- and fast-twitch skeletal muscle fibres from the murine model of Duchenne muscular dystrophy had a reduced sarcoplasmic energy metabolism as measured by the combined direct and indirect calorimeter [69]. The possibility that this could be due to diminished glucose availability was then examined [71] but was dismissed in favour of decreased oxidative utilisation of glucose and free fatty acids, conceivably due to defective mitochondria. 

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