title: Perturbations in intracellular Ca2+ handling in skeletal muscle in the G93A*SOD1 mouse model of amyotrophic lateral sclerosis.
abstract: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by skeletal muscle atrophy and weakness, ultimately leading to respiratory failure. The purpose of this study was to assess changes in skeletal muscle excitation-contraction (E-C) coupling and intracellular Ca(2+) handling during disease progression in the G93A*SOD1 ALS transgenic (ALS Tg) mouse model. To assess E-C coupling, single muscle fibers were electrically stimulated (10-150 Hz), and intracellular free Ca(2+) concentration was assessed using fura-2. There were no differences in peak fura-2 ratio at any stimulation frequency at 70 days (early presymptomatic). However, at 90 days (late presymptomatic) and 120-140 days (symptomatic), fura-2 ratio was increased at 10 Hz in ALS Tg compared with wild-type (WT) fibers (0.670 ± 0.02 vs. 0.585 ± 0.02 for 120-140 days; P < 0.05). There was also a significant increase in resting fura-2 ratio at 90 days (0.351 ± 0.008 vs. 0.390 ± 0.009 in WT vs. ALS Tg; P < 0.05) and 120-140 days (0.374 ± 0.001 vs. 0.415 ± 0.003 in WT vs. ALS Tg; P < 0.05). These increases in intracellular Ca(2+) in ALS Tg muscle were associated with reductions in the sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase proteins SERCA1 (to 54% and 19% of WT) and SERCA2 (to 56% and 11% of WT) and parvalbumin (to 80 and 62% of WT) in gastrocnemius muscle at 90 and 120-140 days, respectively. There was no change in dihydropyridine receptor/l-type Ca(2+) channel at any age. Overall, these data demonstrate minimal changes in electrically evoked Ca(2+) transients but elevations in intracellular Ca(2+) attributable to decreased Ca(2+)-clearance proteins. These data suggest that elevations in cellular Ca(2+) could contribute to muscle weakness during disease progression in ALS mice.
authors.affiliation: School of Public Health, University of Maryland, College Park, Maryland erchin@umd.edu.
authors.forename: Eva R
authors.initials: ER
authors.lastname: Chin
authors.affiliation: School of Public Health, University of Maryland, College Park, Maryland.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Chen
authors.affiliation: School of Public Health, University of Maryland, College Park, Maryland.
authors.forename: Kostyantyn D
authors.initials: KD
authors.lastname: Bobyk
authors.affiliation: School of Public Health, University of Maryland, College Park, Maryland.
authors.forename: Davi A G
authors.initials: DA
authors.lastname: Mázala
mesh_terms: D000375:Aging; D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D053580:Muscle Strength / Q000235:genetics / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
chemical_list: C109415:SOD1 G93A protein; D013482:Superoxide Dismutase; D002118:Calcium
keywords: amyotrophic lateral sclerosis; excitation-contraction coupling; intracellular Ca2+; skeletal muscle