Massive alterations of sarcoplasmic reticulum free calcium in skeletal muscle fibers lacking calsequestrin revealed by a genetically encoded probe.
Proc Natl Acad Sci U S A
; 107(51): 22326-31, 2010 Dec 21.
Article
en En
| MEDLINE
| ID: mdl-21135222
ABSTRACT
The cytosolic free Ca(2+) transients elicited by muscle fiber excitation are well characterized, but little is known about the free [Ca(2+)] dynamics within the sarcoplasmic reticulum (SR). A targetable ratiometric FRET-based calcium indicator (D1ER Cameleon) allowed us to investigate SR Ca(2+) dynamics and analyze the impact of calsequestrin (CSQ) on SR [Ca(2+)] in enzymatically dissociated flexor digitorum brevis muscle fibers from WT and CSQ-KO mice lacking isoform 1 (CSQ-KO) or both isoforms [CSQ-double KO (DKO)]. At rest, free SR [Ca(2+)] did not differ between WT, CSQ-KO, and CSQ-DKO fibers. During sustained contractions, changes were rather small in WT, reflecting powerful buffering of CSQ, whereas in CSQ-KO fibers, significant drops in SR [Ca(2+)] occurred. Their amplitude increased with stimulation frequency between 1 and 60 Hz. At 60 Hz, the SR became virtually depleted of Ca(2+), both in CSQ-KO and CSQ-DKO fibers. In CSQ-KO fibers, cytosolic free calcium detected with Fura-2 declined during repetitive stimulation, indicating that SR calcium content was insufficient for sustained contractile activity. SR Ca(2+) reuptake during and after stimulation trains appeared to be governed by three temporally distinct processes with rate constants of 50, 1-5, and 0.3 s(-1) (at 26 °C), reflecting activity of the SR Ca(2+) pump and interplay of luminal and cytosolic Ca(2+) buffers and pointing to store-operated calcium entry (SOCE). SOCE might play an essential role during muscle contractures responsible for the malignant hyperthermia-like syndrome in mice lacking CSQ.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Retículo Sarcoplasmático
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Calsecuestrina
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Calcio
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Fibras Musculares Esqueléticas
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Señalización del Calcio
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ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico
Límite:
Animals
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Año:
2010
Tipo del documento:
Article
País de afiliación:
Italia