| First Author | Legrand C | Year | 2008 |
| Journal | J Physiol | Volume | 586 |
| Issue | 2 | Pages | 441-57 |
| PubMed ID | 18006577 | Mgi Jnum | J:176413 |
| Mgi Id | MGI:5291592 | Doi | 10.1113/jphysiol.2007.145862 |
| Citation | Legrand C, et al. (2008) Spontaneous and voltage-activated Ca2+ release in adult mouse skeletal muscle fibres expressing the type 3 ryanodine receptor. J Physiol 586(2):441-57 |
| abstractText | The physiological properties and role of the type 3 ryanodine receptor (RyR3), a calcium release channel expressed in a wide variety of cell types, remain mysterious. We forced, in vivo, the expression of RyR3 in adult mouse skeletal muscle fibres using a GFP-RyR3 DNA construct. GFP fluorescence was found within spatially restricted regions of muscle fibres where it exhibited a sarcomere-related banded pattern consistent with a localization within or near the junctional sarcoplasmic reticulum membrane. Immunostaining confirmed the presence of RyR3 together with RyR1 within the GFP-positive areas. In approximately 90% of RyR3-positive fibres microinjected with the calcium indicator fluo-3, we detected repetitive spontaneous transient elevations of intracellular Ca2+ that persisted when fibres were voltage-clamped at -80 mV. These Ca2+ transients remained essentially confined to the RyR3 expression region. They ranged from wide local events to propagating Ca2+ waves and were in some cases associated with local contractile activity. When voltage-clamp depolarizations were applied while fluo-3 or rhod-2 fluorescence was measured within the RyR3-expressing region, no voltage-evoked 'spark-like' elementary Ca2+ release event could be detected. Still global voltage-activated Ca2+ release exhibited a prominent early peak within the RyR3-expressing regions. Measurements were also taken from muscles fibres expressing a GFP-RyR1 construct; positive fibres also yielded a local banded pattern of GFP fluorescence but exhibited no spontaneous Ca2+ release. Results demonstrate that RyR3 is a very potent source of voltage-independent Ca2+ release activity. Conversely we find no evidence that it could contribute to the production of discrete voltage-activated Ca2+ release events in differentiated mammalian skeletal muscle. |
