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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 586/2/441    most recent jphysiol.2007.145862v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Legrand, C. Articles by Jacquemond, V. Search for Related Content PubMed PubMed Citation Articles by Legrand, C. Articles by Jacquemond, V. Related Collections Cellular Related Article

¹ Physiologie Intégrative Cellulaire et Moléculaire, Université Lyon 1, UMR CNRS 5123, Villeurbanne, France
² Molecular Medicine Section, Department of Neuroscience, University of Siena, Siena, Italy

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 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.

(Received 1 October 2007; accepted after revision 9 November 2007; first published online 15 November 2007)
Corresponding author V. Jacquemond: Physiologie Intégrative Cellulaire et Moléculaire, Université Lyon 1, UMR CNRS 5123, Bât. Raphaël Dubois, 43 boulevard du 11 novembre 1918, F69622 Villeurbanne, France. Email: vincent.jacquemond{at}univ-lyon1.fr

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