Premium
Spontaneous and voltage‐activated Ca 2+ release in adult mouse skeletal muscle fibres expressing the type 3 ryanodine receptor
Author(s) -
Legrand Claude,
Giacomello Emiliana,
Berthier Christine,
Allard Bruno,
Sorrentino Vincenzo,
Jacquemond Vincent
Publication year - 2008
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2007.145862
Subject(s) - ryanodine receptor , ryr1 , endoplasmic reticulum , sarcomere , biophysics , calcium , skeletal muscle , calcium in biology , immunostaining , biology , myocyte , intracellular , chemistry , microbiology and biotechnology , anatomy , immunohistochemistry , immunology , organic chemistry
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 Ca 2+ that persisted when fibres were voltage‐clamped at −80 mV. These Ca 2+ transients remained essentially confined to the RyR3 expression region. They ranged from wide local events to propagating Ca 2+ 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 Ca 2+ release event could be detected. Still global voltage‐activated Ca 2+ 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 Ca 2+ release. Results demonstrate that RyR3 is a very potent source of voltage‐independent Ca 2+ release activity. Conversely we find no evidence that it could contribute to the production of discrete voltage‐activated Ca 2+ release events in differentiated mammalian skeletal muscle.