This work was supported by Hungarian Scientific Research Fund OTKA (T049151, K61442).
University of Heidelberg (2006) Proc Physiol Soc 4, PC9
Poster Communications: János Fodor1, Mónika Fehér1, Tamás Deli1, Peter Szentesi1, László Csernoch1, 2
1. Department of Physiology, University of Debrecen, Debrecen, Hungary. 2. RCMM, University of Debrecen, Debrecen, Hungary.
Triadin is localized in the sarcoplasmic reticulum (SR) and is connected to the ryanodine receptor (RyR) and calsequestrin. It has different isoforms in skeletal muscles of vertebrates. So far 32, 49, 51 and 95 kDa isoforms were described in rat skeletal muscle which originate from the same gene. It was suggested earlier that Triadin can play a role in regulating calcium release from the SR and probably in the differentiation of myotubes. The 95 kDa Triadin (TRISK95) was over-expressed in C2C12 cells and primary myotubes from mouse and the properties of EC coupling were examined. Whole cell intracellular calcium concentration was measured using the acetoxymethylesther form of the fluorescent dye fura-2. While the KCl-induced calcium release from the SR was significantly smaller in Triadin over-expressing myotubes, caffeine-induced release was identical in the two cases. The former effects depended on the presence of external calcium concentration. Sparks and embers, the two forms of spontaneous calcium release events, were measured with confocal microscopy using fluo-3 on control and TRISK95 over-expressing cells. Triadin decreased the frequency, from the control 21.1±0.6 Hz (n=577) to 13.3±0.7 Hz (n=332), and the amplitude of sparks, but did not change their duration. In the case of embers the frequency decreased from the control 21.1±1.9 Hz (n=63) to 12.2±2.1 Hz (n=41) and while their duration also decreased, their amplitude was not affected. We propose that Triadin over-expression inhibits RyRs and thus decreases calcium release from the SR.
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