A Possible Role of the Junctional Face Protein Jp-45 in Modulating Ca2+ Release in Skeletal Muscle.
From: University of Ulm, Department of Applied Physiology, Albert-Einstein-Allee 11, D-89069 Ulm, Germany.
The Journal of physiology
- Publish Date: Apr 2006
- ISSN: 0022-3751
- Volume: 572
- Issue: Pt 1
- Pages: 269-80
- Medium: Print
- Language: English
- Citation (JAMA): Gouadon E, Schuhmeier R P, Ursu D, et al. A Possible Role of the Junctional Face Protein Jp-45 in Modulating Ca2+ Release in Skeletal Muscle.. J. Physiol. (Lond.) Apr 2006;572:269-80
Abstract
We investigated the functional role of JP-45, a recently discovered protein of the junctional face membrane (JFM) of skeletal muscle. For this purpose, we expressed JP-45 C-terminally tagged with the fluorescent protein DsRed2 by nuclear microinjection in myotubes derived from the C2C12 skeletal muscle cell line and performed whole-cell voltage-clamp experiments. We recorded in parallel cell membrane currents and Ca(2+) signals using fura-2 during step depolarization. It was found that properties of the voltage-activated Ca(2+) current were not significantly changed in JP-45-DsRed2-expressing C2C12 myotubes whereas the amplitude of depolarization-induced Ca(2+) transient was decreased compared to control myotubes expressing only DsRed2. Converting Ca(2+) transients to Ca(2+) input flux using a model fit approach to quantify Ca(2+) removal, the change could be attributed to an alteration in voltage-activated Ca(2+) permeability rather than to altered removal properties or a lower Ca(2+) content of the sarcoplasmic reticulum (SR). Determining non-linear capacitive currents revealed a reduction of Ca(2+) permeability per voltage-sensor charge. The results may be explained by a modulatory effect of JP-45 related to its reported in vitro interaction with the dihydropyridine receptor and the SR Ca(2+) binding protein calsequestrin (CSQ).
Mesh Headings (Keywords): Animals, Calcium, Calcium Signaling, Cell Line, Humans, Ion Channel Gating, Membrane Potentials, Membrane Proteins, Mice, Muscle Fibers, Muscle, Skeletal, Ryanodine Receptor Calcium Release Channel, Sarcoplasmic Reticulum
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