Mobilizing ER IP3 receptors as a mechanism to enhance calcium signaling

We present here evidence for the enhancement, at rest, of an inositol 1,4,5-trisphosphate (IP3)–mediated calcium signaling pathway in myotubes from dystrophin-deficient cell lines (SolC1(−)) as compared to a cell line from the same origin but transfected with mini-dystrophin (SolD(+)). With confocal microscopy, the number of sites discharging calcium (release site density [RSD]) was quantified and found more elevated in SolC1(−) than in SolD(+) myotubes. Variations of membrane potential had no significant effect on this difference, and higher resting [Ca2+]i in SolC1(−) (Marchand, E., B. Constantin, H. Balghi, M.C. Claudepierre, A. Cantereau, C. Magaud, A. Mouzou, G. Raymond, S. Braun, and C. Cognard. 2004. Exp. Cell Res. 297:363–379) cannot explain alone higher RSD. The exposure with SR Ca2+ channel inhibitors (ryanodine and 2-APB) and phospholipase C inhibitor (U73122) significantly reduced RSD in both cell types but with a stronger effect in dystrophin-deficient SolC1(−) myotubes. Immunocytochemistry allowed us to localize ryanodine receptors (RyRs) as well as IP3 receptors (IP3Rs), IP3R-1 and IP3R-2 isoforms, indicating the presence of both RyRs-dependent and IP3-dependent release systems in both cells. We previously reported evidence for the enhancement, through a Gi protein, of the IP3-mediated calcium signaling pathway in SolC1(−) as compared to SolD(+) myotubes during a high K+ stimulation (Balghi, H., S. Sebille, B. Constantin, S. Patri, V. Thoreau, L. Mondin, E. Mok, A. Kitzis, G. Raymond, and C. Cognard. 2006. J. Gen. Physiol. 127:171–182). Here we show that, at rest, these regulation mechanisms are also involved in the modulation of calcium release activities. The enhancement of resting release activity may participate in the calcium overload observed in dystrophin-deficient myotubes, and our findings support the hypothesis of the regulatory role of mini-dystrophin on intracellular signaling.

Download Full-text

Negative modulation of inositol 1,4,5-trisphosphate type 1 receptor expression prevents dystrophin-deficient muscle cells death

AJP Cell Physiology ◽

10.1152/ajpcell.00048.2009 ◽

2009 ◽

Vol 297 (5) ◽

pp. C1133-C1145 ◽

Cited By ~ 14

Author(s):

Ludivine Mondin ◽

Haouaria Balghi ◽

Bruno Constantin ◽

Christian Cognard ◽

Stéphane Sebille

Keyword(s):

Cell Death ◽

Calcium Signaling ◽

Calcium Release ◽

Receptor Expression ◽

Type I ◽

Ip3 Receptors ◽

Inositol 1,4,5 Trisphosphate ◽

Interesting Approach ◽

Long Time ◽

Short Time

Evidence for a modulatory effect of cyclosporin A (CsA) on calcium signaling and cell survival in dystrophin-deficient cells is presented. Our previous works strongly supported the hypothesis of an overactivation of Ca2+ release via inositol 1,4,5-trisphosphate (IP3) receptors (IP3R) in dystrophin-deficient cells, both during membrane depolarization and at rest, through spontaneous Ca2+ release events. Forced expression of mini-dystrophin in these cells contributed, during stimulation and in resting condition, to the recovery of a controlled calcium homeostasis. In the present work, we demonstrate that CsA exposure displayed a dual-modulator effect on calcium signaling in dystrophin-deficient cells. Short-time incubation induced a decrease of IP3-dependent calcium release, leading to patterns of release similar to those observed in myotubes expressing mini-dystrophin, whereas long-time incubation reduced the expression of the type I of IP3 receptors (IP3R-1) RNA levels. Moreover, both IP3R-1 knockdown and blockade through 2-aminoethoxydiphenyle borate or CsA induced improved survival of dystrophin-deficient myotubes, demonstrating the cell death dependence on the IP3-dependent calcium signaling as well as the protective effect of CsA. Inhibition of the IP3 pathway could be a very interesting approach for reducing the natural cell death of dystrophin-deficient cells in development.

Download Full-text

New Aspects of Cytosloic Calcium Signaling

Physiology ◽

10.1152/physiologyonline.1996.11.1.13 ◽

1996 ◽

Vol 11 (1) ◽

pp. 13-17 ◽

Cited By ~ 3

Author(s):

OH Petersen

Keyword(s):

Endoplasmic Reticulum ◽

Simple Model ◽

Calcium Signaling ◽

Inositol Trisphosphate ◽

Ip3 Receptors ◽

Messenger System ◽

Intracellular Messenger

Hormone- or neurotransmitter-evoked cytosolic Ca2+ signals are generally thought to be initiated by an increase in inositol trisphosphate (IP3) concentration that in turn opens Ca2+ release channels in the endoplasmic reticulum. Recent data challenge this simple model and indicate IP3 receptors in several organelles and an additional intracellular messenger system for Ca2+ regulation.

Download Full-text