Mini-dystrophin expression down-regulates overactivation of G protein-mediated IP3 signaling pathway in dystrophin-deficient muscle cells.
We present here evidence for the enhancement 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, we demonstrated that calcium rise, induced by the perifusion of a solution containing a high potassium concentration, was higher in SolC1(-) than in SolD(+) myotubes. The analysis of amplitude and kinetics of the calcium increase in SolC1(-) and in SolD(+) myotubes during the exposure with SR Ca2+ channel inhibitors (ryanodine and 2-APB) suggested the presence of two mechanisms of SR calcium release: (1) a fast SR calcium release that depended on ryanodine receptors and (2) a slow SR calcium release mediated by IP3 receptors. Detection analyses of mRNAs (reverse transcriptase [RT]-PCR) and proteins (Western blot and immunolocalization) demonstrated the presence of the three known isoforms of IP3 receptors in both SolC1(-) and SolD(+) myotubes. Furthermore, analysis of the kinetics of the rise in calcium revealed that the slow IP3-dependent release may be increased in the SolC1(-) as compared to the SolD(+), suggesting an inhibitory effect of mini-dystrophin in this signaling pathway. Upon incubation with pertussis toxin (PTX), an inhibitory effect similar to that of the IP3R inhibitor (2-APB) was observed on K+-evoked calcium release. This result suggests the involvement of a Gi protein upstream of the IP3 pathway in these stimulation conditions. A hypothetical model is depicted in which both Gi protein and IP3 production could be involved in K+-evoked calcium release as well as a possible interaction with mini-dystrophin. Our findings demonstrate the existence of a potential relationship between mini-dystrophin and SR calcium release as well as a regulatory role of mini-dystrophin on intracellular signaling.
Balghi
Haouaria
H
Institut de Physiologie et Biologie Cellulaires, CNRS UMR 6187, Université de Poitiers, France.
Sebille
Stéphane
S
Constantin
Bruno
B
Patri
Sylvie
S
Thoreau
Vincent
V
Mondin
Ludivine
L
Mok
Elise
E
Kitzis
Alain
A
Raymond
Guy
G
Cognard
Christian
C
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000032:analysis / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D020013:Calcium Signaling; D002460:Cell Line; D015536:Down-Regulation; D016189:Dystrophin / Q000032:analysis / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology; D019204:GTP-Binding Proteins / Q000502:physiology*; D015870:Gene Expression; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D051379:Mice; D008809:Mice, Inbred C3H; D018613:Microscopy, Confocal; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology
D015220:Calcium Channels; D016189:Dystrophin; D053496:Inositol 1,4,5-Trisphosphate Receptors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel; D015544:Inositol 1,4,5-Trisphosphate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D011188:Potassium; D002118:Calcium