Altered IP3 receptors, IP3‐dependent Ca2+ transients and Ca2+‐dependent gene expression in a Duchenne muscular dystrophy cell line

Abstract

Although deregulation of calcium handling has been recognized to play a role in Duchenne muscular dystrophy (DMD), little is known about the role of calcium release in this phenomenon. Inositol 1,4,5 trisphosphate receptors (IP3Rs) are located in the sarcoplasmic reticulum and nucleus of skeletal muscle cells. Upon electrical stimulation (400pulses, 1ms, 45Hz), these receptors mediate slow calcium transients, involved in gene regulation. Using normal (RCMH) and dystrophic (RCDMD) human skeletal muscle cell lines, we explored the distribution of IP3Rs as well as IP3‐dependent calcium dynamics. Mouse oligonucleotide microarrays alowed analysis of total RNA from RCMH and RCDM myotubes obtained 4h post‐stimulus.Dystrophic cells show a five‐fold over expression of type‐2 IP3R; type‐2 IP3R locates in the nucleus in RCDMD cells, while type‐1 and type‐3 IP3Rs appear also to locate differently. Both cell lines displayed a slow calcium transient upon electrical stimulation, the signal being much faster and larger in RCDMD cells. IP3‐mediated calcium signals induced phosphorylation of extra cellular signal‐regulated kinase (ERK1/2) in normal but not in dystrophic cells. Statistical analysis of microarrays resulted in 132 and 150 differentially expressed genes in RCMH and RCDMD respectively. As IP3‐dependent calcium signals appear to be the first step in regulation of gene expression, impairment of this pathway could play an important role in DMD patho‐physiology.FONDAP 15010006