Abnormal distribution of inositol 1,4,5‐trisphosphate receptors in human muscle can be related to altered calcium signals and gene expression in Duchenne dystrophy‐derived cells

Abstract

Inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) drive calcium signals involved in skeletal muscle excitation-transcription coupling and plasticity; IP(3)R subtype distribution and downstream events evoked by their activation have not been studied in human muscle nor has their possible alteration in Duchenne muscular dystrophy (DMD). We studied the expression and localization of IP(3)R subtypes in normal and DMD human muscle and in normal (RCMH) and dystrophic (RCDMD) human muscle cell lines. In normal muscle, both type 1 IP(3)Rs (IP(3)R1) and type 2 IP(3)Rs (IP(3)R2) show a higher expression in type II fibers, whereas type 3 IP(3)Rs (IP(3)R3) show uniform distribution. In DMD biopsies, all fibers display a homogeneous IP(3)R2 label, whereas 24 +/- 7% of type II fibers have lost the IP(3)R1 label. RCDMD cells show 5-fold overexpression of IP(3)R2 and down-regulation of IP(3)R3 compared with RCMH cells. A tetanic stimulus induces IP(3)-dependent slow Ca(2+) transients significantly larger and faster in RCDMD cells than in RCMH cells as well as significant ERK1/2 phosphorylation in normal but not in dystrophic cells. Excitation-driven gene expression was different among cell lines; 44 common genes were repressed in RCMH cells and expressed in RCDMD cells or vice versa. IP(3)-dependent Ca(2+) release may play a significant role in DMD pathophysiology.

Altered Gene Expression Pathways in Duchenne Muscular Dystrophy

“…When human muscle was studied, type II muscle fibers showed a much more intense labeling for the IP 3 R subtype 1 compared to type I (slow) fibers. In biopsies from DMD patients, we found that 24 ± 7% of type II fibers have totally lost type 1 IP 3 R labeling, compared to age-matched control biopsies (Cárdenas et al 2010). On the other hand, RCDMD cells show a five-fold over expression of type 2 IP 3 Rs and down regulation of type 3 IP 3 Rs compared to normal RCMH cells (Cárdenas et al 2010).…”

“…In biopsies from DMD patients, we found that 24 ± 7% of type II fibers have totally lost type 1 IP 3 R labeling, compared to age-matched control biopsies (Cárdenas et al 2010). On the other hand, RCDMD cells show a five-fold over expression of type 2 IP 3 Rs and down regulation of type 3 IP 3 Rs compared to normal RCMH cells (Cárdenas et al 2010). Unlike normal muscle cells, type 2 IP 3 R locate in the nucleus in RCDMD cells, while type 1 and type 3 IP 3 Rs also display a particular subcellular location for each line (Cárdenas et al 2010).…”

“…Moreover, it has been described that IP 3 production after membrane depolarization is significantly elevated in dystrophin-deficient myotubes and that the presence of minidystrophin under the membrane leads to reduced IP 3 production (Balghi et al 2006a). In fact, we have recently demonstrated, using normal (RCMH) and dystrophic (RCDMD) human skeletal muscle cell lines, that IP 3 dependent, slow Ca 2+ transients evoked by electrical stimulation are faster in dystrophic cells, compared to normal myotubes (Cárdenas et al 2010). Electrical stimulation induced an important phosphorylation of ERK½ in normal but not in dystrophic cells, and a differential pattern of gene expression between cell lines.…”

“…On the other hand, RCDMD cells show a five-fold over expression of type 2 IP 3 Rs and down regulation of type 3 IP 3 Rs compared to normal RCMH cells (Cárdenas et al 2010). Unlike normal muscle cells, type 2 IP 3 R locate in the nucleus in RCDMD cells, while type 1 and type 3 IP 3 Rs also display a particular subcellular location for each line (Cárdenas et al 2010). These results showed that IP 3 Rs expression and localization are different in muscle affected by DMD.…”

“…Several studies indicate that IP 3 pathways could be involved in the DMD pathophysiology (Liberona et al 1998;Balghi et al 2006a;Balghi et al 2006b). We recently found that both expression and localization of IP 3 Rs are different in normal and dystrophic human skeletal muscle and cell lines (Cárdenas et al 2010). On the other hand, experiments performed using two types of myotubes originated from the same Sol8 cell line -dystrophin deficient myotubes, SolC1(-), and myotubes transfected to express the minidystrophin, SolD(+) -show that Ca 2+ rise evoked by potassium depolarization was higher in SolC1(-) than in SolD(+) myotubes (Balghi et al 2006a).…”