Co-localization of 1,4-dihydropyridine receptor α2/δ subunit and N-CAM during early myogenesis in vitro

• Published in: Journal of cell science Vol. 107; no. 5; pp. 1217 - 1227
• Main Authors: VANDAELE, S. F, RIEGER, F
• Format: Journal Article
• Language: English
• Published: Cambridge Company of Biologists 01.05.1994
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; Vertebrata; Mammalia; Calcium; Rabbit; Ionic channel; Lagomorpha; Localization; Striated muscle; Myogenesis; Biological receptor
• ISSN: 0021-9533; 1477-9137
• DOI: 10.1242/jcs.107.5.1217

ABSTRACT The surface distribution of the subunit of the 1,4-dihydropyridine receptor and its topographical relationship with the neural cell adhesion molecule (N-CAM) were investigated during early myogenesis in vitro, by double immunocytochemical labeling with the monoclonal antibody 3007 and an anti-N-CAM polyclonal antiserum. The monoclonal antibody 3007 has been previously shown to immunoprecipitate dihydropyridine receptor from skeletal muscle T-tubules. In further immunoprecipitation experiments on such preparations and muscle cell cultures, it was demonstrated here that the monoclonal antibody 3007 exclusively recognizes the α2/δ subunit of the 1,4-dihydropyridine receptor. In rabbit muscle cell cultures, the labeling for both α2/δ and N-CAM was first detected on myoblasts, in the form of spots on the membrane and per-inuclear patches. Spots of various sizes organized in aggregates were then found on the membrane of myotubes. At fusion (T0), aggregates of N-CAM spots alone were found at the junction between fusing cells. At T6and later stages, all α2/δ aggregates present on myotubes co-localized with N-CAM, while less than 3% of N-CAM aggregates did not co-localize with α2/δ. A uniform N-CAM staining also made its appearance. At T12, when myotubes showed prominent contractility, α2/δ–N-CAM aggregates diminished in size. Dispersed α2/δ spots of a small regular size spread over the whole surface of the myotubes and alignments of these spots became visible. Corresponding N-CAM spots were now occasionally seen, and uniform N-CAM staining was prominent. These results show that α2/δ and N-CAM are co-localized and that their distributions undergo concomitant changes during early myogenesis until the T-tubule network starts to be organized. This suggest that these two proteins might jointly participate in morphogenetic events preceding the formation of T-tubules.