Development of an inducible system to assess p94 (CAPN3) function in cultured muscle cells.

p94 belongs to the calpain family of enzymes, also called calcium-activated neutral proteases and is mainly expressed in the skeletal muscle. Mutations affecting the gene coding for p94 are responsible for a myopathy syndrome called Limb Girdle Muscular Dystrophy type 2A (LGMD2A). Although the activity of p94 seems necessary for muscle function, the biological role of the enzyme is still unknown. The goal of this study was to develop a muscle cell line in which the expression level of p94 can be regulated, by an inducible way. In this study, a biological system was developed which allowed mimicking, in vitro, of part of the events occurring in patients (i.e. a decrease of p94 activity). The first results indicate that the decrease in p94 activity results in a significant increase of myogenin level, a high specific transcription factor involved in myoblast fusion. This muscle specific inducible system is an interesting biological tool to assess specifically p94 function(s) in cultured muscle cells. According to the present results, p94 seems at least to be involved in a myogenesis regulation pathway via its action on certain proteins belonging to the myogenic regulator factor family.