M. Broydell et al., INVOLVEMENT OF THE GLUT TRANSPORTER IN MYOGENIC REGULATION, Biochemistry and molecular biology international, 43(4), 1997, pp. 847-866
We have recently demonstrated a close relationship between the GLUT3 t
ransporter and the myogenic ability of rat skeletal L6 myoblasts [1].
This investigation examined the effects of over- and under-expression
of the GLUT3 transporter on both biochemical and morphological differe
ntiation. L6 transfectants expressing two to five times the normal L6
GLUT3 transcript level were impaired in the expression of myogenesis-a
ssociated genes, such as myogenin, MLC, MHC and TnT, and in myotube fo
rmation. Similar defects were also observed in myoblast mutants expres
sing less than 20% of the normal GLUT3 level. Forced expression of an
exogenous GLUT3 cDNA could partially rescue the myogenic defect of the
se GLUT3(-) mutants. However, such myogenic defects were not observed
in L6 GLUT3 antisense transfectants expressing 39% of the normal L6 GL
UT3 level. These data suggest that myogenic differentiation will proce
ed only within a critical level of the GLUT3 transporter. The optimal
GLUT3 content for myogenesis ranges from around 2 x 10(5) to 5 x 10(5)
molecules per cell in day 2 cultures; GLUT3 levels outside this range
have a negative effect on myogenesis. Our data suggest that GLUT3 may
regulate myogenesis by modulating the levels of signal transducers re
quired for expression of myogenin and muscle-specific contractile prot
ein genes.