L. Xia et al., TRANSCRIPTS FOR THE HIGH AND LOW-AFFINITY HEXOSE TRANSPORTERS IN RAT MYOBLASTS, The Journal of biological chemistry, 268(31), 1993, pp. 23258-23266
The present investigation examined the glucose transporter (GLUT) tran
script levels in glucose-grown rat L6 myoblasts, which possessed a hig
h (HAHT) and a low (LAHT) affinity hexose transport system. The most p
rominent GLUT transcript detected in these cells was a GLUT 3-recogniz
able 4.1-kilobase transcript. Mutants defective in HAHT contained only
residual levels of the GLUT 3 transcript and transporter. Correspondi
ng changes in GLUT 3 transcript levels and HAHT activity were observed
in myotubes, confluent cultures, and myogenesis-impaired cells. The o
ther prominent GLUT transcripts detected were the GLUT 4-recognizable
2.8- and 1.4-kilobase transcripts. The close correlation between the G
LUT 4 isoform and LAHT activity was indicated by the absence of this i
soform in LAHT- mutants, and their corresponding changes in myoblasts
grown under different conditions. These findings suggested the HAHT an
d LAHT transporters might be coded or regulated by the genes responsib
le for the GLUT 3 and 4 transcripts, respectively. Although relatively
high levels of the GLUT 1 transcript and transporter were detected in
glucose-grown HAHT-LAHT- mutants, these cells did not exhibit any GLU
T 1 transport activity. Since the GLUT 1 transporter was not functiona
l, it was not likely responsible for the HAHT and LAHT activities obse
rved in glucose-grown L6 myoblasts.