Transcripts for the high and low affinity hexose transporters in rat myoblasts.
The present investigation examined the glucose transporter (GLUT) transcript levels in glucose-grown rat L6 myoblasts, which possessed a high (HAHT) and a low (LAHT) affinity hexose transport system. The most prominent GLUT transcript detected in these cells was a GLUT 3-recognizable 4.1-kilobase transcript. Mutants defective in HAHT contained only residual levels of the GLUT 3 transcript and transporter. Corresponding changes in GLUT 3 transcript levels and HAHT activity were observed in myotubes, confluent cultures, and myogenesis-impaired cells. The other prominent GLUT transcripts detected were the GLUT 4-recognizable 2.8- and 1.4-kilobase transcripts. The close correlation between the GLUT 4 isoform and LAHT activity was indicated by the absence of this isoform in LAHT- mutants, and their corresponding changes in myoblasts grown under different conditions. These findings suggested the HAHT and LAHT transporters might be coded or regulated by the genes responsible 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 GLUT 1 transport activity. Since the GLUT 1 transporter was not functional, it was not likely responsible for the HAHT and LAHT activities observed in glucose-grown L6 myoblasts.
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Department of Biochemistry, University of Western Ontario, London, Canada.
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D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D002460:Cell Line; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D009132:Muscles / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats
D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D005947:Glucose