Z. Lu et al., USE OF TRANSPORT MUTANTS TO EXAMINE THE IDENTITY AND EXPRESSION OF GLUT ISOFORMS IN RAT CARDIAC MYOBLASTS, Biochemistry and molecular biology international, 41(1), 1997, pp. 103-121
Two different spontaneous glucose transport (GLUT) mutants were used t
o examine the identity and properties of proteins involved in rat card
iac myoblast glucose transport processes. The parental clone, H9C2, po
ssessed a high (HAHT) and a low (LAHT) affinity hexose transport proce
ss, and the GLUT 1, 3 and 4 isoforms. Mutant RCM was devoid of HAHT, t
he GLUT 3 transcript, and a 41 kDa protein recognizable by an anti-mou
se GLUT 3 Ab. Mutant EZ-4 was impaired in the GLUT 3 and 4 isoforms, a
nd in HAHT and LAHT. These studies demonstrated a close association of
the GLUT 3 and 4 isoforms with the HAHT and LAHT processes, respectiv
ely. Both GLUT 3 and 4 isoforms were regulated in opposite ways during
myogenesis, and both GLUT 3(-) mutants were impaired in myogenesis. D
espite its normal GLUT I transcript level, mutant EZ-4 was devoid of a
n efficient carrier-mediated glucose transport process, thus suggestin
g that the GLUT 1 transporter was inoperative in rat cardiac myoblasts
. Unlike the rat skeletal L6 GLUT 1 isoform, expression of the rat car
diac GLUT 1 isoform was not affected by glucose starvation, and was no
t reduced in multinucleated myotubes. These studies demonstrated the u
sefulness of transport mutants in determining the identity, expression
and property of GLUT isoforms and their association with specific tra
nsport processes.