Hexose transport in plasma membrane vesicles prepared from L6 rat myoblasts

Mesmer, O. T.; Cheung, Matthias O.; D’Amore, Tony; Lo, Theodore C. Y.

doi:10.1016/s0006-291x(86)80343-6

Cited by 8 publications

(13 citation statements)

References 12 publications

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“…Our studies show that activation of hexose transport could be brought about by covalent modification of the transporter. Both whole cell and plasma membrane vesicle studies showed that the antibody-mediated dirnerization of a cell surface 112K protein resulted in activation of hexose transport (Lo and Duronio, 1984a,b;Mesmer et al, 1986; DAmore and . The transport capacities, but not the affinities, of both hexose transport processes were elevated by this treatment.…”

Section: Discussionmentioning

confidence: 99%

“…Transport studies with plasma membrane vesicles Plasma membrane vesicles were isolated and purified from rat myoblast L6 by a previously described method (Cheung and Lo, 1984;Mesmer et al, 1986), which separated sealed right-side-out plasma membrane vesicles (fraction A) from leaky membrane sheets or inside-out plasma membranes (fraction B). Transport assays were determined by the flow dialysis method; transport rates were indicated by the difference between hexose associated with fraction A and with fraction B.…”

Section: Whole Cell Transport Studiesmentioning

confidence: 99%

“…These studies revealed the presence of a high (HAHTj-and a low (LAHT)-affinity hexose transport system in these undifferentiated myoblasts (Cheung and Lo, 1984;D'Amore and Lo, 1986a-c;Mesmer et al, 1986); 2-deoxyglucose (2-DG) and D-glucose were preferentially transported by HAHT, whereas 3-0-methyl-D-glucose (3-OMG) was taken up predominantly by LAHT. Both cytochalasin B binding and transport studies with hexose transport mutants also confirmed the presence of two different hexose transport systems in rat myoblasts (D'Amore et al, 1986a; D'Amore and Lo, 1 9 8 6~; Chen and Lo, 1988;Mesmer et al, 1986). These studies also revealed that HAHT was much more sensitive to changes in cellular metabolism and to various inhibitors (D'Amore and Lo, 1986a,b).…”

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confidence: 95%

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Regulation of hexose transport in rat myoblasts during growth and differentiation

Chen¹,

Lo²

1989

Journal Cellular Physiology

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We report here the effects of growth conditions and myogenic differentiation on rat myoblast hexose transport activities. We have previously shown that in undifferentiated myoblasts the preferred substrates for the high (HAHT)- and low (LAHT)-affinity hexose transport systems are 2-deoxyglucose (2-DG) and 3-O-methyl-D-glucose (3-OMG), respectively. The present study shows that at cell density higher than 4.4 x 10(4) cells/cm2, the activities of both transport processes decrease with increasing cell densities of the undifferentiated myoblasts. Since the transport affinities are not altered, the observed decrease is compatible with the notion that the number of functional hexose transporters may be decreased in the plasma membrane. Myogenic differentiation is found to alter the 2-DG, but not the 3-OMG, transport affinity. The Km values of 2-DG uptake are elevated upon the onset of fusion and are directly proportional to the extent of fusion. This relationship between myogenesis and hexose transport is further explored by using cultures impaired in myogenesis. Treatment of cells with 5-bromo-2'-deoxyuridine abolishes not only myogenesis but also the myogenesis-induced change in 2-DG transport affinity. Similarly, alteration in 2-DG transport affinity cannot be observed in a myogenesis-defective mutant, D1. However, under myogenesis-permissive condition, the myogenesis of this mutant is also accompanied by changes in its 2-DG transport affinity. The myotube 2-DG transport system also differs from its myoblast counterpart in its response to sulfhydryl reagents and in its turnover rate. It may be surmised from the above observations that myogenesis results in the alteration of the turnover rate or in the modification of the 2-DG transport system. Although glucose starvation has no effect on myogenesis, it is found to alter the substrate specificity and transport capacity of HAHT. In conclusion, the present study shows that hexose transport in rat myoblasts is very sensitive to the growth conditions and the stages of differentiation of the cultures. This may explain why different hexose transport properties have been observed with myoblasts grown under different conditions.

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Section: Discussionmentioning

confidence: 99%

Section: Whole Cell Transport Studiesmentioning

confidence: 99%

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confidence: 95%

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Regulation of hexose transport in rat myoblasts during growth and differentiation

Chen¹,

Lo²

1989

Journal Cellular Physiology

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“…Studies with rat myoblast indicated that the two hexose transport systems were subject to different physiological and metabolic regulations. The expression of the HAHT transporter was increased during glucose starvation Mesmer et al 1986;D'Amore and Lo 1988;Chen andLo 1988, 1990), whereas that for the LAHT transporter was not altered. Studies using a combination of biochemical, physiological, and genetic manipulations also revealed that the expression of the HAHT transporter was decreased dramatically upon the onset of myogenic differentiation (Chen and Lo 1989), whereas that for the LAHT transporter was not affected.…”

Section: Discussionmentioning

confidence: 99%

“…First, treatment of myoblasts with energy uncouplers or ionophores resulted in a dramatic decrease in HAHT activity (D'Amore and Lo, 1986b;Mesmer and Lo 1989;Mesmer et al 1990). Second, dGlc was taken up against a concentration gradient into purified rat myoblast plasma membrane vesicles; and such influx process could be abolished by ionophores (Mesmer et al 1986). Further, studies with rat myoblasts suggested that membrane potentials, rather than ATP, might be involved in the regulation of this active transport process (D'Amore and Lo 1986b).…”

Section: Introductionmentioning

confidence: 99%

Hexose transport properties of myoblasts isolated from a patient with suspected muscle carnitine deficiency

Mesmer¹,

Lo²

1990

Biochem. Cell Biol.

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The human primary carnitine deficiency syndromes are potentially fatal disorders affecting children and adults. The molecular etiologies of these syndromes have not been fully determined. Muscle carnitine deficiency syndrome is characterized by mild to severe muscle weakness, lipid accumulation in muscle, and reduced muscle carnitine concentration. In the present investigation, the hexose transport properties of muscle cells isolated from a patient with suspected muscle carnitine deficiency (MCD) were examined. We have previously shown that myoblasts from normal human subjects possessed at least two hexose transport systems, the low (LAHT) and the high (HAHT) affinity hexose transport systems. Their preferred substrates were 3-O-methyl-D-glucose and 2-deoxyglucose (dGlc), respectively; HAHT, but not LAHT, was sensitive to inhibition by carbonyl cyanide m-chlorophenylhydrazone (CCCP). Here we show that the kinetic properties of HAHT in the MCD myoblasts differ significantly from those of normal myoblasts and that the rates of dGlc transport by MCD myoblasts are restored to normal by growth in 40 microM L-carnitine. We also demonstrate that the kinetic properties of LAHT are quite similar in both normal and MCD myoblasts. It can be inferred from these findings that HAHT and LAHT may be coded or regulated by different genes. Based on the finding that the dGlc transport system in L-carnitine grown cells is no longer sensitive to inhibition by CCCP, it is thought that L-carnitine may play a regulatory role in HAHT, viz., by maintaining the HAHT transporter in a functional state, even in energy-uncoupled cells.(ABSTRACT TRUNCATED AT 250 WORDS)

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Use of hexose transport mutants to examine the expression and properties of the rat myoblast GLUT 1 transport process

Xia

Mesmer

et al. 1995

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Rat L6 myoblasts were recently shown to possess the GLUT 1, 3 and 4 transporters, and not the GLUT 2 isoform [1]. This investigation examined the expression and properties of the GLUT 1 isoform. GLUT 1 transcript level was significantly reduced in cells grown at high densities and during myogenic differentiation. A comparison of the GLUT 1 and 4 transcript levels in myogenesis-competent and impaired cells revealed an inverse relationship between these two isoforms. This relationship was confirmed by studies using two independent spontaneous GLUT 3- GLUT 4- mutants, M1 and M3. These mutants possessed very high level of the GLUT 1 isoform, but negligible amount of the GLUT 3 and 4 isoforms. GLUT 1 expression was also subject to positive regulation. Glucose starvation was found to increase not only the levels of the GLUT 1 transcript and transporter, but also the intrinsic activity of the GLUT 1 transporter. Studies with M1 and M3 mutants revealed that the GLUT 1 transporter was not functional in glucose-grown cells, even though it was present at a very high level in the plasma membrane. This transporter became functional when cells were starved for glucose. The functional GLUT 1 transporter had an apparent Km value of around 0.9 mM, and was sensitive to cytochalasin B, phloretin, phlorizin and pCMBS.

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Hexose transport in plasma membrane vesicles prepared from L6 rat myoblasts

Cited by 8 publications

References 12 publications

Regulation of hexose transport in rat myoblasts during growth and differentiation

Regulation of hexose transport in rat myoblasts during growth and differentiation

Hexose transport properties of myoblasts isolated from a patient with suspected muscle carnitine deficiency

Use of hexose transport mutants to examine the expression and properties of the rat myoblast GLUT 1 transport process

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