The Development of Insulin Receptors and Responsiveness Is an Early Marker of Differentiation in the Muscle Cell Line L6*

Béguinot, Francesco; Kahn, C. Ronald; Ac, Moses; Rj, Smith

doi:10.1210/endo-118-1-446

Cited by 79 publications

(57 citation statements)

References 48 publications

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“…Insulin stimulates glucose uptake in differentiated L6 skeletal muscle cells, with a maximal 40% increase above basal under these conditions at an insulin concentration of 10 .7 mol/1. As previously described [20], the effect reaches a maximum after 8 to 10 h of exposure to insulin. When tolazamide was added to the culture medium for 22 h before the determination of glucose uptake, the effect of insulin was markedly augmented (Fig.…”

Section: Effects Of Insulin and Tolazamide On Glucose Uptakesupporting

confidence: 69%

“…The source and methods for culturing the L6 rat skeletal muscle ceils have previously been described [20,23]; In brief, multiple vials of cells of similar passage were stored frozen in liquid nitrogen. A fresh vial was thawed every 3 weeks, and the myoblasts were maintained by repeat subculturing at low cell density in Eagle's Minimum Essential Medium (MEM) supplemented with 10% (vol/vol) bovine serum.…”

Section: Cell Culturementioning

confidence: 99%

“…Sulfonylureas can augment rapid insulin-mediated changes in glucose uptake in peripheral tissues [7,8], but it is not known whether sulfonylureas can augment long-term insulin effects on glucose uptake. For this reason, we have characterised the effects of sulfonylureas on long-term glucose transport regulation in the insulin-responsive L6 rat skeletal muscle cell line [20]. Since insulin-like metabolic actions in L6 cells are mediated by distinct receptors for insulin, insulin-like growth factor I (IGF I), and IGF II in L6 cells [21], we have evaluated the effects of sulfonylureas on responsiveness to all three of these hormones.…”

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confidence: 99%

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Augmentation of the effects of insulin and insulin-like growth factors I and II on glucose uptake in cultured rat skeletal muscle cells by sulfonylureas

1987

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Summary. The effect of sulfonylureas on long-term regulation of glucose uptake by insulin and insulin-like growth factors has been studied in the L6 line of cultured skeletal muscle cells. These cells have previously been shown to possess many characteristics of differentiated skeletal muscle and to bind and respond to physiological concentrations of insulin and insulin-like growth factors I and II. Tolazamide (halfmaximal at 0.2 mg/ml) augments the effects of insulin, insulin-like growth factor I, and insulin-like growth factor II on glucose uptake, increasing both sensitivity and maximal efficacy of the hormones. In the absence of added hormone, tolazamide has no effect on glucose uptake. A similar increase in insulin-stimulated glucose uptake with unaltered basal uptake occurs with glybufide (half-maximal at 0.5 ~g/ml). The action of tolazamide requires long-term exposure to the sulfonylurea (22 h) and is inhibited by cycloheximide, suggesting a process that involves new protein synthesis. In contrast to glucose uptake, amino acid uptake in L6 cells is increased by tolazamide in the absence of hormones. Insulin and the insulin-like growth factors also stimulate amino acid uptake, but this effect is not further augmented by tolazamide. Thus, sulfonylureas appear to directly modulate amino acid uptake, but to indirectly augment glucose uptake through an effect on insulin and insulin-like growth factor stimulated pathways. Neither insulin binding nor insulin degradation is altered by tolazamide, indicating a post-binding mechanism of action. The L6 cultured skeletal muscle cell line should be useful in future studies on the mechanism of the extrapancreatic actions of sulfonylureas.

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Section: Effects Of Insulin and Tolazamide On Glucose Uptakesupporting

confidence: 69%

Section: Cell Culturementioning

confidence: 99%

mentioning

confidence: 99%

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Augmentation of the effects of insulin and insulin-like growth factors I and II on glucose uptake in cultured rat skeletal muscle cells by sulfonylureas

1987

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“…Similarly, p38 MAPK was activated in 3T3-L1 adipocytes (36) but not in undifferentiated 3T3-L1 fibroblasts. 2 One possible reason for the increased regulation of p38 MAPK by insulin could be the increase in insulin receptor density as L6 and 3T3-L1 cells differentiate (59,60). However, this is unlikely because activation of Akt isoforms in myoblasts is comparable to that in myotubes.…”

Section: Figmentioning

confidence: 99%

Maturation of the Regulation of GLUT4 Activity by p38 MAPK during L6 Cell Myogenesis

Niu

Huang²,

Nawaz³

et al. 2003

Journal of Biological Chemistry

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Insulin stimulates glucose uptake in skeletal muscle cells and fat cells by promoting the rapid translocation of GLUT4 glucose transporters to the plasma membrane. Recent work from our laboratory supports the concept that insulin also stimulates the intrinsic activity of GLUT4 through a signaling pathway that includes p38 MAPK. Here we show that regulation of GLUT4 activity by insulin develops during maturation of skeletal muscle cells into myotubes in concert with the ability of insulin to stimulate p38 MAPK. In L6 myotubes expressing GLUT4 that carries an exofacial myc-epitope (L6-GLUT4myc), insulin-stimulated GLUT4myc translocation equals in magnitude the glucose uptake response. Inhibition of p38 MAPK with SB203580 reduces insulinstimulated glucose uptake without affecting GLUT4myc translocation. In contrast, in myoblasts, the magnitude of insulin-stimulated glucose uptake is significantly lower than that of GLUT4myc translocation and is insensitive to SB203580. Activation of p38 MAPK by insulin is considerably higher in myotubes than in myoblasts, as is the activation of upstream kinases MKK3/ MKK6. In contrast, the activation of all three Akt isoforms and GLUT4 translocation are similar in myoblasts and myotubes. Furthermore, GLUT4myc translocation and phosphorylation of regulatory sites on Akt in L6-GLUT4myc myotubes are equally sensitive to insulin, whereas glucose uptake and phosphorylation of regulatory sites on p38 MAPK show lower sensitivity to the hormone. These observations draw additional parallels between Akt and GLUT4 translocation and between p38 MAPK and GLUT4 activation. Regulation of GLUT4 activity by insulin develops upon muscle cell differentiation and correlates with p38 MAPK activation by insulin.

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“…29 Ϫ5 insulin and was subtracted from the total bound radioactivity to yield the specific binding. The binding data were analyzed using the Ligand program for curve fitting and parameter estimation (30).…”

Section: Methodsmentioning

confidence: 99%

Glucose Regulates Insulin Mitogenic Effect by Modulating SHP-2 Activation and Localization in JAr Cells

Bifulco¹,

Carlo²,

Caruso³

et al. 2002

Journal of Biological Chemistry

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The glucose effect on cell growth has been investigated in the JAr human choriocarcinoma cells. When JAr cells were cultured in the presence of 6 mM glucose (LG), proliferation and thymidine incorporation were induced by serum, epidermal growth factor, and insulinlike growth factor 1 but not by insulin. In contrast, at 25 mM glucose (HG), proliferation and thymidine incorporation were stimulated by insulin, serum, epidermal growth factor, and insulin-like growth factor 1 to a comparable extent, whereas basal levels were 25% lower than those in LG. HG culturing also enhanced insulinstimulated insulin receptor and insulin receptor substrate 1 (IRS1) tyrosine phosphorylations while decreasing basal phosphorylations. These actions of glucose were accompanied by an increase in cellular tyrosine phosphatase activity. The activity of SHP-2 in HGtreated JAr cells was 400% of that measured in LGtreated cells. SHP-2 co-precipitation with IRS1 was also increased in HG-treated cells. SHP-2 was mainly cytosolic in LG-treated cells. However, HG culturing largely redistributed SHP-2 to the internal membrane compartment, where tyrosine-phosphorylated IRS1 predominantly localizes. Further exposure to insulin rescued SHP-2 cytosolic localization, thereby preventing its interaction with IRS1. Antisense inhibition of SHP-2 reverted the effect of HG on basal and insulin-stimulated insulin receptor and IRS1 phosphorylation as well as that on thymidine incorporation. Thus, in JAr cells, glucose modulates insulin mitogenic action by modulating SHP-2 activity and intracellular localization.

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The Development of Insulin Receptors and Responsiveness Is an Early Marker of Differentiation in the Muscle Cell Line L6*

Cited by 79 publications

References 48 publications

Augmentation of the effects of insulin and insulin-like growth factors I and II on glucose uptake in cultured rat skeletal muscle cells by sulfonylureas

Augmentation of the effects of insulin and insulin-like growth factors I and II on glucose uptake in cultured rat skeletal muscle cells by sulfonylureas

Maturation of the Regulation of GLUT4 Activity by p38 MAPK during L6 Cell Myogenesis

Glucose Regulates Insulin Mitogenic Effect by Modulating SHP-2 Activation and Localization in JAr Cells

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