Okadaic acid, insulin, and denervation effects on glucose and amino acid transport and glycogen synthesis in muscle

Effects of okadaic acid (OKA) and calyculin A, cell-permeating specific inhibitors of phosphoprotein phosphatases-1 and -2A, were studied in isolated rat hemidiaphragms. OKA stimulated glucose transport (half-maximum = approximately 0.1 microM; maximum = approximately 1 microM) but was less effective than 6 nM insulin. Insulin and OKA effects were not additive. OKA diminished or abolished glucose transport-stimulation by insulin. System A amino acid transport was also stimulated by OKA, insulin was more effective, and preexposure to OKA inhibited insulin stimulation. Calyculin A affected both transport systems similarly to OKA. OKA did not affect basal glycogen synthesis but abolished its stimulation by insulin. Denervated muscles develop post-receptor insulin resistance. Glucose transport and glycogen synthesis were essentially unresponsive to insulin 3 days postdenervation; however, glucose transport was stimulated by OKA similarly to controls. OKA did not affect glycogen synthesis in denervated muscle except for abolishing a small insulin effect. The data suggest similar acute regulation of glucose and system A amino acid transport in muscle. Enhanced Ser/Thr phosphorylation of unidentified protein(s) stimulates both processes but inhibits their full stimulation by insulin. Postdenervation insulin resistance likely reflects impaired signal transduction.

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A rapid method for the functional reconstitution of amino acid transport systems from rat liver plasma membranes. Partial purification of System A

Biochemical Journal ◽

10.1042/bj2550963 ◽

1988 ◽

Vol 255 (3) ◽

pp. 963-969 ◽

Cited By ~ 8

Author(s):

A R Quesada ◽

J D McGivan

Keyword(s):

Amino Acid ◽

Rapid Method ◽

Amino Acid Transport ◽

Plasma Membranes ◽

Transport Systems ◽

Partial Purification ◽

Acid Transport ◽

Transport Activity ◽

System A ◽

System L

A rapid method for the functional reconstruction of amino acid transport from liver plasma-membrane vesicles using the neutral detergent decanoyl-N-glucamide (‘MEGA-10’) is described. The method is a modification of that previously employed in this laboratory for reconstitution of amino acid transport systems from kidney brush-border membranes [Lynch & McGivan (1987) Biochem. J. 244, 503-508]. The transport activities termed ‘System A’, ‘System N’, and ‘System L’ are all reconstituted. The reconstitution procedure is rapid and efficient and is suitable as an assay for transport activity in studies involving membrane fractionation. By using this reconstitution procedure, System A transport activity was partially purified by lectin-affinity chromatography.

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Effects of prior exercise on the action of insulin-like growth factor I in skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.263.2.e340 ◽

1992 ◽

Vol 263 (2) ◽

pp. E340-E344 ◽

Cited By ~ 5

Author(s):

E. J. Henriksen ◽

L. L. Louters ◽

C. S. Stump ◽

C. M. Tipton

Keyword(s):

Skeletal Muscle ◽

Amino Acid ◽

Growth Factor ◽

Glucose Transport ◽

Amino Acid Transport ◽

Acid Transport ◽

Factor I ◽

System A ◽

Prior Exercise ◽

Igf I

Prior exercise increases insulin sensitivity for glucose and system A neutral amino acid transport activities in skeletal muscle. Insulin-like growth factor I (IGF-I) also activates these transport processes in resting muscle. It is not known, however, whether prior exercise increases IGF-I action in muscle. Therefore we determined the effect of a single exhausting bout of swim exercise on IGF-I-stimulated glucose transport activity [assessed by 2-deoxy-D-glucose (2-DG) uptake] and system A activity [assessed by alpha-(methylamino)isobutyric acid (MeAIB) uptake] in the isolated rat epitrochlearis muscle. When measured 3.5 h after exercise, the responses to a submaximal concentration (0.2 nM), but not a maximal concentration (13.3 nM), of insulin for activation of 2-DG uptake and MeAIB uptake were enhanced. In contrast, prior exercise increased markedly both the submaximal (5 nM) and maximal (20 nM) responses to IGF-I for activation of 2-DG uptake, whereas only the submaximal response to IGF-I (3 nM) for MeAIB uptake was enhanced after exercise. We conclude that 1) prior exercise significantly enhances the response to a submaximal concentration of IGF-I for activation of the glucose transport and system A neutral amino acid transport systems in skeletal muscle and 2) the enhanced maximal response for IGF-I action after exercise is restricted to the signaling pathway for activation of the glucose transport system.

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Placental Glucose and Amino Acid Transport in Calorie-Restricted Wild-Type and Glut3 Null Heterozygous Mice

Endocrinology ◽

10.1210/en.2011-1973 ◽

2012 ◽

Vol 153 (8) ◽

pp. 3995-4007 ◽

Cited By ~ 37

Author(s):

Amit Ganguly ◽

Laura Collis ◽

Sherin U. Devaskar

Keyword(s):

Amino Acid ◽

Family Member ◽

Glucose Transport ◽

Amino Acid Transport ◽

Mammalian Target Of Rapamycin ◽

Acid Transport ◽

Wild Type ◽

System A ◽

Leucine Transport

Calorie restriction (CR) decreased placenta and fetal weights in wild-type (wt) and glucose transporter (Glut) 3 heterozygous null (glut3+/−) mice. Because placental nutrient transport is a primary energy determinant of placentofetal growth, we examined key transport systems. Maternal CR reduced intra- and transplacental glucose and leucine transport but enhanced system A amino acid transport in wt mice. These transport perturbations were accompanied by reduced placental Glut3 and leucine amino acid transporter (LAT) family member 2, no change in Glut1 and LAT family member 1, but increased sodium coupled neutral amino acid transporter (SNAT) and SNAT2 expression. We also noted decreased total and active phosphorylated forms of mammalian target of rapamycin, which is the intracellular nutrient sensor, the downstream total P70S6 kinase, and pS6 ribosomal protein with no change in total and phosphorylated 4E-binding protein 1. To determine the role of placental Glut3 in mediating CR-induced placental transport changes, we next investigated the effect of gestational CR in glut3+/− mice. In glut3+/− mice, a key role of placental Glut3 in mediating transplacental and intraplacental glucose transport was established. In addition, reduced Glut3 results in a compensatory increase of leucine and system A transplacental transport. On the other hand, diminished Glut3-mediated intraplacental glucose transport reduced leucine transport and mammalian target of rapamycin and preserved LAT and enhancing SNAT. CR in glut3+/− mice further reduced transplacental glucose transport and enhanced system A amino acid transport, although the increased leucine transport was lost. In addition, increased Glut3 was seen and preserved Glut1, LAT, and SNAT. These placental changes collectively protect survival of wt and glut3+/− fetuses against maternal CR-imposed reduction of macromolecular nutrients.

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Inactivation of amino acid transport in rat hepatocytes and hepatoma cells by PCMBS

AJP Cell Physiology ◽

10.1152/ajpcell.1988.255.3.c340 ◽

1988 ◽

Vol 255 (3) ◽

pp. C340-C345 ◽

Cited By ~ 18

Author(s):

T. C. Chiles ◽

K. L. Dudeck-Collart ◽

M. S. Kilberg

Keyword(s):

Amino Acid ◽

Amino Acid Transport ◽

Rat Hepatocytes ◽

Cell Types ◽

Hepatoma Cells ◽

Transport Systems ◽

Acid Transport ◽

System A ◽

System L ◽

Normal Rat

the transport of amino acids by both normal rat hepatocytes and rat H4 hepatoma cells has been tested for inactivation by sulfhydryl-preferring, protein-modifying reagents. Amino acid transport by systems A, ASC, N, L, and y+ in the H4 hepatoma cells was relatively resistant to inactivation by the alkylating reagent N-ethylmaleimide (NEM), whereas uptake mediated by systems A, ASC, and L was decreased in normal rat hepatocytes. In contrast, nearly all of the amino acid transport systems in both cell types were inhibited strongly by p-chloromercuribenzene sulfonate (PCMBS). The exceptions were the H4 hepatoma system y+ activity (72% of control) and system L-mediated uptake (121% of control) in normal hepatocytes. Although transport via system A was equally sensitive to inhibition by PCMBS in both cell types, substrate-dependent protection from this inactivation was observed only in the H4 hepatoma cells. These results illustrate the significant differences that exist between normal and transformed liver cells in respect to amino acid transport inactivation by sulfhydryl reagents.

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Differential expression of amino acid transport systems A and ASC during erythroleukemia cell differentiation

AJP Cell Physiology ◽

10.1152/ajpcell.1991.260.3.c392 ◽

1991 ◽

Vol 260 (3) ◽

pp. C392-C399 ◽

Cited By ~ 7

Author(s):

J. V. Vadgama ◽

M. N. Chan ◽

J. M. Wu

Keyword(s):

Cell Cycle ◽

Cell Differentiation ◽

Amino Acid ◽

Amino Acid Transport ◽

Globin Gene ◽

Transport Systems ◽

Acid Uptake ◽

Acid Transport ◽

Potent Inducer ◽

System A

The human erythroleukemic cell K-562 serves as an in vitro model to study changes in cell surface antigens and mechanisms regulating globin gene expression associated with in vivo erythropoiesis. In this report we have examined the regulation of amino acid transport systems, in particular, systems A and ASC, during differentiation of erythroleukemic cells. For additional comparison we examined the uptake of leucine, 3-aminoendobicyclo-(3,2,1)-octane-3-carboxylic acid (BCO), arginine, and glutamate. Hexamethylene-bis-acetamide (HMBA), dimethyl sulfoxide, and butyrate induce cell differentiation with a block in G1-G0 phase of the cell cycle. These agents caused a significant downregulation of 2-(methylamino)isobutyric acid uptake by system A. In contrast, the Na(+)-dependent threonine uptake by system ASC remained unaltered. The uptake of leucine, BCO, arginine, and glutamate by as yet unidentified systems was, however, stimulated after HMBA treatment. Hemin, a potent inducer of hemoglobin synthesis in K-562 cells, does not block cell cycle events and, interestingly, had no significant effect on both systems A and ASC. These differences in inducer actions suggest that system A activity may be related to specific stages of cell differentiation and perhaps to other cellular signals.

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Lipopolysaccharide and double stranded viral RNA mediate insulin resistance and increase system a amino acid transport in human trophoblast cells in vitro

Placenta ◽

10.1016/j.placenta.2017.01.124 ◽

2017 ◽

Vol 51 ◽

pp. 18-27 ◽

Cited By ~ 8

Author(s):

Stella Liong ◽

Martha Lappas

Keyword(s):

Insulin Resistance ◽

Amino Acid ◽

Amino Acid Transport ◽

Viral Rna ◽

Acid Transport ◽

Trophoblast Cells ◽

Human Trophoblast ◽

System A ◽

Human Trophoblast Cells

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System β and System A amino acid transporters in the feline endotheliochorial placenta

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00530.2003 ◽

2004 ◽

Vol 287 (6) ◽

pp. R1369-R1379 ◽

Cited By ~ 15

Author(s):

E. E. Champion ◽

S. J. Mann ◽

J. D. Glazier ◽

C. J. P. Jones ◽

J. M. Rawlings ◽

...

Keyword(s):

Amino Acid ◽

Human Placenta ◽

Amino Acid Transport ◽

Time Course ◽

Transport Systems ◽

Amino Acid Transporters ◽

Transport Mechanisms ◽

Acid Transport ◽

System A ◽

Taurine Uptake

There is no knowledge of the transport mechanisms by which solutes cross the cat placenta or any other endotheliochorial placenta. Here, we investigated whether the amino acid transport systems β and A are present in the cat placenta using a placental fragment uptake technique. Data were compared with studies in the human placenta, in which the presence of these two transport systems has been well established. A time course of [3H]taurine (substrate for system β) and [14C]MeAIB (nonmetabolizable substrate for system A) uptake was determined in the term cat and human placental fragments in the presence and absence (choline substituted) of Na+, and further studies were carried out over 15 min. Taurine uptake into both cat and human placenta fragments was found to be Na+ and Cl− dependent, and Na+-dependent taurine uptake was blocked by excess β-alanine. MeAIB uptake was found to be Na+ dependent, and Na+-dependent MeAIB uptake was blocked by excess MeAIB or glycine. Western blotting and immunohistochemistry performed on cat and human placenta showed expression of TAUT and ATA2 (SNAT2), proteins associated with system β and system A activity, respectively. This study therefore provides the first evidence of the presence of amino acid transport systems β and A in the cat placenta.

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Evidence for two Na+-independent neutral amino acid transport systems in primary cultures of rat hepatocytes. Time-dependent changes in activity.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)33668-8 ◽

1982 ◽

Vol 257 (20) ◽

pp. 12006-12011 ◽

Cited By ~ 6

Author(s):

L Weissbach ◽

M E Handlogten ◽

H N Christensen ◽

M S Kilberg

Keyword(s):

Amino Acid ◽

Amino Acid Transport ◽

Primary Cultures ◽

Rat Hepatocytes ◽

Neutral Amino Acid ◽

Time Dependent ◽

Transport Systems ◽

Acid Transport

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Effect of high altitude on human placental amino acid transport

Journal of Applied Physiology ◽

10.1152/japplphysiol.00691.2019 ◽

2020 ◽

Vol 128 (1) ◽

pp. 127-133 ◽

Cited By ~ 2

Author(s):

Owen. R. Vaughan ◽

Fredrick Thompson ◽

Ramón. A. Lorca ◽

Colleen G. Julian ◽

Theresa L. Powell ◽

...

Keyword(s):

Birth Weight ◽

Amino Acid ◽

High Altitude ◽

Sea Level ◽

Amino Acid Transport ◽

Acid Uptake ◽

Acid Transport ◽

Transport Capacity ◽

System A ◽

Low Altitude

Women residing at high altitudes deliver infants of lower birth weight than at sea level. Birth weight correlates with placental system A-mediated amino acid transport capacity, and severe environmental hypoxia reduces system A activity in isolated trophoblast and the mouse placenta. However, the effect of high altitude on human placental amino acid transport remains unknown. We hypothesized that microvillous membrane (MVM) system A and system L amino acid transporter activity is lower in placentas of women living at high altitude compared with low-altitude controls. Placentas were collected at term from healthy pregnant women residing at high altitude (HA; >2,500 m; n = 14) or low altitude (LA; <1,700 m; n = 14) following planned, unlabored cesarean section. Birth weight, but not placenta weight, was 13% lower in HA pregnancies (2.88 ± 0.11 kg) compared with LA (3.30 ± 0.07 kg, P < 0.01). MVM erythropoietin receptor abundance, determined by immunoblot, was greater in HA than in LA placentas, consistent with lower placental oxygen levels at HA. However, there was no effect of altitude on MVM system A or L activity, determined by Na+-dependent [14C]methylaminoisobutyric acid uptake and [3H]leucine uptake, respectively. MVM abundance of glucose transporters (GLUTs) 1 and 4 and basal membrane GLUT4 were also similar in LA and HA placentas. Low birth weights in the neonates of women residing at high altitude are not a consequence of reduced placental amino acid transport capacity. These observations are in general agreement with studies of IUGR babies at low altitude, in which MVM system A activity is downregulated only in growth-restricted babies with significant compromise. NEW & NOTEWORTHY Babies born at high altitude are smaller than at sea level. Birth weight is dependent on growth in utero and, in turn, placental nutrient transport. We determined amino acid transport capacity in placentas collected from women resident at low and high altitude. Altitude did not affect system A amino acid transport across the syncytiotrophoblast microvillous membrane, suggesting that impaired placental amino acid transport does not contribute to reduced birth weight in this high-altitude population.

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