Insulin-mimetic agents vanadate and pervanadate stimulate glucose but inhibit amino acid uptake

1997 ◽  
Vol 272 (1) ◽  
pp. C156-C162 ◽  
Author(s):  
E. Tsiani ◽  
N. Abdullah ◽  
I. G. Fantus
Keyword(s):  
Amino Acid ◽  
Glucose Uptake ◽  
Tyrosine Phosphatase ◽  
Amino Acid Uptake ◽  
Inhibitory Effect ◽  
Acid Uptake ◽  
Dependent Manner ◽  
Transport Capacity ◽  
Insulin Mimetic ◽  
Biologic Effects

The protein tyrosine phosphatase (PTP) inhibitors vanadate and pervanadate (pV) exert insulin-like biologic effects. In cultured differentiated rat L6 skeletal muscle cells, vanadate and pV stimulated 2-deoxy-D-[3H]glucose uptake in a dose- and time-dependent manner. There was no increase in maximum stimulation by additional insulin. In contrast, whereas insulin stimulated [14C]methylaminoisobutyric acid (MeAIB) uptake, basal uptake was inhibited by vanadate and pV. Insulin-stimulated MeAIB uptake was also inhibited in a dose-dependent manner and completely abolished by 5 mM vanadate or 0.1 mM pV. The inhibitory effect on basal MeAIB uptake was associated with a decrease in transporter affinity and a small decrease in maximum transport capacity, whereas the insulin-stimulated increase in maximum transport capacity was completely inhibited. Inhibition of MeAIB uptake by vanadate and pV was not blocked by cycloheximide, and oubain did not inhibit uptake. Vanadate also inhibited amino acid deprivation-stimulated MeAIB uptake. Insulin-stimulated MeAIB uptake was also inhibited in rat hepatoma cells. Thus vanadate and pV mimic insulin to stimulate glucose uptake but inhibit system A amino acid uptake. The relative inhibitory concentrations of vanadate and pV suggest that the mechanism may involve PTP inhibition.

Somatostatin inhibits insulin-stimulated amino acid uptake into cultured rat myoblasts

1987 ◽  
Vol 114 (4) ◽  
pp. 470-474 ◽  
Author(s):  
G. S. G. Spencer ◽  
D. J. Hill ◽  
G. J. Garssen ◽  
J. P. G. Williams
Keyword(s):  
Amino Acid ◽  
Nutrient Uptake ◽  
Monolayer Culture ◽  
Amino Acid Uptake ◽  
Inhibitory Effect ◽  
Isobutyric Acid ◽  
Acid Uptake ◽  
Newborn Rat ◽  
Amino Isobutyric Acid

Abstract. The effects of somatostatin on the acute metabolic actions of insulin on newborn rat myoblasts in culture has been examined during monolayer culture. Somatostatin significantly inhibited the insulin-stimulated uptake of [3H]leucine and [3H]amino-isobutyric acid into myoblasts but had no effect on basal (unstimulated) uptake of these two substances. The lowest concentration of somatostatin to have a significant effect was 10 μg/l, and this was apparent in all the experiments undertaken. The inhibitory effect of somatostatin was seen at all effective concentrations of insulin used (0.3–1 U/l). These findings lend support to the concept of an endocrine role for somatostatin in vivo and suggest that a peripheral antagonism may exist between circulating insulin and somatostatin on anabolic processes such as nutrient uptake into cells.

Anionic amino acid uptake by microvillous membrane vesicles from human placenta

1989 ◽  
Vol 257 (5) ◽  
pp. C1005-C1011 ◽  
Author(s):  
A. J. Moe ◽  
C. H. Smith
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Glutamate Uptake ◽  
Membrane Vesicles ◽  
Amino Acid Uptake ◽  
Maternal Blood ◽  
Acid Uptake ◽  
Dependent Manner ◽  
Concentration Dependent Manner

The transport mechanisms for anionic amino acids in trophoblast microvillous (maternal facing) membrane were investigated by characterization of L-[3H]aspartate and L-[3H]glutamate uptake in membrane vesicles. Uptake of the anionic amino acids was by a single high-affinity Na+-dependent K+-stimulated cotransporter that is pH sensitive and electrogenic. A second Na+-dependent transporter could not be discriminated, and there was no observable Na+-independent uptake. An outwardly directed K+ gradient (100 mM KCl inside) resulted in a 5- to 10-fold stimulation in glutamate uptake in the presence of Na+. Intravesicular KCl had no effect on transporter affinity but increased transporter velocity in a concentration-dependent manner. Inhibition of Na+-K+-dependent uptake of L-aspartate and L-glutamate (20 mM, 30 s) by 2 mM unlabeled amino acids demonstrated stereoselectivity for L-glutamate but not for L-aspartate. The neutral amino acids (L-alanine, L-threonine, L-serine, L-cysteine, L-phenylalanine) were not effective inhibitors. These data are consistent with an anionic amino acid transporter in the microvillous membrane of the trophoblast, which has characteristics qualitatively similar to the X-AG system found in other epithelia. This system may mediate the concentrative placental uptake of anionic amino acids from maternal blood in utero.

scholarly journals PERIODIC CHANGES IN RATE OF AMINO ACID UPTAKE DURING YEAST CELL CYCLE

1973 ◽  
Vol 58 (2) ◽  
pp. 401-409 ◽  
Author(s):  
B. L. A. Carter ◽  
H. O. Halvorson
Keyword(s):  
Cell Cycle ◽  
Amino Acids ◽  
Amino Acid ◽  
Uptake Rate ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Uptake System ◽  
Transport Capacity ◽  
Initial Uptake Rate ◽  
Initial Uptake

Uptake of amino acids is a complex process but in cells growing with ammonia as sole nitrogen source the initial uptake rate of amino acids is a measure of the transport capacity of the uptake system (permease). In synchronous cultures of Saccharomyces cerevisiae amino acids were transported at all stages of the cell cycle. However, for any one amino acid the initial uptake rate was constant for most of the cycle and doubled during a discrete part of the cycle. Thus, for a variety of amino acids the functioning amino acid transport capacity of the membrane doubles once per cycle at a characteristic stage of the cycle. Arginine, valine, and phenylalanine exhibit periodic doubling of uptake rate at different stages of the cell cycle indicating that the transport of these amino acids is mediated by three different systems. Serine, phenylalanine, and leucine exhibit periodic doubling of the uptake rate at the same stage of the cycle. However, it is unlikely that serine and phenylalanine share the same transport system since the uptake of one is not inhibited by the other amino acid. This phenomenon is analogous to the periodic synthesis of soluble enzymes observed in S. cerevisiae.

scholarly journals Vasoactive Intestinal Peptide induces glucose and neutral amino acid uptake through mTOR signalling in human cytotrophoblast cells

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Fatima Merech ◽  
Elizabeth Soczewski ◽  
Vanesa Hauk ◽  
Daniel Paparini ◽  
Rosanna Ramhorst ◽  
...  
Keyword(s):  
Amino Acid ◽  
Vasoactive Intestinal Peptide ◽  
Amino Acid Uptake ◽  
Nutrient Sensing ◽  
Neutral Amino Acid ◽  
Acid Uptake ◽  
Dependent Manner ◽  
System A ◽  
Cytotrophoblast Cells ◽  
Mtor Signalling

AbstractThe transport of nutrients across the placenta involves trophoblast cell specific transporters modulated through the mammalian target of rapamycin (mTOR). The vasoactive intestinal peptide (VIP) has embryotrophic effects in mice and regulates human cytotrophoblast cell migration and invasion. Here we explored the effect of VIP on glucose and System A amino acid uptake by human trophoblast-derived cells (Swan 71 and BeWo cell lines). VIP activated D-glucose specific uptake in single cytotrophoblast cells in a concentration-dependent manner through PKA, MAPK, PI3K and mTOR signalling pathways. Glucose uptake was reduced in VIP-knocked down cytotrophoblast cells. Also, VIP stimulated System A amino acid uptake and the expression of GLUT1 glucose transporter and SNAT1 neutral amino acid transporter. VIP increased mTOR expression and mTOR/S6 phosphorylation whereas VIP silencing reduced mTOR mRNA and protein expression. Inhibition of mTOR signalling with rapamycin reduced the expression of endogenous VIP and of VIP-induced S6 phosphorylation. Our findings support a role of VIP in the transport of glucose and neutral amino acids in cytotrophoblast cells through mTOR-regulated pathways and they are instrumental for understanding the physiological regulation of nutrient sensing by endogenous VIP at the maternal-foetal interface.

4F2hc stabilizes GLUT1 protein and increases glucose transport activity

2011 ◽  
Vol 300 (5) ◽  
pp. C1047-C1054 ◽  
Author(s):  
Haruya Ohno ◽  
Yusuke Nakatsu ◽  
Hideyuki Sakoda ◽  
Akifumi Kushiyama ◽  
Hiraku Ono ◽  
...  
Keyword(s):  
Amino Acid ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Fluorescent Protein ◽  
Amino Acid Uptake ◽  
Amino Acid Transporters ◽  
Acid Uptake ◽  
Mrna Levels ◽  
Glucose Transporter 1 ◽  
Glut1 Protein

Glucose transporter 1 (GLUT1) is widely distributed throughout various tissues and contributes to insulin-independent basal glucose uptake. Using a split-ubiquitin membrane yeast two-hybrid system, we newly identified 4F2 heavy chain (4F2hc) as a membrane protein interacting with GLUT1. Though 4F2hc reportedly forms heterodimeric complexes between amino acid transporters, such as LAT1 and LAT2, and regulates amino acid uptake, we investigated the effects of 4F2hc on GLUT1 expression and the associated glucose uptake. First, FLAG-tagged 4F2hc and hemagglutinin-tagged GLUT1 were overexpressed in human embryonic kidney 293 cells and their association was confirmed by coimmunoprecipitation. The green fluorescent protein-tagged 4F2hc and DsRed-tagged GLUT1 showed significant, but incomplete, colocalization at the plasma membrane. In addition, an endogenous association between GLUT1 and 4F2hc was demonstrated using mouse brain tissue and HeLa cells. Interestingly, overexpression of 4F2hc increased the amount of GLUT1 protein in HeLa and HepG2 cells with increased glucose uptake. In contrast, small interfering RNA (siRNA)-mediated 4F2hc gene suppression markedly reduced GLUT1 protein in both cell types, with reduced glucose uptake. While GLUT1 mRNA levels were not affected by overexpression or gene silencing of 4F2hc, GLUT1 degradation after the addition of cycloheximide was significantly suppressed by 4F2hc overexpression and increased by 4F2hc siRNA treatment. Taken together, these observations indicate that 4F2hc is likely to be involved in GLUT1 stabilization and to contribute to the regulation of not only amino acid but also glucose metabolism.

Chloramphenicol-resistant variants of Pseudomonas aeruginosa defective in amino acid transport

1980 ◽  
Vol 58 (10) ◽  
pp. 1165-1171 ◽  
Author(s):  
Jean E. Irvin ◽  
Jordan M. Ingram
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Amino Acid ◽  
Respiratory Activity ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Acid Transport ◽  
Transport Capacity ◽  
Wild Type ◽  
High Concentrations ◽  
High Level

High-level chloramphenicol (CM) resistant variants of Pseudomonas aeruginosa were isolated after culture of the wild-type (WT) strain in broth containing high concentrations of the drug. These variants exhibit reduced ability to accumulate several amino acids. The extent of reduction in transport capacity is a function of the concentration of CM in which the variants are grown. Respiratory activity is not reduced in these strains. Amino acid uptake is not affected by the presence of CM during assay. An isogenic strain carrying a plasmid coding for CM resistance does not show this response to CM. Transport capacity is restored to the WT level in CM-sensitive revertants. These results suggest that the acquisition of CM resistance in P. aeruginosa is associated with a fundamental alteration in membrane permeability which is regulated by metabolism in the presence of the drug. The ramifications of this for the study of CM action and resistance are discussed.

scholarly journals The SHR3 homologue from S. pombe demonstrates a conserved function of ER packaging chaperones

2000 ◽  
Vol 113 (23) ◽  
pp. 4351-4362 ◽  
Author(s):  
P. Martinez ◽  
P.O. Ljungdahl
Keyword(s):  
Endoplasmic Reticulum ◽  
Amino Acid ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Dependent Manner ◽  
Transport Vesicles ◽  
Transport Vesicle ◽  
Amino Acid Permeases ◽  
Mutant Phenotypes ◽  
High Degree

In Saccharomyces cerevisiae cells lacking SHR3, amino acid permeases do not enter into COPII transport vesicles and specifically accumulate in the membrane of the endoplasmic reticulum. Shr3p functions as a packaging chaperone to prime transport vesicle formation in the proximity of amino acid permeases. A genetic screen was developed that enabled the Schizosaccharomyces pombe SHR3 functional homologue, designated psh3(+) (pombe SHR3), to be cloned. The psh3(+) gene encodes a protein of 215 amino acids, which shares a high degree of structural and functional similarity with Shr3p. The heterologous expression of psh3(+) complements many, but not all, shr3 null mutant phenotypes in S. cerevisiae in a temperature-dependent manner. Psh3p is localised to the endoplasmic reticulum of S. pombe cells, and strains lacking the psh3(+)gene exhibit decreased rates of amino acid uptake due to reduced levels of functional permeases in the plasma membrane. No packaging chaperones, or proteins exhibiting homology with packaging chaperones, have so far been identified in other eukayotic organisms. The findings reported here are the first to establish that specific packaging chaperones exist in divergent organisms, and demonstrate a conserved function of packaging chaperones in facilitating the export of large polytopic membrane proteins from the endoplasmic reticulum.

Amino acid transport by the cultured human placental trophoblast: effect of insulin on AIB transport

1992 ◽  
Vol 262 (4) ◽  
pp. C834-C839 ◽  
Author(s):  
P. I. Karl ◽  
K. L. Alpy ◽  
S. E. Fisher
Keyword(s):  
Amino Acid ◽  
Human Placenta ◽  
Insulin Treatment ◽  
Maximum Velocity ◽  
Amino Acid Uptake ◽  
Continuous Exposure ◽  
Acid Uptake ◽  
Dependent Manner ◽  
Significant Stimulation ◽  
Insulin Responsiveness

Insulin responsiveness in the human placenta is controversial. This study evaluated insulin stimulation of alpha-aminoisobutyric acid (AIB) uptake in cultured human placental trophoblasts. Both Na(+)-dependent and -independent components of AIB uptake were present in cultured trophoblasts. Na(+)-dependent AIB uptake was significantly stimulated by insulin in a time-dependent manner, as early as 2 h, with a maximum at 12 h of continuous exposure to hormone. Insulin treatment for 4 h increased both the initial uptake rate and the final intracellular concentration. Stimulation was dependent on insulin concentration, with significant stimulation beginning at 10(-9) M. Insulin treatment increased maximum velocity but not the Michaelis constant. Approximately 75% of basal (unstimulated) AIB uptake was inhibited by 10 mM alpha-methylaminoisobutyric acid (MeAIB). The insulin-stimulated increment above basal AIB uptake was completely inhibited by 10 mM MeAIB. Cycloheximide treatment significantly reduced basal and stimulated AIB uptake, although a significant response to insulin persisted. Na(+)-dependent AIB uptake was also stimulated by glucagon, dexamethasone, and 8-bromoadenosine 3',5'-cyclic monophosphate, but not by vasopressin. This study further characterizes amino acid uptake by the human placenta and demonstrates that the Na(+)-dependent component of AIB uptake by the cultured trophoblasts is stimulated by physiological concentrations of insulin.

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