Osmoregulation of amino acid transport activity in cultured fibroblasts

Tramacere, Mariarosaria; Petronini, Pier Giorgio; Severini, Alberto; Borghetti, Angelo F.

doi:10.1016/0014-4827(84)90356-2

Cited by 41 publications

(30 citation statements)

References 14 publications

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“…For these studies a 32, 40, and 50% (w/w) discontinuous sucrose gradient was utilized. The membranes that float on top of the 32% sucrose cushion have been shown previously to be enriched with plasma membrane (PM) markers such as the ␣1 subunit of the Na,K-ATPase (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Membranes from the 32/40% and 40/50% sucrose interfaces are depleted in PM markers but are enriched with proteins of intracellular origin.…”

Section: Resultsmentioning

confidence: 99%

“…In addition to adaptive regulation, System A can also be stimulated acutely by hormones such as insulin (9 -11), growth factors (12), and cell stresses (11)(12)(13). These stimuli induce a rapid increase in the V max of System A transport that does not rely upon synthesis of new carriers, but which is thought to involve the acute modulation of carrier function effected by molecules participating in early insulin and growth factor signaling.…”

mentioning

confidence: 99%

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Insulin Promotes the Cell Surface Recruitment of the SAT2/ATA2 System A Amino Acid Transporter from an Endosomal Compartment in Skeletal Muscle Cells

Hyde¹,

Peyrollier²,

Hundal

2002

Journal of Biological Chemistry

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SAT1-3 comprise members of the recently cloned family of System A transporters that mediate the sodiumcoupled uptake of short chain neutral amino acids, and their activity is regulated extensively by stimuli such as insulin, growth factors, and amino acid availability. In skeletal muscle, insulin stimulates System A activity rapidly by a presently ill-defined mechanism. Here we demonstrate that insulin induces an increase in the plasma membrane abundance of SAT2 in a phosphatidylinositol 3-kinase-dependent manner and that this increase is derived from an endosomal compartment that is required for the hormonal activation of System A. Chloroquine, an acidotropic weak base that impairs endosomal recycling of membrane proteins, induced a complete inhibition in the insulin-mediated stimulation of System A, which was associated with a loss in SAT2 recruitment to the plasma membrane. The failure to stimulate System A and recruit SAT2 to the cell surface could not be attributed to a block in insulin signaling, as chloroquine had no effect on the insulin-mediated phosphorylation of protein kinase B or glycogen synthase kinase 3 or upon insulin-stimulated GLUT4 translocation and glucose transport. Our data indicate strongly that insulin increases System A transport in L6 cells by stimulating the exocytosis of SAT2 carriers from a chloroquine-sensitive endosomal compartment.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Insulin Promotes the Cell Surface Recruitment of the SAT2/ATA2 System A Amino Acid Transporter from an Endosomal Compartment in Skeletal Muscle Cells

Hyde¹,

Peyrollier²,

Hundal

2002

Journal of Biological Chemistry

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“…(b) Cell proliferation decreases (Petronini et al, 1992). (c) The activity of amino acid transport system A increases (Tramacere et al, 1984). (d) There is induced synthesis of a protein that is either identical with or closely homologous to a 70 kDa heat-shock protein (HSP70) (Petronini et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Effect of betaine on HSP70 expression and cell survival during adaptation to osmotic stress

Petronini

Angelis

Borghetti

et al. 1993

Biochemical Journal

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Induced expression of the HSP70 gene in 3T3 and SV-3T3 cells was monitored by measurements of the synthesis of HSP70 and of the cellular contents of both HSP70 and its mRNA. The presence of betaine (N-trimethylglycine) at concentrations of 2.5-25 mM decreased the induction of HSP70 gene expression caused by incubation of 3T3 and SV-3T3 cells in hypertonic (0.5 osM) medium. This effect was accompanied by an enhancement of SV-3T3 cell adaptation, assayed by colony formation, to the hyperosmotic conditions. In contrast, the presence of betaine did not affect HSP70 gene expression induced in these

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“…Up-regulation of system A activity has also been described upon hypertonic incubation (11)(12)(13)(14)(15)(16). In cultured human fibroblasts (17) and human endothelial cells (18), the hypertonic increase in system A activity is responsible for the regulatory volume increase that follows cell shrinkage and restores cell volume.…”

mentioning

confidence: 99%

Adaptive Increase of Amino Acid Transport System A Requires ERK1/2 Activation

Franchi-Gazzola

Visigalli

Bussolati

et al. 1999

Journal of Biological Chemistry

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Amino acid starvation markedly stimulates the activity of system A, a widely distributed transport route for neutral amino acids. The involvement of MAPK (mitogen-activated protein kinase) pathways in this adaptive increase of transport activity was studied in cultured human fibroblasts. In these cells, a 3-fold stimulation of system A transport activity required a 6-h amino acidfree incubation. However, a rapid tyrosine phosphorylation of ERK (extracellular regulated kinase) 1 and 2, and JNK (Jun N-terminal kinase) 1, but not of p38, was observed after the substitution of complete medium with amino acid-free saline solution. ERK1/2 activity was 4-fold enhanced after a 15-min amino acid-free incubation and maintained at stimulated values thereafter. A transient, less evident stimulation of JNK1 activity was also detected, while the activity of p38 was not affected by amino acid deprivation. PD98059, an inhibitor of ERK1/2 activation, completely suppressed the adaptive increase of system A transport activity that, conversely, was unaffected by inhibitors of other transduction pathways, such as rapamycin and wortmannin, as well as by chronic treatment with phorbol esters. In the presence of either L-proline or 2-(methylaminoisobutyric) acid, two substrates of system A, the transport increase was prevented and no sustained stimulation of ERK1/2 was observed. To identify the stimulus that maintains MAPK activation, cell volume was monitored during amino acid-free incubation. It was found that amino acid deprivation caused a progressive cell shrinkage (30% after a 6-h starvation). If proline was added to amino acid-starved, shrunken cells, normal values of cell volume were rapidly restored. However, proline-dependent volume rescue was hampered if cells were pretreated with PD98059. It is concluded that (a) the triggering of adaptive increase of system A activity requires a prolonged activation of ERK1 and 2 and that (b) cell volume changes, caused by the depletion of intracellular amino acid pool, may underlie the activation of MAPKs.

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Osmoregulation of amino acid transport activity in cultured fibroblasts

Cited by 41 publications

References 14 publications

Insulin Promotes the Cell Surface Recruitment of the SAT2/ATA2 System A Amino Acid Transporter from an Endosomal Compartment in Skeletal Muscle Cells

Insulin Promotes the Cell Surface Recruitment of the SAT2/ATA2 System A Amino Acid Transporter from an Endosomal Compartment in Skeletal Muscle Cells

Effect of betaine on HSP70 expression and cell survival during adaptation to osmotic stress

Adaptive Increase of Amino Acid Transport System A Requires ERK1/2 Activation

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