Role of Amino Acid Transport System A in the Control of Cell Volume in Cultured Human Fibroblasts

Gazzola, Gian C.; DallˈAsta, Valeria; Nucci, Franca A.; Rossi, Patrizia A.; Bussolati, Ovidio; Hoffmann, Else K.; Guidotti, Guido

doi:10.1159/000154601

Cited by 37 publications

(26 citation statements)

References 26 publications

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“…2). However, the mechanism(s) is not well characterized and the hypertonicity-mediated effect has somehow been related to the derepression ofthe system that occurred after amino acid starvation (22,23). Results of our earlier studies (11) showed that system A activity was not expressed in NBL-1 cells exposed to hypertonic shock when cultured in Ham's F-12 Ag/ml).…”

Section: Discussionmentioning

confidence: 99%

Evidence for a regulatory protein involved in the increased activity of system A for neutral amino acid transport in osmotically stressed mammalian cells.

Ruiz-Montasell

Gómez‐Angelats

Casado

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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System A for neutral amino acid transport is Increased by hypertonic shock in NBL-1 cells previously induced to express system A activity by amino acid starvation. The hypertonicity-medated effect can be blocked by cyclobeximide but is insensitive to tuncmycin. The activity induced may be inactivated Irreversibly by the addition of system A substrates, by a rapid mehanism insensitive to cycloheximide. In CHO-Ki cells, hypertonicity increases system A activity, as has been shown in NBL-1 cells. This effect is additive to the activity produced by derepression of system A by amino acid starvation and is insensitive to tuncmycin. Furthermore, the alanine-resistant mutant CHO-K1 alar4, which bears a mutation affecting the regulatory gene RI, involved in the derepression ofsystem A activity after amino acid starvation, is still able to respond to the hypertonic shock by increasing system A activiy to a level slmllar to that described in hypertonicityinduced derepressed CHO-Ki (wild type) cells. These results suggest (i) that the hypertonicity-medated increase of system A activity occurs o h a mechanism other than that involved in system A derepresslon and (is) that a regulatory protein coded by an osmotically sensitive gene is responsible for further activation of preexisting A carriers.

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Section: Discussionmentioning

confidence: 99%

Evidence for a regulatory protein involved in the increased activity of system A for neutral amino acid transport in osmotically stressed mammalian cells.

Ruiz-Montasell

Gómez‐Angelats

Casado

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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“…A cell shrinkage occurring upstream of caspase-8 activation has been also induced in CEM cells by hyperosmotic stress (Fumarola, La Monica and Guidotti, unpublished results) and recently reported for Jurkat T cells treated with agonistic anti-CD95 antibodies. 41 The replacement of L-glutamine in the culture medium with 10 mM betaine, a surrogate compatible organic osmolyte, 12 fully counteracted the cell volume decrement at 3 h and allowed CEM cells to retain more than 85% of their initial volume at 6 h ( Figure 4a). Under these conditions the cells were significantly protected from apoptosis (Figure 4b,c).…”

Section: Cell Shrinkage Induces the Cd95-dependent Apoptotic Pathwaymentioning

confidence: 99%

“…12 Labeled OMG was added during the last 30 ± 40 min of incubation to control or modified mediums (see Results) whose glucose concentration had been reduced to 0.5 mM. The cells were then quickly washed twice in icecold PBS containing 0.1 mM phloretin and extracted in ice-cold 10% trichloroacetic acid.…”

Section: Cell Volumementioning

confidence: 99%

“…L-Glutamine, the most abundant free amino acid of the human body, has a central role in the energy metabolism of many tissues, 1 ± 5 is a growth-limiting amino acid for several cell types including lymphocytes 6 ± 9 and leukemia cell lines, 10,11 engages in cell volume control as compatible osmolyte 12,13 and serves as a precursor of neurotransmitters. 14 Previous studies with cultured human leukemia/lymphoma cell lines (CEM, HL-60, U937, Namalwa) indicated that glutamine restriction induces loss of cell viability by apoptosis.…”

Section: Introductionmentioning

confidence: 99%

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Glutamine deprivation-mediated cell shrinkage induces ligand-independent CD95 receptor signaling and apoptosis

2001

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Cell shrinkage and loss of cell viability by apoptosis have been examined in cultured CD95(Fas/Apo-1)-expressing leukemiaderived CEM and HL-60 cells subjected to acute deprivation of glutamine, a major compatible osmolyte engaged in cell volume control. Glutamine deprivation-mediated cell shrinkage promoted a ligand-independent activation of the CD95-mediated apoptotic pathway. Cell transfection with plasmids expressing FADD-DN or v-Flip viral proteins pointed to a functional clustering of CD95 receptors at the cell surface with activation of the`extrinsic pathway' caspase cascade. Accordingly, cell shrinkage did not induce apoptosis in CD95 receptor-negative lymphoma L1210 cells. Replacement of glutamine with surrogate compatible osmolytes counteracted cell volume decrement and protected the CD95-expressing cells from apoptosis. A glutamine deprivationdependent cell shrinkage with activation of the CD95-mediated pathway was also observed when asparaginase was added to the medium. Asparagine depletion had no role in this process. The cell-size shrinkage-dependent apoptosis induced by glutamine restriction in CD95-expressing leukemic cells may therefore be of clinical relevance in amidohydrolase enzyme therapies. Cell Death and Differentiation (2001) 8, 1004 ± 1013.

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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.…”

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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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Role of Amino Acid Transport System A in the Control of Cell Volume in Cultured Human Fibroblasts

Cited by 37 publications

References 26 publications

Evidence for a regulatory protein involved in the increased activity of system A for neutral amino acid transport in osmotically stressed mammalian cells.

Evidence for a regulatory protein involved in the increased activity of system A for neutral amino acid transport in osmotically stressed mammalian cells.

Glutamine deprivation-mediated cell shrinkage induces ligand-independent CD95 receptor signaling and apoptosis

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

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