The pleiotypic response in mammalian cells: Search for an intracellular mediator

Mamont, Pierre S.; Hershko, Avram; Kram, Raphaël; Schacter, Lee; Lust, Jean; Tomkins, Gordon M.

doi:10.1016/0006-291x(72)90865-0

Cited by 43 publications

(12 citation statements)

References 10 publications

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“…Thus, we have not detected the appearance of any unusual nucleotides, such as ppGpp on severe amino acid starvation of two different mammalian cell lines, namely 3T3 and BHK, nor in a human diploid cell culture WI38 and in early passage mouse embryo fibroblast cultures. It should be noted that our results are consistent with earlier reports of failure to detect ppGpp and pppGpp production in HeI_a [4], 3T3 [5] and CHO cells [6] .…”

Section: Methodssupporting

confidence: 93%

Absence of ppGpp production in synchronised balb/c mouse 3T3 cells on isoleucine starvation

1976

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Section: Methodssupporting

confidence: 93%

Absence of ppGpp production in synchronised balb/c mouse 3T3 cells on isoleucine starvation

1976

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“…Under these conditions the cellular Ap4A levels dropped more than a 100-fold, suggesting a link between the rate of protein synthesis and intracellular Ap4A levels. We presently assume, without proof, that the synthesis of Ap4A in vivo proceeds through the backreaction of the amino acid activation process, which was demonstrated by the in vitro studies (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). The level of Ap4A can thus be controlled by a combination of its rate of synthesis (11)(12)(13)(14)(15) nd rate of degradation (19).…”

Section: Methodsmentioning

confidence: 99%

“…The stringent response in bacteria, whereby a set of intracellular biochemical events is controlled by the availability of an essential amino acid, leads to the accumulation of ppGpp upon amino acid starvation in stringent but not in relaxed strains of bacteria (5). This nucleotide, however, has not been identified in various mammalian cells in vivo (6,7). Nevertheless, various mammalian cells in culture respond to environmental conditions that tend to slow growth in a fashion similar to the bacterial stringent response, in what has been termed a "pleiotypic response" (8).…”

mentioning

confidence: 99%

Presence of diadenosine 5',5''' -P1, P4-tetraphosphate (Ap4A) in mamalian cells in levels varying widely with proliferative activity of the tissue: a possible positive "pleiotypic activator".

Rapaport¹,

Zamecnik²

1976

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

251

119

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An accurate assay of diadenosine 5',5'''- P1,P4-tetraphosphate [A(5') pppp(5')A], which was shown to be formed in vitro in the backreaction of the amino acid activation step, has been developed in various cell lines in culture and in normal mouse liver or hepatoma in vivo. Use of radioactive labeling of acid-soluble nucleotides to high specific activity followed by chromatographic separation techniques yielded levels of Ap4A varying from 5 to 0.05 muM (from 30 pmol/mg of protein to 0.15 pmol), depending on the doubling time of the cell line or the proliferative state of the cells. The levels of Ap4A incells is inversely related to their doubling time, varying from 0.1 X 10(-4) of the cellular ATP levels in slowly growing cells to 20 X 10(-4) of the ATP levels of cells with rapid doubling times. The steady-state levels of ATP of different cell lines, although showing some fluctuations, are not related to the doubling time of the cells. Arrest of cellular proliferation by serum deprivation or amino acid starvation, which does not alter the cellular ATP levels more than 2-fold, does nevertheless cause a decrease of 30 to 50-fold in the Ap4A levels. Inhibition of protein synthesis by pactamycin or puromycin, or inhibition of DNA synthesis by hydroxyurea, leads to a more dramatic decrease of 50 to 100-fold in intracellular Ap4A levels. The metabolic lability of Ap4A is also demonstrated by its rapid depletion after decreases in the ATP/ADP ratio. The possibility of Ap4A being a metabolic "signal nucleotide" that is formed at the onset of protein synthesis and is active in positive growth regulation (positive pleiotypic activation) is discussed.

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“…Because of the resemblance of this regulatory program to "stringent control" in bacteria, we inquired whether guanosine 5'-diphosphate, 2'-or 3'-diphosphate (ppGpp) (a possible mediator of stringent control) (3,4) could be involved in control in animal cells. However, this nucleotide was not detected in cultured 3T3 cells under conditions that should have elicited its appearance (5).…”

mentioning

confidence: 86%

Pleiotypic Control by Adenosine 3′:5′-Cyclic Monophosphate: A Model for Growth Control in Animal Cells

Kram

Mamont

Tomkins

1973

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

Self Cite

145

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The effects of serum deprivation on several general cellular biochemical processes ("pleiotypic response") related to the growth of normal fibroblasts can be mimicked by treatment of these cells with prostaglandin El in the presence of serum. N8,02'-Dibutyryl adenosine 3': 5'-cyclic monophosphate and theophylline inhibit the membrane transport processes without much effect on other pleiotypic reactions such as overall protein and RNA synthesis and protein degradation. The amount of intracellular cyclic AMP increases during serum starvation and returns to the initial concentration in unstarved cells when growth is initiated again upon addition of serum. Fibroblasts transformed by simian virus 40 have a lower cyclic AMP content than their untransformed parents. Serum deprivation neither increases cyclic AMP content nor significantly affects the pleiotypic reactions in transformed cells. Cycloheximide causes a decrease in cyclic AMP content of normal fibroblasts coincidentally with the ability of this inhibitor to stimulate uridine transport and slow protein degradation in cells deprived of serum.In normal cells, several biochemical parameters, including membrane transport, overall rates of protein and RNA synthesis, and protein degradation, fluctuate coordinately with changes in cell-growth rate. These mechanistically unrelated processes and their coordinated response to environmental changes comprise what we have defined as the "pleiotypic program" and "pleiotypic control," respectively. In malignant cells, the pleiotypic program and the rate of growth are relatively insensitive to changes in cultural conditions; we thus picture transformed cells as having a defect in the pleiotypic control mechanism (1).In cultured fibroblasts, insulin as well as serum activates the pleiotypic program (1, 2). Moreover, the same set of reactions is regulated in many other cell types by specific hormones or growth factors. Thus, certain general features of hormonal regulation may also be exerted through the pleiotypic mechanism (1).We have postulated that a "mediator", probably formed at the cell membrane, coordinates the responses of the different reactions under pleiotypic control. Because of the resemblance of this regulatory program to "stringent control" in bacteria, we inquired whether guanosine 5'-diphosphate, 2'-or 3'-diphosphate (ppGpp) (a possible mediator of stringent control) (3, 4) could be involved in control in animal cells. However, this nucleotide was not detected in cultured 3T3 cells under conditions that should have elicited its appearance (5).In the meantime, numerous reports have implicated cAMP as a regulator of growth, morphology, and contact inhibition in cultured cells (6-11). We report here that altering the inAbbreviations: Bu2cAMP, N6,02'-dibutyryl adenosine 3':5'-cyclic monophosphate; PGE,, prostaglandin El; SV40, simian virus 40. tracellular cAMP content by various means can affect all the reactions under pleiotypic control in a way, suggesting that cAMP is very likely the pleiotypic mediator...

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The pleiotypic response in mammalian cells: Search for an intracellular mediator

Cited by 43 publications

References 10 publications

Absence of ppGpp production in synchronised balb/c mouse 3T3 cells on isoleucine starvation

Absence of ppGpp production in synchronised balb/c mouse 3T3 cells on isoleucine starvation

Presence of diadenosine 5',5''' -P1, P4-tetraphosphate (Ap4A) in mamalian cells in levels varying widely with proliferative activity of the tissue: a possible positive "pleiotypic activator".

Pleiotypic Control by Adenosine 3′:5′-Cyclic Monophosphate: A Model for Growth Control in Animal Cells

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