A cell‐density sensing factor regulates the lifetime of a chemoattractant‐induced Gα‐GTP conformation

Brazill, Derrick; Gundersen, Robert E.; Gomer, Richard H.

doi:10.1016/s0014-5793(97)00104-x

Cited by 14 publications

(28 citation statements)

References 41 publications

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“…3 H]GTP to membranes was measured following Snaar-Jagalska and Van Haastert (40) with the exception that instead of spinning membranes through silicone oil, membranes were collected by centrifugation for 2 min at 14,000 ϫ g. cAMP-induced high affinity GTPase activity was measured following Brazill et al (41), adding the creatine phosphokinase to the mixture immediately before use.…”

Section: Methodsmentioning

confidence: 99%

A Cell Number-counting Factor Regulates Group Size inDictyostelium by Differentially Modulating cAMP-induced cAMP and cGMP Pulse Sizes

Tang¹,

Ammann²,

Gao³

et al. 2001

Journal of Biological Chemistry

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A secreted counting factor (CF), regulates the size of Dictyostelium discoideum fruiting bodies in part by regulating cell-cell adhesion. Aggregation and the expression of adhesion molecules are mediated by relayed pulses of cAMP. Cells also respond to cAMP with a short cGMP pulse. We find that CF slowly down-regulates the cAMP-induced cGMP pulse by inhibiting guanylyl cyclase activity. A 1-min exposure of cells to purified CF increases the cAMP-induced cAMP pulse. CF does not affect the cAMP receptor or its interaction with its associated G proteins or the translocation of the cytosolic regulator of adenylyl cyclase to the membrane in response to cAMP. Pulsing streaming wild-type cells with a high concentration of cAMP results in the formation of small groups, whereas reducing cAMP pulse size with exogenous cAMP phosphodiesterase during stream formation causes cells to form large groups. Altering the extracellular cAMP pulse size does not phenocopy the effects of CF on the cAMP-induced cGMP pulse size or cell-cell adhesion, indicating that CF does not regulate cGMP pulses and adhesion via CF's effects on cAMP pulses. The results suggest that regulating cell-cell adhesion, the cGMP pulse size, or the cAMP pulse size can control group size and that CF regulates all three of these independently.

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Section: Methodsmentioning

confidence: 99%

A Cell Number-counting Factor Regulates Group Size inDictyostelium by Differentially Modulating cAMP-induced cAMP and cGMP Pulse Sizes

Tang¹,

Ammann²,

Gao³

et al. 2001

Journal of Biological Chemistry

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“…CMF accomplishes this by controlling the GTPase rate of G␣2. We found that in lysates, approximately 250 molecules of GTP bind to a cell's membrane in response to a pulse of cAMP, regardless of whether CMF is present or absent (4,45). After cAMP stimulation, GTP is hydrolyzed to GDP at a rate of approximately 240 molecules in 3 min in the absence of CMF.…”

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confidence: 89%

PldB, a Putative Phospholipase D Homologue in Dictyostelium discoideum Mediates Quorum Sensing during Development

et al. 2005

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Quorum sensing, also known as cell-density sensing in the unicellular eukaryote Dictyostelium discoideum, is required for efficient entry into the differentiation and development segment of its life cycle. Quorum sensing is accomplished by simultaneously secreting and sensing the glycoprotein Conditioned Medium Factor, or CMF. When the density of starving cells is high, CMF levels are high, which leads to aggregation followed by development. Here, we describe the role of pldB, a gene coding for a putative phospholipase D (PLD) homologue, in quorum sensing. We find that in submerged culture, adding butanol, an inhibitor of PLDcatalyzed phosphatidic acid production, allows cells to bypass the requirement for CMF mediated quorum sensing and aggregate at low cell density. Deletion of pldB mimics the presence of butanol, allowing cells to aggregate at low cell density. pldB ؊ cells also initiate and finish aggregation rapidly. Analysis of early developmental gene expression in pldB ؊ cells reveals that the cyclic AMP receptor cAR1 is expressed at higher levels earlier than in wild-type cells, which could explain the rapid aggregation phenotype. As would be predicted, cells overexpressing pldB are unable to aggregate even at high cell density. Adding CMF to these pldB ؊ overexpressing cells does not rescue aggregation. Both of these phenotypes are cell autonomous, as mixing a small number of pldB ؊ cells with wild-type cells does not cause the wild-type cells to behave like pldB ؊ cells.

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“…This activates phospholipase C, which through an unknown mechanism causes the G␣ 2 GTPase to be inhibited, prolonging the lifetime of the cAMP-activated G␣ 2 -GTP configuration. This, in turn, allows cAR1-mediated cAMP signal transduction to take place (19,21).…”

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confidence: 99%

A Putative Receptor Mediating Cell-density Sensing inDictyostelium

Deery

Gomer

1999

Journal of Biological Chemistry

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When Dictyostelium cells starve, they begin secreting a glycoprotein called conditioned medium factor (CMF). When there is a high density of starved cells, as indicated by a high concentration of CMF, the cells begin expressing some genes and aggregate using pulses of cAMP as a chemoattractant. CMF regulates gene expression via a G protein-independent pathway, whereas CMF regulates cAMP signal transduction via a G proteindependent pathway. To elucidate receptors mediating cell density sensing, we used CMF-Sepharose to isolate membrane proteins that bind CMF. We identified a 50-kDa protein, CMFR1, that is sensitive to trypsin treatment of whole cells. We obtained partial amino acid sequence of CMFR1 and isolated the cDNA encoding it. The derived amino acid sequence has no significant similarity to known proteins and has two or three predicted transmembrane domains. Expression of CMFR1 in insect cells caused an increase in CMF binding. Repression of CMFR1 in Dictyostelium by gene disruption resulted in a ϳ50% decrease of the CMF binding and a loss of CMF-induced G protein-independent gene expression. The G protein-dependent CMF signal transduction pathways appear to be functional in cmfr1 cells, suggesting that cells sense the density-sensing factor CMF using two or more different receptors.

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A cell‐density sensing factor regulates the lifetime of a chemoattractant‐induced Gα‐GTP conformation

Cited by 14 publications

References 41 publications

A Cell Number-counting Factor Regulates Group Size inDictyostelium by Differentially Modulating cAMP-induced cAMP and cGMP Pulse Sizes

A Cell Number-counting Factor Regulates Group Size inDictyostelium by Differentially Modulating cAMP-induced cAMP and cGMP Pulse Sizes

PldB, a Putative Phospholipase D Homologue in Dictyostelium discoideum Mediates Quorum Sensing during Development

A Putative Receptor Mediating Cell-density Sensing inDictyostelium

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