scholarly journals Differential mechanisms of inositol phosphate generation at the receptors for bombesin and platelet-derived growth factor

1989 ◽  
Vol 262 (2) ◽  
pp. 665-668 ◽  
Author(s):  
M G Cattaneo ◽  
L M Vicentini
Keyword(s):  
Growth Factor ◽  
Kinase Activity ◽  
Inositol Phosphate ◽  
Growth Factor Receptor ◽  
Platelet Derived Growth Factor ◽  
3T3 Cells ◽  
Tyrosine Kinase Activity ◽  
Independent Manner ◽  
Streptolysin O ◽  
Bombesin Receptor

We investigated the mechanism(s) whereby activation of a growth-factor receptor typically endowed with tyrosine kinase activity, such as the platelet-derived growth factor (PDGF) receptor, triggers phosphoinositide hydrolysis. In Swiss 3T3 cells permeabilized with streptolysin O, an analogue of GTP, guanosine 5′-[gamma-thio]triphosphate, was found to potentiate the coupling of the bombesin receptor to phospholipase C. In contrast, the activation of the enzyme by PDGF occurred in a GTP-independent manner. Moreover, the inactive analogue of GTP, guanosine 5′-[beta-thio]diphosphate, significantly inhibited the bombesin-induced InsP3 generation, whereas it did not decrease the same effect when stimulated by PDGF.

scholarly journals Role of tyrosine kinase and membrane-spanning domains in signal transduction by the platelet-derived growth factor receptor.

1988 ◽  
Vol 8 (12) ◽  
pp. 5126-5131 ◽  
Author(s):  
J A Escobedo ◽  
P J Barr ◽  
L T Williams
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Kinase Activity ◽  
Growth Factor Receptor ◽  
Platelet Derived Growth Factor ◽  
Tyrosine Kinase Activity ◽  
Down Regulation ◽  
Atp Binding Site ◽  
Membrane Spanning ◽  
Membrane Spanning Domains

Three types of mutations were introduced into the platelet-derived growth factor (PDGF) receptor to cause a loss of PDGF-stimulated tyrosine kinase activity: (i) a point mutation of the ATP-binding site, (ii) a deletion of the carboxyl-terminal region, and (iii) replacement of the membrane-spanning sequences by analogous transmembrane sequences of other receptors. Transfectants expressing mutated receptors bind, 125I-labeled PDGF with a high affinity but had no PDGF-sensitive tyrosine kinase activity, phosphatidylinositol turnover, increase in the intracellular calcium concentration, change in cellular pH, or stimulation of DNA synthesis. However, PDGF-induced receptor down regulation was normal in the mutant cells. These results indicate that the transmembrane sequence has a specific signal-transducing function other than merely serving as a membrane anchor and that the receptor kinase activity is necessary for most responses to PDGF but is not required for receptor down regulation.

Role of tyrosine kinase and membrane-spanning domains in signal transduction by the platelet-derived growth factor receptor

1988 ◽  
Vol 8 (12) ◽  
pp. 5126-5131
Author(s):  
J A Escobedo ◽  
P J Barr ◽  
L T Williams
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Kinase Activity ◽  
Growth Factor Receptor ◽  
Platelet Derived Growth Factor ◽  
Tyrosine Kinase Activity ◽  
Down Regulation ◽  
Atp Binding Site ◽  
Membrane Spanning ◽  
Membrane Spanning Domains

Three types of mutations were introduced into the platelet-derived growth factor (PDGF) receptor to cause a loss of PDGF-stimulated tyrosine kinase activity: (i) a point mutation of the ATP-binding site, (ii) a deletion of the carboxyl-terminal region, and (iii) replacement of the membrane-spanning sequences by analogous transmembrane sequences of other receptors. Transfectants expressing mutated receptors bind, 125I-labeled PDGF with a high affinity but had no PDGF-sensitive tyrosine kinase activity, phosphatidylinositol turnover, increase in the intracellular calcium concentration, change in cellular pH, or stimulation of DNA synthesis. However, PDGF-induced receptor down regulation was normal in the mutant cells. These results indicate that the transmembrane sequence has a specific signal-transducing function other than merely serving as a membrane anchor and that the receptor kinase activity is necessary for most responses to PDGF but is not required for receptor down regulation.

scholarly journals Transactivation of Platelet-Derived Growth Factor Receptor α by the GTPase-Deficient Activated Mutant of Gα12

2006 ◽  
Vol 26 (1) ◽  
pp. 50-62 ◽  
Author(s):  
Rashmi N. Kumar ◽  
Ji Hee Ha ◽  
Rangasudhagar Radhakrishnan ◽  
Danny N. Dhanasekaran
Keyword(s):  
Growth Factor ◽  
Cell Growth ◽  
Signaling Pathway ◽  
Growth Factor Receptor ◽  
Platelet Derived Growth Factor ◽  
Dominant Negative Mutant ◽  
Dependent Manner ◽  
3T3 Cells ◽  
Nih 3T3 ◽  
Nih 3T3 Cells

ABSTRACT The GTPase-deficient, activated mutant of Gα12 (Gα12Q229L, or Gα12QL) induces neoplastic growth and oncogenic transformation of NIH 3T3 cells. Using microarray analysis, we have previously identified a role for platelet-derived growth factor receptor α (PDGFRα) in Gα12-mediated cell growth (R. N. Kumar et al., Cell Biochem. Biophys. 41:63-73, 2004). In the present study, we report that Gα12QL stimulates the functional expression of PDGFRα and demonstrate that the expression of PDGFRα by Gα12QL is dependent on the small GTPase Rho. Our results indicate that it is cell type independent as the transient expression of Gα12QL or the activation of Gα12-coupled receptors stimulates the expression of PDGFRα in NIH 3T3 as well as in human astrocytoma 1321N1 cells. Furthermore, we demonstrate the presence of an autocrine loop involving PDGF-A and PDGFRα in Gα12QL-transformed cells. Analysis of the functional consequences of the Gα12-PDGFRα signaling axis indicates that Gα12 stimulates the phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathway through PDGFR. In addition, we show that Gα12QL stimulates the phosphorylation of forkhead transcription factor FKHRL1 via AKT in a PDGFRα- and PI3K-dependent manner. Since AKT promotes cell growth by blocking the transcription of antiproliferative genes through the inhibitory phosphorylation of forkhead transcription factors, our results describe for the first time a PDGFRα-dependent signaling pathway involving PI3K-AKT-FKHRL1, regulated by Gα12QL in promoting cell growth. Consistent with this view, we demonstrate that the expression of a dominant negative mutant of PDGFRα attenuated Gα12-mediated neoplastic transformation of NIH 3T3 cells.

scholarly journals Involvement of a phosphotyrosine protein phosphatase in the suppression of platelet-derived growth factor receptor autophosphorylation in ras-transformed cells

1993 ◽  
Vol 293 (1) ◽  
pp. 215-221 ◽  
Author(s):  
L Tomáska ◽  
R J Resnick
Keyword(s):  
Growth Factor ◽  
Phosphatase Activity ◽  
Receptor Tyrosine Kinase ◽  
Protein Phosphatase ◽  
Kinase Activity ◽  
Platelet Derived Growth Factor ◽  
Transformed Cells ◽  
Pdgf Receptor ◽  
Tyrosine Kinase Activity ◽  
Phosphotyrosine Protein Phosphatase

The nature of the suppression of platelet-derived growth factor (PDGF) receptor autophosphorylation in ras-transformed NIH 3T3 fibroblasts was investigated. The PDGF receptor from ras-transformed cells that had been purified by wheatgerm-lectin affinity chromatography displayed normal PDGF-induced autophosphorylation, indicating that the receptor is not irreversibly modified. Various phosphotyrosine-protein-phosphatase inhibitors did not reverse the inhibition of PDGF-receptor kinase in crude membrane preparations from ras-transformed cells. However, treatment of intact ras-transformed cells both with 2 mM sodium orthovanadate and with 20 microM phenylarsine oxide restored PDGF-receptor tyrosine-kinase activity to a level similar to that observed in normal cells. Direct measurement of the phosphatase activities in crude cellular fractions revealed a 2.5-fold higher membrane-associated phosphotyrosine-protein-phosphatase activity in ras-transformed cells, whereas phosphoserine-protein-phosphatase activity remained unchanged between the cell lines. These data suggest that the suppression of the PDGF-receptor tyrosine-kinase activity in ras-transformed cells is mediated via an inhibitory component, distinct from the receptor, that may be positively regulated by the dephosphorylation of tyrosine residue(s).

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