scholarly journals Growth hormone activates mitogen-activated protein kinase and S6 kinase and promotes intracellular tyrosine phosphorylation in 3T3-F442A preadipocytes

1992 ◽  
Vol 284 (3) ◽  
pp. 649-652 ◽  
Author(s):  
N G Anderson
Keyword(s):  
Growth Hormone ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Tyrosine Phosphorylation ◽  
Phorbol Esters ◽  
Mitogen Activated Protein Kinase ◽  
S6 Kinase ◽  
Kinase C ◽  
Transient Activation ◽  
Mitogen Activated Protein

Physiological concentrations of growth hormone induced a rapid and transient activation of mitogen-activated protein kinase (MAP kinase) and S6 kinase in 3T3-F442A preadipocytes. These effects were abrogated by staurosporine and in cells chronically pretreated with phorbol esters, suggesting that protein kinase C is involved in the mechanism of activation. In addition, three cytosolic proteins exhibited a growth-hormone-dependent increase in tyrosine phosphorylation.

scholarly journals Ca2+ and protein kinase C-dependent mechanisms involved in gastrin-induced Shc/Grb2 complex formation and P44-mitogen-activated protein kinase activation

1997 ◽  
Vol 325 (2) ◽  
pp. 383-389 ◽  
Author(s):  
Laurence DAULHAC ◽  
Aline KOWALSKI-CHAUVEL ◽  
Lucien PRADAYROL ◽  
Nicole VAYSSE ◽  
Catherine SEVA
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tyrosine Phosphorylation ◽  
Phorbol Esters ◽  
Receptor Occupancy ◽  
Mitogen Activated Protein Kinase ◽  
Free Calcium ◽  
Mapk Activation ◽  
Kinase C ◽  
Mitogen Activated Protein

The proliferative effects of gastrin on normal and neoplastic gastro-intestinal tissues have been shown to be mediated by the gastrin/CCKB (G/CCKB) G-protein-coupled receptors. We have recently reported that gastrin stimulates the tyrosine phosphorylation of Shc proteins and their subsequent association with the Grb2/Sos complex, leading to mitogen-activated protein kinase (MAPK) activation, a pathway known to play an important role in cell proliferation. We undertook the present study to characterize the signalling pathways used by this receptor to mediate the activation of the Shc/Grb2 complex. Since G/CCKB receptor occupancy leads to the activation of the phospholipase C (PLC)/protein kinase C (PKC) pathway, we examined whether PKC stimulation and Ca2+ mobilization contribute to the phosphorylation of Shc proteins and their association with Grb2 in response to gastrin. Our results indicate that Shc proteins are tyrosine phosphorylated and associate with Grb2 in response to phorbol esters, suggesting that activation of PKC is a potential signalling pathway leading to activation of the Shc/Grb2 complex. Inhibition of PKC by GF109203X completely blocked the effect of PMA on Shc tyrosine phosphorylation and its subsequent association with Grb2, but had a partial inhibitory effect on the response to gastrin. Depletion of the intracellular Ca2+ pools by treatment with thapsigargin blocked the increase in intracellular free calcium concentration induced by gastrin and diminished the ability of the peptide to stimulate Shc phosphorylation and recruitment of Grb2. In addition, removal of extracellular Ca2+ partially inhibited the effect of gastrin on Shc phosphorylation as well as its association with Grb2, indicating that the effects of gastrin are also mediated by Ca2+-dependent mechanisms. Furthermore, we show that blockage of the two major early signals generated by activation of PLC, which induced the activation of the Shc/Grb2 complex, also blocked gastrin-induced MAPK activation.

scholarly journals Rab6 is phosphorylated in thrombin-activated platelets by a protein kinase C-dependent mechanism: effects on GTP/GDP binding and cellular distribution

1999 ◽  
Vol 342 (2) ◽  
pp. 353-360 ◽  
Author(s):  
Michael L. FITZGERALD ◽  
Guy L. REED
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Kinase Inhibitor ◽  
Mitogen Activated Protein Kinase ◽  
Secretory Cells ◽  
Kinase C ◽  
Kd Values ◽  
Mitogen Activated Protein ◽  
Thrombin Activation

In platelets and other secretory cells, protein kinase C (PKC) plays a role in exocytosis stimulated by physiological extracellular signals, although its linkage to the secretory machinery is poorly understood. We investigated whether Rab6, a GTP-binding protein that fractionates with platelet α-granules, may be involved in linking these processes. We found that Rab6 contains two PKC consensus phosphorylation sites that are evolutionarily conserved. In platelets metabolically labelled with [32P]Pi, Rab6 phosphorylation was induced by phorbol esters or by thrombin. This phosphorylation was blocked by a specific PKC inhibitor (Ro-31-8220), but not by a p38 mitogen-activated protein kinase inhibitor (PD-169316). Physiological stimulation of platelets caused a PKC-dependent translocation of Rab6 from platelet particulate fractions, nearly doubling the fraction of Rab6 in the cytosol. A human Rab6 isoform (Rab6C) that is preferentially expressed in human platelet RNA was cloned and its phosphorylation by PKC was characterized. Rab6C incorporated up to 2 mol of [32P]Pi per mol of active protein. Rab6C bound GDP and GTP with Kd values of 113±12 and 119±27 nM respectively, and hydrolysed GTP at a rate of 100±15 μmol of GTP/mol of Rab6C per min. PKC phosphorylation of Rab6C increased the affinity for GTP by 3-fold, although it had lesser effects on GDP (1.6-fold). Phosphorylation did not alter the GTPase activity. In summary, thrombin activation of platelets leads to PKC-dependent phosphorylation of Rab6 and a translocation of Rab6 to the cytosol. We suggest that PKC phosphorylation may be an important mechanism through which Rab functional interactions in vesicle trafficking and secretion can be altered in response to an external stimulus.

scholarly journals The m3 muscarinic acetylcholine receptor is coupled to mitogen-activated protein kinase via protein kinase C and epidermal growth factor receptor kinase

2000 ◽  
Vol 348 (2) ◽  
pp. 381-387 ◽  
Author(s):  
Barbara E. SLACK
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Egf Receptor ◽  
Mitogen Activated Protein Kinase ◽  
Negative Feedback Regulation ◽  
Kinase C ◽  
Mitogen Activated Protein ◽  
M3 Receptor

The acetylcholine analogue carbachol rapidly activated mitogen-activated protein kinase (MAPK), and caused tyrosine phosphorylation of the adapter protein p52 Shc and the epidermalgrowth factor (EGF) receptor, in human embryonic kidney cells stably expressing m3 muscarinic receptors. The protein kinase C (PKC) inhibitor GF109203X caused a significant partial inhibition of m3 receptor-mediated activation of MAPK. The PKC-independent MAPK activity elicited by carbachol in the presence of GF109203X was reproducibly abolished by AG1478, an inhibitor of EGF-receptor tyrosine kinase activity, and by the Src tyrosine kinase inhibitor PP1. In a subset of these experiments, GF109203X concomitantly increased carbachol-induced tyrosine phosphorylation of p52 Shc and the EGF receptor. In co-stimulation experiments, carbachol and EGF activated MAPK in a non-additive fashion; moreover, EGF-induced association of Shc with the phosphorylated EGF receptor was inhibited by carbachol. This effect of carbachol was blocked by GF109203X. The results indicate that MAPK activation by m3 receptor stimulation is regulated by two pathways; one dependent on PKC, and the other mediated via the EGF receptor and Src. Moreover, the EGF-receptor-dependent pathway may be subject to negative-feedback regulation via m3 receptor-coupled activation of PKC.

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