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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Our recent studies with cell mutants indicate that a cascade shared by the epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) signals exists in NRK cells and mediates oncogenic signals induced by many oncogenes (A. Masuda, S. Kizaka-Kondoh, H. Miwatani, Y. Terada, H. Nojima, and H. Okayama, New Biol. 4:489-503, 1992). We have employed the antisense RNA technique to investigate possible involvement of Raf-1 kinase in this signal transduction cascade. NRK cell clones highly reduced in the Raf-1 production are generated by the expression of a c-raf-1 antisense RNA. They have no apparent growth defects and retain proper mitotic responses to growth factors but are refractory to transformation by EGF or PDGF plus transforming growth factor beta, v-erbB, v-fms, v-K-ras, v-mos, v-fos, v-src, simian virus 40 large T, and polyomavirus middle T but not by v-raf or adenovirus E1A. These results not only support our model for the oncogenic signal cascade but also lead to the conclusion that Raf-1 protein kinase is a downstream component of this oncogenic signal cascade shared by EGF and PDGF.
Mol Cell Biol 1992 Nov
PMID:Raf-1 protein kinase is an integral component of the oncogenic signal cascade shared by epidermal growth factor and platelet-derived growth factor. 140 83

The CD4 and CD8 antigens on T cells have been shown to associate with the Src family member p56lck and a GTP-binding protein, p32. The identification of receptor interactions with intracellular mediators is essential in the elucidation of downstream signals mediated by engagement of these receptor complexes. In this study, we report the detection of an additional 110-kDa polypeptide (p110) associated with the CD4-p56lck complex in human peripheral blood T lymphocytes and leukemic T-cell lines. p110 bound preferentially to CD4-p56lck as an assembled complex and poorly, if at all, to the individual components. p110 was recognized directly by an antiserum to the C-terminal region of the serine/threonine kinase Raf-1 and is related to a p110 polypeptide detected in anti-Raf-1 immunoprecipitates. Despite its association with the CD4-p56lck complex, p110 was found to be phosphorylated predominantly on serine residues. Furthermore, phorbol ester treatment of cells resulted in a transient increase in the detection of p110 associated with CD4-p56lck, concomitant with the modulation of CD4-p56lck from the cell surface. This Raf-1-related p110 is therefore likely to play a role in signals generated from the CD4-p56lck complex. p110 may serve as a bridge between the CD4-p56lck complex and the serine/threonine kinase pathways of T-cell activation.
Mol Cell Biol 1992 Nov
PMID:A Raf-1-related p110 polypeptide associates with the CD4-p56lck complex in T cells. 140 95

In resting cells, c-Jun is phosphorylated on five sites. Three of these sites reside next to its DNA binding domain and negatively regulate DNA binding. In response to expression of oncogenic Ha-Ras, phosphorylation of these sites decreases, while phosphorylation of two other sites within c-Jun's activation domain is greatly enhanced. Phosphorylation of these residues, serines 63 and 73, stimulates the transactivation function of c-Jun and is required for oncogenic cooperation with Ha-Ras. We now show that the same changes in c-Jun phosphorylation are elicited by a variety of transforming oncoproteins with distinct biochemical activities. These oncoproteins, v-Sis, v-Src, Ha-Ras, and Raf-1, participate in a signal transduction pathway that leads to increased phosphorylation of serines 63 and 73 on c-Jun. While oncogenic Ha-Ras is a constitutive stimulator of c-Jun activity and phosphorylation, the normal c-Ha-Ras protein is a serum-dependent modulator of c-Jun's activity. c-Jun is therefore a downstream target for a phosphorylation cascade involved in cell proliferation and transformation.
Mol Cell Biol 1992 Aug
PMID:Oncoprotein-mediated signalling cascade stimulates c-Jun activity by phosphorylation of serines 63 and 73. 163 Apr 58

We investigated the interaction of phospholipase C-gamma (PLC-gamma) with wild-type and mutant forms of the platelet-derived growth factor (PDGF) beta-receptor both in vivo and in vitro. After PDGF treatment of CHO cell lines expressing wild-type or either of two mutant (delta Ki and Y825F) PDGF receptors, PLC-gamma became tyrosine phosphorylated and associated with the receptor proteins. The receptor association and tyrosine phosphorylation of PLC-gamma correlated with the ability of these receptors to mediate ligand-induced phosphatidylinositol turnover. However, both the delta Ki and Y825F mutant receptors were deficient in transmitting mitogenic signals, suggesting that the PDGF-induced tyrosine phosphorylation and receptor association of PLC-gamma are not sufficient to account for the growth-stimulatory activity of PDGF. Wild-type and delta Ki mutant PDGF receptor proteins expressed with recombinant baculovirus vectors also associated in vitro with mammalian PLC-gamma. However, baculovirus-expressed c-fms, v-fms, c-src, and Raf-1 proteins failed to associate with PLC-gamma under similar conditions. Phosphatase treatment of the baculovirus-expressed PDGF receptor greatly decreased its association with PLC-gamma. This requirement for receptor phosphorylation was also observed in vivo, where PLC-gamma could not associate with a mutant PDGF receptor (K602A) defective in autophosphorylation. PLC-gamma also coimmunoprecipitated with two other putative receptor substrates, the serine-threonine kinase Raf-1 and the 85-kilodalton phosphatidylinositol-3' kinase, presumably through its association with the ligand-activated receptor. Furthermore, baculovirus-expressed Raf-1 phosphorylated purified PLC-gamma in vitro at sites which showed increased serine phosphorylation in vivo in response to PDGF. These results suggest that PDGF directly influences PLC activity by inducing the association of PLC-gamma with a receptor signaling complex, resulting in increased tyrosine and serine phosphorylation of PLC-gamma.
Mol Cell Biol 1990 May
PMID:Platelet-derived growth factor (PDGF)-dependent association of phospholipase C-gamma with the PDGF receptor signaling complex. 169 40

A genomic DNA fragment containing the Raf-1 promoter region was isolated by using a cDNA extension clone. Nucleotide sequencing of genomic DNA clones, primer extension, and S1 nuclease assays have been used to identify the 5' ends of Raf-1 RNAs. Consistent with its ubiquitous expression, the Raf-1 promoter region had features of a housekeeping gene in that it was GC-rich (HTF-like), lacked TATA and CAAT boxes, and contained heterogeneous RNA start sites and four potential binding sites for the transcription factor SP1. In addition, an octamer motif (ATTTCAT), a potential binding site for the octamer family of transcription factors, was located at -734 base pairs. The Raf-1 promoter region drove reporter gene expression 30-fold over the promoterless reporter in Cos 7 cells.
Mol Cell Biol 1990 Jul
PMID:Molecular organization of the human Raf-1 promoter region. 169 10

To gain further insight into the role of Raf-1 in normal cell growth, c-raf-1 mRNA expression, Raf-1 protein production, and Raf-1-associated kinase activity in normal human T cells were analyzed. In contrast to the constitutive expression of Raf-1 in continuously proliferating cell lines, c-raf-1 mRNA and Raf-1 protein levels were barely detectable in freshly isolated G0 T lymphocytes. Previous work with fibroblasts has suggested that Raf-1 plays a signaling role in the G0-G1 phase transition. In T cells, triggering via the T-cell antigen receptor (TCR)-CD3 complex (TCR/CD3) resulted in an approximately fourfold increase in c-raf-1 mRNA. In addition, the promotion of G1 progression by interleukin 2 (IL-2) was associated with a 5- to 10-fold immediate/early induction of c-raf-1 mRNA, resulting in up to a 12-fold increase in Raf-1 protein expression. TCR/CD3 activation did not alter the phosphorylation state of Raf-1, whereas interleukin 2 receptor stimulation resulted in a rapid increase in the phosphorylation state of a subpopulation of Raf-1 molecules progressively increasing throughout G1. These findings were complemented by assays for Raf-1-associated kinase activity which revealed a gradual accumulation of serine and threonine autokinase activity in Raf-1 immunoprecipitates during G1, which remained elevated throughout DNA replication.
Mol Cell Biol 1991 May
PMID:Interleukin-2-triggered Raf-1 expression, phosphorylation, and associated kinase activity increase through G1 and S in CD3-stimulated primary human T cells. 170 96

Raf-1 serine- and threonine-specific protein kinase is transiently activated in cells expressing the epidermal growth factor (EGF) receptor upon treatment with EGF. The stimulated EGF receptor coimmunoprecipitates with Raf-1 kinase and mediates protein kinase C-independent phosphorylation of Raf-1 on serine residues. Hyperphosphorylated Raf-1 has lower mobility on sodium dodecyl sulfate gels and has sixfold-increased activity in immunocomplex kinase assay with histone H1 or Raf-1 sequence-derived peptide as a substrate. Raf-1 activation requires kinase-active EGF receptor; a point mutant lacking tyrosine kinase activity in inactive in Raf-1 coupling and association. It is noteworthy that tyrosine phosphorylation of c-Raf-1 induced by EGF was not detected in these cells. These observations suggest that Raf-1 kinase may act as an important downstream effector of EGF signal transduction.
Mol Cell Biol 1991 Feb
PMID:Epidermal growth factor (EGF) stimulates association and kinase activity of Raf-1 with the EGF receptor. 199 Feb 91

In cells transformed by v-raf, an oncogenic counterpart of the serine/threonine kinase Raf-1, regulatory elements of the c-fos promoter were active under conditions of cell growth or stimulation for which they were inactive in untransformed control cells. This suggests that v-raf transforms by deregulating transcription of early response genes.
Mol Cell Biol 1990 Nov
PMID:Altered transcriptional activity of c-fos promoter plasmids in v-raf-transformed NIH 3T3 cells. 212 38

A novel type of serotonergic binding site, termed the 5-HT1c site, was recently identified on choroid plexus epithelial cells. In the present study, we describe the solubilization of pig choroid plexus 5-HT1c sites by the zwitterionic detergent 3-(3-cholamidopropyl)dimethylammonio-1-propanesulfonate (CHAPS). High affinity labeling of both membrane-bound and solubilized 5-HT1c sites was obtained by use of the serotonergic radioligand N1-methyl-2-[125I]lysergic acid diethylamide (125I-MIL). In solubilized preparations, 125I-MIL exhibited a dissociation constant (Kd) of 2.0 nM and a 60-75% ratio of specific to total binding. Approximately 45% of the membrane binding sites were solubilized by CHAPS as measured by a postlabeling, polyethylene glycol precipitation method. The CHAPS-solubilized 5-HT1c site fulfilled the accepted criteria for receptor solubilization. The affinities of a series of serotonergic antagonists for the 5-HT1c site showed little or no change upon solubilization of the site. Serotonin, however, showed a 20-fold increase in affinity for the 5-HT1c site after solubilization, which may indicate the loss of a modulatory component during detergent treatment. Both gel filtration and equilibrium sedimentation experiments indicate that the CHAPS-solubilized site is a large molecular weight complex. These studies demonstrate that the pig choroid plexus 5-HT1c site can be solubilized with retention of its binding activity in a form suitable for further purification and characterization.
Mol Pharmacol 1986 Feb
PMID:Solubilization and characterization of the serotonin 5-HT1c site from pig choroid plexus. 395 27

We have investigated the ability of a constitutively active Gq-alpha mutant, Q209L-alpha q, to regulate target gene expression. Transient expression in GH3 pituitary cells of a rat proximal prolactin promoter-chloramphenicol acetyltransferase construct (-187)PRL-CAT, was stimulated by co-expression of Q209L alpha q, but not by wild-type alpha q. Q209L-alpha q stimulated expression of constructs driven by promoters for either rat prolactin or growth hormone, but not of a control construct driven by the thymidine kinase promoter. Thus, transcriptional effects of alpha q are specific both for the activated state of this G-alpha subunit and the promoter examined. Since both the prolactin and growth hormone promoters are activated by the pituitary cell-specific transcription factor Pit-1, we examined whether a Pit-1 binding site could direct a response to Q209L-alpha q. Two copies of prolactin promoter Pit-1 binding site 1P conferred upon a heterologous metallothionein promoter a response to Q209L-alpha q, implying an involvement of this site in the transcriptional action of Q209L-alpha q on the prolactin promoter. The phorbol ester activator of protein kinase C, 12-O-tetradecanoylphorbol-13-acetate, stimulated (-187)PRL-CAT activity, but opposed the action of Q209L-alpha q on activity of this PRL-CAT construct. Q209L-alpha q stimulation of (-187)PRL-CAT activity was inhibited by co-expression of a dominant negative Raf mutant, Raf-C4, but not by a point mutant of Raf-C4 with reduced inhibitory properties. These results imply that activated alpha q subunits can stimulate prolactin promoter activity via a pathway that involves a Pit-1 DNA binding site(s), is opposed by protein kinase C, and is mediated by a pathway in which Raf-1 kinase plays a role.
Mol Cell Endocrinol 1995 Aug 11
PMID:Constitutively active Gq-alpha stimulates prolactin promoter activity via a pathway involving Raf activity. 748 29


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