%0 Journal Article %1 Hafner1994 %A Hafner, S. %A Adler, H. S. %A Mischak, H. %A Janosch, P. %A Heidecker, G. %A Wolfman, A. %A Pippig, S. %A Lohse, M. %A Ueffing, M. %A Kolch, W. %D 1994 %J Mol Cell Biol %K *MAP 1 3T3 AMP-Dependent Activation Animals Binding C-alpha C/metabolism Cell Cyclic Enzyme Isoenzymes/metabolism Kinase Kinases/*metabolism Kinases/metabolism Lymphocyte Mice Neoplastic Oncogene Oncogenic/metabolism Phosphorylation Protein Protein-Serine-Threonine Protein-Tyrosine Proteins Proteins, Proto-Oncogene Retroviridae Specific Specificity Substrate Transformation, Tyrosine c-raf p21(ras)/metabolism p56(lck) v-raf Proteins/metabolism %N 10 %P 6696-703 %T Mechanism of inhibition of Raf-1 by protein kinase A %U http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=7935389 %V 14 %X The cytoplasmic Raf-1 kinase is essential for mitogenic signalling by growth factors, which couple to tyrosine kinases, and by tumor-promoting phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate, which activate protein kinase C (PKC). Signalling by the Raf-1 kinase can be blocked by activation of the cyclic AMP (cAMP)-dependent protein kinase A (PKA). The molecular mechanism of this inhibition is not precisely known but has been suggested to involve attenuation of Raf-1 binding to Ras. Using purified proteins, we show that in addition to weakening the interaction of Raf-1 with Ras, PKA can inhibit Raf-1 function directly via phosphorylation of the Raf-1 kinase domain. Phosphorylation by PKA interferes with the activation of Raf-1 by either PKC alpha or the tyrosine kinase Lck and even can downregulate the kinase activity of Raf-1 previously activated by PKC alpha or amino-terminal truncation. This type of inhibition can be dissociated from the ability of Raf-1 to associate with Ras, since (i) the isolated Raf-1 kinase domain, which lacks the Ras binding domain, is still susceptible to inhibition by PKA, (ii) phosphorylation of Raf-1 by PKC alpha alleviates the PKA-induced reduction of Ras binding but does not prevent the downregulation of Raf-1 kinase activity by PKA and (iii) cAMP agonists antagonize transformation by v-Raf, which is Ras independent.

@article{Hafner1994, abstract = {The cytoplasmic Raf-1 kinase is essential for mitogenic signalling by growth factors, which couple to tyrosine kinases, and by tumor-promoting phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate, which activate protein kinase C (PKC). Signalling by the Raf-1 kinase can be blocked by activation of the cyclic AMP (cAMP)-dependent protein kinase A (PKA). The molecular mechanism of this inhibition is not precisely known but has been suggested to involve attenuation of Raf-1 binding to Ras. Using purified proteins, we show that in addition to weakening the interaction of Raf-1 with Ras, PKA can inhibit Raf-1 function directly via phosphorylation of the Raf-1 kinase domain. Phosphorylation by PKA interferes with the activation of Raf-1 by either PKC alpha or the tyrosine kinase Lck and even can downregulate the kinase activity of Raf-1 previously activated by PKC alpha or amino-terminal truncation. This type of inhibition can be dissociated from the ability of Raf-1 to associate with Ras, since (i) the isolated Raf-1 kinase domain, which lacks the Ras binding domain, is still susceptible to inhibition by PKA, (ii) phosphorylation of Raf-1 by PKC alpha alleviates the PKA-induced reduction of Ras binding but does not prevent the downregulation of Raf-1 kinase activity by PKA and (iii) cAMP agonists antagonize transformation by v-Raf, which is Ras independent.}, added-at = {2010-12-14T18:12:02.000+0100}, author = {Hafner, S. and Adler, H. S. and Mischak, H. and Janosch, P. and Heidecker, G. and Wolfman, A. and Pippig, S. and Lohse, M. and Ueffing, M. and Kolch, W.}, biburl = {https://www.bibsonomy.org/bibtex/23b58951152f00b33f213c30ad5709716/pharmawuerz}, endnotereftype = {Journal Article}, interhash = {f940b69187a015fdff26465ff9fb66ac}, intrahash = {3b58951152f00b33f213c30ad5709716}, issn = {0270-7306 (Print) 0270-7306 (Linking)}, journal = {Mol Cell Biol}, keywords = {*MAP 1 3T3 AMP-Dependent Activation Animals Binding C-alpha C/metabolism Cell Cyclic Enzyme Isoenzymes/metabolism Kinase Kinases/*metabolism Kinases/metabolism Lymphocyte Mice Neoplastic Oncogene Oncogenic/metabolism Phosphorylation Protein Protein-Serine-Threonine Protein-Tyrosine Proteins Proteins, Proto-Oncogene Retroviridae Specific Specificity Substrate Transformation, Tyrosine c-raf p21(ras)/metabolism p56(lck) v-raf Proteins/metabolism}, month = Oct, note = {Hafner, S Adler, H S Mischak, H Janosch, P Heidecker, G Wolfman, A Pippig, S Lohse, M Ueffing, M Kolch, W United states Molecular and cellular biology Mol Cell Biol. 1994 Oct;14(10):6696-703.}, number = 10, pages = {6696-703}, shorttitle = {Mechanism of inhibition of Raf-1 by protein kinase A}, timestamp = {2010-12-14T18:21:42.000+0100}, title = {Mechanism of inhibition of Raf-1 by protein kinase A}, url = {http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=7935389}, volume = 14, year = 1994 }