title: Characterization of a peptide inhibitor of Janus kinase 2 that mimics suppressor of cytokine signaling 1 function.
abstract: Positive and negative regulation of cytokines such as IFN-gamma are key to normal homeostatic function. Negative regulation of IFN-gamma in cells occurs via proteins called suppressors of cytokine signaling (SOCS)1 and -3. SOCS-1 inhibits IFN-gamma function by binding to the autophosphorylation site of the tyrosine kinase Janus kinase (JAK)2. We have developed a short 12-mer peptide, WLVFFVIFYFFR, that binds to the autophosphorylation site of JAK2, resulting in inhibition of its autophosphorylation as well as its phosphorylation of IFN-gamma receptor subunit IFNGR-1. The JAK2 tyrosine kinase inhibitor peptide (Tkip) did not bind to or inhibit tyrosine autophosphorylation of vascular endothelial growth factor receptor or phosphorylation of a substrate peptide by the protooncogene tyrosine kinase c-src. Tkip also inhibited epidermal growth factor receptor autophosphorylation, consistent with the fact that epidermal growth factor receptor is regulated by SOCS-1 and SOCS-3, similar to JAK2. Although Tkip binds to unphosphorylated JAK2 autophosphorylation site peptide, it binds significantly better to tyrosine-1007 phosphorylated JAK2 autophosphorylation site peptide. SOCS-1 only recognizes the JAK2 site in its phosphorylated state. Thus, Tkip recognizes the JAK2 autophosphorylation site similar to SOCS-1, but not precisely the same way. Consistent with inhibition of JAK2, Tkip inhibited the ability of IFN-gamma to induce an antiviral state as well as up-regulate MHC class I molecules on cells at a concentration of approximately 10 microM. This is similar to the K(d) of SOCS-3 for the erythropoietin receptor. These data represent a proof-of-concept demonstration of a peptide mimetic of SOCS-1 that regulates JAK2 tyrosine kinase function.
authors.affiliation: Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Lawrence O
authors.initials: LO
authors.lastname: Flowers
authors.forename: Howard M
authors.initials: HM
authors.lastname: Johnson
authors.forename: Mustafa G
authors.initials: MG
authors.lastname: Mujtaba
authors.forename: Morgan R
authors.initials: MR
authors.lastname: Ellis
authors.forename: S Mohammed I
authors.initials: SM
authors.lastname: Haider
authors.forename: Prem S
authors.initials: PS
authors.lastname: Subramaniam
mesh_terms: D000818:Animals; D001011:Aorta; D002352:Carrier Proteins / Q000737:chemistry / Q000502:physiology*; D002417:Cattle; D002460:Cell Line; D018844:Cyclin-Dependent Kinases; D004730:Endothelium, Vascular / Q000166:cytology; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D005347:Fibroblasts; D005786:Gene Expression Regulation / Q000187:drug effects; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis; D006801:Humans; D007371:Interferon-gamma / Q000037:antagonists & inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D051379:Mice; D018716:Molecular Mimicry; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D011518:Proto-Oncogene Proteins; D040262:Receptors, Vascular Endothelial Growth Factor / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000502:physiology*; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors / Q000737:chemistry / Q000502:physiology
chemical_list: D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D015395:Histocompatibility Antigens Class I; D047908:Intracellular Signaling Peptides and Proteins; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; C108944:SOCS1 protein, human; C106644:SOCS3 protein, human; C491590:Socs1 protein, mouse; C491411:Socs3 protein, mouse; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; D007371:Interferon-gamma; D011505:Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D018844:Cyclin-Dependent Kinases