title: New mimetic peptides of the kinase-inhibitory region (KIR) of SOCS1 through focused peptide libraries.
abstract: SOCS (suppressor of cytokine signalling) proteins are negative-feedback regulators of the JAK (Janus kinase)/STAT (signal transducer and activator of transcription) pathway. Their expression levels are low under physiological conditions, but they are up-regulated in response to cytokine stimulation in many immune and inflammatory processes. Overexpression of SOCS1 in keratinocyte clones abrogates the IFNγ (interferon γ)-induced expression of many pro-inflammatory genes and the release of related chemokines by blocking the JAK/STAT pathway. SOCS1 inhibits JAK2 kinase activity by binding the catalytic site of JAK2, with its KIR (kinase-inhibitory region) acting as a pseudo-substrate of the enzyme. In the present study, we screened a focused combinatorial peptide library of KIR to identify new peptides able to mimic its function with an improved affinity towards the JAK2 catalytic site. Using an alanine-scanning method, KIR residues that are crucial for the interaction with JAK2 were unveiled. In this way, the KIR sequence was restricted to a shorter segment and ‘non-essential’ residues were replaced by different amino acids following a simplified combinatorial approach. We selected a new unnatural sequence able to bind to JAK2 with Kd values in the nanomolar range. This peptide was tested in human keratinocyte cultures and reduced the phosphorylation of STAT1 and the expression levels of IRF-1 (interferon regulatory factor-1).
authors.affiliation: Institute of Biostructures and Bioimaging–IBB-CNR, Via Mezzocannone 16, 80134, Naples, Italy.
authors.forename: Nunzianna
authors.initials: N
authors.lastname: Doti
authors.forename: Pasqualina L
authors.initials: PL
authors.lastname: Scognamiglio
authors.forename: Stefania
authors.initials: S
authors.lastname: Madonna
authors.forename: Claudia
authors.initials: C
authors.lastname: Scarponi
authors.forename: Menotti
authors.initials: M
authors.lastname: Ruvo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Perretta
authors.forename: Cristina
authors.initials: C
authors.lastname: Albanesi
authors.forename: Daniela
authors.initials: D
authors.lastname: Marasco
mesh_terms: D000595:Amino Acid Sequence; D001667:Binding, Competitive; D020134:Catalytic Domain; D002478:Cells, Cultured; D002942:Circular Dichroism; D004353:Drug Evaluation, Preclinical; D004355:Drug Stability; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000235:genetics / Q000378:metabolism; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D050794:STAT1 Transcription Factor / Q000378:metabolism; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000737:chemistry*
chemical_list: C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D019151:Peptide Library; D010455:Peptides; C108944:SOCS1 protein, human; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C507924:JAK2 protein, human; D053614:Janus Kinase 2