title: Direct interaction of natural and synthetic catechins with signal transducer activator of transcription 1 affects both its phosphorylation and activity.
abstract: Our previous studies showed that (-)-epigallocatechin-3-gallate (EGCG) inhibits signal transducer activator of transcription 1 (STAT1) activation. Since EGCG may be a promising lead compound for new anti-STAT1 drug design, 15 synthetic catechins, characterized by the (-)-gallocatechin-3-gallate stereochemistry, were studied in the human mammary MDA-MB-231 cell line to identify the minimal structural features that preserve the anti-STAT1 activity. We demonstrate that the presence of three hydroxyl groups of B ring and one hydroxyl group in D ring is essential to preserve their inhibitory action. Moreover, a possible molecular target of these compounds in the STAT1 pathway was investigated. Our results demonstrate a direct interaction between STAT1 protein and catechins displaying anti-STAT1 activity. In particular, surface plasmon resonance (SPR) analysis and molecular modeling indicate the presence of two putative binding sites (a and b) with different affinity. Based on docking data, site-directed mutagenesis was performed, and interaction of the most active catechins with STAT1 was studied with SPR to test whether Gln518 on site a and His568 on site b could be important for the catechin-STAT1 interaction. Data indicate that site b has higher affinity for catechins than site a as the highest affinity constant disappears in the H568A-STAT1 mutant. Furthermore, Janus kinase 2 (JAK2) kinase assay data suggest that the contemporary presence in vitro of STAT1 and catechins inhibits JAK2-elicited STAT1 phosphorylation. The very tight catechin-STAT1 interaction prevents STAT1 phosphorylation and represents a novel, specific and efficient molecular mechanism for the inhibition of STAT1 activation.
authors.affiliation: Department of Life and Reproduction Sciences, Biochemistry Section, University of Verona, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Menegazzi
authors.forename: Sofia
authors.initials: S
authors.lastname: Mariotto
authors.forename: Martina
authors.initials: M
authors.lastname: Dal Bosco
authors.forename: Elena
authors.initials: E
authors.lastname: Darra
authors.forename: Nadia
authors.initials: N
authors.lastname: Vaiana
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shoji
authors.forename: Abdel-Azeim
authors.initials: AA
authors.lastname: Safwat
authors.forename: Jean Didier
authors.initials: JD
authors.lastname: Marechal
authors.forename: David
authors.initials: D
authors.lastname: Perahia
authors.forename: Hisanori
authors.initials: H
authors.lastname: Suzuki
authors.forename: Sergio
authors.initials: S
authors.lastname: Romeo
mesh_terms: D019943:Amino Acid Substitution; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D045744:Cell Line, Tumor; D015195:Drug Design; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008958:Models, Molecular; D008968:Molecular Conformation; D050505:Mutant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D050505:Mutant Proteins; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; C417940:gallocatechin gallate; D002392:Catechin
keywords: STAT1; gallocatechin-3-gallate; molecular docking; site-directed mutagenesis; surface plasmon resonance; synthetic catechins