title: Treatment of cells with n-alpha-tosyl-L-phenylalanine-chloromethyl ketone induces the proteolytic loss of STAT6 transcription factor.
abstract: The implication of the STAT6 transcription factor in several human diseases makes the regulation of its activity a topic of great biological interest. The activation of this transcription factor is tightly regulated by kinases, phosphatases, and proteases. The initial aim of this study was to investigate the utility of protease inhibitors in controlling STAT6 activation. Among all inhibitors analyzed, n-alpha-tosyl-L-phenylalanine-chloromethyl ketone (TPCK) was found to inhibit the IL-4-induced STAT6 activation. Unexpectedly, this inhibition was accompanied by a loss of STAT6 protein. Thus, TPCK promoted the loss of STAT6 by a mechanism sensitive to the serine-protease inhibitor 4-(2-aminoetyl)-benzenesulfonyl fluoride. However, the effects of TPCK seemed not to be mediated by its protease inhibitory activity since multiple protease inhibitors tested had no effect on STAT6 expression. The results found suggest that the effect of TPCK was mediated by its alkylating activity. Thus, cysteine reactive and thiol antioxidant compounds prevented the loss of STAT6 induced by TPCK. The reactivity of thiol groups on STAT6 was moreover demonstrated with biotinylated sulfhydryl-reactive compounds. Analysis of other signaling molecules indicated that STAT5, but not other STATs, Shc, or c-Rel, was also affected by TPCK, suggesting a common downregulatory mechanism for STAT6 and STAT5. These results reveal a novel mechanism of action of TPCK in inducing a selective loss of STAT proteins. These findings may have implications for diseases in which STAT proteins are involved.
authors.affiliation: Unidad de Investigacion, Hospital San Pedro de Alcantara, Avenida Pablo Naranjo s/n, 10003 Caceres, Spain.
authors.forename: Moises
authors.initials: M
authors.lastname: Perez-G
authors.forename: Jose R
authors.initials: JR
authors.lastname: Cortes
authors.forename: Maria D
authors.initials: MD
authors.lastname: Rivas
authors.forename: F
authors.initials: F
authors.lastname: Masa
authors.forename: Jose
authors.initials: J
authors.lastname: Zamorano
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002460:Cell Line; D051379:Mice; D011480:Protease Inhibitors / Q000494:pharmacology*; D020569:Proto-Oncogene Proteins c-rel / Q000502:physiology; D050799:STAT5 Transcription Factor / Q000378:metabolism; D050800:STAT6 Transcription Factor / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins / Q000502:physiology; D015398:Signal Transduction; D013450:Sulfones / Q000494:pharmacology; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D011480:Protease Inhibitors; D020569:Proto-Oncogene Proteins c-rel; D050799:STAT5 Transcription Factor; D050800:STAT6 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; C494100:Stat6 protein, mouse; D013450:Sulfones; C002010:4-(2-aminoethyl)benzenesulfonylfluoride; D014108:Tosylphenylalanyl Chloromethyl Ketone