Regulation of nuclear factor KappaBsignalling by FK-506 binding protein 52.

GALIGNIANA M.D.; DE LEO S.A.; MAZAIRA G.I.; ERLEJMAN A.G.; CAMISAY M.F.

CABA

Jornada; Jornadas Interdisciplinarias de Química Biológica; 2017

Departamento de Química Biológica FCEN UBA

Nuclear Factor KappaB (NF-kB) is key regulator of the transcription of genes involved in cell death, inflammation and invasion. Recently, we have demonstrated that FKBPs (FK506-binding proteins), especially FKBP51 and FKBP52, are able to modulate NF-kB transcriptional activity. The aim of this work is to determine the participation of FKBP52 in different steps of NF-kB signaling and the expression of NF-kB target genes. Thus, we over expressed FKBP52,FKBP52 F130Y (a mutant lacking peptidylprolyl-isomerase activity (PPIase)), or empty vector (control group).Different hallmarks in NF-kB (p65/p50) activation after PMA or TNF-α stimulation were evaluated: total and phosphorylated p65 protein levels and NF-kB inhibitor´s phosphorylation (p-ikB) by Western blot, p65 nuclear traslocation by immunofluorescence, and the expression of NF-kB target genes by real time PCR. After PMA stimulation neither FKBP52 nor FKBP52 mutant transfection showed significant differences in ikB phosphorylation kinetics compared to control, suggesting an ikB independent mechanism. Also, p65 phosphorylation at Ser536 was not altered by overexpression of FKBP52 or FKBP52 F130Y, compared to control. However, basal p-p65 and total p65 were increased after overexpression of FKBP52 vs. control (p<0,001). Furthermore, after TNF-α treatment FKBP52 favored p65 nuclear retention (vs control and FKBP52 F130Y, p<0,05), in accordance with previous results obtained after PMA simulation. The expression of target genes such as MMP-9 and Bax(evaluated by real time PCR) was regulated by FKBP52 in a peptidylprolylisomerase dependent manner, since overexpression of FKBP52 F130Y resulted in decreased expression of these genes compared to FKBP52 wild type. In summary, we propose FKBP52 as a new key regulator of NF-kB target genes expression, evidencing FKBP52´sPPIase enzymatic activity is essential for this regulation.