Progesterone-Induced Blocking Factor Activates STAT6 via Binding to a Novel IL-4 Receptor

Abstract

Progesterone-induced blocking factor (PIBF) induces Th2-dominant cytokine production. Western blotting and EMSA revealed phosphorylation as well as nuclear translocation of STAT6 and inhibition of STAT4 phosphorylation in PIBF-treated cells. The silencing of STAT6 by small interfering RNA reduced the cytokine effects. Because the activation of the STAT6 pathway depends on the ligation of IL-4R, we tested the involvement of IL-4R in PIBF-induced STAT6 activation. Although PIBF does not bind to IL-4R, the blocking of the latter with an Ab abolished PIBF-induced STAT6 activation, whereas the blocking of the IL-13R had no effect. PIBF activated suppressor of cytokine signaling-3 and inhibited IL-12-induced suppressor of cytokine signaling-1 activation. The blocking of IL-4R counteracted all the described effects, suggesting that the PIBF receptor interacts with IL-4R α-chain, allowing PIBF to activate the STAT6 pathway. PIBF did not phosphorylate Jak3, suggesting that the γ-chain is not needed for PIBF signaling. Confocal microscopic analysis revealed a colocalization and at 37°C a cocapping of the FITC PIBF-activated PIBF receptor and PE anti-IL-4R-labeled IL-4R. After the digestion of the cells with phosphatidylinositol-specific phospholipase C, the STAT6-activating effect of PIBF was lost, whereas that of IL-4 remained unaltered. These data suggest the existence of a novel type of IL-4R composed of the IL-4R α-chain and the GPI-anchored PIBF receptor.

Progesterone-induced blocking factor differentially regulates trophoblast and tumor invasion by altering matrix metalloproteinase activity

“…Earlier we showed that the PIBF receptor is a GPI-anchored protein, which -upon ligation -forms a temporary association with the alpha chain of IL-4 receptor [7] and activates STAT6 in peripheral lymphocytes. Therefore, we investigated the involvement of IL-4Rα in PIBF regulated invasion.…”

“…PIBF inhibits Natural Killer (NK) cell activity and enhances Th2-type cytokine production via the JAK1/STAT6 and PKC/Ca++ pathways [6,7], thus supports the maintenance of pregnancy.…”

Investigation of the interleukin (IL)‐4/IL‐4 receptor system in promyelocytic leukaemia PLB‐985 cells during differentiation toward neutrophil‐like phenotype: mechanism involved in IL‐4‐induced SOCS3 protein expression

“…To date, there is no available antibody that could be used in flow cytometry studies to detect its cell surface expression. In the report by Kozma et al (2006), the presence of PIBR was suggested by the observation that blocking of IL-4Ra interfered with PIBF-mediated effects.…”

“…Thus, our results are the first to provide evidence that expression of IL-4Ra alone can lead to activation, including that of JAK1, in cells other than B lymphocytes, namely in promyelocytes. More recently, the existence of a novel type of IL-4R has been proposed in peripheral blood lymphocytes, which is composed of IL-4Ra and progesterone-induced blocking factor receptor (PIBFR; Kozma et al, 2006). Whether this receptor is present on the surface of PLB-985 and/or PLB-985D cells is unknown.…”

IL-4 Independent Nuclear Translocalization of STAT6 in HeLa Cells by Entry of Toxoplasma gondii

“…STAT6 activation was shut down directly by interference with transcribed STAT6 mRNA by 5′ -AAG CAG GAA GAA CUC AAG UUU TT-3 ′ and 5′ -AAA CUU GAG UUC UUC CUG CUU TT-3′ [13]. Cells cultured on coverslips in a 24-well plate were transfected with a premix of 6 pmole siRNA and Lipofectamin RNAi MAX (Invitrogen) in Opti-MEM for 6 hr.…”