Progesterone-induced blocking factor activates STAT6 via binding to a novel IL-4 receptor.
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 alpha-chain, allowing PIBF to activate the STAT6 pathway. PIBF did not phosphorylate Jak3, suggesting that the gamma-chain is not needed for PIBF signaling. Confocal microscopic analysis revealed a colocalization and at 37 degrees 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 alpha-chain and the GPI-anchored PIBF receptor.
Kozma
Noemi
N
Department of Medical Microbiology and Immunology, Pecs University, Pecs, Hungary.
Halasz
Melinda
M
Polgar
Beata
B
Poehlmann
Tobias G
TG
Markert
Udo R
UR
Palkovics
Tamas
T
Keszei
Marton
M
Par
Gabriella
G
Kiss
Katalin
K
Szeberenyi
Jozsef
J
Grama
Laszlo
L
Szekeres-Bartho
Julia
J
D001483:Base Sequence; D016207:Cytokines / Q000096:biosynthesis; D006801:Humans; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D011257:Pregnancy Proteins / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D019948:Receptors, Interleukin-4 / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D050800:STAT6 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013491:Suppressor Factors, Immunologic
D016207:Cytokines; D008562:Membrane Glycoproteins; C110058:PIBF1 protein, human; D011257:Pregnancy Proteins; D034741:RNA, Small Interfering; D019948:Receptors, Interleukin-4; D011994:Recombinant Proteins; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D013491:Suppressor Factors, Immunologic