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Receptor‐dependent compartmentalization of PPIP5K1
Author(s) -
Zaremba Angelika,
Shears Stephen
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.lb123
Subject(s) - wortmannin , compartmentalization (fire protection) , microbiology and biotechnology , cytoplasm , chemistry , receptor , phosphorylation , signal transduction , kinase , biochemistry , enzyme , biophysics , biology , phosphatidylinositol
Inositol pyrophosphates (InsP7, InsP8) have been reported to modulate cell signaling pathways at the plasma membrane that control insulin secretion from pancreatic beta cells [1] and insulin action at target tissues [2]. We now demonstrate that the plasma membrane is also a site for receptor‐dependent compartmentalization of inositol pyrophosphate metabolism. We have studied PPIP5K1, a kinase that converts (a) InsP6 to 1/3‐InsP7 and (b) 5‐InsP7 to InsP8. Our kinetic data indicate that phosphorylation of 5‐InsP7 is the preferred reaction. We have studied the cellular distribution of FLAG‐tagged PPIP5K1 in NIH3T3 cells by confocal immunofluorescence microscopy. We recorded the concentration of enzyme at the plasma membrane relative to the cytoplasm (PM/C). This ratio was 1.7 ± 0.09 in control cells, rising to 2.9 ± 0.27 (P < 0.01) after 5 min stimulation with 50 ng/ml PDGF. Pre‐treatment with wortmannin largely prevented this effect of PDGF (PM/C = 2.1 ± 0.14), indicating a role for the PtdIns 3‐kinase pathway in directing PPIP5K1 translocation. Indeed, these results are consistent with our discovery of a novel PtdIns(3,4,5)P3‐binding domain in PPIP5K1 [3]. Following the translocation of PPIP5K1 to the plasma membrane, the enzyme's capacity to bind PtdIns(3,4,5)P3 and the expected localized synthesis of InsP8 could both influence cell‐signaling at the plasma membrane.