title: Fyn kinase regulates type II PtdIns 4-kinases in RBL 2H3 cells.
abstract: Type II phosphatidylinositol 4-kinases are implicated in FcεRI-mediated signaling cascades leading to release of inflammatory molecules. Cross-linking of FcεRI on RBL 2H3 cells results in protein tyrosine phosphorylation and activation of type II PtdIns 4-kinase activity. Protein tyrosine kinase(s) that phosphorylate type II PtdIns 4-kinase(s) in RBL 2H3 cells remains elusive and is being addressed in this manuscript. Anti-Fyn kinase antibodies co-immunoprecipitated type II PtdIns 4-kinase activity from FcεRI cross-linked RBL 2H3 cells. In reciprocal assays, His-tagged types II PtdIns 4-kinases were shown to pull down Fyn kinase. Further, anti-Fyn immunoprecipitates were shown to phosphorylate type II PtdIns 4-kinase α and β in in vitro assays. Pull down studies with GST-Fyn-SH2 and GST-Fyn-SH3 domains showed that type II PtdIns 4-kinases associate with Fyn-SH2 domain. Knockdown of Fyn kinase in RBL 2H3 cells abrogated activation of type II PtdIns 4-kinase activity in response to FcεRI cross-linking and type II PtdIns 4-kinase activity in anti-phosphotyrosine immunoprecipitates. Knockdown of Fyn kinase was also strongly correlated with a reduction in β-hexosaminidase release in response to FcεRI cross-linking. These results suggest that type II PtdIns 4-kinases act downstream of Fyn kinase in FcεRI signaling cascades and are regulated by Fyn kinase.
authors.affiliation: Department of Biosciences and Bioengineering, Wadhwani Research Centre for Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India, naveenb@u.washington.edu.
authors.forename: Naveen
authors.initials: N
authors.lastname: Bojjireddy
authors.forename: Ranjeet Kumar
authors.initials: RK
authors.lastname: Sinha
authors.forename: Gosukonda
authors.initials: G
authors.lastname: Subrahmanyam
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D006801:Humans; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D011499:Protein Processing, Post-Translational; D051076:Proto-Oncogene Proteins c-fyn / Q000737:chemistry / Q000502:physiology*; D051381:Rats; D017455:Receptors, IgE / Q000378:metabolism; D015398:Signal Transduction; D001619:beta-N-Acetylhexosaminidases / Q000378:metabolism
chemical_list: D017455:Receptors, IgE; D019870:1-Phosphatidylinositol 4-Kinase; C494961:Fyn protein, rat; D051076:Proto-Oncogene Proteins c-fyn; D001619:beta-N-Acetylhexosaminidases