title: Molecular basis for a direct interaction between the Syk protein-tyrosine kinase and phosphoinositide 3-kinase.
abstract: After engagement of the B cell receptor for antigen, the Syk protein-tyrosine kinase becomes phosphorylated on multiple tyrosines, some of which serve as docking sites for downstream effectors with SH2 or other phosphotyrosine binding domains. The most frequently identified binding partner for catalytically active Syk identified in a yeast two-hybrid screen was the p85 regulatory subunit of phosphoinositide 3-kinase. The C-terminal SH2 domain of p85 was sufficient for mediating an interaction with tyrosine-phosphorylated Syk. Interestingly, this domain interacted with Syk at phosphotyrosine 317, a site phosphorylated in trans by the Src family kinase, Lyn, and identified previously as a binding site for c-Cbl. This site interacted preferentially with the p85 C-terminal SH2 domain compared with the c-Cbl tyrosine kinase binding domain. Molecular modeling studies showed a good fit between the p85 SH2 domain and a peptide containing phosphotyrosine 317. Tyr-317 was found to be essential for Syk to support phagocytosis mediated by FcgammaRIIA receptors expressed in a heterologous system. These studies establish a new type of p85 binding site that can exist on proteins that serve as substrates for Src family kinases and provide a molecular explanation for observations on direct interactions between Syk and phosphoinositide 3-kinase.
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology and the Purdue Cancer Center, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Kyung D
authors.initials: KD
authors.lastname: Moon
authors.forename: Carol B
authors.initials: CB
authors.lastname: Post
authors.forename: Donald L
authors.initials: DL
authors.lastname: Durden
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhou
authors.forename: Pradip
authors.initials: P
authors.lastname: De
authors.forename: Marietta L
authors.initials: ML
authors.lastname: Harrison
authors.forename: Robert L
authors.initials: RL
authors.lastname: Geahlen
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D019556:COS Cells; D002384:Catalysis; D004792:Enzyme Precursors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004912:Erythrocytes / Q000276:immunology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008958:Models, Molecular; D008970:Molecular Weight; D010587:Phagocytosis; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism; D012756:Sheep; D000072377:Syk Kinase; D020798:Two-Hybrid System Techniques; D051746:ZAP-70 Protein-Tyrosine Kinase; D018909:src Homology Domains
chemical_list: D015703:Antigens, CD; D004792:Enzyme Precursors; C080568:Fc gamma receptor IIA; D047908:Intracellular Signaling Peptides and Proteins; D021122:Protein Subunits; D017452:Receptors, IgG; D019000:Phosphotyrosine; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; C497262:Zap70 protein, mouse