title: Direct transmembrane clustering and cytoplasmic dimerization of focal adhesion kinase initiates its tyrosine phosphorylation.
abstract: We investigated mechanisms for inducing focal adhesion kinase (FAK) tyrosine phosphorylation and their ability to trigger MAP kinase signaling using transmembrane chimeras that localize FAK and its mutants to the plasma membrane. We tested whether tyrosine phosphorylation was triggered by FAK transmembrane aggregation using antibodies against the chimeric extracellular domain. Experimental clustering of chimeras containing integrin beta cytoplasmic domains or FAK induced FAK tyrosine phosphorylation and trans-phosphorylation of endogenous FAK, as well as strong ERK activation. Next, we examined whether lower-order molecular proximity, namely dimerization, could regulate FAK tyrosine phosphorylation. We found that even relatively low-affinity FAK dimerization (K(d)=3.9 x 10(-5) M), in either of two different orientations, could induce FAK tyrosine phosphorylation. However, this cytoplasmic FAK dimerization could not induce MAP kinase activation or trans-phosphorylation of endogenous FAK. We conclude that dimerization of FAK is sufficient to induce its tyrosine phosphorylation, but that higher-order molecular proximity (clustering) at the cell membrane is apparently needed for additional biochemical events. This study identifies a proximity mechanism for regulating the initiation of FAK-mediated biochemical signaling.
authors.affiliation: Craniofacial Developmental Biology and Regeneration Branch, National Institutes of Health, Bethesda, MD 20892-4370, USA. sbkatz@netvision.net.il
authors.forename: Ben-Zion
authors.initials: BZ
authors.lastname: Katz
authors.forename: Shingo
authors.initials: S
authors.lastname: Miyamoto
authors.forename: Hidemi
authors.initials: H
authors.lastname: Teramoto
authors.forename: Muriel
authors.initials: M
authors.lastname: Zohar
authors.forename: Dmitry
authors.initials: D
authors.lastname: Krylov
authors.forename: Charles
authors.initials: C
authors.lastname: Vinson
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Yamada
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002448:Cell Adhesion; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology / Q000378:metabolism; D019281:Dimerization; D004789:Enzyme Activation; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D016350:Leucine Zippers; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism*
chemical_list: D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D020928:Mitogen-Activated Protein Kinases