The NH2-terminal region of focal adhesion kinase reconstitutes high affinity IgE receptor-induced secretion in mast cells.
Focal adhesion kinase (FAK) is tyrosine-phosphorylated by adherence of cells and also by FcepsilonRI aggregation in RBL-2H3 mast cells. Using phosphorylation site-specific antibodies, we observed that FcepsilonRI activation in these cells led to an increase in FAK phosphorylation at the same tyrosine residues that are phosphorylated by integrin-induced activation. Previous studies in the 3B6 line, a FAK-deficient variant of the RBL-2H3 cells, suggest that FAK plays a role in FcepsilonRI-induced secretion. Stable cell lines expressing either full-length or truncated forms of FAK were isolated after transfection of the FAK-deficient 3B6 variant cells. The NH(2) domain of FAK, which lacks the enzymatic and the COOH-terminal regions, was sufficient to reconstitute secretion. The different truncated forms of FAK were still tyrosine-phosphorylated after FcepsilonRI aggregation. Therefore, the kinase domain and the COOH-terminal region are not essential for FcepsilonRI-induced tyrosine phosphorylation of FAK or for secretion. Taken together, our data demonstrate that the reconstitution of secretion is dissociated from FAK activation and that the NH(2)-terminal region of FAK is the only critical element that may play a role in FcepsilonRI-induced secretion by acting as an adaptor or linker molecule.
Vial
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Receptors and Signal Transduction Section, OIIB, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA. dvial@dir.nidr.nih.gov
Okazaki
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Siraganian
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D000818:Animals; D002449:Cell Aggregation; D002460:Cell Line; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D014644:Genetic Variation; D008262:Macrophage Activation; D008407:Mast Cells / Q000276:immunology / Q000502:physiology*; D051379:Mice; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017455:Receptors, IgE / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion
D017455:Receptors, IgE; D011994:Recombinant Proteins; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse