The EIIIA segment of fibronectin is a ligand for integrins alpha 9beta 1 and alpha 4beta 1 providing a novel mechanism for regulating cell adhesion by alternative splicing.
Alternative splicing of the fibronectin gene transcript gives rise to forms that include the EIIIA (or ED-A) segment. EIIIA-containing fibronectins are prominently expressed during embryogenesis and wound healing and appear to mediate changes in cell adhesion and gene expression. Nonetheless, integrins that bind the EIIIA segment have not been identified. We previously mapped the epitope for two function-blocking monoclonal antibodies to the C-C' loop region of the EIIIA segment (Liao, Y.-F., Wieder, K. G., Classen, J. M., and Van De Water, L. (1999) J. Biol. Chem. 274, 17876-17884). The sequence of this epitope ((39)PEDGIHELFP(48)) resembles the sequence within tenascin-C to which the integrin alpha(9)beta(1) binds. We now report that either integrin alpha(9)beta(1) or alpha(4)beta(1) can mediate cell adhesion to the EIIIA segment. Moreover, this interaction is blocked both by epitope-mapped EIIIA antibodies as well as by the respective anti-integrins. Deletion mutants of the EIIIA segment that include the C-C' loop and flanking sequence bind cells expressing either alpha(9)beta(1) or alpha(4)beta(1). Adhesion of alpha(4)beta(1)-containing MOLT-3 cells to the EIIIA segment stimulates phosphorylation of p44/42 MAP kinase. Our observation that two integrins bind the EIIIA segment establishes a novel mechanism by which cell adhesion to fibronectin is regulated by alternative splicing.
Liao
Yung-Feng
YF
Center for Engineering in Medicine and Surgical Service, Massachusetts General Hospital and Harvard Medical School, the Shriners Burns Hospital, Boston, Massachusetts 02114, USA.
Gotwals
Philip J
PJ
Koteliansky
Victor E
VE
Sheppard
Dean
D
Van De Water
Livingston
L
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D002448:Cell Adhesion / Q000502:physiology*; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D039041:Integrin alpha4beta1; D016023:Integrins / Q000378:metabolism*; D008024:Ligands; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D016201:Receptors, Lymphocyte Homing / Q000378:metabolism*; D017384:Sequence Deletion; D014443:Tyrosine / Q000378:metabolism
D005353:Fibronectins; D039041:Integrin alpha4beta1; D016023:Integrins; D008024:Ligands; D016201:Receptors, Lymphocyte Homing; C113256:integrin alpha 9 beta 1; D014443:Tyrosine; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases