The integrin alpha 9 beta 1 mediates cell attachment to a non-RGD site in the third fibronectin type III repeat of tenascin.
We have previously reported the sequence of the integrin alpha 9 subunit, a partner of the beta 1 subunit that is expressed in basal keratinocytes, hepatocytes, airway epithelial cells, and smooth and skeletal muscle. In the present study, we have stably expressed alpha 9 beta 1 on the surface of the human embryonic kidney cell line 293 and the human colon carcinoma cell line SW480 and used these transfected cells lines to identify ligand(s) for this integrin. Transfected cells did not appear to utilize alpha 9 beta 1 for attachment to the extracellular matrix proteins fibronectin, laminin, vitronectin, fibrinogen, thrombospondin, or type I or IV collagen. However, in contrast to mock transfectants, both 293 cells and SW480 cells expressing alpha 9 beta 1 adhered to intact chicken tenascin. By utilizing a variety of recombinant fragments of tenascin, we were able to localize the binding site for alpha 9 beta 1 to the third type III repeat. This repeat contains the arginine-glycine-aspartic acid (RGD) tripeptide that has been shown to serve as a binding site in tenascin for alpha v-integrins. However, the RGD site does not appear to be the binding site for alpha 9 beta 1, as the attachment of alpha 9 transfectants to this fragment was not inhibited by RGD peptide, nor by changing the RGD site to RAD or RAA.
Yokosaki
Y
Y
Department of Medicine, University of California, San Francisco 94143.
Palmer
E L
EL
Prieto
A L
AL
Crossin
K L
KL
Bourdon
M A
MA
Pytela
R
R
Sheppard
D
D
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002448:Cell Adhesion / Q000502:physiology*; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002645:Chickens; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D005353:Fibronectins / Q000235:genetics; D006801:Humans; D016023:Integrins / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000235:genetics; D010446:Peptide Fragments / Q000378:metabolism; D038981:Receptors, Collagen; D011994:Recombinant Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D013329:Structure-Activity Relationship; D019063:Tenascin; D014162:Transfection
D015816:Cell Adhesion Molecules, Neuronal; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D016023:Integrins; D008024:Ligands; D009842:Oligopeptides; D010446:Peptide Fragments; D038981:Receptors, Collagen; D011994:Recombinant Proteins; D019063:Tenascin; C047981:arginyl-glycyl-aspartic acid