Utilization of a soluble integrin-alkaline phosphatase chimera to characterize integrin alpha 8 beta 1 receptor interactions with tenascin: murine alpha 8 beta 1 binds to the RGD site in tenascin-C fragments, but not to native tenascin-C.
Biochemistry
; 37(16): 5464-74, 1998 Apr 21.
Article
in En
| MEDLINE
| ID: mdl-9548928
ABSTRACT
The integrin alpha 8 beta 1 has been reported to bind to fibronectin, vitronectin, and tenascin-C in cell adhesion or neurite outgrowth assays. Here, we describe cDNA cloning of the murine alpha 8 subunit, purification of a recombinant soluble heterodimer consisting of the extracellular domains of the murine alpha 8 and beta1 subunits, and development of a sensitive binding assay using a modified form of this heterodimer fused to alkaline phosphatase (AP). In binding assays, the purified alpha 8 beta 1-AP chimera exhibited the same divalent ion requirements for activation and binding specificity as cell surface alpha 8 beta 1 in the presence of Mn2+ it bound to fibronectin and vitronectin in an RGDS-peptide inhibitable manner. Contrary to previous reports, we found no evidence that alpha 8 beta 1, expressed on K562 cells or as an AP chimera, interacts strongly with native tenascin-C. In binding, adhesion, and spreading assays, significant interactions were observed only to short fragments of tenascin-C containing the third fibronectin type III repeat which contains an RGD sequence. Full length tenascin-C and longer fragments containing this repeat did not appear to serve as ligands, implying that the RGD site in native tenascin-C is a cryptic binding site for this integrin, exposed by removal of adjacent domains. Soluble integrin-AP chimeras should be generally useful for identifying and characterizing integrin interactions with ligands.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Oligopeptides
/
Peptide Fragments
/
Recombinant Fusion Proteins
/
Integrins
/
Tenascin
/
Integrin alpha Chains
/
Alkaline Phosphatase
Limits:
Animals
/
Humans
Language:
En
Journal:
Biochemistry
Year:
1998
Document type:
Article
Affiliation country:
United States