Identification of amino acid sequences in fibrinogen γ-chain and tenascin C C-terminal domains critical for binding to integrin α(v)β3

Abstract

Integrin α(v)β3 recognizes fibrinogen γ and α(E) chain C-terminal domains (γC and α(E)C) but does not require the γC dodecapeptide sequence HHLGGAKQAGDV400-411 for binding to γC. We have localized the α(v)β3 binding sites in γC using γC-derived synthetic peptides. We found that two peptides GWTVFQKRLDGSV190-202 and GVYYQGGTYSKAS346-358 block the α(v)β3 binding to γC or α(E)C, block the a{v)β3-mediated clot retraction, and induce the ligand-induced binding site 2 (LIBS2) epitope in a{v)β3. Neither peptide affects fibrinogen binding to α(IIb)β3. Scrambled or inverted peptides were not effective. These results suggest that the two γC-derived peptides directly interact with α(v)β3 and specifically block a{v)β3-γC or α(E)C interaction. The two sequences are located next to each other in the γC crystal structure, although they are separate in the primary structure. Asp-199, Ser-201, Gln-350, Thr-353, Lys- 356, Ala-357, and Ser-358 residues are exposed to the surface. This suggests that the two sequences are part of α(v)β3 binding sites in fibrinogen γC domain. We also found that tenascin C C-terminal fibrinogen-like domain specifically binds to α(v)β3. Notably, a peptide WYRNCHRVNLMGRYGDNHSQGVNWFHWKG from this domain that includes the sequence corresponding to γC GVYYQGGTYSKAS346-358 specifically binds to α(v)β3, suggesting that fibrinogen and tenascin C C-terminal domains interact with α(v)β3 in a similar manner.