Several receptors for the
extracellular matrix protein collagen have been described which belong to the superfamily of receptors collectively known as
integrins. Although several
integrins have been shown to interact with extracellular matrix molecules via a common recognition site,
arginine-glycine-aspartic Acid (RGD), within the beta 1
integrin subfamily, only the
fibronectin receptor (alpha 5 beta 1) has been convincingly shown to interact with RGD. In the present study, we tested whether a
collagen receptor could interact with RGD. Adhesion of an
osteosarcoma cell line, MG-63, to immobilized
collagen I was inhibited by the
cyclic RGD-containing
peptide, C*
GRGDSPC* (where C* indicates that Cys participates in
disulfide), and not by the linear
GRGDSP or the non-RGD-containing
cyclic peptide, C*GKGESPC*. Similarly, using
collagen-
Sepharose affinity chromatography, a heterodimeric
protein could be specifically eluted from the column by the
cyclic RGD peptide. Immunoprecipitations of the eluted material with
monoclonal antibodies showed reactivity with the
collagen receptor alpha 2 beta 1 and not alpha 3 beta 1. Our data demonstrate that RGD
peptides can interact with the
collagen receptor, and the differences seen with the linear and
cyclic peptide suggest that the cyclic C*
GRGDSPC* has a higher avidity for the receptor than the more flexible linear
GRGDSP. In this paper, we provide supportive evidence that one possible mode of
collagen interaction with alpha 2 beta 1 is via the RGD recognition sequence.