Tp. Ugarova et al., IDENTIFICATION OF A NOVEL RECOGNITION SEQUENCE FOR INTEGRIN ALPHA(M)BETA(2) WITHIN THE GAMMA-CHAIN OF FIBRINOGEN, The Journal of biological chemistry, 273(35), 1998, pp. 22519-22527
The interaction of leukocyte integrin alpha(M)beta(2) (CD11b/CD18, Mac
-1) with fibrinogen has been implicated in the inflammatory response b
y contributing to leukocyte adhesion to the endothelium and subsequent
transmigration. Previously, it has been demonstrated that a peptide,
P1, corresponding to residues 190-202 in the gamma-chain of fibrinogen
, binds to alpha(M)beta(2) and blocks the interaction of fibrinogen wi
th the receptor and that Asp(199) within P1 is important to activity.
We have demonstrated, however, that a double mutation of Asp(199)-Gly(
200) to Gly-Ala in the recombinant gamma-module of fibrinogen, spannin
g region 148-411, did not abrogate alpha(M)beta(2) recognition and con
sidered that other binding sites in the gamma-module may participate i
n the receptor recognition. We have found that synthetic peptide P2, d
uplicating gamma 377-395, inhibited adhesion of alpha(M)beta(2)-transf
ected cells to immobilized D-100 fragment of fibrinogen in a dose-depe
ndent manner. In addition, immobilized Pa directly supported efficient
adhesion of the alpha(M)beta(2)-expressing cells, including activated
and non-activated monocytoid cells. The I domain of alpha(M)beta(2) w
as implicated in recognition of P2, as the biotinylated recombinant al
pha(M)I domain specifically bound to both P2 and P1 peptides, Analysis
of overlapping peptides spanning P2 demonstrated that it may contain
two functional sequences: gamma 377-386 (P2-N) and gamma 383-395 (P2-C
), with the latter sequence being more active. In the three-dimensiona
l structure of the gamma-module, gamma 190-202 and gamma 377-395 resid
e in close proximity, forming two antiparallel beta strands. The juxta
positioning of these two sequences may form an unique and complex bind
ing site for alpha(M)beta(2).