T. Ishibashi et al., FUNCTIONAL-SIGNIFICANCE OF PLATELET MEMBRANE GLYCOPROTEIN P62 (GP-VI), A PUTATIVE COLLAGEN RECEPTOR, International journal of hematology, 62(2), 1995, pp. 107-115
We previously suggested that platelet 62 kDa protein (p62, GP VI) is a
putative collagen receptor by the studies on platelets and antiplatel
et antibody in a patient (YA) with idiopathic thrombocytopenic purpura
(ITP) who showed defective collagen-induced platelet function. Herein
, we confirm that p62/p57 (reduced/unreduced conditions) is a specific
membrane protein recognized by YA antibody using an improved, immunop
recipitation technique. To further study the functional role of this p
rotein, a crude p57 fraction ('p57') was obtained from human platelets
by serial chromatography including DEAE-Sepharose CL-6B and WGA-agaro
se followed by preparative sodium dodecyl sulfate polyacrylamide gel e
lectrophoresis (SDS-PAGE). This 'p57' diminished the platelet-aggregat
ing activity of collagen and of YA immunoglobulin G (IgG), N-terminal
amino acid sequence analysis of 'p57' showed that it contained interce
llular adhesion molecule 2 (ICAM-2). Immunoprecipitation experiments u
sing platelet lysates and anti-ICAM-2 monoclonal antibody demonstrated
that ICAM-2 molecules had a molecular weight similar to p62 on SDS-PA
GE. However, ICAM-2 was also expressed on YA's p62-deficient platelets
both on immunoprecipitation and flow cytometric analysis. Thus, ICAM-
2 seems to be different from p62.