The Journal of Immunology, Vol 145, Issue 9 2984-2988, Copyright © 1990 by American Association of Immunologists

ARTICLES

Platelet C1q receptor interactions with collagen- and C1q-coated surfaces

EI Peerschke and B Ghebrehiwet
Department of Pathology, SUNY, Stony Brook 11794.

We recently described specific binding sites for C1q on human blood platelets. Structural similarities between the amino-terminal of C1q and collagen have suggested that receptors for both molecules on platelets might be the same. The present study thus compared the interaction of purified C1q receptors (C1qR) and whole platelets with collagen- and C1q-coated polystyrene surfaces. Surfaces coated with BSA or gelatin served as controls. Purified 125I-labeled C1qR recognized both C1q- and collagen-coated surfaces in a divalent, cation- independent manner. This adhesion was inhibited by polyclonal or monoclonal (II1/D1) anti-C1qR antibodies. Although C1qR adhered preferentially to C1q-coated surfaces, adhesion to bovine and human type I collagen, as well as to human type III and V collagen, was also noted. In parallel studies, 51Cr-labeled platelets bound equally well to collagen- or C1q-coated surfaces, albeit in a magnesium-dependent manner. Partial inhibition of platelet adhesion was observed in the presence of RGDS, despite the inability of RGDS to modify C1qR interaction with C1q or collagen. Moreover, anti C1qR antibodies selectively inhibited platelet adhesion to C1q-coated surfaces, whereas antibodies specific for the GPIa/IIa collagen receptor (6F1) preferentially inhibited platelet collagen interactions. These data support the presence of distinct platelet membrane C1qR, which may cross-react with collagen, and suggest that C1qR are necessary but not sufficient for platelet adhesion to C1q-coated surfaces. Additional divalent cation and/or RGD-sensitive binding sites may participate.

This article has been cited by other articles:

				A. P. Lillis, L. B. Van Duyn, J. E. Murphy-Ullrich, and D. K. Strickland LDL Receptor-Related Protein 1: Unique Tissue-Specific Functions Revealed by Selective Gene Knockout Studies Physiol Rev, July 1, 2008; 88(3): 887 - 918. [Abstract] [Full Text] [PDF]

				G. Lasser, P. Guchhait, J. L. Ellsworth, P. Sheppard, K. Lewis, P. Bishop, M. A. Cruz, J. A. Lopez, and J. Fruebis C1qTNF-related protein-1 (CTRP-1): a vascular wall protein that inhibits collagen-induced platelet aggregation by blocking VWF binding to collagen Blood, January 15, 2006; 107(2): 423 - 430. [Abstract] [Full Text] [PDF]

				B. T. Edelson, T. P. Stricker, Z. Li, S. K. Dickeson, V. L. Shepherd, S. A. Santoro, and M. M. Zutter Novel collectin/C1q receptor mediates mast cell activation and innate immunity Blood, January 1, 2006; 107(1): 143 - 150. [Abstract] [Full Text] [PDF]

				C. A. Ogden, A. deCathelineau, P. R. Hoffmann, D. Bratton, B. Ghebrehiwet, V. A. Fadok, and P. M. Henson C1q and Mannose Binding Lectin Engagement of Cell Surface Calreticulin and CD91 Initiates Macropinocytosis and Uptake of Apoptotic Cells J. Exp. Med., September 17, 2001; 194(6): 781 - 796. [Abstract] [Full Text] [PDF]