The Primary Role of Fibrinogen-Related Proteins in Invertebrates Is Defense, Not Coagulation

In vertebrates, the conversion of fibrinogen into fibrin is an essential process that underlies the establishment of the supporting protein framework required for coagulation. In invertebrates, fibrinogen-domain-containing proteins play a role in the defense response generated against pathogens; however, they do not function in coagulation, suggesting that this role has been recently acquired. Molecules containing fibrinogen motifs have been identified in numerous invertebrate organisms, and most of these molecules known to date have been linked to defense. Moreover, recent genome projects of invertebrate animals have revealed surprisingly high numbers of fibrinogen-like loci in their genomes, suggesting important and perhaps diverse functions of fibrinogen-like proteins in invertebrates. The ancestral role of molecules containing fibrinogen-related domains (FReDs) with immunity is the focus of this review, with emphasis on specific FReDs called fibrinogen-related proteins (FREPs) Received: August 31, 2010 Accepted after revision: October 8, 2010 Published online: November 9, 2010 Journal of Innate Immunity Dr. Si-Ming Zhang Center for Evolutionary and Theoretical Immunology Department of Biology, MSC03 2020, University of New Mexico Albuquerque, NM 87131 (USA) Tel. +1 505 277 4589, Fax +1 505 277 0304, E-Mail zhangsm @ unm.edu © 2010 S. Karger AG, Basel Accessible online at: www.karger.com/jin Abbreviations used in this paper