Characterization of the murine homolog of C1qR(P): identical cellular expression pattern, chromosomal location and functional activity of the human and murine C1qR(P)

Human C1qR(p) is a highly glycosylated transmembrane protein that is the hu man Clq receptor/receptor component that in vitro mediates enhancement of F c- and C3b-mediated phagocytosis. A human genomic clone and a murine genomi c clone that is 73% identical in sequence with the coding region for human C1qR(p) cDNA have been isolated. Chromosomal localization of the human and murine gene demonstrates that these genes are syntenic. Murine cell lines o f diverse myeloid origins are shown to respond to interaction of Clq with t he enhancement of phagocytosis similar to that seen previously in human per ipheral blood monocytes. Northern blot, RT-PCR, Western blot and FAGS analy ses demonstrated that mC1qR(p) is expressed in these murine myeloid cell li nes, but not in a mouse epithelial cell line, similar to the cell type expr ession of the human gene product. A polyclonal antibody to a peptide sequen ce common to the deduced sequence from the both murine and human C1qR(p) in hibited the enhancement of phagocytosis response to Clq when cells were per meabilized to permit access of the antibody to the intracellular milieu. Th ese data support the postulate that the identified murine and human genes a re homologs, confirm the previously predicted intracellular location of the C-terminus of the molecule, and indicates the necessary role of this intra cellular domain in transducing the signal that leads to enhancement of phag ocytic function. (C) 2000 Elsevier Science Ltd. Ail rights reserved.