Distinct receptor and regulatory properties of recombinant mouse complement receptor 1 (CR1) and crry, the two genetic homologues of human CR1

Hector Molina, Winnie Wong, Taroh Kinoshita, Carol Brenner, Sharon Foley, V. Michael Holers

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


The relationship between the characterized mouse regulators of complement activation (RCA) genes and the 190-kD mouse complement receptor 1 (MCK1), 155-kD mouse complement receptor 2 (MCR2), and mouse p65 is unclear. One mouse RCA gene, designatedMCR2 (or Cr2), encodes alternatively spliced 21 and 15 short consensus repeat (SCR)-containing transcripts that crosshybridize with cDNAs of both human CR2 and CR1, or CR2 alone, respectively. A five SCR-containing transcript derived from a second unique gene, designated Crry, also crosshybridizes with human CR1. We have previously shown that the 155-kD MCR2 is encoded by the 15 SCR-containing transcript. To analyze the protein products of the other transcripts, which are considered the genetic homologues of human CRI, we have expressed the 21 and the 5 SCR-containing cDNAs in the human K562 erythroleukemia cell line. We demonstrate that cells expressing the 21 SCK transcript express the 190-kD MCR1 protein. These cells react with five unique rat anti-MCR1 monodonal antibodies, including the 8C12 antibody considered to be monospecific for MCK1. In addition, these cells efficiently form rosettes with mouse C3bbearing sheep erythrocytes. In contrast, cells expressing the five SCR-containing Crry transcript are strongly recognized by an anti-human CR1 antibody that also defines the mouse p65 protein. Using a functional assay that measures the surface deposition of C3 activated via the classical complement pathway, we show that Crry/p65-expressing cells have a markedly decreased amount of C3 deposited on them as compared with control cells expressing the antisense construct or cells expressing MCR1 or MCR2. This suggests that Crry has intrinsic complement regulatory activity. Overall, these studies demonstrate that mouse has an RCA gene family that encodes proteins with similar activities and biologic roles, as compared with their human counterparts, but with very unique structures.

Original languageEnglish
Pages (from-to)121-123
Number of pages3
JournalJournal of Experimental Medicine
Issue number1
StatePublished - Jan 1 1992


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