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Lookup NU author(s): Professor Tim Goodship
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Mutations in complement regulatory proteins predispose to the development of aHUS. Approximately 50% of patients bear a mutation in one of three complement control proteins, factor H, factor I, or membrane cofactor protein (MCP; CD46). Another membrane regulator that is closely related to MCP, decay accelerating factor (DAF; CD55) thus far has shown no association with aHUS and continues to be investigated. The goal of this study was to compare the regulatory profile of MCP and DAF and to assess how alterations in MCP predispose to complement dysregulation. We employed a model system of complement activation on Chinese hamster ovary (CHO) cell transfectants. The four regularly expressed isoforms of MCP and DAF inhibited C3b deposition by the alternative pathway. DAF, but not MCP, inhibited the classical pathway. Most patients with MCP-aHUS are heterozygous and express only 25-50% of the wild-type protein. We, therefore, analyzed the effect of reduced levels of wild-type MCP and found that cells with lowered expression levels were less efficient in inhibiting alternative pathway activation. Further, a dysfunctional MCP mutant, expressed at normal levels and identified in five patients with aHUS (S206P), failed to protect against C3b amplification on CHO cells, even if expression levels were increased 10-fold. Our results add new information relative to the necessity for appropriate expression levels of MCP and further implicate the alternative pathway in disease processes such as aHUS.
Author(s): Liszewski MK, Leung MK, Schraml B, Goodship THJ, Atkinson JP
Publication type: Article
Publication status: Published
Journal: Molecular Immunology
Year: 2007
Volume: 44
Issue: 7
Pages: 1570-1579
Print publication date: 01/03/2007
ISSN (print): 0161-5890
ISSN (electronic): 1872-9142
Publisher: Pergamon
URL: http://dx.doi.org/10.1016/j.molimm.2006.08.024
DOI: 10.1016/j.molimm.2006.08.024
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