The Binding of Factor H to a Complex of Physiological Polyanions and C3b on Cells Is Impaired in Atypical Hemolytic Uremic Syndrome

Viviana P. Ferreira, Andrew P. Herbert, Claudio Cortes, Kristi A. McKee, Baerbel S. Blaum, Stefan T. Esswein, Dusan Uhrin, Paul N. Barlow, Michael K. Pangburn, David Kavanagh

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Factor H (fH) is essential for complement homeostasis in fluid-phase and on surfaces. Its two C-terminal domains (CCP 19-20) anchor fH to self-surfaces where it prevents C3b amplification in a process requiring its N-terminal four domains. In atypical hemolytic uremic syndrome (aHUS), mutations clustering toward the C terminus of fH may disrupt interactions with surface-associated C3b or polyanions and thereby diminish the ability of fH to regulate complement. To test this, we compared a recombinant protein encompassing CCP 19-20 with 16 mutants. The mutations had only very limited and localized effects on protein structure. Although we found four aHUS-linked M mutations that decreased binding to C3b and/or to heparin (a model compound for cell surface polyanionic carbohydrates), we identified five aHUS-associated mutants with increased affinity for either or both ligands. Strikingly, these variable affinities for the individual ligands did not correlate with the extent to which all the aHUS-associated mutants were found to be impaired in a more physiological assay that measured their ability to inhibit cell surface complement functions of full-length fH. Taken together, our data suggest that disruption of a complex M-self-surface recognition process, involving a balance of affinities for protein and physiological carbohydrate ligands, predisposes to aHUS. The Journal of Immunology, 2009, 182: 7009-7018.
Original languageEnglish
Pages (from-to)7009-7018
Number of pages10
JournalThe Journal of Immunology
Volume182
Issue number11
DOIs
Publication statusPublished - Jun 2009

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