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The AMD‐associated complement factor H (CFH) polymorphism Y402H results in decreased CFH localisation to Bruch’s membrane
Author(s) -
BISHOP PN,
ZAMBRANO I,
MORGAN BP,
HAKOBYAN S,
DAY AJ,
CLARK SJ
Publication year - 2009
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2009.2222.x
Subject(s) - factor h , bruch's membrane , retinal pigment epithelium , complement membrane attack complex , complement system , chemistry , alternative complement pathway , retinal , complement factor i , microbiology and biotechnology , complement factor b , biochemistry , biology , immunology , antibody
Purpose CFH down‐regulates the alternative pathway of the complement system by binding to polyanionic structures on host cells/tissues and inactivating surface associated C3b. Recently, the Y402H polymorphism in CFH has been shown to be a major risk factor for AMD. Here we investigated the functional consequences of the Y402H polymorphism by testing the hypothesis that the resultant amino acid substitution alters CFH binding to macular tissue Methods The 402H and 402Y forms of full‐length CFH and recombinant CFH fragments (composed of CCP6‐8) were labelled with different fluorophores (402Y with AlexFluor‐488 and 402H with AlexaFluor‐594). These were simultaneously incubated with frozen sections of human macular tissue from donor eyes and the relative binding of the two forms was investigated. In some experiments the tissue sections were digested with glycosidic enzymes prior to incubation with the fluorescently‐labelled proteins. Results Whilst the 402H and 402Y variants showed similar levels of binding to the RPE, there was a marked reduction in binding of the 402H form to Bruch’s membrane. The binding of both forms to Bruch’s membrane was dependent upon interactions with heparan sulfates, and to a lesser extent dermatan sulfates. Conclusion Complement mediated damage is important in the pathogenesis of AMD and the relative failure of the 402H form of CFH to localise to Bruch’s membrane may result in over activation of the complement system at the retinal pigment epithelium/Bruch's membrane interface.