Functional and structural implications of the complement factor H Y402H polymorphism associated with age-related macular degeneration.
OBJECTIVE
A Tyr-to-His (Y402H) sequence variant in the factor H (FH) and factor H-like protein (FHL-1) gene is strongly associated with an increased susceptibility for age-related macular degeneration (AMD). The purpose of this study was to understand how the Y402H variant in FH/FHL-1 contributes to the pathogenesis of AMD and, in particular, whether interactions mediated by FH/FHL-1, including binding to C-reactive protein (CRP), group A streptococcal M protein (GAS M6), heparin, and retinal pigment epithelial cells (RPE), are affected.


METHODS
FH was purified from sera of patients homozygous for FH(Y402) or (H402), and recombinant FH fragments representing FHL-1 were generated. Proteins were analyzed for binding to CRP, GAS M6, heparin, and RPE cells.


RESULTS
Binding of the FH and FH1 to seven polymorphic variants to CRP and M protein was reduced. The variant did not influence the interaction of FH with heparin but did reduce binding of FHL-1. Binding of the FH and FHL-1 polymorphic variant to RPE cells was not affected.


CONCLUSIONS
The FH Y402H polymorphism associated with AMD causes a reduction in binding of FH and FHL-1 to CRP and M protein. Both variants show comparable binding to RPE cells, indicating that AMD is unlikely to manifest as a result of impaired host cell-surface recognition. The decreased interaction between FH and CRP, which is essential for the anti-inflammatory function of CRP, provides a possible pathophysiological explanation for the association of the Y402H variant with AMD.
Ormsby
Rebecca J
RJ
Department of Microbiology and Infectious Diseases, Flinders Medical Centre and Flinders University of South Australia, Bedford Park, SA 5042, Australia. rebecca.ormsby@flinders.edu.au
Ranganathan
Shoba
S
Tong
Joo Chuan
JC
Griggs
Kim M
KM
Dimasi
David P
DP
Hewitt
Alex W
AW
Burdon
Kathryn P
KP
Craig
Jamie E
JE
Hoh
Josephine
J
Gordon
David L
DL
D000368:Aged; D000942:Antigens, Bacterial / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D002097:C-Reactive Protein / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D018929:Cell Culture Techniques; D002846:Chromatography, Affinity; D003180:Complement C3b Inactivator Proteins; D017242:Complement Factor H / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006493:Heparin / Q000378:metabolism; D006801:Humans; D008268:Macular Degeneration / Q000235:genetics*; D008875:Middle Aged; D008958:Models, Molecular; D010857:Pigment Epithelium of Eye / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide / Q000502:physiology*; D011485:Protein Binding
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; C493495:CFH protein, human; C517621:CFHR1 protein, human; D002352:Carrier Proteins; D003180:Complement C3b Inactivator Proteins; C014689:streptococcal M protein; D017242:Complement Factor H; D006493:Heparin; D002097:C-Reactive Protein