Biochemical analysis of a common human polymorphism associated with age-related macular degeneration

Biochemistry. 2007 Jul 17;46(28):8451-61. doi: 10.1021/bi700459a. Epub 2007 Jun 20.

Abstract

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in developed countries. A large number of human genetic studies have associated a common variant (Y402H) of complement factor H (CFH) with a highly significant increase in AMD risk. CFH is a modular protein with 20 homologous short consensus repeats (SCRs). The Y402H variant is located in SCR7 of both CFH and factor H-like protein 1 (FHL-1), a splice variant of CFH (containing SCR1-7) with unique biochemical properties. Because SCR7 is known to bind to heparin, C-reactive protein (CRP), and M protein from Streptococcus pyogenes, it has been hypothesized that the AMD-associated polymorphism may affect interactions with these CFH ligands. In this study, we tested this hypothesis in the context of full-length CFH (SCR1-20) and FHL-1. We systematically analyzed the interactions of the Y402 and H402 variants of CFH and FHL-1 with heparin, CRP, and several bacterial ligands: M6 protein of Streptococcus pyogenes, PspC of Streptococcus pneumoniea, and BbCRASP-1 of Borrelia burgdorferi. In comparing the Y and H variants of CFH and FHL-1, we found no significant difference in their protein secretion, cofactor activity, or interactions with heparin, BbCRASP-1, or PspC, but a significant difference in binding to CRP and M6 protein. This study reveals the fundamental properties of a common polymorphism of CFH and lays the groundwork for elucidating the role of CFH in AMD pathogenesis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / metabolism
  • C-Reactive Protein / metabolism
  • Cell Line
  • Complement C3b Inactivator Proteins
  • Complement Factor H / genetics*
  • Complement Factor H / metabolism
  • Heparin / metabolism
  • Humans
  • Ligands
  • Macular Degeneration / genetics*
  • Molecular Sequence Data
  • Polymorphism, Single Nucleotide*

Substances

  • Bacterial Proteins
  • CFH protein, human
  • CFHR1 protein, human
  • Complement C3b Inactivator Proteins
  • Ligands
  • Complement Factor H
  • Heparin
  • C-Reactive Protein