New functional and structural insights from updated mutational databases for complement factor H, Factor I, membrane...

Area of Science:

• Immunology
• Genetics
• Structural Biology

Background:

• Defective regulation of the complement alternative pathway (AP) is implicated in diseases such as atypical haemolytic uraemic syndrome (aHUS) and age-related macular degeneration (AMD).
• Key proteins involved in AP regulation include complement factor H (CFH), complement factor I (CFI), membrane cofactor protein (MCP), and C3.
• Genetic alterations in these proteins are frequently associated with disease pathogenesis.

Purpose of the Study:

• To update an interactive structural database with genetic alterations in key AP proteins.
• To identify functionally important regions within CFH, CFI, MCP, and C3 based on mutation mapping.
• To elucidate the impact of these mutations on protein function and their relevance to disease.

Main Methods:

• Compilation and analysis of 324 genetic alterations from existing literature.
• Structural mapping of mutations onto consensus and individual protein structures (CFH, CFI, MCP, C3).
• Classification of mutation types (missense) and their distribution within protein domains.

Main Results:

• The majority of short complement regulator (SCR) domain mutations occur in hypervariable loops and conserved cysteine residues.
• Over half of CFH missense mutations are in C-terminal SCR domains (SCR-15 to -20), with SCR-20 crucial for C3d and heparin binding.
• Mutations in CFH, CFI, and MCP typically result in loss-of-function, while C3 mutations lead to gain-of-function.

Conclusions:

• The complement alternative pathway plays a critical role in inflammatory diseases.
• Specific regions within CFH, CFI, MCP, and C3 are functionally vital and susceptible to disease-associated mutations.
• This updated structural and mutational data will aid in the diagnosis and therapeutic strategies for AP-related disorders.