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Defining the Glycosaminoglycan Interactions of Complement Factor H-Related Protein 5

Frederick Gyapon-Quast1,2, Elena Goicoechea de Jorge3, Talat Malik2

  • 1Glycosciences Laboratory, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, United Kingdom.

Journal of Immunology (Baltimore, Md. : 1950)
|July 1, 2021
PubMed

Insights

Complement factor H-related protein 5 (FHR-5) binds to kidney glycosaminoglycans (GAGs), enhancing its role in complement-mediated kidney injury. This interaction influences how FHR-5 regulates complement activation in glomerular diseases.

Area of Science:

  • Immunology
  • Molecular Biology
  • Nephrology

Background:

  • Complement activation is key in glomerulonephritis pathogenesis.
  • Complement factor H (FH) and FH-related protein 5 (FHR-5) differentially regulate glomerular complement.
  • FH inhibits complement C3 activation, while FHR-5 can promote it.

Purpose of the Study:

  • To investigate the role of carbohydrates in the interaction between FHR-5 and complement C3b.
  • To determine if FHR-5 binds to glycosaminoglycans (GAGs) and how this affects its function.

Main Methods:

  • Plate-based assays and microarray technologies were used to study FHR-5-GAG interactions.
  • The influence of GAG sulfation patterns on FHR-5 binding was assessed.
  • The functional relevance of FHR-5-GAG interaction was evaluated by examining FH binding to C3b.

Main Results:

  • FHR-5 was demonstrated to interact with sulfated GAGs.
  • The FHR-5-GAG interaction is dependent on the pattern and degree of GAG sulfation.
  • Surface kidney heparan sulfate enhances FHR-5's ability to inhibit FH binding to C3b.

Conclusions:

  • FHR-5 binds to sulfated GAGs, particularly heparan sulfate in the kidney.
  • This interaction modulates FHR-5's regulation of complement C3b deposition.
  • Findings elucidate the molecular basis of FHR-5's role in complement-mediated glomerular diseases.

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