Glycoproteomics analysis of complement factor H and its complement-regulatory function during Streptococcus...

Area of Science:

• Immunology
• Glycobiology
• Pediatric Nephrology

Background:

• Hemolytic uremic syndrome (HUS) caused by invasive Streptococcus pneumoniae (SP-HUS) is a severe pediatric disease with unclear pathophysiology.
• Complement factor H (FH) regulates the complement system, and its N-glycans may be implicated in SP-HUS pathogenesis.
• Loss of sialic acids on FH N-glycans is hypothesized to impair its function, leading to endothelial damage.

Purpose of the Study:

• To investigate N-glycosylation patterns of FH in SP-HUS patients during acute and remission phases.
• To compare FH glycosylation in SP-HUS patients with healthy controls.
• To assess the functional impact of observed FH glycosylation changes on complement regulation.

Main Methods:

• LC-MS/MS-based glycopeptide profiling was used to analyze FH N-glycosylation at three sites.
• Four SP-HUS patients and healthy controls were included in the comparative analysis.
• Functional assays measured FH's ability to facilitate C3b degradation and prevent complement-mediated hemolysis.

Main Results:

• Significant alterations in FH glycosylation were identified during the acute phase of SP-HUS.
• Increased N-glycans lacking sialic acids, galactose, and N-acetylglucosamine (GlcNAc) were observed in SP-HUS patients compared to controls.
• Despite major glycosylation changes, FH's complement regulatory activity remained unaffected in functional assays.

Conclusions:

• FH N-glycosylation is significantly altered in SP-HUS patients, extending beyond just sialic acid loss.
• These observed N-glycosylation changes do not directly impair the complement regulatory function of FH.
• The study underscores the complex role of N-glycosylation in infection and FH's contribution to complement dysregulation in SP-HUS.