Advisor(s)
Matthew Renfrow
Committee Member(s)
Anupam Agarwal
Brittany Lasseigne
Jan Novak
Matthew Might
School
Joint Health Sciences (Interdisciplinary)
Document Type
Dissertation
Department (new version)
Biochemistry and Molecular Genetics
Date of Award
1-7-2025
Abstract
Immunoglobulin A1 (IgA1) is the second most abundantly produced immunoglobulin in circulation per day and plays a key role in human immunity. Two molecular complexities of IgA1 make accurately studying the protein challenging. The first is that IgA1 exists in three main molecular forms in the serum of humans: monomeric (mIgA1, 80-90% of serum IgA1), polymeric (pIgA1, 10-20% of serum IgA1), and IgA1-containing immune complexes (IgA1-IC, <0.5% of serum IgA1). The second complexity is that the hinge-region of IgA1 is extensively O-glycosylated and exhibits a high level of variation in its O-glycans, particularly in the degree of sialylation. In context of the autoimmune disease IgA nephropathy (IgAN), patients have elevated levels of IgA1 that has reduced levels of galactose (Gal) in the IgA1 hinge-region (Gal-deficient IgA1). This Gal-deficient IgA1 forms immune complexes with IgG autoantibodies (IgA1-IC), deposits in the glomeruli, and induces kidney injury. While it is established that these large IgA1-IC (>700 kDa) formed in the circulation are pathogenic, there remains a gap in knowledge about other blood proteins that may be associating with IgA1 in complexes. It is also necessary to understand the native O-glycosylation of IgA1 in healthy individuals before investigating the Gal-deficient O-glycosylation of patients with IgAN. Currently, it is underreported what the native sialylation of IgA1 looks like. Therefore, to analyze the composition of the IgA1-IC, we used a novel method to isolate serum IgA1-IC. I showed that the proteomes of the molecular forms of IgA1 are unique and should be considered when investigating IgA1. I identified 21 proteins that are higher in abundance in the IgA1-IC from patients with IgAN compared to those from healthy controls. From this, we informatically inferred that the complement system is being activated in the circulation via the alternative or lectin pathways. I then designed Heron Data Suite software to streamline the quantitative analysis of IgA1 native, sialylated hinge-region O-glycopeptides. I improved our protein digestion to allow for consistent proteomics analysis of tryptic fragments of IgA1 hinge-region O-glycoforms without the need for prior removal of sialic acid residues. Finally, I identified 42 native O-glycoforms in the serum IgA1 hinge-region of healthy individuals, revealed which are in high abundance, and the possible threshold for sialylation.
ProQuest ID
Recommended Citation
Cunningham, Mary A., "Characterizing The Molecular Complexities Of Iga1 By Serum Proteomics In The Context Of Iga Nephropathy" (2025). All ETDs from UAB. 7261.
https://digitalcommons.library.uab.edu/etd-collection/7261
