IgA1 O-glycosylation

Analysis of clustered sites of O-glycosylation:

Our group makes use of high resolution FT-ICR MS to provide an accurate profile of entire population of O-glycosylated IgA1 proteins to identify the pathogenic forms contributing to the pathogenesis of IgA nephropathy. This includes the site-specific localization and characterization of individual O-glycan chains by use of electron capture/transfer dissociation (ECD & ETD). Our goal is to identify the aberrant IgA1 O-glycosylation pattern that leads to the mesangial deposits of IgA1-containing immune complexes. This may lead to alternative methods for diagnosing and monitoring the disease as well as identifying targets for therapeutic intervention.

Clustered sites of O-glycosylation

See Larger Image

See Larger Image

Glycosylation is one of the most common post-translational modifications of proteins. It is estimated that over half of mammalian proteins are glycosyalted. Several autoimmune disorders and chronic inflammatory diseases exhibit abnormal glycosylation of serum immunoglobulins. A variety of proteins are postranslationally modified with clustered sites of O-glycosylation. Serine and Threonine rich stretches within the amino acid sequence that have short O-glycan chains. Examples include the immunoglobulin A (A1 isotype), mucins, and bacterial cell surface proteins. For a given protein with sites of clustered O-glycans, the protein isolated from a single source is a population of variably O-glycosylated isoforms that usually show a distinct distribution of microheterogeneity in terms of number of chains, the sites of attachment and O-glycan composition at a given amino acid. Characterizing these clustered sites and understanding how the distributions change under differenct biological conditions or disease states is an analytical challenge.

Iga Nephropathy

IgA nephropathy (IgAN, also known as Berger's disease) is the most common primary glomerulonephritis worldwide, with about 20-40% of patients developing end-stage renal failure. It is characterized by mesangial deposits of IgA1-containing immune complexes. The carbohydrate side chains of IgA1 molecules play a pivotal role in the pathogenesis of IgAN. IgA1 contains a hinge region between the first and second heavy chain constant region domains with a high content of proline, serine, and threonine and usually have three to five O-linked glycan chains.

Renfrow Lab Publications related to IgAN

1. Gomes MM, Wall SB, Takahashi K, Novak J, Renfrow MB, Herr AB.
   Analysis of IgA1 N-glycosylation and its contribution to FcalphaRI binding.
   Biochemistry. 28;47(43):11285-99, 2008
   
   
2. Mestecky J, Tomana M, Moldoveanu Z, Julian BA, Suzuki H, Matousovic K, Renfrow MB, Novak L, Wyatt RJ, Novak J.
   Role of aberrant glycosylation of IgA1 molecules in the pathogenesis of IgA nephropathy. Kidney Blood Press Res. 31:29-37, 2008
   
   
3. Novak, J., Moldoveanu, Z., Renfrow, M.B, Yanagihara, T., Suzuki, H., Raska, M., Hall, S., Brown, R., Huang, W.-Q., Goepfert, A., Kilian, M., Poulsen, K., Tomana, M., Wyatt, R.J., Julian, B.A., Mestecky, J.
   IgA Nephropathy and Henoch-Schoenlein Purpura Nephritis: Aberrant Glycosylation of IgA1, Formation of IgA1-Containing Immune Complexes, and Activation of Mesangial Cells.
   Contrib Nephrol. 157:134-8, 2007
   
   
4. Renfrow, M.B., Mackay, C.L., Chalmers, M.J., Julian, B.A., Mestecky, J., Kilian, M., Poulsen, K., Emmett, M.R., Marshall, A.G., Novak, J.
   Analysis of O-glycan Heterogeneity in IgA1 Myeloma Proteins by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry: Implications for IgA Nephropathy.
   Anal. Bioanal. Chem., 389:1397-407, 2007
   
   
5. Renfrow MB, Cooper HJ, Tomana M, Kulhavy R, Hiki Y, Toma K, Emmett MR, Mestecky J, Marshall AG, Novak J.
   Determination of aberrant O-glycosylation in the IgA1 hinge region by electron capture dissociation fourier transform-ion cyclotron resonance mass spectrometry.
   J Biol Chem. 280:19136-19145, 2005.
   
   

UAB IgA Nephropathy Group Publications

• See Pubmed

More information on IgA Nephropathy

• NIH/NIDDK
• IgA Nephropathy support network
• IgA Nephropathy Today (2007 publication of the latest research in IgA Nephropathy)

Basic descriptions of IgA Nephropathy

• American Association of Kidney Patients
• National Kidney Foundation

Support for this work

NIH- NIDDK

• R21 DK077279-01A2 (Matthew Renfrow, University of Alabama at Birmingham, P.I.)
  Accurate profiles of IgA1 O-glycan Heterogeneity in IgA Nephropathy
• R01 DK 71802-01A1 (Andy Herr, University of Cincinnati, P.I.)
  IgA1 Glycosylation and Receptor Interactions in IgA Nephropathy
• R01 DK78244-01 (Jan Novak, University of Alabama at Birmingham P.I.)
  Molecular Basis of Pathogenicity of IgA1-containing Immune Complexes
• R21 DK080301-02 (Jan Novak, University of Alabama at Birmingham, P.I.)
  IgA-secreting B cell lines: a novel tool for studies of IgA nephropathy
• R21 DK75868 (Jan Novak, University of Alabama at Birmingham, P.I.)
  Urinary Polypeptide Biomarkers of IgA Nephropathy