IgA nephropathy (IgAN) is the most common primary glomerulonephritis and an important cause of end-stage kidney failure. It is a mesangioproliferative glomerulonephritis defined by IgA1 mesangial deposits. Although it has been speculated for some time that the pathogenesis of IgAN is driven by deposition of circulating immune complexes (IC), this has been difficult to prove due to the lack of animal models of IgAN. Our development of new protocols that permit formation of engineered IC in vitro and establishment of a passive mouse model of IgAN provide an unprecedented opportunity to elucidate the pathophysiology of IgAN and identify potential therapeutic targets. In IgAN, a fraction of circulating IgA1 has galactose-deficient O-glycans (Gd-IgA1) and is present in circulating IC bound by glycan-specific autoantibodies. We now have characterized Gd-IgA1 and the anti-Gd-IgA1 autoantibodies that are present in these IC and used targeted proteomic approaches to both define the serum factors that associate with these IC and may contribute to their pathogenic effects and to identify the mesangial-cell receptors for the ICs. Rational extension of these studies required analysis of the molecular effects of these pathogenic IgAN ICs on the signaling events that lead to mesangial-cell activation. Global kinase-activity profilin using an innovative peptide substrate microarray platform of human mesangial cells stimulated with Gd-IgA1 IC identified robust tyrosine kinase activity as a major player in IC-induced signaling in three predominant pathways. Similar results were obtained with native and engineered ICs. The mesangial-cell responses after stimulation with these IC were typical of IgAN but differed from those obtained by using IC lacking all of the components in pathogenic ICs. An association with pathogenesis was demonstrated using protein-kinase inhibitors, which confirmed that one of the inhibitors completely blocked IC- mediated mesangial cell proliferation in vitro as well as in vivo in the passive mouse model of IgAN. These data suggest the hypothesis that Gd-IgA1-containing ICs represent a key hit in the pathogenesis of IgAN by activating mesangial cells through specific signaling pathways;the corollary is that this IC-drive signaling in mesangial cells can be blocked by small-molecular-mass inhibitors of protein kinases and thus represents a feasible therapeutic target(s). The team of basic and clinical investigators that has developed the powerful proteomic, kinomic, and cellular approaches used to generate the preliminary data will now test this hypothesis by: 1) Defining the characteristics of Gd-IgA1-containing ICs from sera of patients with IgAN that activate human mesangial cells;2) Characterizing the signaling pathways activated by Gd-IgA1-containing ICs in mesangial cells;and 3) Determining the efficacy of small-molecular-mass inhibitors of key protein kinases on mesangial cell activation in vivo using the animal model of IgAN. Relevance: The results will shed light on the pathogenesis of IgAN and identify therapeutic targets for disease-specific treatment of IgAN as well as potential response/prognostic biomarkers.

Public Health Relevance

IgA nephropathy causes kidney damage those progresses to end-stage kidney failure in a substantial number of patients, as there are no disease-specific therapies available. We propose to define the molecular responses of the kidney cells to the circulating complexes that trigger the disease by using state-of-the-art molecular profiling in combination with the novel cell and in vivo models that we have developed. The results of the proposed experimental and clinical studies will suggest disease-specific therapeutic strategies and provide the basis for development of noninvasive tests for detection of disease activity prior to irreversible kidney damage. 1

National Institute of Health (NIH)
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Pathobiology of Kidney Disease Study Section (PBKD)
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Moxey-Mims, Marva M
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University of Alabama Birmingham
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Suzuki, Hitoshi; Raska, Milan; Yamada, Koshi et al. (2014) Cytokines alter IgA1 O-glycosylation by dysregulating C1GalT1 and ST6GalNAc-II enzymes. J Biol Chem 289:5330-9
Schmitt, Roland; Ståhl, Anne-Lie; Olin, Anders I et al. (2014) The combined role of galactose-deficient IgA1 and streptococcal IgA-binding M Protein in inducing IL-6 and C3 secretion from human mesangial cells: implications for IgA nephropathy. J Immunol 193:317-26
Franc, Vojtech; Rehulka, Pavel; Raus, Martin et al. (2013) Elucidating heterogeneity of IgA1 hinge-region O-glycosylation by use of MALDI-TOF/TOF mass spectrometry: role of cysteine alkylation during sample processing. J Proteomics 92:299-312
Novak, Jan (2012) Induction of IgA deposits and glomerulonephritis by IgA rheumatoid factor. J Am Soc Nephrol 23:371-3
Takahashi, Kazuo; Smith, Archer D; Poulsen, Knud et al. (2012) Naturally occurring structural isomers in serum IgA1 o-glycosylation. J Proteome Res 11:692-702
Horynova, Milada; Takahashi, Kazuo; Hall, Stacy et al. (2012) Production of N-acetylgalactosaminyl-transferase 2 (GalNAc-T2) fused with secretory signal Igýý in insect cells. Protein Expr Purif 81:175-80
Suzuki, Hitoshi; Kiryluk, Krzysztof; Novak, Jan et al. (2011) The pathophysiology of IgA nephropathy. J Am Soc Nephrol 22:1795-803
Novak, Jan; Moldoveanu, Zina; Julian, Bruce A et al. (2011) Aberrant glycosylation of IgA1 and anti-glycan antibodies in IgA nephropathy: role of mucosal immune system. Adv Otorhinolaryngol 72:60-3
McCarthy, Douglas D; Kujawa, Julie; Wilson, Cheryl et al. (2011) Mice overexpressing BAFF develop a commensal flora-dependent, IgA-associated nephropathy. J Clin Invest 121:3991-4002
Herzenberg, Andrew M; Fogo, Agnes B; Reich, Heather N et al. (2011) Validation of the Oxford classification of IgA nephropathy. Kidney Int 80:310-7

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