Soluble Urokinase Receptor as a Biomarker in Kidney Disease

Urokinase receptor (uPAR), a glycosylphosphatidylinositol (GPI)-anchored protein, engages in multiple protein-protein interactions and various biological functions. Its soluble form, soluble uPAR (suPAR), has been linked to various diseases and conditions including focal segmental glomerulosclerosis (FSGS). It T. Wada (*) Division of Nephrology, Endocrinology and Metabolism, Tokai University School of Medicine, Isehara, Japan e-mail: twada-tky@umin.ac.jp; twada@tsc.u-tokai.ac.jp # Springer Science+Business Media Dordrecht 2015 V.B. Patel, V.R. Preedy (eds.), Biomarkers in Kidney Disease, DOI 10.1007/978-94-007-7743-9_50-1 1 has been long speculated that a circulating permeability factor should be implicated in the pathogenesis of the disease because a substantial portion of the patients experience recurrence shortly after renal transplantation. In 2011, Reiser and colleagues suggested that suPAR might be not only a potential pathogenic permeability factor but also a diagnostic biomarker. Following this report, renal researchers worldwide have analyzed the validity of suPAR as a diagnostic biomarker for primary FSGS and posttransplant FSGS. Furthermore, the utility of suPAR as a biomarker in other renal diseases including diabetic nephropathy and immunoglobulin A (IgA) nephrosis has been also suggested. In this chapter, a comprehensive review of suPAR as a diagnostic biomarker and as a predictive biomarker in kidney diseases is provided.