Proteolytic Enzymes as Biomarkers of Focal Segmental Glomerulosclerosis

Abstract

Proteases play an important role in many cellular functions and represent promising biomarkers in addition to being targets for many diseases ranging from cardiovascular and neurological disorders to respiratory problems and cancer. Sensitive and robust methods are necessary to quantify proteolytic activities in complex biological samples, e.g., serum and plasma to compliment existing techniques. We have previously utilized a combinatorial library of internally quenched fluorogenic probes to map the proteolytic profiles of guinea pig serum and bronchoalveolar lavage fluid (BALF). The technique was extended to identify disease-specific proteolytic activity in guinea pig BALF infected with invasive aspergillosis. Here, the library was utilized to map the global proteolytic specificities of plasma samples obtained from patients with the nephrotic syndrome, known as focal segmental glomerulosclerosis (FSGS). FSGS compromises both native and transplanted kidneys and has limited treatment options due to poorly understood pathophysiology. The circulating factor hypothesis suggests that some factor (or lack thereof) within the blood causes FSGS and recent research points to proteases as one of these. Comparison of the global proteolytic profiles of FSGS and healthy plasma samples identified many peptide motifs that were cleaved only in FSGS or in healthy plasma samples. The observed results reveal not only the protease specificities of plasma samples but also potential targets that can be pursued further to understand the role of proteases in FSGS pathology.