Mass spectrometry of urinary β2 microglobulin oligomer in patients with proteinuria

• Published in: Therapeutic apheresis and dialysis 2021-04, Vol.25 (2), p.197-203
• Main Authors: Akizuki, Setsuko, Kawano, Katsumi, Iwamoto, Takeo, Nakada, Koji, Ohnishi, Akihiro
• Format: Article
• Language: English
• Subjects: high proteinuria; matrix‐assisted laser desorption ionization‐time‐of‐flight mass spectrometry (MALDI‐TOF‐MS); oligomer; posttranslational modification; urinary β2 microglobulin
• ISSN: 1744-9979; 1744-9987
• DOI: 10.1111/1744-9987.13547

Urinary β2 microglobulin (β2‐m) is a marker of renal tubule dysfunction; however, β2‐m might become degraded under acidic conditions. To confirm the degradation and consequent deactivation of β2‐m under acidic conditions, we used matrix‐assisted laser desorption ionization‐time‐of‐flight mass spectrometry (MALDI‐TOF MS) to detect the levels and forms of β2‐m in the urine samples of patients with high proteinuria (n = 21) and healthy subjects (n = 6). β2‐m was purified in crude form using immunoprecipitation. A signal of 11.74 kDa, corresponding to the molecular weight of β2‐m, was detected in all samples. In addition, several high‐molecular‐weight proteins were detected in a patient as integrals of the intensity at 11.74 kDa. These results indicate that posttranslational modifications of β2‐m might be involved in the pathological process of proteinuria. Therefore, MS can be used for monitoring proteinuria and predicting the risk of progression.