Abstract: FR-PO472
Post-Translational Modified Albumin in CKD Patients
Session Information
- CKD: Risk Factors for Incidence and Progression - II
November 03, 2017 | Location: Hall H, Morial Convention Center
Abstract Time: 10:00 AM - 10:00 AM
Category: Chronic Kidney Disease (Non-Dialysis)
- 301 CKD: Risk Factors for Incidence and Progression
Authors
- Jankowski, Joachim, RWTH Aachen, Aachen, BE, Germany
- Jankowski, Vera, University hospital RWTH Aachen, Aachen, Germany
Background
Since post-translational modifications (PTM) of proteins may have an impact on the pathogenesis of diseases like atherosclerosis, diabetes mellitus and CKD, PTMs are currently gaining increasing interest. However, a comprehensive method for analysis of these PTMs is not established for the clinical diagnostic routine yet. Therefore, we have set up a MALDI-mass-spectrometric approach to detect post-translational modifications of plasma proteins for diagnostics.
Methods
In order to prove the significance of the approach, we analysed albumin –the most abundant plasma protein in human– isolated from CKD patients and healthy controls by mass-spectrometry. Post-translational modifications of albumin were identified after digestion by analysing mass-signal shifts of albumin peptides using pertinent mass-databases.
Results
Albumin isolated from plasma of CKD patients but not from healthy control subjects was specifically post-translationally modified by guanidylation of lysines. After identification of guanidylations as post-translational modifications of albumin isolated from CKD patients, these modifications were quantified by mass-spectrometry demonstrating a significant increase in the corresponding mass-signal intensities in CKD patients. The relative amount of guanidylation of lysine at position 468 in CKD patients was determined as 63% ± 32 (N=3). In-vitro guanidylation of albumin from healthy control subjects caused a decreased binding capacity of albumin in a time-dependent manner.
Binding of indoxyl sulfate decreased from 82 ± 1 % of non post-translationally modified albumin to 56 ± 1 % after in-vitro guanidylation whereas the binding of tryptophan decreased from 20 to 4%. These results are in accordance with the binding of indoxyl sulfate to albumin from healthy control subjects and CKD patients. Thus, in-vitro post-translational guanidylation of albumin had a direct effect on the binding capacity of hydrophobic metabolites like indoxyl sulfate and tryptophan.
Conclusion
In conclusion, we established a mass spectrometry-based method for the characterisation of PTM and demonstrated the pathophysiological impact of a representative post-translational modification of plasma albumin. The approach described in this study may help to elucidate the pathophysiological role of protein modifications.