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Detection of Podocin in Human Urine Sediment Samples by Charge Derivatization and LC-MS-MRM Method.

International journal of molecular sciences (2020-05-07)
Remigiusz Bąchor, Dorota Gąszczyk, Karolina Panek-Laszczyńska, Andrzej Konieczny, Wojciech Witkiewicz, Piotr Stefanowicz, Zbigniew Szewczuk
ABSTRACT

Detection of podocytes in urine might serve as a useful diagnostic tool in both primary and secondary glomerular diseases. The utility of podocyturia has been confirmed for both pre-eclampsia and glomerulonephritis. Here, we present a new and sensitive method for qualitative LC-MS-multiple-reaction-monitoring (MRM) analysis of podocin, serving as a podocyturia biomarker in urine sediments. The following podocin tryptic peptides with the 169LQTLEIPFHEIVTK182, 213AVQFLVQTTMK223, 240SIAQDAK246, and 292MIAAEAEK299 sequences were applied as a model. The selective chemical derivatization of the ε amino group of C-terminal lysine residue in tryptic peptides, by 2,4,6-triphenylpyrylium salt (TPP) as a fixed charge tag, was employed to increase the ionization efficiency, in routine ESI-MS analysis. Additionally, the generation of a reporter ion, in the form of a protonated 2,4,6-triphenylpyridinium cation, makes the derivatized peptide analysis in the MRM mode unambiguous. Identification of derivatized and non-derivatized peptides were performed, and the obtained results suggest that the peptide with the 292MIAAEAEK299 sequence may serve as a marker of podocyturia.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Triisopropylsilane, 98%
Sigma-Aldrich
Tetraethylammonium bicarbonate, ≥95.0% (T)
Sigma-Aldrich
2,4,6-Triphenylpyrylium tetrafluoroborate, 98%
Sigma-Aldrich
meso-Tetraphenylporphyrin, BioReagent, suitable for fluorescence, ≥99.0% (HPLC)
Sigma-Aldrich
Tetraethylammonium borohydride, technical, ≥95% (T)