Lysozyme Mutants Accumulate in Cells while Associated at their N-terminal Alpha-domain with the Endoplasmic Reticulum Chaperone GRP78/BiP

International Journal of Biological Sciences
Yoshiki KamadaYasushi Sugimoto

Abstract

Amyloidogenic human lysozyme variants deposit in cells and cause systemic amyloidosis. We recently observed that such lysozymes accumulate in the endoplasmic reticulum (ER) with the ER chaperone GRP78/BiP, accompanying the ER stress response. Here we investigated the region of lysozyme that is critical to its association with GRP78/BiP. In addition to the above-mentioned variants of lysozyme, we constructed lysozyme truncation or substitution mutants. These were co-expressed with GRP78/BiP (tagged with FLAG) in cultured human embryonic kidney cells, which were analyzed by western blotting and immunocytochemistry using anti-lysozyme and anti-FLAG antibodies. The amyloidogenic variants were confirmed to be strongly associated with GRP78/BiP as revealed by the co-immunoprecipitation assay, whereas N-terminal mutants pruned of 1-41 or 1-51 residues were found not to be associated with the chaperone. Single amino acid substitutions for the leucine array along the α-helices in the N-terminal region resulted in wild-type lysozyme remaining attached to GRP78/BiP. These mutations also tended to show lowered secretion ability. We conclude that the N-terminal α-helices region of the lysozyme is pivotal for its strong adhesion to GRP78/BiP...Continue Reading

Citations

Jul 30, 2016·Toxicology in Vitro : an International Journal Published in Association with BIBRA·Weiping ZhangJianming Xu
Nov 2, 2019·Biological & Pharmaceutical Bulletin·Ling ChengShinan Nie
Mar 22, 2020·Scientific Reports·Sungmun LeeTae-Yeon Kim

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Methods Mentioned

BETA
ubiquitination
reverse transcription-PCR
transfection
PCR
co-immunoprecipitation
protein folding

Software Mentioned

Molecular Operating Environment ( MOE )

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