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International Journal Of Bilogical Sciences

.: Home > International Journal Of Bilogical Sciences > 2016 > Volume 12 Number 2 > Yoshiki Kamada, Yusuke Nawata, Yasushi Sugimoto

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

Yoshiki Kamada, Yusuke Nawata, Yasushi Sugimoto
Laboratory of Biochemistry and Bioscience, The United Graduate School of Agricultural Sciences, Kagoshima University, Kagoshima 890-0065, Japan  Corresponding author: Yasushi Sugimoto: Tel: 81+ 99-285-8781 Fax: 81+99-285-8799
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. We suspect that wild-type lysozyme interacts with the GRP at this region as a step in the proper folding monitored by the ER chaperone

Keywords :
lysozyme, variants, aggregate, amyloidosis, GRP78/BiP, endoplasmic reticulum stress

Date Deposited : 15 Mar 2016 13:20

Last Modified : 15 Mar 2016 13:20

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Volume 12, Number 2, - 2016 , ISSN 1449-2288

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