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Protein disulfide isomerase associates with misfolded human lysozyme in vivo
1Protein Engineering Research Institute, Osaka, Japan.
Abstract:
Wild-type human lysozyme (hLZM) is quantitatively secreted into the media when expressed in mouse fibroblast cells, but some misfolded hLZMs are retained and rapidly degraded in a pre-Golgi compartment (Omura, F., Otsu, M., Yoshimori, T., Tashiro, Y., and Kikuchi, M. (1992) Eur. J. Biochem. 210, 591-599). To detect the association with misfolded hLZMs of cellular proteins involved in their folding, retention, and pre-Golgi degradation, a co-precipitation experiment was carried out using anti-hLZM antibody and metabolically labeled cell lysates, which were treated with a membrane-permeable cross-linking reagent. Here we report that protein disulfide isomerase associated in vivo with misfolded hLZMs, but not with the wild-type protein, and discuss the possible role of protein disulfide isomerase in the quality control of newly synthesized proteins in the endoplasmic reticulum.
Insights
Misfolded human lysozyme (hLZM) interacts with protein disulfide isomerase in a pre-Golgi compartment. This suggests protein disulfide isomerase plays a role in endoplasmic reticulum protein quality control and degradation pathways.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Wild-type human lysozyme (hLZM) is secreted by mouse fibroblast cells.
- Misfolded hLZM variants are retained and degraded in a pre-Golgi compartment.
- Cellular proteins involved in folding, retention, and degradation of misfolded hLZM require identification.
Purpose of the Study:
- To identify cellular proteins associated with misfolded hLZM.
- To investigate the role of these proteins in hLZM processing and degradation.
- To elucidate the endoplasmic reticulum protein quality control mechanisms.
Main Methods:
- Co-precipitation experiments were performed using anti-hLZM antibody.
- Metabolically labeled cell lysates were treated with a membrane-permeable cross-linking reagent.
- Association of cellular proteins with wild-type and misfolded hLZM was analyzed.
Main Results:
- Protein disulfide isomerase was found to associate in vivo specifically with misfolded hLZM.
- No association was observed between protein disulfide isomerase and wild-type hLZM.
- This indicates a specific interaction in the context of protein misfolding.
Conclusions:
- Protein disulfide isomerase is implicated in the quality control of newly synthesized proteins.
- The findings suggest a role for protein disulfide isomerase in the endoplasmic reticulum's handling of misfolded proteins.
- Further research can explore therapeutic strategies targeting protein folding pathways.