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ERp57 does not require interactions with calnexin and calreticulin to promote assembly of class I histocompatibility molecules and it enhances peptide loading independently of its redox activity

ERp57 does not require interactions with calnexin and calreticulin to promote assembly of class I histocompatibility molecules and it enhances peptide loading independently of its redox activity
ERp57 does not require interactions with calnexin and calreticulin to promote assembly of class I histocompatibility molecules and it enhances peptide loading independently of its redox activity
ERp57 is a thiol oxidoreductase that catalyzes disulfide formation in heavy chains of class I histocompatibility molecules. It also forms a mixed disulfide with tapasin within the class I peptide loading complex, stabilizing the complex and promoting efficient binding of peptides to class I molecules. Since ERp57 associates with the lectin chaperones calnexin and calreticulin, it is thought that ERp57 requires these chaperones to gain access to its substrates. To test this idea, we examined class I biogenesis in cells lacking calnexin or calreticulin or that express an ERp57 mutant that fails to bind to these chaperones. Remarkably, heavy chain disulfides formed at the same rate in these cells as in wild type cells. Moreover, ERp57 formed a mixed disulfide with tapasin and promoted efficient peptide loading in the absence of interactions with calnexin and calreticulin. These findings suggest that ERp57 has the capacity to recognize its substrates directly in addition to being recruited through lectin chaperones. We also found that calreticulin could be recruited into the peptide loading complex in the absence of interactions with both ERp57 and substrate oligosaccharides, demonstrating the importance of its polypeptide binding site in substrate recognition. Finally, by inactivating the redox-active sites of ERp57, we demonstrate that its enzymatic activity is dispensable in stabilizing the peptide loading complex and in supporting efficient peptide loading. Thus, ERp57 appears to play a structural rather than catalytic role within the peptide loading complex.
0021-9258
10160-10173
Zhang, Yinan
1d9125a7-e7e6-4640-9259-d4b67e6622a8
Kozlov, Guennadi
57c5270d-b3fc-48b7-979a-3b97a4fd4ad9
Poscanschi, Cosmin L.
8cf5d3f5-7006-4925-b77b-ea5e6154650a
Brockmeier, Ulf
9b016802-917e-45b0-a66e-e522973e4537
Ireland, Breanna S.
453f7f1e-362e-4e89-bbd6-647509a7910d
Maattanen, Pekka
8089a2fa-8704-4747-901a-5c6a72975dcd
Howe, Chris
b52ae6ae-02cf-45f9-b095-e752ce929db6
Elliott, Tim
16670fa8-c2f9-477a-91df-7c9e5b453e0e
Gehring, Kalle
225d7c91-f769-4c0d-91dd-9933bf868b5f
Williams, David B.
df9861fe-10e3-4cff-af42-6c9ee36a8a2f
Zhang, Yinan
1d9125a7-e7e6-4640-9259-d4b67e6622a8
Kozlov, Guennadi
57c5270d-b3fc-48b7-979a-3b97a4fd4ad9
Poscanschi, Cosmin L.
8cf5d3f5-7006-4925-b77b-ea5e6154650a
Brockmeier, Ulf
9b016802-917e-45b0-a66e-e522973e4537
Ireland, Breanna S.
453f7f1e-362e-4e89-bbd6-647509a7910d
Maattanen, Pekka
8089a2fa-8704-4747-901a-5c6a72975dcd
Howe, Chris
b52ae6ae-02cf-45f9-b095-e752ce929db6
Elliott, Tim
16670fa8-c2f9-477a-91df-7c9e5b453e0e
Gehring, Kalle
225d7c91-f769-4c0d-91dd-9933bf868b5f
Williams, David B.
df9861fe-10e3-4cff-af42-6c9ee36a8a2f

Zhang, Yinan, Kozlov, Guennadi, Poscanschi, Cosmin L., Brockmeier, Ulf, Ireland, Breanna S., Maattanen, Pekka, Howe, Chris, Elliott, Tim, Gehring, Kalle and Williams, David B. (2009) ERp57 does not require interactions with calnexin and calreticulin to promote assembly of class I histocompatibility molecules and it enhances peptide loading independently of its redox activity The Journal of Biological Chemistry, 284, (15), pp. 10160-10173. (doi:10.1074/jbc.M808356200).

Record type: Article

Abstract

ERp57 is a thiol oxidoreductase that catalyzes disulfide formation in heavy chains of class I histocompatibility molecules. It also forms a mixed disulfide with tapasin within the class I peptide loading complex, stabilizing the complex and promoting efficient binding of peptides to class I molecules. Since ERp57 associates with the lectin chaperones calnexin and calreticulin, it is thought that ERp57 requires these chaperones to gain access to its substrates. To test this idea, we examined class I biogenesis in cells lacking calnexin or calreticulin or that express an ERp57 mutant that fails to bind to these chaperones. Remarkably, heavy chain disulfides formed at the same rate in these cells as in wild type cells. Moreover, ERp57 formed a mixed disulfide with tapasin and promoted efficient peptide loading in the absence of interactions with calnexin and calreticulin. These findings suggest that ERp57 has the capacity to recognize its substrates directly in addition to being recruited through lectin chaperones. We also found that calreticulin could be recruited into the peptide loading complex in the absence of interactions with both ERp57 and substrate oligosaccharides, demonstrating the importance of its polypeptide binding site in substrate recognition. Finally, by inactivating the redox-active sites of ERp57, we demonstrate that its enzymatic activity is dispensable in stabilizing the peptide loading complex and in supporting efficient peptide loading. Thus, ERp57 appears to play a structural rather than catalytic role within the peptide loading complex.

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Published date: April 2009

Identifiers

Local EPrints ID: 73380
URI: http://eprints.soton.ac.uk/id/eprint/73380
ISSN: 0021-9258
PURE UUID: 60ff8de3-fc23-4717-be78-74deba4fbb9c
ORCID for Tim Elliott: ORCID iD orcid.org/0000-0003-1097-0222

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Date deposited: 09 Mar 2010
Last modified: 18 Jul 2017 23:50

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Contributors

Author: Yinan Zhang
Author: Guennadi Kozlov
Author: Cosmin L. Poscanschi
Author: Ulf Brockmeier
Author: Breanna S. Ireland
Author: Pekka Maattanen
Author: Chris Howe
Author: Tim Elliott ORCID iD
Author: Kalle Gehring
Author: David B. Williams

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