Endoplasmic Reticulum Degradation–Enhancing α-Mannosidase–like Protein 1 targets misfolded HLA–B27 dimers for Endoplasmic Reticulum–Associated Degradation
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Objective. HLA-B27 forms misfolded heavy chain dimers, which may predispose individuals to inflammatory arthritis by inducing endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). We wanted to define the role of the UPR induced ER associated degradation (ERAD) pathway in the disposal of HLA-B27 dimeric conformers. Methods. HeLa cell lines expressing only two copies of a carboxy terminally Sv5 tagged HLA-B27 were generated. The ER stress induced EDEM1 protein was over expressed by transfection and dimer levels monitored by immunoblotting. EDEM1, the UPR associated transcription factor XBP-1, the E3 ubiquitin ligase HRD1, the degradation associated derlin 1 and 2 proteins were inhibited by either short hairpin RNA or dominant negative mutants. The UPR associated ERAD of HLA-B27 was confirmed using ER stress inducing pharamacological agents in kinetic and pulse chase assays. Results. We demonstrate that UPR induced machinery can target HLA-B27 dimers, and that dimer formation can be controlled by alterations to expression levels of components of the UPR induced ERAD pathway. HLA-B27 dimers and misfolded MHC class I monomeric molecules were detected bound to EDEM1, with overexpression of EDEM1 inhibiting HLA-B27 dimer formation. EDEM1 inhibition resulted in upregulation of HLA-B27 dimers, whilst UPR induced ERAD of dimers was prevented in the absence of EDEM1. HLA-B27 dimer formation was also enhanced in the absence of XBP-1, HRD1 and derlin1/2. Conclusion. The UPR ERAD pathway as described here can dispose of HLA-B27 dimers and presents a potential novel therapeutic target for the modulation of HLA-B27 associated inflammatory disease. © 2014 American College of Rheumatology.
Guiliano , D B , Fussell , H , Lenart , I , Tsao , E , Nesbeth , D , Fletcher , A J , Campbell , E C , Yousaf , N , Williams , S , Santos , S , Cameron , A , Towers , G J , Kellam , P , Hebert , D N , Gould , K , Powis , S J & Antoniou , A N 2014 , ' Endoplasmic Reticulum Degradation–Enhancing α-Mannosidase–like Protein 1 targets misfolded HLA–B27 dimers for Endoplasmic Reticulum–Associated Degradation ' Arthritis & Rheumatology , vol 66 , no. 11 , pp. 2976-2988 . DOI: 10.1002/art.38809
Arthritis & Rheumatology
© 2014. American College of Rheumatology. Published by Wiley Periodicals, Inc. This is the accepted version of the following article: Endoplasmic Reticulum Degradation–Enhancing α-Mannosidase–like Protein 1 Targets Misfolded HLA–B27 Dimers for Endoplasmic Reticulum–Associated Degradation, Guiliano, D. B., Fussell, H., Lenart, I., Tsao, E., Nesbeth, D., Fletcher, A. J., Campbell, E. C., Yousaf, N., Williams, S., Santos, S., Cameron, A., Towers, G. J., Kellam, P., Hebert, D. N., Gould, K., Powis, S. J. & Antoniou, A. N. 6 Aug 2014 In : Arthritis & Rheumatology (Hoboken, N.J.)., which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/art.38809/abstract
H.F is supported by an Arthritis Research (AR) UK project grant (17222). I.L is supported by ARUK studentship (17868) A.N.A is supported by an ARUK Fellowship (15293). E.C.C is supported by the Chief Scientist Office of the Scottish Government. D.N.H. is supported by US Public Health grant GM086874. G.J.T. is supported by a Wellcome Trust Senior Biomedical Fellowship.
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