N–linked glycosylation modulates dimerization of protein disulfide isomerase family A member 2 (PDIA2)

Authors

  • Adam K. Walker,

    1. Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
    2. Florey Institute of Neuroscience and Mental Health, Florey Department of Neuroscience, University of Melbourne, Parkville, Victoria, Australia
    Current affiliation:
    1. Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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  • Kai Ying Soo,

    1. Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
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  • Vita Levina,

    1. Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
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  • Gert H. Talbo,

    1. Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
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  • Julie D. Atkin

    Corresponding author
    1. Florey Institute of Neuroscience and Mental Health, Florey Department of Neuroscience, University of Melbourne, Parkville, Victoria, Australia
    • Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria, Australia
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Correspondence

J. D. Atkin, Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia

Fax: +61 3 9479 2467

Tel: +61 3 9479 5480

E-mail: j.atkin@latrobe.edu.au

Website: http://www.latrobe.edu.au/biochemistry

Abstract

Protein disulfide isomerase (PDI) family members are important enzymes for the correct folding and maturation of proteins that transit or reside in the endoplasmic reticulum (ER). The human PDI family comprises at least 19 members that differ in cell type expression, substrate specificity and post-translational modifications. PDI family A member 2 (PDIA2, previously known as PDIp) has a similar domain structure to prototypical PDI (also known as PDIA1), but the function and post-translational modifications of PDIA2 remain poorly understood. Unlike most PDI family members, PDIA2 contains three predicted N-linked glycosylation sites. By site-directed mutagenesis and enzymatic deglycosylation, we show here that all three Asn residues within the potential N-linked glycosylation sites of human PDIA2 (N127, N284 and N516) are glycosylated in human cells. Furthermore, mutation of N284 to glycosylation-null Gln increases formation of a highly stable disulfide-bonded PDIA2 dimer. Nevertheless, in HeLa cells, both wild-type and N127/284/516Q mutant PDIA2 proteins localize to the ER, but not the ER–Golgi intermediate compartment, suggesting that glycosylation is important for PDIA2 protein–protein interactions but not subcellular localization. Finally, we identified human major histocompatibility complex class 1 antigens (HLA-A,B,C) as potential binding partners of PDIA2, suggesting an involvement for PDIA2 in antigen presentation in addition to its previously described roles in autoimmunity and Parkinson's disease. These results further characterize this poorly defined member of the PDI family.

Structured digital abstract

• Calreticulin and PDIA2 colocalize by fluorescence microscopy (View interaction)

• PDIA2 and PDIA1 colocalize by fluorescence microscopy (View interaction)

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