Arabidopsis protein disulfide isomerase-8 is a type I endoplasmic reticulum transmembrane protein with thiol-disulfide oxidase activity

BACKGROUND: In eukaryotes, classical protein disulfide isomerases (PDIs) facilitate the oxidative folding of nascent secretory proteins in the endoplasmic reticulum by catalyzing the formation, breakage, and rearrangement of disulfide bonds. Terrestrial plants encode six structurally distinct subfamilies of PDIs. The novel PDI-B subfamily is unique to terrestrial plants, and in Arabidopsis is represented by a single member, PDI8. Unlike classical PDIs, which lack transmembrane domains (TMDs), PDI8 is unique in that it has a C-terminal TMD and a single N-terminal thioredoxin domain (instead of two). No PDI8 isoforms have been experimentally characterized to date. Here we describe the characterization of the membrane orientation, expression, sub-cellular localization, and biochemical function of this novel member of the PDI family.

RESULTS: Histochemical staining of plants harboring a PDI8 promoter:β-glucuronidase (GUS) fusion revealed that the PDI8 promoter is highly active in young, expanding leaves, the guard cells of cotyledons, and in the vasculature of several organs, including roots, leaves, cotyledons, and flowers. Immunoelectron microscopy studies using a PDI8-specific antibody on root and shoot apical cells revealed that PDI8 localizes to the endoplasmic reticulum (ER). Transient expression of two PDI8 fusions to green fluorescent protein (spGFP-PDI8 and PDI8-GFP-KKED) in leaf mesophyll protoplasts also resulted in labeling of the ER. Protease-protection immunoblot analysis indicated that PDI8 is a type I membrane protein, with its catalytic domain facing the ER lumen. The lumenal portion of PDI8 was able to functionally complement the loss of the prokaryotic protein foldase, disulfide oxidase (DsbA), as demonstrated by the reconstitution of periplasmic alkaline phosphatase in Escherichia coli.

CONCLUSION: The results indicate that PDI8 is a type I transmembrane protein with its catalytic domain facing the lumen of the ER and functions in the oxidation of cysteines to produce disulfide bonds. It likely plays a role in folding newly-synthesized secretory proteins as they translocate across the ER membrane into the lumen. These foundational results open the door to identifying the substrates of PDI8 to enable a more thorough understanding of its function in plants.

Medienart:

E-Artikel

Erscheinungsjahr:

2016

Erschienen:

2016

Enthalten in:

Zur Gesamtaufnahme - volume:16

Enthalten in:

BMC plant biology - 16(2016), 1 vom: 22. Aug., Seite 181

Sprache:

Englisch

Beteiligte Personen:

Yuen, Christen Y L [VerfasserIn]
Shek, Roger [VerfasserIn]
Kang, Byung-Ho [VerfasserIn]
Matsumoto, Kristie [VerfasserIn]
Cho, Eun Ju [VerfasserIn]
Christopher, David A [VerfasserIn]

Links:

Volltext

Themen:

Arabidopsis Proteins
Cysteine
EC 5.3.4.1
Endoplasmic reticulum
Journal Article
K848JZ4886
Protein Disulfide-Isomerases
Protein disulfide isomerase
Protein folding
Research Support, U.S. Gov't, Non-P.H.S.
Sulfhydryl Compounds
Transmembrane

Anmerkungen:

Date Completed 15.08.2017

Date Revised 13.11.2018

published: Electronic

Citation Status MEDLINE

doi:

10.1186/s12870-016-0869-2

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM263650596