Molecular cloning of the cDNA encoding a novel protein disulfide isomerase‐related protein (PDIR)

Abstract

We isolated the cDNA of a novel protein disulfide isomerase (PDI)-related protein, designated PDIR, from a human placental cDNA library. Deduced from its nucleotide sequence, PDIR has the three CXXC-like motifs (Cys-Ser-MetCys, Cys-Giy-His-Cys and Cys-Pro-His-Cys), which are found in proteins within the PDI superfamily and are responsible for oxidoreductase activity. PD|R has a hydrophobic stretch at its amino terminus, which may serve as a signal sequence, and the putative endoplasmic reticulum (ER) retention signal 'Lys-GluGlu-Leu' at its carboxy terminus, indicating that PDIR is an ER resident protein. Northern blots showed that PDIR is preferentially expressed in cells actively secreting proteins and that the expression of PDIR is stress-inducible. These results suggested that PDIR has oxidoreductase activity of disulfide bonds against polypeptides and that it acts as a catalyst of protein folding in the lumen of the ER.Key words: Protein disulfide isomerase; CXXC motif; Endoplasmic reticulum; Stress response; Protein folding ence of the CGHC sequence in a variety of proteins, such as P5, ERp60 and ERp72, in mammalian tissues led to their inclusion in the PDI superfamily [6]. While P5 and ERp60 have two CGHC sequences like PDI, ERp72 has three. P5 and ERp72 catalyze the reduction, oxidation and isomerization of disulfide-bonded proteins in vitro [7,8]. However, they are less active in these reactions than PDI, indicating that P5 and ERp72 have functions other than those involved in disulfide bond formation. In addition to catalyzing protein folding, PDI functions as a fl-subunit of prolyl-4-hydroxylase [9], a component of a triglyceride transfer protein [10] and a triiodothyronine (T3)-binding protein [11]. The relationship between the motif and the function of these members of the PDI superfamily remains unclear. Identifying other members of this superfamily should lead to further understanding of the precise functions and the molecular evolution of proteins with the CXXC motif.Here we report the isolation of the cDNA clone encoding a novel human PDl-related protein (PDIR) with three CXXC motifs and discuss the possible cellular role of this member of the PDI superfamily.

Protective Roles of NF-κB for Chromium(VI)-induced Cytotoxicity Is Revealed by Expression of IκB Kinase-β Mutant

“…A limited amount of ROS can be buffered in cells by glutathione and thioredoxin (54,55). This raises the possibility that the increased vulnerability of IKK␤-KM-expressing cells to Cr(VI) may be partially due to a reduced generation of oxidative buffering molecules.…”

“…Indeed, the gene expression profiling study showed that the lowest expressed gene in IKK␤-KM cells, compared with that in IKK␤ cells, is the gene encoding proteindisulfide isomerase-related protein (Fig. 5), an important member of the thioredoxin superfamily participating in redox regulation (55). Lowered oxidative buffering could lead to oxidative stress.…”

The protein disulphide-isomerase family: unravelling a string of folds

“…Although little is known about the function of PDIR [140], its domain structure (b-a o -a-ah) is interesting. Each a-type domain has a different active-site sequence : -Cys-Ser-Met-Cys-, -CysGly-His-Cys-and -Cys-Pro-His-Cys-.…”

Thyroid Hormone-dependent Gene Expression Program for Xenopus Neural Development

“…The 300-bp xh20 cDNA fragment exhibits 68.5% identity to human protein disulfide isomerase (PDI; Ref. 40) over a 178-nucleotide span covering the first thioredoxin-like domain of human PDI. Protein disulfide isomerases are multifunctional proteins; a major role is to assist in the folding of proteins containing disulfide bonds, and significantly, PDIs are also cellular T 3 binding proteins (41).…”