Hydroxylated Polychlorinated Biphenyls (PCBs) Interact with Protein Disulfide Isomerase and Inhibit Its Activity

Abstract

Protein disulfide isomerase (PDI) is a catalyst of isomerization of substrate protein intra- and extra-molecular disulfide bridges and also has 3,3',5-triiodo-l-thyronine (T(3))-binding activity and molecular chaperone-like activity. We previously found that halogenated derivatives of bisphenol A as well as bisphenol A itself bind to PDI and thereby suppress the oxidative refolding of reduced RNaseA by PDI. Polychlorinated biphenyls (PCBs) are environmental endocrine-disrupting chemicals that cause various abnormalities in many organs such as the central nervous system. PCBs are metabolized to hydroxylated compounds (HO-PCBs) in humans and other animals, and HO-PCBs gain toxicity by metabolism. In the present study, 2',3,3',4',5'-pentachlorobiphenyl (penCB), 2',3,3',5,5',6'-hexachlorobiphenyl (hexCB), and their 4-hydroxylated metabolites (HO-penCB and HO-hexCB, respectively) were used to examine whether they interact with PDI and inhibit its activity. HO-penCB and HO-hexCB markedly inhibited the binding of T(3) to PDI. However, nonhydroxylated PCBs did not show any interaction with PDI. The effects of PCBs and HO-PCBs on PDI activity were also investigated using an RNaseA refolding assay. Both HO-PCBs inhibited the oxidative refolding of reduced RNaseA by PDI. We also assessed the effects of HO-PCBs and PCBs on the chaperone activity of PDI, which was measured by a thermal aggregation assay, and found that neither HO-PCBs nor PCBs have significant inhibitory or promoting effects. These findings suggest that the metabolites of PCBs have the potential to cause defective protein folding via PDI.

Biological Functions of Protein Disulfide Isomerase as a Target of Phenolic Endocrine-disrupting Chemicals

“…It is suspected that T 3 , BPA, and hydroxylated PCBs share identical binding sites. 99) The manner in which HO-PCBs inhibit the isomerase activity of PDI is the same as that for T 3 or BPA binding. HO-pentaCB but not HO-hexaCB inhibited the isomerase activity of PDI although both compounds bind to PDI, suggesting that substituents at the 3,5-positions of the phenyl ring, besides the 4-hydroxyl …”

Effects of Polybrominated Diphenyl Ethers (PBDEs) and Their Derivatives on Protein Disulfide Isomerase Activity and Growth Hormone Release of GH3 Cells

“…21,22 Moreover, it was demonstrated that hydroxylated polychlorinated biphenyls (OH-PCBs) interact with PDI and inhibit its activity. 23 Compounds with a halogenated substitution at the ortho position of phenol such as OH-PCB and T 3 have stronger binding affinity to PDI, which confers on these compounds stronger inhibitory effects on isomerase activity than that of BPA. 22,23 Moreover, we previously investigated the effects of BPA on the T 3 -evoked response of rat pituitary tumor (GH3) cells.…”

“…23 Compounds with a halogenated substitution at the ortho position of phenol such as OH-PCB and T 3 have stronger binding affinity to PDI, which confers on these compounds stronger inhibitory effects on isomerase activity than that of BPA. 22,23 Moreover, we previously investigated the effects of BPA on the T 3 -evoked response of rat pituitary tumor (GH3) cells. 24 In GH3 cells, the production of growth hormone (GH) is stimulated by T 3 via the thyroid hormone receptor (TR).…”

Fluorescence probe techniques to study the interaction between hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and protein disulfide isomerase (PDI)

“…However, some research teams have reported that bisphenol A (BPA), hydroxylated polychlorinated biphenyls (PCB), PBDEs and their derivatives, as well as a series of environmental phenolic compounds, specically inhibit T3 binding to PDI competitively and suppress the oxidative refolding of the reduced RNase A by PDI. [25][26][27] The competitive replacement of T3 by the targets from PDI may result in decreasing the enzyme activity, erroneous intracellular protein folding, and destroying the physiological functions of PDI. Therefore, the reaction has caused widespread concern, and there are some research teams paying a lot of attention to it.…”

“…Therefore, the reaction has caused widespread concern, and there are some research teams paying a lot of attention to it. 25,26 However, the method they used was competitive radioligand binding assay. By using 125 I labeled T3 and 4 H labeled E2 as the radioactive tracers in the assay, they revealed that BPA, hydroxylated polychlorinated biphenyls (OH-PCBs), T3 and E2 share the same binding site on PDI.…”