The components of the AhR-molecular chaperone complex differ depending on whether the ligands are toxic or non-toxic.

The aryl hydrocarbon receptor (AhR) forms a complex with the HSP90-XAP2-p23 molecular chaperone when the cells are exposed to toxic compounds. Recently, 1,4-dihydroxy-2-naphthoic acid (DHNA) was reported to be an AhR ligand. Here, we investigated the components of the molecular chaperone complex when DHNA binds to AhR. Proteins eluted from the 3-Methylcolanthrene-affinity column were AhR-HSP90-XAP2-p23 complex. The AhR-molecular chaperone complex did not contain p23 in the eluents from the DHNA-affinity column. In 3-MC-treated cells, AhR formed a complex with HSP90-XAP2-p23 and nuclear translocation occurred within 30 min, while in DHNA-treated cells, AhR formed a complex with AhR-HSP90-XAP2, and translocation was slow from 60 min. Thus, the AhR activation mechanism may differ when DHNA is the ligand compared to toxic ligands.

A rapid and precise method for measuring plasma apoE-rich HDL using polyethylene glycol and cation-exchange chromatography: a pilot study on the clinical significance of apoE-rich HDL measurements.

BACKGROUND: High-density lipoprotein (HDL) containing apolipoprotein E (apoE-rich HDL) represents only a small portion of plasma HDL. Reliable methods for determining and isolating apoE-rich HDL have not been well studied. METHODS: We established a novel analytical method for apoE-rich HDL using polyethylene glycol and a cation-exchange column (PEG-column method). Furthermore, we examined biochemical correlates of apoE-rich HDL-cholesterol (HDL-C) in 36 patients who underwent coronary computed tomographic angiography. RESULTS: Our PEG-column method demonstrated high reproducibility (coefficient of variation <3.52%) and linearity up to 15mg/dl for apoE-rich HDL-C concentrations. Isolated apoE-rich HDL exhibited a larger diameter (14.8nm) than apoE-poor HDL (10.8nm) and contained both apoE and apoA-I. ApoE-rich HDL-C concentrations correlated significantly with triglycerides (rs=-0.646), LDL size (rs=0.472), adiponectin (rs=0.476), and other lipoprotein components. No significant correlation was obtained with the coronary calcium score. Multiple regression analysis revealed that plasma triglycerides and adiponectin concentrations remained significant independent predictors of apoE-rich (adjusted R2=0.486) but not apoE-poor HDL-C. CONCLUSIONS: The PEG-column method demonstrated, to various degrees, significant correlations between HDL subfractions and several lipid-related biomarkers involved in an atherogenic lipoprotein profile. Our separation technique for apoE-rich HDL is useful to clarify the role of apoE-rich HDL in atherosclerosis.

High dose of antibiotic colistin induces oligomerization of molecular chaperone HSP90.

Colistin is an antimicrobial cationic peptide that belongs to the polymyxin family. Colistin was clinically used for the treatment of gram-negative infections but fell out of favour because of its significant side effects including neurotoxicity and nephrotoxicity. More recently, colistin has been regarded as one of the important options for nosocomial infections caused by multidrug resistant bacteria. Mechanisms of both the side effect onset of the drug and the side effect reduction are yet to be elucidated. In this study, we identified the specific binding protein of colistin using an affinity column chromatography. Colistin binds to the molecular chaperone HSP90. Although colistin slightly suppressed the chaperone activity of HSP90, there are no effects on the ATPase activity for a low concentration of colistin. Interestingly, colistin-induced aggregation of HSP90 via the N-domain. As for the cell viability of the SHSY5Y cell, the cell viability decreased to approximately 80% by the colistin 300 µM. However, the cell viability recovered to approximately 100% by adding ATP dosage. The same result was obtained by dot blot assay using anti-HSP90 antibody. Our results may help to understand the side effect mechanism of colistin.

Geranylgeranylacetone selectively binds to the HSP70 of Helicobacter pylori and alters its coccoid morphology.

Geranylgeranylacetone (GGA) is used to treat patients suffering from peptic ulcers and gastritis. We examined the effect of GGA on Helicobacter pylori, which is a causative factor of gastrointestinal diseases. Previously, we have reported that GGA binds specifically to the molecular chaperone HSP70. In this paper, we report that GGA bounds to H. pylori HSP70 (product of the DnaK gene) with 26-times higher affinity than to human HSP70, and induced large conformational changes as observed from surface plasmon resonance and circular dichroism. Binding of GGA suppressed the activity of the H. pylori chaperone. GGA also altered several characteristics of H. pylori cells. GGA-treated cells elicited enhanced interleukin-8 production by gastric cancer cell lines and potentiated susceptibility to complement as compared to untreated cells. GGA also caused morphological alterations in H. pylori as reflected in fewer coccoid-like cells, suggesting that GGA converts H. pylori to an actively dividing, spiral state (vegetative form) from a non-growing, coccoid state. This morphological conversion by GGA resulted in accelerated growth of H. pylori. These results suggest a model in which GGA sensitizes H. pylori to antibiotic treatment by converting the cells to an actively growing state.