Gastrin-responsiveness of the <i>PAI-2</i> and <i>Reg1</i> promoters following PSMA5 knockdown.

<p>Response of the <i>PAI-2</i> (left panel) and <i>Reg1</i> (right panel) promoters to gastrin (G17, 2×10⁻⁹ M) in AGS cells transfected with PSMA5 siRNA (KD) or scrambled RNA (Scr). Open bars, unstimulated cells; closed bars, cells stimulated with gastrin (G17, 2×10⁻⁹ M) for 6 h. Values are mean ± SEM, n = 4–6.</p

Knockdown of proteasome subunits in AGS-GR cells.

<p>Representative western blots of PSMB1 (left panel) and PSMA5 (right panel), in AGS-GR cells 72 hours after transfection with validated siRNA or scrambled control. Left lanes, scrambled control (Scr), right panels, knockdown (KD). Blots were re-probed for HSP90.</p

Gastrin-responsiveness of the <i>PAI-2</i> and <i>Reg1</i> promoters following PSMB1 knockdown.

<p>Response of the <i>PAI-2</i> (left panel) and <i>Reg1</i> (right panel) promoters to gastrin (G17, 2×10⁻⁹ M) in AGS cells transfected with PSMB1 siRNA (KD) or scrambled RNA (Scr). Open bars, unstimulated cells; closed bars, cells stimulated with gastrin (G17, 2×10⁻⁹ M) for 6 h. Values are mean ± SEM, n = 5–9. ***, p<0.001; *, p<0.05.</p

Nuclear and cytoplasmic abundance of proteasome subunits in gastrin-stimulated AGS-GR cells.

<p>A, representative western blot of proteasome subunits in cytoplasmic (left panel) and nuclear (right panel) extracts of AGS-GR cells, 0, 60, 90 or 120 minutes after stimulation with gastrin (G17, 2×10⁻⁹ M). Blots were re-probed with HSP90 (cytoplasmic) or lamin (nuclear). B, signals at 0 (control) and 120 (gastrin) minutes of gastrin stimulation were quantified by densitometry and normalized to HSP90 or lamin. Nuclear to cytoplasmic ratios at 0 min ( = 1.0) versus 120 min are shown for PSMB1, PSMA5 and PSMC1. ***, p<0.001; n = 7, ANOVA.</p

Detection of Drug Bioactivation in Vivo: Mechanism of Nevirapine–Albumin Conjugate Formation in Patients

The non-nucleoside reverse transcriptase inhibitor nevirapine (NVP) is widely used for the treatment of human immunodeficiency virus type 1 (HIV-1), particularly in developing countries. Despite its therapeutic benefits, NVP has been associated with skin and liver injury in exposed patients. Although the mechanism of the tissue injury is not yet clear, it has been suggested that reactive metabolites of NVP may be involved. The detection of NVP mercapturate in the urine of patients undergoing standard antiretroviral chemotherapy indicates that NVP undergoes bioactivation in vivo. However, covalent binding of drug to protein in patients remains to be determined. In this study, we investigate the chemical basis of NVP protein adduct formation by using human serum albumin (HSA) and glutathione <i>S</i>-transferase pi (GSTP) as model proteins in vitro. In addition, HSA was isolated from serum samples of HIV-1 patients undergoing NVP therapy to measure NVP haptenation. Mass spectrometric analysis of 12-sulfoxyl-NVP-treated HSA revealed that the drug bound selectively to histidine (His146, His242, and His338) and a cysteine residue (Cys34). The reaction proceeds most likely by a concerted elimination–addition mechanism. This pathway was further confirmed by the observation of NVP-modified Cys47 in GSTP. Importantly, the same adduct (His146) was detected in HSA isolated from the blood of patients receiving NVP, providing direct evidence that NVP modifies protein in vivo, via the formation of a reactive metabolite