Glutathione S-transferase omega 1-1 is a target of cytokine release inhibitory drugs and may be responsible for their effect on interleukin-1β posttranslational processing

Abstract

Stimulus-induced posttranslational processing of human monocyte interleukin-1β (IL-1β) is accompanied by major changes to the intracellular ionic environment, activation of caspase-1, and cell death. Certain diarylsulfonylureas inhibit this response, and are designated cytokine release inhibitory drugs (CRIDs). CRIDs arrest activated monocytes so that caspase-1 remains inactive and plasma membrane latency is preserved. Affinity labeling with [14C]CRIDs and affinity chromatography on immobilized CRID were used in seeking potential protein targets of their action. Following treatment of intact human monocytes with an epoxide-bearing [14C]CRID, glutathione S-transferase (GST) Omega 1-1 was identified as a preferred target. Moreover, labeling of this polypeptide correlated with irreversible inhibition of ATP-induced IL-1β posttranslational processing. When extracts of human monocytic cells were chromatographed on a CRID affinity column, GST Omega 1-1 bound selectively to the affinity matrix and was eluted by soluble CRID. Recombinant GST Omega 1-1 readily incorporated [14C]CRID epoxides, but labeling was negated by co-incubation with S-substituted glutathiones or by mutagenesis of the catalytic center Cys32 to alanine. Peptide mapping by high performance liquid chromatography-mass spectrometry also demonstrated that Cys32 was the site of modification. Although S-alkylglutathiones did not arrest ATP-induced IL-1β posttranslational processing or inhibit [14C]CRID incorporation into cell-associated GST Omega 1-1, a glutathione-CRID adduct effectively demonstrated these attributes. Therefore, the ability of CRIDs to arrest stimulus-induced IL-1β posttranslational processing may be attributable to their interaction with GST Omega 1-1.