Deglycosylation of Fas receptor and chronic morphine treatment up-regulate high molecular mass Fas aggregates in rat brain

Abstract

[eng] This study was designed to immunodetect and characterize Fas receptor aggregates (oligomerization) in the brain and to assess its possible modulation in opiate addiction. High molecular mass, sodium dodecyl sulfate (SDS)- and β-mercaptoethanol-resistant Fas aggregates (∼110/120 and ∼203 kDa specific peptides) were immunodetected with a cytoplasmic domain-specific antibody in brain tissue (rat, mouse and human) and SH-SY5Y cells by Western blot analysis. Preincubation of rat cortical membranes with N-ethylmaleimide (NEM; 1 mM for 1 h at 37 °C) reduced the immunodensity of ∼203 kDa Fas aggregates (51%) and increased that of 35 kDa native Fas (172%) and 51/48 kDa glycosylated Fas (47%), indicating that disulfide bonds are involved in Fas dimerization. Enzymatic N-deglycosylation of Fas receptor increased the content of Fas aggregates (∼110/120 kDa: five- to sixfold, and ∼203 kDa: two- to threefold), suggesting that Fas glycosylation is involved in regulating receptor dimerization. Chronic (10-100 mg/kg for 5 days), but not acute (30 mg/kg for 2 h), treatment with morphine (a μ-opioid peptide receptor agonist) induced up-regulation of Fas aggregates in the brain (∼110/120 kDa: 39%, and ∼203 kDa: 89%). The acute and/or chronic treatments with δ- and κ-opioid peptide receptor agonists and with a σ1-receptor agonist did not readily alter the content of Fas aggregates in the rat brain. The results indicate that Fas aggregates are natively expressed in the brain and that its density is regulated by the state of Fas glycosylation. These forms of Fas (receptor homodimerization) are functionally relevant because they were up-regulated in the brain of morphine-dependent rats.