The mouse pancreatic βTC3 and βTC6-F7 cell lines were used to characterize the effects of interferon-γ (IFN-γ) on (β-cell phenotype and function. Initially, intracellular and secreted insulin were compared in glucose-stimulated cells over time. A significant reduction in insulin content and secretion was observed on a per-cell basis in glucose-stimulated βTC3 and βTC6-F7 cells after 12 h of exposure to IFN-γ. The steadystate level of pre-proinsulin mRNA expression was not affected by IFN-γ. Thus, we postulate that IFN-γ's inhibitory actions occur after transcription of preproinsulin genes. Time-course analysis of IFN-γ–regulated mRNA expression of the two intra-MHC-encoded subunits of the proteasome (low–molecular-mass polypeptide [Lmp]-2 and Lmp-7) revealed a correlation between their induction and the inhibitory effects of IFN-γ on glucose-stimulated insulin production. Increased expression of Lmp-2 and Lmp-7 mRNA was accompanied by a corresponding induction of LMP2 and LMP7 protein expression. Subsequently, major histocompatibility complex (MHC) class I cell-surface expression was significantly increased in IFN-γ–treated βTC3 and βTC6-F7 cells. Exposure of IFN-γ-treated β-cells to a peptide aldehyde inhibitor of the proteasome (MG132) significantly attenuated MHC class I cell-surface expression but did not prevent the negative effects of IFN-γ on glucose responsiveness. Enhanced expression of the MHC class I antigen processing and presentation pathway and diminished insulin production appear to be distinct pathological alterations in β-cells exposed to the insulitic cytokine IFN-γ.
Interferon-γ Independently Activates the MHC Class I Antigen Processing Pathway and Diminishes Glucose Responsiveness in Pancreatic β-Cell Lines
DMEM, Dulbecco's minimal essential medium; FACS, fluorescence-activated cell sorter; FC, fetal clone II; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HS, horse serum; IFN-γ, interferon-γ; IFN-γr, interferon-γ receptor; LMP, low–molecular-mass polypeptide; MFI, mean fluorescence intensity; MHC, major histocompatibility complex; PBS, phosphate-buffered saline; RT-PCR, reverse transcription–polymerase chain reaction.
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Manuel E Baldeón, David J Neece, Dipankar Nandi, John J Monaco, H Rex Gaskins; Interferon-γ Independently Activates the MHC Class I Antigen Processing Pathway and Diminishes Glucose Responsiveness in Pancreatic β-Cell Lines. Diabetes 1 May 1997; 46 (5): 770–778. https://doi.org/10.2337/diab.46.5.770
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