Interferon (IFN) gamma induces replacements of the proteasomal subunits X and Y by LMP7 and LMP2, respectively, resulting in an alteration of the proteolytic specificity. We found a third pair of proteasome subunits expressed reciprocally in response to IFN-gamma. Molecular cloning of a cDNA encoding one subunit designated as Z, downregulated by IFN-gamma, showed that it is a novel proteasomal subunit with high homology to MECL1, which is markedly induced by IFN-gamma. Thus, IFN-gamma induces subunit replacements of not only X and Y by LMP7 and LMP2, respectively, but also of Z by MECL1, producing proteasomes responsible for immunological processing of endogenous antigens. When processed from their precursors, three pairs of the 10 homologous, but distinct, beta-type subunits of eukaryotic proteasomes, that is, X/LMP7, Y/LMP2, and Z/MECL1, have an NH2-terminal threonine residue, assumed to be part of a catalytic center. These findings suggest that the altered molecular organization of the proteasome induced by IFN-gamma may be responsible for acquisition of its functional change.
Newly identified pair of proteasomal subunits regulated reciprocally by interferon gamma.
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H Hisamatsu, N Shimbara, Y Saito, P Kristensen, K B Hendil, T Fujiwara, E Takahashi, N Tanahashi, T Tamura, A Ichihara, K Tanaka; Newly identified pair of proteasomal subunits regulated reciprocally by interferon gamma.. J Exp Med 1 April 1996; 183 (4): 1807–1816. doi: https://doi.org/10.1084/jem.183.4.1807
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