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Ljudmila Borissenko, Michael Groll
Diversity of proteasomal missions: fine tuning of the immune response
Keywords: antigen, -interferon, MHC class I, Ntn-hydrolase, splicing, ubiquitin
The majority of cellular proteins are degraded by proteasomes within the ubiquitin-proteasome ATP-dependent degradation pathway. Products of proteasomal activity are short peptides which are further hydrolysed by proteases to single amino acid. Some peptides though can escape the degradation, being selected and uptaken by MHC class I molecules for presentation to the immune system on the cell surface. MHC class I molecules are highly selective and specific in terms of ligand binding. Variability of peptides produced in living cells is created by a variety of ways which allow ensuring fast and efficient immune response. Substitution of constitutive proteasomal subunits with immuno-subunits leads to conformational changes in the substrate binding channels, resulting in a modified protein cleavage pattern and consequently, in the generation of new antigenic peptides. The recently discovered event of proteasomal peptide splicing opens new horizons in the understanding of additional functions proteasomes apparently possess. Whether peptide splicing is an occasional side product of the proteasomal activity still needs to be clarified. Both γ-interferon induced immuno-proteasomes and peptide splicing represent two significant events providing increased diversity of antigenic peptides for flexible and fine-tuned immune response.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 2007
Pages: -