ABSTRACT The major enzyme system catalysing the degradation of intracellular proteins is the proteasome system. A central inner chamber of the cylinder-shaped 20 S proteasome contains the active site, formed by N-terminal threonine residues. The 20 S proteasomes are extremely inefficient in degrading folded protein substrates and therefore one or two multisubunit 19 S regulatory particles bind to one or both ends of the 20 S proteasome cylinder, forming 26 S and 30 S proteasomes respectively. These regulatory complexes are able to bind proteins marked as proteasome substrates by prior conjugation with polyubiquitin chains, and initiate their unfolding and translocation into the proteolytic chamber of the 20 S proteasome, where they are broken down into peptides of 3-25 amino acids. The polyubiquitin tag is removed from the substrate protein by the deubiquitinating activity of the 19 S regulator complex. Under conditions of an intensified immune response, many eukaryotic cells adapt by replacing standard 20 S proteasomes with immuno-proteasomes and/or generating the proteasome activator complex, PA28. Both of these adaptations change the protein-breakdown process for optimized generation of antigenic peptide epitopes that are presented by the class I MHCs. Hybrid proteasomes (19 S regulator-20 S proteasome-PA28) may have a special function during the immune response. The functions of other proteasome accessory complexes, such as PA200 and PI31 are still under investigation.
- SourceAvailable from: Zhentao Lei
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- "We treated the cells with MG132, a specific inhibitor of the proteasome, and observed accumulation of CYP6N3, strongly suggesting proteosomal degradation of CYP6N3. The 26S proteasome is a large multiprotein complex comprised of a 20S proteolytic subunit that is capped at both ends by 19S regulatory subunits , . Recent studies revealed that the core catalytic complex of the eukaryotic 20S proteasome has at least five different peptidase activities, and the functions of the 19S regulatory complex are recognition of the polyubiquitinated substrate, release of the polyubiquitin chain, and translocation of the unfolded substrate towards the catalytic sites of the 20S proteasome , . "
ABSTRACT: Many diseases are transmitted by mosquitoes, including malaria, dengue fever, yellow fever, filariasis, and West Nile fever. Chemical control plays a major role in managing mosquito-borne diseases. However, excessive and continuous application of insecticides has caused the development of insecticide resistance in many species including mosquito, and this has become the major obstacle to controlling mosquito-borne diseases. Insecticide resistance is the result of complex polygenic inheritance, and the mechanisms are not well understood. Ribosomal protein RPS29 was found to be associated with DM resistance in our previous study. In this study, we aim to further investigate the involvement of RPS29 in deltamethrin resistance. In this study, tandem affinity purification was used to identify proteins that can interact with RPS29. Among the candidate proteins, CYP6N3, a member of the CYP450 superfamily, was identified, and binding to RPS29 was confirmed in vitro and in vivo by GST pull-down and immunofluorescence. CCK-8 assay was used to investigate the RPS29-CTP6N3 interaction in relation to DM resistance. CYP6N3 overexpression significantly enhanced DM resistance and insect cell viability, but this was reversed by RPS29 overexpression. Western blot was used to study the mechanism of interaction between RPS29 and CYP6N3. RPS29 increases CYP6N3 protein degradation through the proteasome. These observations indicate that CYP6N3, a novel RPS29-interacting partner, could stimulate deltamethrin resistance in mosquito cells and RPS29 overexpression targeted CYP6N3 for proteosomal degradation, abrogating the CYP6N3-associated resistence to deltamethrin. Our findings provide a novel mechanism associated with CYP450s mediated DM resistance.PLoS ONE 04/2014; 9(4):e94611. DOI:10.1371/journal.pone.0094611 · 3.23 Impact Factor
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ABSTRACT: The proteasome is the main proteolytic system implicated in the removal of oxidatively damaged proteins, general turnover of intracellular proteins and targeted degradation of proteins that have been marked by poly-ubiquitination. Impairment of proteasome function has been associated with cellular aging in a variety of tissues and cell types including lymphocytes, and is believed to contribute to the age-related accumulation of oxidized proteins due to their decreased elimination by the proteasomal pathway. This chapter first summarizes the most relevant features of the proteasomal system and then expands on the current knowledge on the impact of aging on proteasome structure and function, taking in account the fate of proteasome upon oxidative stress situations. Finally, the possible implication of age-related alterations of the proteasomal system in the process of immunosenescence is presented.
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ABSTRACT: This paper proposes the image rejection architecture for broadband direct conversion receiver using Weaver image rejection method. In proposed architecture, the first local oscillator (LO) frequency selected in the center of desired signal bandwidth makes the upper and lower signal band for the first LO, interfering each other. However, it is possible to output those signals separately near the second LO frequency after the second mixer. This architecture also enables to suppress the secondary image more than conventional architecture by downconverting signal near DC. Basic performance of the proposed direct conversion architecture is confirmed by a prototype model of receiver front-end.Microwave Symposium Digest, 2004 IEEE MTT-S International; 07/2004