cDNA cloning of rat proteasome subunit RC1, a homologue of RING10 located in the human MHC class II region

AbstractThe nucleotide sequence of a cDNA that encodes a new subunit, named RC1, of rat proteasomes (multicatalytic proteinase complexes) has been determined. The polypeptide predicted from the open reading frame consisted of 208 amino acid residues with a calculated molecular mass of 23,130, which is consistent with the size obtained by electrophoretic analysis of purified RC1. The partial amino acid sequences of several fragments of RC1, obtained by protein chemical analyses, were found to be in excellent accordance with those deduced from the cDNA sequence. Surprisingly, the overall structure of RC1 was found to be almost identical to that of recently isolated RING10, whose gene is located in the class II region of the human MHC gene cluster. This finding suggests that RC1 is a homologue of human RING10, supporting the proposal that proteasomes are involved in the antigen processing pathway

The effects of insulin-induced hypoglycemia on the human SEP (Somatosensory Evoked Potential) and EEG

The effects of insulin-induced hypoglycemia on the central nervous system were studied by somatosensory evoked potential (SEP), with 8 schizophrenic patients (31~47 y. o.), during the 'kleine Insulinbehandlung'. In each of three experimental session on different days, human regular insulin was injected subcutaneously to the patients, whose consciousness level was lowered to the stage of somnolence, and recovered by intake of a glucose solution (100 g). EEG containig SEPs evoked by electric simuli was derived from the two derivations (1 st ch: C3'→A1+2, 4 th ch: C3'→F3'). In the experimental session, EEG containing SEPs was recorded before and 20, 40, 60, 80, 100 and 120 min after the injection of insulin, and 20 min after intake of glucose. Consecutive changes of group mean SEP were studied. Individual SEPs were subjected to the component analysis, and to the statistical assessment together with EEG power%. As a result, the middle and long latency components of SEP significantly prolonged in latency and significantly decreased in amplitude 60 min after the injection of insulin. On the other hand, the short latency components of SEP significantly prolonged in latency 100~120 min after the injection of insulin. These results suggested that the activity of cerebral cortex was inhibited, but subcortex was not affected to hypoglycemia in the early stage. In the results of the present study with SEP, the noradrenergic activities in the early stage of hypoglycemia, observed with AEP previously reported, were not confirmed

Replacement of proteasome subunits X and Y by LMP7 and LMP2 induced by interferon-γ for acquirement of the functional diversity responsible for antigen processing

AbstractProteasomes catalyze the non-lysosomal, ATP-dependent selective breakdown of ubiquitinated proteins and are thought to be responsible for MHC class I-restricted antigen presentation. Recently, we reported that gamma interferon (IFN-γ) induced not only marked synthesis of the MHC-encoded proteasome subunits LMP2 and LMP7, but also almost complete loss of two unidentified proteasome subunits tentatively designated as X and Y in various human cells. Here, we show that subunit X is a new proteasomal subunit highly homologous to LMP7, and that subunit Y is identical to the LMP2-related proteasomal subunit delta. Thus, IFN-γ appears to induce subunit replacements of X and Y by LMP7 and LMP2, respectively, producing 'immuno-proteasomes' with the functional diversity responsible for processing of endogenous antigens