Inhibition of Proteasome Activity Induces Concerted Expression of Proteasome Genes and de Novo Formation of Mammalian Proteasomes

Abstract

The 26 S proteasome is a high molecular mass proteinase complex that is built by at least 32 different protein subunits. Such protease complexes in bacteria and yeast are systems that undergo a highly sophisticated network of gene expression regulation. However, regulation of mammalian proteasome gene expression has been neglected so far as a possible control mechanism for the amount of proteasomes in the cell. Here, we show that treatment of cells with proteasome inhibitors and the concomitant impairment of proteasomal enzyme activity induce a transient and concerted up-regulation of all mammalian 26 S proteasome subunit mRNAs. Proteasome inhibition in combination with inhibition of transcription revealed that the observed up-regulation is mediated by coordinated transcriptional activation of the proteasome genes and not by post-transcriptional events. Our experiments also demonstrate that inhibitor-induced proteasome gene activation results in enhanced de novo protein synthesis of all subunits and in increased de novo formation of proteasomes. This phenomenon is accompanied by enhanced expression of the proteasome maturation factor POMP. Thus, our experiments present the first evidence that the amount of proteasomes in mammalia is regulated at the transcriptional level and that there exists an autoregulatory feedback mechanism that allows the compensation of reduced proteasome activity.

z-Leucinyl-Leucinyl-Norleucinal Induces Apoptosis of Human Glioblastoma Tumor–Initiating Cells by Proteasome Inhibition and Mitotic Arrest Response

“…The upregulation of the expression of some genes coding for proteasomal proteins, as a consequence of the inhibition of proteasome activity by both RNA interference and small molecules such as GM132, is a well-established phenomenon observed in several organisms including mammals (48)(49)(50)(51). Therefore, the data reported here, which show the ability of LLNle to inhibit the proteasome activity and concomitantly to upregulate the expression of genes coding for several proteasome subunits, are in line with these previous studies.…”

“…Therefore, we treated PT1 GBM TICs with lactacystin for 48 hours and found that this compound was indeed active with a IC 50 of 145.8 μmol/L (Fig. 9).…”

Analysis of changes in the proteome of HL-60 promyeloid leukemia cells induced by the proteasome inhibitor PSI

“…Multiple myeloma cells have thus been reported to upregulate various proteasomal subunits in response to bortezomib treatment [59], which in conjunction with an altered subunit composition may result in increased overall catabolic activity by the ubiquitin proteasome pathway. Similar observations were also made in Burkitt lymphoma [62] and in vascular smooth muscle cells [63]. In addition upregulation of heat shock proteins is a characteristic feature of tumor cells that have acquired a drug resistant phenotype and Chuahan et al indeed demonstrated that the blockage of Hsp27 is sufficient to resensitize bortezomib-resistant lymphoma cells to proteasome inhibitor-mediated cytotoxicity [64].…”

TNF potentiates anticancer activity of bortezomib (Velcade®) through reduced expression of proteasome subunits and dysregulation of unfolded protein response

“…48 48 h treatment of C-26 cells with 7.5 nM bortezomib induced an upregulation of both 20S proteasome subunits, as detected with an antibody against the entire 20S core (127% comparing with the controls) and against the a7 core subunit (120%). At the same time, the Rpt5 subunit of the PA700 was upregulated (280%) while Rpn11 subunit of the PA700 was downregulated (74%) (Fig.…”