Comparative proteomic analysis reveals a function of the novel death receptor-associated protein BRE in the regulation of prohibitin and p53 expression and proliferation.

The brain and reproductive organ expressed (BRE) gene encodes a highly conserved stress-modulating protein. To gain further insight into the function of this gene, we used comparative proteomics to investigate the protein profiles of C2C12 and D122 cells resulting from small interfering RNA (siRNA)-mediated silencing as well as overexpression of BRE. Silencing of BRE in C2C12 cells, using siRNA, resulted in up-regulated Akt-3 and carbonic anhydrase III expression, while the 26S proteasome regulatory subunit S14 and prohibitin were down-regulated.

BRE enhances in vivo growth of tumor cells.

Human BRE, a death receptor-associating intracellular protein, attenuates apoptotic response of human and mouse tumor cell lines to death receptor stimuli in vitro. In this report, we addressed whether the in vitro antiapoptotic effect of BRE could impact on tumor growth in vivo. We have shown that the mouse Lewis lung carcinoma D122 stable transfectants of human BRE expression vector developed into local tumor significantly faster than the stable transfectants of empty vector and parental D122, in both the syngeneic C57BL/6 host and nude mice.

A death receptor-associated anti-apoptotic protein, BRE, inhibits mitochondrial apoptotic pathway.

BRE, brain and reproductive organ-expressed protein, was found previously to bind the intracellular juxtamembrane domain of a ubiquitous death receptor, tumor necrosis factor receptor 1 (TNF-R1), and to down-regulate TNF-alpha-induced activation of NF-kappaB. Here we show that BRE also binds to another death receptor, Fas, and upon overexpression conferred resistance to apoptosis induced by TNF-alpha, anti-Fas agonist antibody, cycloheximide, and a variety of stress-related stimuli. However, down-regulation of the endogenous BRE by small interfering RNA increased apoptosis to TNF-alpha, but nottoetoposide, indicating that the physiological antiapoptotic role of this protein is specific to death receptor-mediated apoptosis.

Expression of a conserved mouse stress-modulating gene, Bre: comparison with the human ortholog.

Mouse Bre, an evolutionarily conserved stress-modulating gene, like its human counterpart, is expressed in multiple alternative transcripts. The main transcript, which is ubiquitously expressed, encodes a protein that binds tumor necrosis factor receptor 1 (TNF-R1) and downregulates TNF-induced activation of NF-kappaB. Alternative splicing of mouse Bre occurs only at the 5' region of the gene, generating either nonfunctional transcripts or transcripts that can encode putative protein isoforms differ at the N-terminal sequence.