Analysis of Npl4 deletion mutants in mammalian cells unravels new Ufd1-interacting motifs and suggests a regulatory role of Npl4 in ERAD.

Npl4 is a 67 kDa protein forming a stable heterodimer with Ufd1, which in turn binds the ubiquitous p97/VCP ATPase. According to a widely accepted model, VCP(Ufd1-Npl4) promotes the retrotranslocation of emerging ER proteins, their ubiquitination by associated ligases, and handling to the 26S proteasome for degradation in a process known as ERAD (ER-associated degradation). Using a series of Npl4 deletion mutants we have revealed that the binding of Ufd1 to Npl4 is mediated by two regions: a conserved stretch of amino acids from 113 to 255 within the zf-Npl4 domain and by the Npl4 homology domain between amino acids 263 and 344.

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

Bortezomib (Velcade) exploits proteasome inhibition as a unique mechanism of anticancer activity. The effectiveness of bortezomib is, however, limited, therefore, the search for therapeutic regimens combining bortezomib with other agents. In the present work we demonstrate enhanced anticancer activity of bortezomib by its combination with tumor necrosis factor (TNF) in the experimental model of C-26 colon carcinoma in mice.