An engineered cell line with a hRpn1-attached handle to isolate proteasomes

Regulated protein degradation in eukaryotes is performed by the 26S proteasome, which contains a 28-subunit hollow core particle (CP) within which proteolysis occurs, and a 19-subunit regulatory particle (RP) that binds, processes, and translocates substrates to the CP. In addition to its intrinsic subunits, myriad proteins interact with the proteasome transiently, including factors that assist and/or regulate its degradative activities. Efforts to identify proteasome-interacting components and/or to solve its structure have relied on over-expression of a tagged plasmid, establishing stable cell lines, or laborious purification protocols to isolate native proteasomes from cells. Here, we describe an engineered human cell line, derived from colon cancer HCT116 cells, with a biotin handle on the RP subunit hRpn1/PSMD2 for purification of 26S proteasomes. A 75-residue sequence from Propionibacterium shermanii that is biotinylated in mammalian cells was added following a TEV protease cut site at the C-terminus of hRpn1. We tested and found that 26S proteasomes can be isolated from this modified HCT116 cell line by using a simple purification protocol. More specifically, biotinylated proteasomes were purified from the cell lysates by using neutravidin agarose resin and released from the resin following incubation with TEV protease. The purified proteasomes had equivalent activity in degrading a model ubiquitinated substrate, namely ubiquitinated p53, compared to commercially available bovine proteasomes that were purified by fractionation. In conclusion, advantages of this approach to obtain 26S proteasomes over others is the simple purification protocol and that all cellular proteins, including the tagged hRpn1 subunit, remain at endogenous stoichiometry. Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.

See More