PT  - JOURNAL ARTICLE
AU  - Emily E. Blythe
AU  - Kristine C. Olson
AU  - Vincent Chau
AU  - Raymond J. Deshaies
TI  - Ubiquitin- and ATP-dependent unfoldase activity of P97/VCP•NPLOC4•UFD1L1 is enhanced by a mutation that causes multisystem proteinopathy
AID  - 10.1101/129528
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 129528
4099  - http://biorxiv.org/content/early/2017/04/21/129528.short
4100  - http://biorxiv.org/content/early/2017/04/21/129528.full
AB  - p97 is a ‘segregase’ that plays a key role in numerous ubiquitin-dependent pathways, such as ER-associated degradation (ERAD). It has been hypothesized that p97 extracts proteins from membranes or macromolecular complexes to enable their proteasomal degradation; however, the complex nature of p97 substrates has made it difficult to directly observe the fundamental basis for this activity. To address this issue, we developed a soluble p97 substrate—Ub-GFP modified with K48-linked ubiquitin chains—for in vitro p97 activity assays. We demonstrate for the first time that wild type p97 can unfold proteins and that this activity is dependent on the p97 adaptor NPLOC4-UFD1L, ATP hydrolysis, and substrate ubiquitination, with branched chains providing maximal stimulation. Furthermore, we show that a p97 mutant that causes inclusion body myopathy, Paget’s Disease of bone, and frontotemporal dementia (IBMPFD) in humans unfolds substrate faster, suggesting that excess activity may underlie pathogenesis. This work overcomes a significant barrier in the study of p97 and will allow the future dissection of p97 mechanism at a level of detail previously unattainable.