USP25 regulates Wnt signaling by controlling the stability of tankyrases

Abstract

Aberrant activation of the Wnt signaling pathway plays an important role in human cancer development. Wnt signaling is negatively regulated by Axin, a scaffolding protein that controls a rate-limiting step in the destruction of β-catenin, the central activator of the Wnt pathway. In Wnt-stimulated cells, Axin is rapidly modified by tankyrasemediated poly(ADP-ribosyl)ation, which promotes the proteolysis of Axin and consequent stabilization of β-catenin. Thus, regulation of the levels and activity of tankyrases is mechanistically important in controlling Wnt signaling. Here, we identify ubiquitin-specific protease 25 (USP25) as a positive regulator of Wnt/β-catenin signaling. We found that USP25 directly interacted with tankyrases to promote their deubiquitination and stabilization. We demonstrated that USP25 deficiency could promote the degradation of tankyrases and consequent stabilization of Axin to antagonize Wnt signaling. We further characterized the interaction between TNKS1 and USP25 by X-ray crystal structure determination. Our results provide important new insights into the molecular mechanism that regulates the turnover of tankyrases and the possibility of targeting the stability of tankyrases by antagonizing their interaction with USP25 to modulate the Wnt/β-catenin pathway.

Usp25m protease regulates ubiquitin-like processing of TUG proteins to control GLUT4 glucose transporter translocation in adipocytes

“…How the 70 additional residues (out of 1125 total) present in Usp25m, but not Usp25a, confer a specific function to cleave TUG is also uncertain (23,24). The Usp25a splice form functions in inflammation (53)(54)(55)(56), cancer (57), endoplasmic reticulum-associated degradation (58,59), and Wnt signaling (60). In general, Usp25 proteins contain three ubiquitin-binding domains near the N terminus, which can bind the small ubiquitin-like modifier (SUMO) as well as ubiquitin (22,61).…”

LPS promotes HBO1 stability via USP25 to modulate inflammatory gene transcription in THP-1 cells

“…USP25, a member of ubiquitin-specific proteases sub-family, hydrolyzes both K48 and K63 linkages of polyubiquitin moieties where link to the substrate protein [18]. USP25 stabilizes tankyrases to enhance the Wnt/β-catenin signaling contributing to cancer development [19]. Aberrant expression of USP25 has been noted in breast cancer and non-small cell lung cancer patients as well [20, 21].…”

Regulation of Wnt/β‐catenin signalling by tankyrase‐dependent poly(ADP‐ribosyl)ation and scaffolding

“…This process, known as PAR‐dependent ubiquitylation (PARdU) (DaRosa et al, ), is thought to occur constitutively and tune the receptiveness of cells to Wnt stimuli by limiting destruction complex formation (Wang et al, ). A tankyrase‐associated ubiquitin‐specific protease (USP25) can de‐ubiquitylate tankyrase, thereby stabilizing it and supporting PARdU of AXIN (Xu et al, ). Recent studies point toward another role of tankyrase, namely in promoting the formation of active, membrane‐localized Wnt signalosomes upon Wnt stimulation (Yang et al, ; Wang et al, ) (Figure B).…”

“…Furthermore, additional tankyrase interactors in the Wnt/β‐catenin pathway, other than AXIN, are emerging (Croy et al, ). Structure–function studies are providing a detailed picture of the molecular mechanisms by which tankyrase controls Wnt/β‐catenin signalling and are revealing non‐catalytic scaffolding roles of tankyrase (Guettler et al, ; Morrone et al, ; DaRosa et al, , ; Eisemann et al, ; Mariotti et al, ; Riccio et al, ; Xu et al, ). Conserved functions of tankyrase in the Wnt/β‐catenin pathway are being increasingly appreciated from studies in Drosophila and human CRC cell lines (Lau et al, ; de la Roche et al, ; Yang et al, ; Wang et al, , ).…”

“…A small, hydrophobic residue or glycine is preferred at position 4, and acidic residues are optimal at positions 5 and 8, while proline is disallowed at position 7. Crystal structures of human TNKS2 ARC4 with various TBM peptides (Guettler et al, ), of murine Tnks ARC2–3 in complex with Axin1 (Morrone et al, ), of human TNKS ARC1–3 bound to TBM peptides derived from leucyl‐cystinyl aminopeptidase (LNPEP), combined with in‐solution structural studies (Eisemann et al, ), and of human TNKS ARC5 bound to the TBM of USP25 (Xu et al, ), revealed the architecture of the ARCs and the principles of their substrate recognition. AXIN contains two TBMs in its N‐terminus (Morrone et al, ), with the second motif bearing an unusual insertion (Figure B–E).…”