Cell signalling
How does USP8 turn on Smoothened?
Open access · cc by · source: Europe PMC
USP8 deubiquitinates Smoothened, promoting Hh-dependent cell-surface accumulation and signaling while limiting early-endosome localization.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Multiple empirical papers in this library examine cell signalling with mechanistic biological findings.
Evidence for the claim as stated.
USP8 prevents Smo ubiquitination and enhances signaling; Hh promotes Smo–USP8 interaction; USP8 is required for Hh-induced surface accumulation and keeps Smo out of Rab5 early endosomes.
Evidence for the claim as stated.
Systems and scales differ across cell signalling studies (species, tissues, methods), so mechanisms should not be over-generalised.
Evidence for the claim as stated.
An RNAi screen of Drosophila deubiquitinases in wings and S2 cells found that USP8 prevents Smoothened ubiquitination, enhances Hedgehog signalling, and is required for Hh-induced surface accumulation of Smo, keeping it out of Rab5 early endosomes. The opposing ubiquitin ligase is not fully identified in every tissue.
Evidence for the claim as stated.
Loss-of-function tools are not interchangeable. CK1ε used shRNA plus inhibitors in mammalian cancer models; USP8 used Drosophila RNAi; IFN work used receptor knockouts and siRNA in macrophages; PDLP used plant combined KOs. A 'knockdown paper' in flies is not the same genetic lesion as a mouse IFNAR1 knockout or an Arabidopsis double mutant.
Evidence for the claim as stated.
USP8 limits Smoothened ubiquitination: RNAi and biochemical readouts showed less ubiquitin on Smo, stronger Hedgehog signalling, and Hh-stimulated Smo–USP8 interaction. Ubiquitin blots here are a modification assay tied to trafficking, not a complete ligase identification.
Evidence for the claim as stated.
Westerns here answer different biochemical questions. Caveolar work asks which subunits co-purify; N–p50 asks which domain is required for association and HR; USP8 asks whether Smo is ubiquitinated; spike work asks whether glycan occupancy and palmitoylation change S2 mobility and trafficking. A darker band is not a universal 'more protein' story across those designs.
Evidence for the claim as stated.
USP8 is required for Hedgehog-induced Smoothened surface accumulation and keeps Smo out of Rab5 early endosomes. Site-specific monoubiquitination of Rab5 at K140 and K165 (not K116) downregulates the endocytic pathway via disrupted effectors and nucleotide conversion. Both papers use localisation of Smo or Rab5 as a trafficking IF readout.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Systems and scales differ across cell signalling studies (species, tissues, methods), so mechanisms should not be over-generalised.
- Supports · Shared class A GPCR activation path
- Supports · LOX1 oxylipins close stomata in defense
Loss-of-function tools are not interchangeable. CK1ε used shRNA plus inhibitors in mammalian cancer models; USP8 used Drosophila RNAi; IFN work used receptor knockouts and siRNA in macrophages; PDLP used plant combined KOs. A 'knockdown paper' in flies is not the same genetic lesion as a mouse IFNAR1 knockout or an Arabidopsis double mutant.
Westerns here answer different biochemical questions. Caveolar work asks which subunits co-purify; N–p50 asks which domain is required for association and HR; USP8 asks whether Smo is ubiquitinated; spike work asks whether glycan occupancy and palmitoylation change S2 mobility and trafficking. A darker band is not a universal 'more protein' story across those designs.
- Supports · What proteins build the caveolar coat?
- Supports · Plant TIR domain binds viral elicitor
- Supports · Spike glycosylation and palmitoylation trafficking
Study at a glance
- Design
- Animal / in-vitro — RNAi screen of Drosophila DUBs in wings and S2 cells focused on USP8–Smo regulation
- N
- Drosophila genetics and S2 cell assays — no single sample N
- Population
- Drosophila tissues and S2 cells
- Outcome
- USP8 prevention of Smoothened ubiquitination promoting Hedgehog signaling
Structured fields used in claim comparison tables when every cited study has a complete layer.
Inspect source passages
How does USP8 turn on Smoothened?
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
What DUB prevents Smo ubiquitination?
By using an RNAi screen that targets Drosophila DUBs in both the wings and cultured S2 cells, we identified USP8 as a DUB that prevents Smo ubiquitination and enhances the signaling activity of the protein.
What is Smoothened’s role in Hh signaling?
The seven transmembrane protein Smoothened (Smo) acts as a signal transducer, and the activity of Smo is inhibited by Ptc in the absence of Hh –.
Key findings
USP8 prevents Smo ubiquitination and enhances signaling; Hh promotes Smo–USP8 interaction; USP8 is required for Hh-induced surface accumulation and keeps Smo out of Rab5 early endosomes.
Methodology
RNAi screen of Drosophila DUBs in wings and S2 cells, then tested USP8 effects on Smo ubiquitination, localization, and Hh responses.
Limitations
Does not fully identify the ubiquitin ligase opposing USP8 on Smo in every tissue.
Related papers in this topic
Same topic cluster — not a recommendation engine.