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dSmurf selectively degrades decapentaplegic-activated MAD, and its overexpression disrupts imaginal disc development
Yao-Yun Liang1, Xia Lin, Min Liang
1Michael E. DeBakey Department of Surgery, Department of Molecular & Cellular Biology, Ophthalmology, Program of Developmental Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Abstract:
MAD plays an important role in decapentaplegic (DPP) signaling throughout Drosophila development. Despite a recent study describing the restriction of DPP signaling via putative ubiquitin E3 ligase dSmurf (1), the molecular mechanisms of how dSmurf affects DPP signaling remain unexplored. Toward this goal we demonstrated the degradation of phosphorylated MAD by dSmurf. dSmurf selectively interacted with MAD, but not Medea and Dad, and the MAD-dSmurf interaction was induced by constitutively active DPP type I receptor thickveins. Wild type dSmurf, but not its C1029A mutant, mediated ubiquitination-dependent degradation of MAD. Silencing of dSmurf using RNA interference stabilized MAD protein in Drosophila S2 cells. Targeted expression of dSmurf in various tissues abolished phosphorylated MAD and disrupted patterning and growth. In contrast, similar overexpression of inactive dSmurf(C1029A) showed no significant effects on development. We conclude that dSmurf specifically targets phosphorylated MAD to proteasome-dependent degradation and regulates DPP signaling during development.
Insights
The E3 ligase dSmurf targets phosphorylated MAD for degradation, controlling Decapentaplegic (DPP) signaling. This discovery clarifies how dSmurf regulates crucial developmental pathways in Drosophila.
Area of Science:
- Molecular Biology
- Developmental Biology
- Cell Signaling
Background:
- MAD proteins are crucial for Decapentaplegic (DPP) signaling in Drosophila development.
- The role of the ubiquitin E3 ligase dSmurf in restricting DPP signaling was recently proposed but its molecular mechanism remained unclear.
Purpose of the Study:
- To elucidate the molecular mechanisms by which dSmurf affects DPP signaling.
- To investigate the interaction between dSmurf and MAD proteins.
Main Methods:
- Demonstrated degradation of phosphorylated MAD by dSmurf.
- Investigated dSmurf-MAD interaction using various constructs and cell lines.
- Utilized RNA interference to silence dSmurf expression.
- Examined developmental effects of dSmurf expression in Drosophila tissues.
Main Results:
- dSmurf selectively interacts with MAD, inducing its ubiquitination-dependent degradation.
- The interaction and degradation are mediated by active Thickveins receptor.
- Silencing dSmurf stabilizes MAD, while its overexpression disrupts development.
- Inactive dSmurf mutants do not affect MAD stability or development.
Conclusions:
- dSmurf specifically targets phosphorylated MAD for proteasomal degradation.
- dSmurf acts as a key regulator of DPP signaling pathway during Drosophila development.