👤 Subbareddy Maddika

Dishvelled-2 (Dvl2) is an essential component of Wnt pathway, which controls several cell fate decisions during development, such as proliferation, survival and differentiation. Dvl2 forms higher-order protein assemblies in the cell that are critical for relaying the signal from upstream Wnt ligand-frizzled receptor binding to downstream effector β-catenin activation. However, the precise molecular nature and contribution of Dvl2 protein assemblies during Wnt signalling is unknown. Here, we show that Dvl2 forms protein condensates driven by liquid-liquid phase separation. An intrinsically disordered region (IDR) at the N-terminus is essential for Dvl2 phase separation. Importantly, we identified the HECT-E3 ligase WWP2 as an essential driver of Dvl2 phase separation in vitro and in cells. We demonstrated that ubiquitylation of Dvl2 through K63 linkage by WWP2 is required for formation of Dvl2 condensates. Phase-separated Dvl2 activates Wnt signaling by sequestering the components of destruction complex and thus relieving β-catenin. Together, our results reveal a ubiquitylation-dependent liquid-liquid phase separation as a new process through which Dvl2 forms condensates, which is necessary for transduction of Wnt signalling. This article has an associated First Person interview with the first author of the paper. Show less

The balance between transcription factor p73 and its functionally opposing N-terminally truncated ΔNp73 isoform is critical for cell survival, but the precise mechanism that regulates their levels is not clear. In our study, we identified WWP2, an E3 ligase, as a novel p73-associated protein that ubiquitinates and degrades p73. In contrast, WWP2 heterodimerizes with another E3 ligase, WWP1, which specifically ubiquitinates and degrades ΔNp73. Further, we identified phosphatase PPM1G as a functional switch that controls the balance between monomeric WWP2 and a WWP2/WWP1 heterodimeric state in the cell. During cellular stress, WWP2 is inactivated, leading to upregulation of p73, whereas WWP2-WWP1 complex is intact to degrade ΔNp73, thus playing an important role in shifting the balance between p73 and ΔNp73. Collectively, our results reveal a new functional E3 ligase complex controlled by PPM1G that differentially regulates cellular p73 and ΔNp73. Show less

PTEN, a lipid phosphatase, is one of the most frequently mutated tumour suppressors in human cancer. Several recent studies have highlighted the importance of ubiquitylation in regulating PTEN tumour-suppressor function, but the enzymatic machinery required for PTEN ubiquitylation is not clear. In this study, by using a tandem affinity-purification approach, we have identified WWP2 (also known as atrophin-1-interacting protein 2, AIP-2) as a PTEN-interacting protein. WWP2 is an E3 ubiquitin ligase that belongs to the NEDD4-like protein family, which is involved in regulating transcription, embryonic stem-cell fate, cellular transport and T-cell activation processes. We show that WWP2 physically interacts with PTEN and mediates its degradation through a ubiquitylation-dependent pathway. Functionally, we show that WWP2 controls cellular apoptosis and is required for tumorigenicity of cells. Collectively, our results reveal a functional E3 ubiquitin ligase for PTEN that plays a vital role in tumour-cell survival. Show less