| In eukaryotic cells, autophagy, a highly regulated self-eating process, mediates degradation of certain proteins in lysosomes. Malfunction of autophagy contributes to a variety of diseases, including neurodegeneration, cardiovascular disorders and cancer. Wnt signaling plays an important role in the process of embryogenesis and cancer development. The previous data of our lab have showed that autophagy could downregulate Wnt signaling by promoting Dishevelled (Dvl) degradation in mammalian cells. However, little is known about the molecular basis.Here, we provide evidence that autophagy can promote Dvl2 ubiquitination. And more importantly, we found that von Hippel-Lindau protein (pVHL), which is a component of a SCF (Skp1-Cdc53-F-box)-like ubiquitin E3 ligase complex, can enhance Dvl2 ubiquitination in vivo and the ubiquitin-ligase complex can ubiquitinate Dvl2 in vitro. Dvl directly interacts with pVHL via its DEP domain. In HEK293T cells, pVHL knockdown lead to an increased Dvl2 protein level under starvation.It has been reported that the ubiquitin-binding protein p62 can mediate ubiquitinated protein aggregates for autophagic degradation. We also found that the direct interaction of p62 with Dvl2 depends on Dvl2 ubiquitination, and the starvation-elevated Dvl2-p62 interaction is eliminated by pVHL knockdown. Meanwhile, using immunofluorescence assay, we observed that p62 is required for Dvl2 aggregation from small puncta to big ones.Although Dvl2 can directly interact with LC3, we found that the endogenous interaction between LC3 and Dvl2 can be facilitated by p62 and pVHL through immunoprecipitation assay.Taken together, our findings suggest that upon starvation, Dvl2 is ubiquitinated by pVHL. p62 recognizes and associates with the ubiquitinated Dvl2, and the association promotes Dvl aggregation. Dvl aggregates are then selectively recruited by LC3 into autophagosomes via p62 as a bridge, followed by their degradation in lysosomes. |
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