Open AccessRegulation of Smoothened ubiquitination and cell surface expression by a Cul4-DDB1-Gβ E3 ubiquitin ligase complex
Author(s) -
Shuang Li,
Yong Suk Cho,
Bing Wang,
Jin Jen
Publication year - 2018
Publication title -
journal of cell science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.384
H-Index - 278
eISSN - 1477-9137
pISSN - 0021-9533
DOI - 10.1242/jcs.218016
Subject(s) - ddb1 , smoothened , ubiquitin ligase , ubiquitin , microbiology and biotechnology , biology , dna ligase , protein subunit , biochemistry , signal transduction , hedgehog signaling pathway , enzyme , gene
Hedgehog (Hh) transduces signal by promoting cell surface accumulation and activation of the G protein coupled receptor (GPCR)-family protein Smoothened (Smo) in Drosophila, but the molecular mechanism underlying the regulation of Smo trafficking has remained poorly understood. Here we identify a Cul4-DDB1 E3 ubiquitin ligase complex as essential for Smo ubiquitination and cell surface clearance. We find that the C-terminal intracellular domain of Smo recruits Cul4-DDB1 through the β subunit of trimeric G protein (Gβ), and that Cul4-DDB1-Gβ promotes the ubiquitination of both Smo and its binding partner G-protein-coupled-receptor-kinase 2 (Gprk2) and induces the internalization and degradation of Smo. Hh dissociates Cul4-DDB1 from Smo by recruiting the catalytic subunit of protein kinase A (PKA) to phosphorylate DDB1, which disrupts its interaction with Gβ. Inactivation of the Cul4-DDB1 complex resulted in elevated Smo cell surface expression whereas excessive Cul4-DDB1 blocked Smo accumulation and attenuated Hh pathway activation. Taken together, our study identifies an E3 ubiquitin ligase complex targeting Smo for ubiquitination and provides new insight into how Hh signaling regulates Smo trafficking and cell surface expression.