FBXL5 interacts with p150Glued and regulates its ubiquitination

The microtubule motor cytoplasmic dynein and its activator dynactin drive vesicular transport and mitotic spindle organization. p150Glued is the dynactin subunit responsible for binding to dynein and microtubules. The F-box proteins constitute one of the four subunits of ubiquitin protein ligase complex called SCFs (SKP1-cullin-F-box), which governs phosphorylation-dependent ubiquitination and subsequent proteolysis. Our recent study showed that the proteolysis of mitotic kinesin CENP-E is mediated by SCF via a direct Skp1 link [D. Liu, N. Zhang, J. Du, X. Cai, M. Zhu, C. Jin, Z. Dou, C. Feng, Y. Yang, L. Liu, K. Takeyasu, W. Xie, X. Yao, Interaction of Skp1 with CENP-E at the midbody is essential for cytokinesis, Biochem. Biophys. Res. Commun. 345 (2006) 394–402]. Here we show that F-box protein FBXL5 interacts with p150Glued and orchestrates its turnover via ubiquitination. FBXL5 binds to p150Gluedin vitro and in vivo. FBXL5 and p150Glued co-localize primarily in the cytoplasm with peri-nuclear enrichment in HeLa cells. Overexpression of FBXL5 promotes poly-ubiquitination of p150Glued and protein turnover of p150Glued. Our findings provide a potential mechanism by which p150Glued protein function is regulated by SCFs.