Phosphorylation of serine 323 of ASB2α is pivotal for the targeting of filamin A to degradation

• Published in: Cellular signalling 2013-12, Vol.25 (12), p.2823-2830
• Main Authors: Zakaria, Rim, Lamsoul, Isabelle, Uttenweiler-Joseph, Sandrine, Erard, Monique, Monsarrat, Bernard, Burlet-Schiltz, Odile, Moog-Lutz, Christel, Lutz, Pierre G.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; ASB; Control; Cullin-RING E3 ubiquitin ligase; Degradation; Erk; Extracellular Signal-Regulated MAP Kinases - metabolism; Filamin; Filamins - metabolism; HeLa Cells; Humans; Kinases; Life Sciences; Localization; Mass spectrometry; Models, Molecular; Molecular Sequence Data; Mutations; Phosphates; Phosphorylation; Post-translational modifications; Proteins; Proteolysis; Serine - analysis; Serine - metabolism; Suppressor of Cytokine Signaling Proteins - chemistry; Suppressor of Cytokine Signaling Proteins - metabolism; Ubiquitin-Protein Ligases - metabolism
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2013.09.011

ASB proteins are the specificity subunits of cullin5-RING E3 ubiquitin ligases (CRL5) that play roles in ubiquitin-mediated protein degradation. However, how their activity is regulated remains poorly understood. Here, we unravel a novel mechanism of regulation of a CRL5 through phosphorylation of its specificity subunit ASB2α. Indeed, using mass spectrometry, we showed for the first time that ASB2α is phosphorylated and that phosphorylation of serine-323 (Ser-323) of ASB2α is crucial for the targeting of the actin-binding protein filamin A (FLNa) to degradation. Mutation of ASB2α Ser-323 to Ala had no effect on intrinsic E3 ubiquitin ligase activity of ASB2α but abolished the ability of ASB2α to induce degradation of FLNa. In contrast, the ASB2α Ser-323 to Asp phosphomimetic mutant induced acute degradation of FLNa. Moreover, inhibition of the extracellular signal-regulated kinases 1 and 2 (Erk1/2) activity reduced ASB2α-mediated FLNa degradation. We further showed that the subcellular localization of ASB2α to actin-rich structures is dependent on ASB2α Ser-323 phosphorylation and propose that the interaction with FLNa depends on the electrostatic potential redistribution induced by the Ser-323 phosphate group. Taken together, these data unravel an important mechanism by which ASB2α-mediated FLNa degradation can be regulated. [Display omitted] •ASB2α is a serine-phosphorylated protein.•We unravel a novel mechanism of regulation of a cullin5-RING E3 ubiquitin ligase.•We unravel an important mechanism by which filamin A degradation can be regulated.