title: 14-3-3 proteins sequester a pool of soluble TRIM32 ubiquitin ligase to repress autoubiquitylation and cytoplasmic body formation.
abstract: Deregulated expression of tripartite motif-containing protein 32 (TRIM32, an E3 ubiquitin-protein ligase) contributes to various diseases. Here we report, using quantitative proteomics and biochemistry, that 14-3-3 proteins bind to phosphorylated TRIM32 and prevent TRIM32 autoubiquitylation and the formation of TRIM32-containing cytoplasmic bodies, which are potential autoregulatory mechanisms that can reduce the concentration of soluble free TRIM32. The 14-3-3-TRIM32 interaction is dependent on protein-kinase-A-catalyzed phosphorylation of TRIM32 at Ser651. We found that the inhibitory effect of 14-3-3 is, in part, a consequence of disrupting the propensity of TRIM32 to undergo higher-order self-association without affecting its dimerization. Consequently, dimerized TRIM32 bound to 14-3-3 was sequestered in a distinct cytoplasmic pool away from the microtubule network, whereas a TRIM32 mutant that cannot bind 14-3-3 underwent multimerization and was unavailable to facilitate cell growth. Our results reveal a novel connection between ubiquitylation and phosphorylation pathways, which could modulate a variety of cell events by stimulating the formation of the 14-3-3-TRIM32 signaling complex.
authors: Department of Applied Chemistry, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan. ichimura@nda.ac.jp)
authors: Tohru
authors: T
authors: Ichimura
authors: Masato
authors: M
authors: Taoka
authors: Ikuo
authors: I
authors: Shoji
authors: Hiroki
authors: H
authors: Kato
authors: Tomonobu
authors: T
authors: Sato
authors: Shigetsugu
authors: S
authors: Hatakeyama
authors: Toshiaki
authors: T
authors: Isobe
authors: Naomi
authors: N
authors: Hachiya
mesh_terms: D048948:14-3-3 Proteins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D057809:HEK293 Cells; D006801:Humans; D002479:Inclusion Bodies / Q000235:genetics / Q000378:metabolism; D051379:Mice; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination / Q000502:physiology*
chemical_list: D048948:14-3-3 Proteins; D046912:Multiprotein Complexes; D014157:Transcription Factors; D000070584:Tripartite Motif Proteins; C094027:TRIM32 protein, human; C514011:TRIM32 protein, mouse; D044767:Ubiquitin-Protein Ligases
keywords: 14-3-3; PKA; Phosphorylation; TRIM32; Ubiquitylation