A Competitive Binding Mechanism between Skp1 and Exportin 1 (CRM1) Controls the Localization of a Subset of F-box Proteins

Nelson, David E.; Laman, Heike

doi:10.1074/jbc.m111.220079

Cited by 24 publications

(27 citation statements)

References 25 publications

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“…As previously reported, Fbxo7 is predominantly cytosolic and a minority is present in the membranous fraction [14,23]. Consistent with a delay in mitochondrial clearance and altered mitophagic flux, autophagy (p62 and LC3-II) and lysosomal (LAMP2) proteins were elevated in Fbxo7 LacZ/LacZ cells compared with WT.…”

Section: Resultssupporting

confidence: 82%

Defective erythropoiesis in a mouse model of reduced Fbxo7 expression due to decreased p27 expression

Randle

Nelson

Patel

et al. 2015

The Journal of Pathology

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During the final stages of erythropoiesis, lineage-restricted progenitors mature over three to five cell divisions, culminating with withdrawal from the cell cycle and the loss of most organelles, including mitochondria and nuclei. Recent genome-wide association studies in human populations have associated several SNPs near or within FBXO7 with erythrocyte phenotypes. Fbxo7 encodes a multi-functional F-box protein known to bind p27 and participate in selective mitophagy. One SNP causes an amino acid substitution (Met115Ile) and is associated with smaller erythrocytes. We find that the less common IIe115 allele of Fbxo7 binds less efficiently to p27, and cells expressing this allele proliferate faster than cells expressing Met115. We show that an erythroleukaemic cell line with reduced Fbxo7 expression fails to stabilize p27 levels, exit the cell cycle, and produce haemoglobin. In addition, mice deficient in Fbxo7 expression are anaemic due to a reduction in erythrocyte numbers, and this is associated with lower p27 levels, increased numbers of late-stage erythroblasts with greater than 2N DNA content, and delayed mitophagy during terminal differentiation. Collectively, these data support an important physiological, cell cycle regulatory role for Fbxo7 during erythropoiesis. © 2015 Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

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Section: Resultssupporting

confidence: 82%

Defective erythropoiesis in a mouse model of reduced Fbxo7 expression due to decreased p27 expression

Randle

Nelson

Patel

et al. 2015

The Journal of Pathology

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“…Although we did not observe an increased association of these chaperones with FLAG-FbxD in phyA -relative to wt cells, Hsp70 and Cct/TriC proteins have been implicated in the assembly of the related CRL2 E3 Ub ligases (41). In mammalian cells, some FBPs can bind nuclear exportin-1 in place of Skp1 (49). Although the related Dictyostelium protein Xpo2 was detected, it was not enriched in the Skp1 co-IPs from phyA -versus wt cells.…”

Section: Discussionmentioning

confidence: 57%

Glycosylation of Skp1 Promotes Formation of Skp1–Cullin-1–F-box Protein Complexes in Dictyostelium

Sheikh¹,

Xu²,

Wel³

et al. 2015

Molecular & Cellular Proteomics

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O 2 sensing in diverse protozoa depends on the prolyl 4 hydroxylation of Skp1 and modification of the resulting hydroxyproline with a series of five sugars. In yeast, plants, and animals, Skp1 is associated with F-box proteins. The Skp1-F-box protein heterodimer can, for many F-box proteins, dock onto cullin-1 en route to assembly of the Skp1-cullin-1-F-box protein-Rbx1 subcomplex of E3 SCF Ub ligases. E3 SCF Ub ligases conjugate Lys48-polyubiquitin chains onto targets bound to the substrate receptor domains of F-box proteins, preparing them for recognition by the 26S proteasome. In the social amoeba Dictyostelium, we found that O 2 availability was rate-limiting for the hydroxylation of newly synthesized Skp1. To investigate the effect of reduced hydroxylation, we analyzed knockout mutants of the Skp1 prolyl hydroxylase and each of the Skp1 glycosyltransferases. Proteomic analysis of co-immunoprecipitates showed that wild-type cells able to fully glycosylate Skp1 had a greater abundance of an SCF complex containing the cullin-1 homolog CulE and FbxD, a newly described WD40-type F-box protein, than the complexes that predominate in cells defective in Skp1 hydroxylation or glycosylation. Similarly, the previously described FbxA-Skp1CulA complex was also more abundant in glycosylation-competent cells. The CulE interactome also included higher levels of proteasomal regulatory particles when Skp1 was glycosylated, suggesting increased activity consistent with greater association with F-box proteins. Finally, the interactome of FLAG-FbxD was modified when it harbored an F-box mutation that compromised Skp1 binding, consistent with an effect on the abundance of potential substrate proteins. We Timely protein degradation is a cornerstone of cell cycling and the regulation of numerous physiological and developmental processes. Eukaryotes have evolved an extensive array of polyubiquitination enzymes to tag proteins on a proteinby-protein basis as a recognition marker for degradation in the 26S proteasome. The cullin-RING ubiquitin ligases (CRLs) 1 are a prominent subgroup of these enzymes (1) and consist of an E3 architecture that includes a substrate receptor, an adaptor (in most cases), the cullin scaffold, the RING protein, and an exchangeable E2 ubiquitin donor that has been charged with ubiquitin (Ub) by an E1 enzyme. The first discovered and still prototypic example is the CRL1 class (2), also referred to as SCF on account of the names of its founding subunits, Skp1, cullin-1, and F-box proteins (FBPs). The CRL1 (or SCF) complexes utilize FBPs as substrate receptors, Skp1 as the adaptor linking the FBP to the N-terminal region of cullin-1 (Cul1), and Rbx1 as the RING protein that tethers the E2 Ub donor to the Cul1 C-terminal region (see Fig. 2B). CRL1s can be activated by neddylation of Cul1 by a Nedd8-specific E2, which mobilizes Rbx1 to afford rotational flexibility of the E2 and displaces the inhibitor Cand1, permitting docking of the Skp1-FBP heterodimer (3-5). Deneddylation mediated by the eight-subunit COP...

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“…during the cell cycle [34]. We therefore investigated if the subcellular localization of FBXO45 may be altered by Hey1 co-expression.…”

Section: Resultsmentioning

confidence: 99%

Hey bHLH Proteins Interact with a FBXO45 Containing SCF Ubiquitin Ligase Complex and Induce Its Translocation into the Nucleus

Salat

Winkler

Urlaub³

et al. 2015

PLoS ONE

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The Hey protein family, comprising Hey1, Hey2 and HeyL in mammals, conveys Notch signals in many cell types. The helix-loop-helix (HLH) domain as well as the Orange domain, mediate homo- and heterodimerization of these transcription factors. Although distinct interaction partners have been identified so far, their physiological relevance for Hey functions is still largely unclear. Using a tandem affinity purification approach and mass spectrometry analysis we identified members of an ubiquitin E3-ligase complex consisting of FBXO45, PAM and SKP1 as novel Hey1 associated proteins. There is a direct interaction between Hey1 and FBXO45, whereas FBXO45 is needed to mediate indirect Hey1 binding to SKP1. Expression of Hey1 induces translocation of FBXO45 and PAM into the nucleus. Hey1 is a short-lived protein that is degraded by the proteasome, but there is no evidence for FBXO45-dependent ubiquitination of Hey1. On the contrary, Hey1 mediated nuclear translocation of FBXO45 and its associated ubiquitin ligase complex may extend its spectrum to additional nuclear targets triggering their ubiquitination. This suggests a novel mechanism of action for Hey bHLH factors.

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A Competitive Binding Mechanism between Skp1 and Exportin 1 (CRM1) Controls the Localization of a Subset of F-box Proteins

Cited by 24 publications

References 25 publications

Defective erythropoiesis in a mouse model of reduced Fbxo7 expression due to decreased p27 expression

Defective erythropoiesis in a mouse model of reduced Fbxo7 expression due to decreased p27 expression

Glycosylation of Skp1 Promotes Formation of Skp1–Cullin-1–F-box Protein Complexes in Dictyostelium

Hey bHLH Proteins Interact with a FBXO45 Containing SCF Ubiquitin Ligase Complex and Induce Its Translocation into the Nucleus

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