Control of Deneddylation by the COP9 Signalosome

Schmaler, Tilo; Dubiel, Wolfgang

doi:10.1007/978-1-4419-6676-6_5

Cited by 30 publications

(23 citation statements)

References 98 publications

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“…However, comparison of this activity with that of the CSN complex reveals, as observed for Nedd8-AMC, that the CSN complex is a more efficient deneddylase than CSN5 R106T. It is noteworthy that, although we observed robust isopeptidase activity on Nedd8-AMC by the CSN complex, this is in contrast with the observations reported by the Dubiel's group (26,27), in which no activity was found. Even though the CSN isopeptidase activity measured in our experiments corresponds to a weaker level than the activity recorded on a physiological substrate reported in ref.…”

Section: Discussioncontrasting

confidence: 78%

Insights into the regulation of the human COP9 signalosome catalytic subunit, CSN5/Jab1

Echalier

Pan

Birol

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The COP9 (Constitutive photomorphogenesis 9) signalosome (CSN), a large multiprotein complex that resembles the 19S lid of the 26S proteasome, plays a central role in the regulation of the E3-cullin RING ubiquitin ligases (CRLs). The catalytic activity of the CSN complex, carried by subunit 5 (CSN5/Jab1), resides in the deneddylation of the CRLs that is the hydrolysis of the cullin-neural precursor cell expressed developmentally downregulated gene 8 (Nedd8)isopeptide bond. Whereas CSN-dependent CSN5 displays isopeptidase activity, it is intrinsically inactive in other physiologically relevant forms. Here we analyze the crystal structure of CSN5 in its catalytically inactive form to illuminate the molecular basis for its activation state. We show that CSN5 presents a catalytic domain that brings essential elements to understand its activity control. Although the CSN5 active site is catalytically competent and compatible with di-isopeptide binding, the Ins-1 segment obstructs access to its substrate-binding site, and structural rearrangements are necessary for the Nedd8-binding pocket formation. Detailed study of CSN5 by molecular dynamics unveils signs of flexibility and plasticity of the Ins-1 segment. These analyses led to the identification of a molecular trigger implicated in the active/inactive switch that is sufficient to impose on CSN5 an active isopeptidase state. We show that a single mutation in the Ins-1 segment restores biologically relevant deneddylase activity. This study presents detailed insights into CSN5 regulation. Additionally, a dynamic monomer-dimer equilibrium exists both in vitro and in vivo and may be functionally relevant.C ell signaling processes mediated by ubiquitinylation, the posttranslational covalent conjugation of ubiquitin molecules, are of prime importance for cellular activity and particularly for protein turnover. Ubiquitin-ligase enzymes (E3s) are responsible for the last step of the ubiquitinylation reaction, and the multisubunit cullin-RING E3 ubiquitin ligases (CRLs) represent the most prominent of E3 enzymes. Among the several factors that regulate CRL activity, cullin neddylation/deneddylation cycles are central (1).The Cop9 signalosome (CSN), which is an eight-subunit complex largely conserved through evolution, deneddylates CRLs and thereby regulates CRL activity. As a large number of proteins are ubiquitinylated by CRLs, the CSN complex is implicated in the control of a significant proportion of the proteome, including prooncogenes, tumor suppressors, and other important cellular protagonists (1). Not surprisingly, the CSN has been implicated in various cellular functions, ranging from cell cycles to circadian rhythm and to immunity in various organisms. Furthermore, many studies have found a strong link between the CSN and cancers (2).The CSN, a multi-protein complex of about 320 kDa, contains six proteasome Cop9 eIF3 (PCI)-based subunits and two MPR1-Pad1-N-terminal (MPN)-based subunits. The subunit 5 [CSN5; also known as c-Jun activation domain-binding protein-1 (...

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Section: Discussioncontrasting

confidence: 78%

Insights into the regulation of the human COP9 signalosome catalytic subunit, CSN5/Jab1

Echalier

Pan

Birol

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…CSN has intrinsic de-neddylation and deubiquitylation enzymatic activities, which regulate CRLs biogenesis and function (for a review see [13], [14]). Similarly to CRL4s, CSN has been associated with several aspects of DDR [15], [16].…”

Section: Introductionmentioning

confidence: 99%

Non-Canonical CRL4A/4BCDT2 Interacts with RAD18 to Modulate Post Replication Repair and Cell Survival

et al. 2013

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The Cullin-4CDT2 E3 ubiquitin ligase plays an essential role in DNA replication origin licensing directing degradation of several licensing factors at the G1/S transition in order to prevent DNA re-replication. Recently a RAD18-independent role of Cullin-4CDT2 in PCNA monoubiquitylation has been proposed. In an effort to better understand the function of Cullin-4CDT2 E3 ubiquitin ligase in mammalian Post-Replication Repair during an unperturbed S-phase, we show that down-regulation of Cullin-4CDT2 leads to two distinguishable independent phenotypes in human cells that unveil at least two independent roles of Cullin-4CDT2 in S-phase. Apart from the re-replication preventing activity, we identified a non-canonical Cullin-4CDT2 complex, containing both CUL4A and CUL4B, associated to the COP9 signalosome, that controls a RAD18-dependent damage avoidance pathway essential during an unperturbed S-phase. Indeed, we show that the non-canonical Cullin-4A/4BCDT2 complex binds to RAD18 and it is required to modulate RAD18 protein levels onto chromatin and the consequent dynamics of PCNA monoubiquitylation during a normal S-phase. This function prevents replication stress, ATR hyper-signaling and, ultimately, apoptosis. A very similar PRR regulatory mechanism has been recently described for Spartan. Our findings uncover a finely regulated process in mammalian cells involving Post-Replication Repair factors, COP9 signalosome and a non-canonical Cullin4-based E3 ligase which is essential to tolerate spontaneous damage and for cell survival during physiological DNA replication.

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“…The CSN is a regulator of the UPS in all eukaryotic cells (Kato and Yoneda-Kato, 2009; Schmaler and Dubiel, 2010; Wei et al, 2008). This function of the CSN is predominantly executed by influencing the activity of cullin-RING Ub ligases (CRLs).…”

Section: Introductionmentioning

confidence: 99%

The COP9 signalosome, cullin 3 and Keap1 supercomplex regulates CHOP stability and adipogenesis

et al. 2012

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SummaryObesity is one of the most serious health problems of the 21st century. It is associated with highly increased risk of type 2 diabetes, high blood pressure, cardiovascular disease as well as several cancers. The expansion of the fat tissue needs the differentiation of preadipocytes to adipocytes, a process called adipogenesis. Dysfunction of adipogenesis is a hallmark of obesity and delineation of underlying mechanisms has high priority for identifying targets for pharmacological intervention. Here we investigate the impact of the COP9 signalosome (CSN), a regulator of cullin-RING ubiquitin ligases (CRLs), and of C/EBP homologous protein (CHOP) on the differentiation of LiSa-2 preadipocytes. CHOP induced by piceatannol or by permanent overexpression in LiSa-2 cells blocks adipocyte differentiation as characterized by inhibited fat droplet formation and vascular endothelial growth factor (VEGF) production. Knockdown of the CSN by permanent downregulation of CSN1 in LiSa-2 cells elevates CHOP and retards adipogenesis. The effect of the CSN knockdown on CHOP stability can be explained by the protection of the CRL component Keap1 by the CSN associated ubiquitin-specific protease 15 (USP15). Pulldowns and glycerol gradients reveal that CHOP interacts with a supercomplex consisting of the CSN, cullin 3 and Keap1. Transient knockdown of Keap1 increases CHOP steady state level and retards its degradation. We conclude that CHOP stability is controlled by a CSN-CRL3Keap1 complex, which is crucial for adipogenesis. Our data show that CHOP is a distinguished target for pharmacological intervention of obesity.

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Control of Deneddylation by the COP9 Signalosome

Cited by 30 publications

References 98 publications

Insights into the regulation of the human COP9 signalosome catalytic subunit, CSN5/Jab1

Insights into the regulation of the human COP9 signalosome catalytic subunit, CSN5/Jab1

Non-Canonical CRL4A/4BCDT2 Interacts with RAD18 to Modulate Post Replication Repair and Cell Survival

The COP9 signalosome, cullin 3 and Keap1 supercomplex regulates CHOP stability and adipogenesis

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