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San Sebastián de los Reyes, Spain

Xolalpa W.,Ubiquitylation and Cancer Molecular Biology Laboratory
Current pharmaceutical design | Year: 2013

The Ubiquitin-Proteasome System (UPS) has been considered as privileged pharmacological target for drug development due to the tremendous potential for intervention on multiple pathologies including cancer, neurodegenerative diseases, immune diseases and multiple infections. The pharmacological potential of the UPS was revealed after the unpredicted success of proteasome inhibitors for the treatment of some haematological malignancies. After a decade of clinical use of bortezomib, this review summarizes part of the learned experience and recent advances on the development of alternative inhibitors of the UPS. A new generation of inhibitors, including those targeting subsets of proteasomes, are under investigation and it is likely that some of them will reach clinical trials. Beyond the proteasome inhibition, there are also other targets that can be blocked to attain directly or indirectly the UPS system. The ubiquitylation status of protein substrates is intimately linked to other post-translational modifications of the ubiquitin family, increasing the number of potential targets for clinical intervention. In addition to the obvious subsets of ubiquitin-conjugating and de-conjugating enzymes, a group of enzymatic activities regulating SUMOylation or NEDDylation have a potential impact on the activity of the UPS. The novel strategies explore the active site of those enzymes and/or the target recognition surfaces. The first inhibitors of these parallel pathways appeared to tackle a limited number of protein targets playing important roles on diverse pathologies. Although, a large majority of them have not yet been tested in clinical trials, the new inhibitors are expected to have fewer side effects than proteasome inhibitors.

Marcos-Villar L.,Autonomous University of Madrid | Gallego P.,Autonomous University of Madrid | Munoz-Fontela C.,Heinrich Pette Institute | De La Cruz-Herrera C.F.,Autonomous University of Madrid | And 6 more authors.
Oncogene | Year: 2014

The pocket proteins retinoblastoma protein (pRb), p107 and p130 are the key targets of oncoproteins expressed by DNA tumor viruses. Some of these viral proteins contain an LXCXE motif that mediates the interaction with the three pocket proteins and the inhibition of the pRb SUMOylation. Kaposi's sarcoma herpesvirus (KSHV) contains at least two proteins that can regulate pRb function but, so far, a KSHV-encoded protein targeting p107 and p130 has not been identified. Here, we show that the KSHV latent protein LANA2 binds to pRb, p107 and p130. LANA2 contains an LXCXE motif that is required for bypassing pRb-mediated cell-cycle arrest and for inhibiting pRb SUMOylation. Finally, we demonstrate that, in addition to pRb, both p107 and p130 can be SUMOylated, and this modification is also inhibited by LANA2 in an LXCXE-dependent manner. These results demonstrate, for the first time, the SUMOylation of p107 or p130 and, so far, they represent the first example of a KSHV protein able to interact with the three pocket proteins and to inhibit their conjugation to SUMO. © 2014 Macmillan Publishers Limited All rights reserved.

Gonzalez-Santamaria J.,Autonomous University of Madrid | Campagna M.,Autonomous University of Madrid | Ortega-Molina A.,CSIC - National Center for Metallurgical Research | Marcos-Villar L.,Autonomous University of Madrid | And 9 more authors.
Cell Death and Disease | Year: 2012

The crucial function of the PTEN tumor suppressor in multiple cellular processes suggests that its activity must be tightly controlled. Both, membrane association and a variety of post-translational modifications, such as acetylation, phosphorylation, and mono- and polyubiquitination, have been reported to regulate PTEN activity. Here, we demonstrated that PTEN is also posttranslationally modified by the small ubiquitin-like proteins, small ubiquitin-related modifier 1 (SUMO1) and SUMO2. We identified lysine residue 266 and the major monoubiquitination site 289, both located within the C2 domain required for PTEN membrane association, as SUMO acceptors in PTEN. We demonstrated the existence of a crosstalk between PTEN SUMOylation and ubiquitination, with PTEN-SUMO1 showing a reduced capacity to form covalent interactions with monoubiquitin and accumulation of PTEN-SUMO2 conjugates after inhibition of the proteasome. Moreover, we found that virus infection induces PTEN SUMOylation and favors PTEN localization at the cell membrane. Finally, we demonstrated that SUMOylation contributes to the control of virus infection by PTEN. © 2012 Macmillan Publishers Limited All rights reserved.

De La Cruz-Herrera C.F.,CSIC - National Center for Biotechnology | Baz-Martinez M.,University of Santiago de Compostela | Lang V.,Ubiquitylation and Cancer Molecular Biology Laboratory | El Motiam A.,University of Santiago de Compostela | And 13 more authors.
Oncogene | Year: 2016

Class IA phosphatidylinositol 3-kinases (PI3Ks) are composed of p110 catalytic and p85 regulatory subunits. How regulatory subunits modulate PI3K activity remains only partially understood. Here we identified SUMO (small ubiquitin-related modifier) as a new player modulating this regulation. We demonstrate that both p85β and p85α are conjugated to SUMO1 and SUMO2. We identified two lysine residues located at the inter-SH2 domain on p85β, a critical region required for inhibition of p110, as being required for SUMO conjugation. A SUMOylation-defective mutant p85β shows higher activation of the PI3K pathway, and increased cell migration and transformation. Moreover, the cancer-related KS459del mutant in p85α was less efficiently SUMOylated compared with the wild-type protein. Finally, our results show that SUMO modulates p85 tyrosine phosphorylation, a modification correlating with PI3K pathway activation. Thus, SUMO reduces the levels of tyrosine-phosphorylated-p85 while loss of SUMOylation results in increased tyrosine phosphorylation of p85. In summary, we identify SUMO as a new important player in the regulation of the PI3K pathway through modulation of p85. © 2016 Macmillan Publishers Limited.

Aillet F.,CIC Biomagune | Aillet F.,Ubiquitylation and Cancer Molecular Biology Laboratory | Lopitz-Otsoa F.,CIC Biomagune | Egana I.,CIC Biomagune | And 7 more authors.
PLoS ONE | Year: 2012

The NF-κB pathway is regulated by SUMOylation at least at three levels: the inhibitory molecule IκBα, the IKK subunit γ/NEMO and the p52 precursor p100. Here we investigate the role of SUMO-2/3 in the degradation of IκBα and activation of NF-κB mediated by TNFα. We found that under conditions of deficient SUMOylation, an important delay in both TNFα-mediated proteolysis of IκBα and NF-κB dependent transcription occurs. In vitro and ex vivo approaches, including the use of ubiquitin-traps (TUBEs), revealed the formation of chains on IκBα containing SUMO-2/3 and ubiquitin after TNFα stimulation. The integration of SUMO-2/3 appears to promote the formation of ubiquitin chains on IκBα after activation of the TNFα signalling pathway. Furthermore, heterologous chains of SUMO-2/3 and ubiquitin promote a more efficient degradation of IκBα by the 26S proteasome in vitro compared to chains of either SUMO-2/3 or ubiquitin alone. Consistently, Ubc9 silencing reduced the capture of IκBα modified with SUMO-ubiquitin hybrid chains that display a defective proteasome-mediated degradation. Thus, hybrid SUMO-2/3-ubiquitin chains increase the susceptibility of modified IκBα to the action of 26S proteasome, contributing to the optimal control of NF-κB activity after TNFα-stimulation. © 2012 Aillet et al.

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