Protease Addiction and Synthetic Lethality in Cancer

The “oncogene addiction” concept refers to the dependence of cancer cells on the function of the oncogenes responsible for their transformed phenotype, while the term “non-oncogene addiction” has been introduced to define the exacerbated necessity of the normal function of non-mutated genes. In this Perspective, we focus on the importance of proteolytic enzymes to maintain the viability of cancer cells and hypothesize that most, if not all, tumors present “addiction” to a number of proteolytic activities, which in turn may represent valuable targets of anti-cancer therapies, even without being mutated or over-expressed by the malignant cells

USP49 deubiquitinase regulates the mitotic spindle checkpoint and prevents aneuploidy.

The spindle assembly checkpoint (SAC) is an essential mechanism that ensures the accurate chromosome segregation during mitosis, thus preventing genomic instability. Deubiquitinases have emerged as key regulators of the SAC, mainly by determining the fate of proteins during cell cycle progression. Here, we identify USP49 deubiquitinase as a novel regulator of the spindle checkpoint. We show that loss of USP49 in different cancer cell lines impairs proliferation and increases aneuploidy. In addition, USP49-depleted cells overcome the arrest induced by the SAC in the presence of nocodazole. Finally, we report new binding partners of USP49, including ribophorin 1, USP44, and different centrins.We thank A.P. Ugalde, D. Rodríguez, J.G. Pérez-Silva, Y. Español and F. Rodríguez for helpful comments and advice. We also thank S.A. Miranda, D. Álvarez-Puente and C. Garabaya for excellent technical assistance, as well as the staff of the scientific core facilities from the University of Oviedo (Unidad de Ensayos Biotecnológicos y Biomédicos, Servicios Científico-Técnicos). This work was supported by the Ministerio de Ciencia e Innovación (SAF2017-87655-R, PDI2020-118394RB-100 and PGC2018- 097019-B-I00), “la Caixa” Banking Foundation (project code HR17-00247), and the European Research Council (742067, DeAge). The IUOPA is funded by the Asturian Government and Fundación Cajastur-Liberbank.S

Nuclear envelope defects cause stem cell dysfunction in premature-aging mice

Nuclear lamina alterations occur in physiological aging and in premature aging syndromes. Because aging is also associated with abnormal stem cell homeostasis, we hypothesize that nuclear envelope alterations could have an important impact on stem cell compartments. To evaluate this hypothesis, we examined the number and functional competence of stem cells in Zmpste24-null progeroid mice, which exhibit nuclear lamina defects. We show that Zmpste24 deficiency causes an alteration in the number and proliferative capacity of epidermal stem cells. These changes are associated with an aberrant nuclear architecture of bulge cells and an increase in apoptosis of their supporting cells in the hair bulb region. These alterations are rescued in Zmpste24−/−Lmna+/− mutant mice, which do not manifest progeroid symptoms. We also report that molecular signaling pathways implicated in the regulation of stem cell behavior, such as Wnt and microphthalmia transcription factor, are altered in Zmpste24−/− mice. These findings establish a link between age-related nuclear envelope defects and stem cell dysfunction

Autophagy-linked plasma and lysosomal membrane protein PLAC8 is a key host factor for SARS-CoV-2 entry into human cells

Better understanding on interactions between SARS-CoV-2andhost cells should help to identify host factors that may be tar-getable to combat infection and COVID-19pathology. To this end,we have conducted a genome-wide CRISPR/Cas9-based loss-of-function screen in human lung cancer cells infected with SARS-CoV-2-pseudotyped lentiviruses. Our results recapitulate manyfindings from previous screens that used full SARS-CoV-2viruses,but also unveil two novel critical host factors: the lysosomal effluxtransporter SPNS1and the plasma and lysosomal membrane pro-tein PLAC8. Functional experiments with full SARS-CoV-2virusesconfirm that loss-of-function of these genes impairs viral entry.We find that PLAC8is a key limiting host factor, whose overexpres-sion boosts viral infection in eight different human lung cancer celllines. Using single-cell RNA-Seq data analyses, we demonstratethat PLAC8is highly expressed in ciliated and secretory cells of therespiratory tract, as well as in gut enterocytes, cell types that arehighly susceptible to SARS-CoV-2infection. Proteomics and cellbiology studies suggest that PLAC8and SPNS1regulate theautophagolysosomal compartment and affect the intracellular fateof endocytosed virions.This work was supported by Instituto de Salud Carlos III(COV20/00652, MS19/00100,  PI20/01267, COV20/00571 and PT17/0019/0003), Ministerio de Ciencia e Innovación (Spain) (PDI2020-118394RB-100, SAF2017-87655-R, PID2021-127534OB-100, and PGC2018-097019-B-I00), “laCaixa” Banking Foundation (HR17-00247) and Consejería de Ciencia, Innovación y Universidad del Gobierno del Principado de Asturias (AYUD/2021/57167). D.R.V and D.M are supported by PhD fellowships from Ministerio de Ciencia e Innovación(Spain).Peer reviewe

Lamins, guardians of the soma and the genome

Peer Reviewe

A functional link between the tumour suppressors ARF and p33ING1

The ARF tumour suppressor protein plays a critical role in the activation of p53 in response to oncogenic stress. ARF can activate p53 through nucleolar sequestration of Mdm2. However, several lines of evidence indicate that this is not the only way of action of ARF, and alternative mechanisms must exist. p33ING1 is a putative tumour suppresor, which induces cell-cycle arrest and apoptosis in a p53-dependent manner. Here, we describe that ARF and p33ING1 can interact in vivo. We also show that the subcellular localization of ING1 can be modulated by ARF protein levels, causing a displacement from nuclear to nucleolar localization. Finally, the ability of p33ING1 to cause cell-cycle arrest and induction of p21CIP1, or Mdm2, is impaired in ARF-deficient primary mouse fibroblasts. Based on these observations, we propose that the interaction with p33ING1 represents a novel mechanism for the tumour suppression function of ARF. © 2006 Nature Publishing Group All rights reserved.This work was supported by Grants INTACT (to MS) from the EU, and by Grants SAF2005-03018 (to MS), SAF03-0244 (to CLO) and SAF2003-00801 (to IP) from the Spanish Ministry of Science and Technology.Peer Reviewe

Structure and expression in E. coli of the gene coding for protein p10 of African swine fever virus

The gene encoding protein p10, a structural protein of African swine fever (ASF) virus, has been mapped, sequenced and expressed inE. coli. Protein p10 was purified from dissociated virus by reverse-phase HPLC, and its NH2-terminal end identified by automated Edman degradation. To map the gene encoding protein p10, a mixture of 20-mer oligonucleotides based upon a part of the amino acid sequence was hybridized to cloned ASF virus restriction fragments. This allowed the localization of the gene in fragmentEco RI K of the ASF virus genome. The nucleotide sequence obtained from this region revealed an open reading frame encoding 78 amino acids, with a high content of Ser and Lys residues. Several of the Ser residues are found in Ser-rich regions, which are also found in some nucleic acid-binding proteins. The gene coding for protein p10 has been inserted in an expression vector which contains the promoter for T 7 RNA polymerase. The recombinant plasmid was used to produce the ASF virus protein inE. coli. The bacterially produced p10 protein shows a strong DNA binding activity with similar affinity for both double-stranded and single-stranded DNA.This work was supported by grants from Comisi6n Interministerial de Ciencia y Tecnologia, the European Economic Community, and the Fundaci6n Ram6n Areces. M. Mufioz and J. P. Freije are recipients of fellowships from Fondo de Investigaciones Sanitarias and Formaci6n de Personal Investigador del Ministerio de Educaci6n y Ciencia, respectively

Cell autonomous and systemic factors in progeria development

Abstract Progeroid laminopathies are accelerated aging syndromes caused by defects in nuclear envelope proteins. Accordingly, mutations in the LMNA gene and functionally related genes have been described to cause HGPS (Hutchinson-Gilford progeria syndrome), MAD (mandibuloacral dysplasia) or RD (restrictive dermopathy). Functional studies with animal and cellular models of these syndromes have facilitated the identification of the molecular alterations and regulatory pathways involved in progeria development. We have recently described a novel regulatory pathway involving miR-29 and p53 tumour suppressor which has provided valuable information on the molecular components orchestrating the response to nuclear damage stress. Furthermore, by using progeroid mice deficient in ZMPSTE24 (zinc metalloprotease STE24 homologue) involved in lamin A maturation, we have demonstrated that, besides these abnormal cellular responses to stress, dysregulation of the somatotropic axis is responsible for some of the alterations associated with progeria. Consistent with these observations, pharmacological restoration of the somatotroph axis in these mice delays the onset of their progeroid features, significantly extending their lifespan and supporting the importance of systemic alterations in progeria progression. Finally, we have very recently identified a novel progeroid syndrome with distinctive features from HGPS and MAD, which we have designated NGPS (Néstor-Guillermo progeria syndrome) (OMIM #614008). This disorder is caused by a mutation in BANF1, a gene encoding a protein with essential functions in the assembly of the nuclear envelope, further illustrating the importance of the nuclear lamina integrity for human health and providing additional support to the study of progeroid syndromes as a valuable source of information on human aging

Identification, functional expression and enzymic analysis of two distinct CaaX proteases from Caenorhabditis elegans.

Post-translational processing of proteins such as the Ras GTPases, which contain a C-terminal CaaX motif (where C stands for cysteine, a for aliphatic and X is one of several amino acids), includes prenylation, proteolytic removal of the C-terminal tripeptide and carboxy-methylation of the isoprenyl-cysteine residue. In the present study, we report the presence of two distinct CaaX-proteolytic activities in membrane extracts from Caenorhabditis elegans, which are sensitive to EDTA and Tos-Phe-CH(2)Cl (tosylphenylalanylchloromethane; 'TPCK') respectively. A protein similar to the mammalian and yeast farnesylated-proteins converting enzyme-1 (FACE-1)/Ste24p CaaX metalloprotease, encoded by a hypothetical gene (CeFACE-1/C04F12.10) found in C. elegans chromosome I, probably accounts for the EDTA-sensitive activity. An orthologue of FACE-2/Rce1p, the enzyme responsible for the proteolytic maturation of Ras oncoproteins and other prenylated substrates, probably accounts for the Tos-Phe-CH(2)Cl-sensitive activity, even though the gene for FACE-2/Rce1 has not been previously identified in this model organism. We have identified a previously overlooked gene in C. elegans chromosome V, which codes for a 266-amino-acid protein (CeFACE-2) with 30% sequence identity to human FACE-2/Rce1. We show that both CeFACE-1 and CeFACE-2 have the ability to promote production of the farnesylated yeast pheromone a -factor in vivo and to cleave a farnesylated peptide in vitro. These results indicate that CeFACE-1 and CeFACE-2 are bona fide CaaX proteases and support the evolutionary conservation of this proteolytic system in eukaryotes