Person: García Ortega, Lucía
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First Name
Lucía
Last Name
García Ortega
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Bioquímica y Biología Molecular
Area
Bioquímica y Biología Molecular
Identifiers
12 results
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Now showing 1 - 10 of 12
Item Characterization of a new toxin from the entomopathogenic fungus Metarhizium anisopliae: the ribotoxin anisoplin(Biological chemistry, 2017) Olombrada, Miriam; Medina, Pilar; Budia, Flor; Gavilanes, José; Martínez Del Pozo, Álvaro; García Ortega, LucíaMetarhizium anisopliae is an entomopathogenic fungus relevant in biotechnology with applications like malaria vector control. Studies of its virulence factors are therefore of great interest. Fungal ribotoxins are toxic ribonucleases with extraordinary efficiency against target ribosomes and suggested as potential insecticides. Here, we describe this ribotoxin characteristic activity in M. anisopliae cultures. Anisoplin has been obtained as a recombinant protein and further characterized. It is structurally similar to hirsutellin A, the ribotoxin from the entomopathogen Hirsutella thompsonii. Moreover, anisoplin shows the ribonucleolytic activity typical of ribotoxins and cytotoxicity against insect cells. How Metarhizium uses this toxin and possible applications are on perspective.Item The ribotoxin -sarcin can cleave the sarcin/ricin loop on late 60S pre-ribosomes(Nucleic Acids Research, 2020) Olombrada, Miriam; Peña, Cohue; Rodríguez Galán, Olga; Klingauf Nerurkar, Purnima; Portugal Calisto, Daniela; Oborská Oplová, Michaela; Altvater, Martin; Gavilanes, José G.; Martínez Del Pozo, Álvaro; Cruz, Jesús de la; García Ortega, Lucía; Govind Panse, VikramThe ribotoxin -sarcin belongs to a family of ribonucleases that cleave the sarcin/ricin loop (SRL), a critical functional rRNA element within the large ribosomal subunit (60S), thereby abolishing translation. Whether -sarcin targets the SRL only in mature 60S subunits remains unresolved. Here, we show that, in yeast, -sarcin can cleave SRLs within late 60S pre-ribosomes containing mature 25S rRNA but not nucleolar/nuclear 60S pre-ribosomes containing 27S pre-rRNA in vivo. Conditional expression of -sarcin is lethal, but does not impede early pre-rRNA processing, nuclear export and the cytoplasmic maturation of 60S pre-ribosomes. Thus, SRL-cleaved containing late 60S pre-ribosomes seem to escape cytoplasmic proofreading steps. Polysome analyses revealed that SRL-cleaved 60S ribosomal subunits form 80S initiation complexes, but fail to progress to the step of translation elongation. We suggest that the functional integrity of a -sarcin cleaved SRL might be assessed only during translation.Item Characterization of a new toxin from the entomopathogenic fungus Metarhizium anisopliae: the ribotoxin anisoplin(Biological Chemistry, 2016) Olombrada, Miriam; Medina, Pilar; Budia, Flor; Gavilanes, José G.; Martínez Del Pozo, Álvaro; García Ortega, LucíaMetarhizium anisopliae is an entomopathogenic fungus relevant in biotechnology with applications like malaria vector control. Studies of its virulence factors are therefore of great interest. Fungal ribotoxins are toxic ribonucleases with extraordinary efficiency against target ribosomes and suggested as potential insecticides. Here, we describe this ribotoxin characteristic activity in M. anisopliae cultures. Anisoplin has been obtained as a recombinant protein and further characterized. It is structurally similar to hirsutellin A, the ribotoxin from the entomopathogen Hirsutella thompsonii. Moreover, anisoplin shows the ribonucleolytic activity typical of ribotoxins and cytotoxicity against insect cells. How Metarhizium uses this toxin and possible applications are on perspective.Item Fungal Ribotoxins(ELS, 2018) García Ortega, Lucía; Palacios Ortega, Juan; Martínez Del Pozo, ÁlvaroFungal ribotoxins constitute a family of extracellular ribonucleases with exquisite specificity against rRNA (ribonucleic acid). They induce apoptotic death of cells after inhibiting protein translation. Ribosomes become functionally incompetent because ribotoxins cleave one single phosphodiester bond, located at a unique and universally conserved loop, needed for elongation factors function. As secreted proteins, ribotoxins need to cross the membrane of their target cells in order to exert their catalytic activity, and they do it without receptor mediation. Using lipid model systems, it has been shown that they are able to enter cells with membranes enriched in acidic phospholipids. Both membrane-interacting and ribosomal-recognition activities are characterised by distinct structural features. Even though the natural function of ribotoxins is not known yet, their production by entomopathogenic fungi has suggested their insecticidal role. After decades of detailed study, the biotechnological potential of ribotoxins in pest control and as antitumour agents is becoming evident.Item Fungal extracellular ribotoxins as insecticidal agents(Insect Biochemistry and Molecular Biology, 2013) Olombrada Sacristán, Miriam; Herrero Galán, Elías; Tello, Daniel; Oñaderra Sánchez, Mercedes; Gavilanes, José G.; Martínez Del Pozo, Álvaro; García Ortega, LucíaFungal ribotoxins were discovered almost 50 years ago as extracellular ribonucleases (RNases) with antitumoral properties. However, the biological function of these toxic proteins has remained elusive. The discovery of the ribotoxin HtA, produced by the invertebrates pathogen H. thompsonii, revived the old proposal that insecticidal activity would be their long searched function. Unfortunately, HtA is rather singular among all ribotoxins known in terms of sequence and structure similarities. Thus, it was intriguing to answer the question of whether HtA is just an exception or, on the contrary, the paradigmatic example of the ribotoxins function. The work presented uses HtA and -sarcin, the most representative member of the ribotoxins family, to show their strong toxic action against insect larvae and cells.Item Pulmonary surfactant-derived antiviral actions at the respiratory surface(Current Opinion in Colloid & Interface Science, 2023) Isasi Campillo, Miriam; Losada Oliva, Paula; Pérez Gil, Jesús; Olmeda Lozano, Bárbara; García Ortega, LucíaLung surfactant (LS) is a membrane-based lipid-protein complex that lines the alveoli, reducing the surface tension at the air-liquid interface and thus minimizing the work of breathing. Besides this function, LS is also the first physical barrier between the outside air and the systemic circulation, therefore playing a key role in the defense against harmful particles and microorganisms. Viral respiratory tract infections (RTIs), and especially acute lower RTIs, are one of the leading causes of morbidity and mortality worldwide. LS participates in the network of interactions between viruses and the immune system to prevent or lessen the effects of the infection, but it is also altered by these pathogens, which can potentially impair its function. The aim of this review is to provide an integrated multidisciplinary overview toward understanding the interplay between respiratory viruses and LS and its health impact on the respiratory system. The review is centered on the antiviral mechanisms of both LS proteins and lipids, and their different interactions that lead to varying outcomes. Finally, a summary of the clinical application of surfactant in the scene of lung viral infection is disclosed, including state-of-the-art approaches of the therapeutic use of surfactant components.Item The ribotoxin α-sarcin can cleave the sarcin/ricin loop on late 60S pre-ribosomes(Nucleic Acids Research, 2020) Olombrada, Miriam; Peña, Cohue; Rodríguez Galán, Olga; Klingauf Nerurkar, Purnima; Portugal Calisto, Daniela; Oborská Oplová, Michaela; Altvater, Martin; Gavilanes, José G.; Martínez Del Pozo, Álvaro; De la Cruz, Jesús; García Ortega, Lucía; Govind Panse, VikramThe ribotoxin -sarcin belongs to a family of ribonucleases that cleave the sarcin/ricin loop (SRL), a critical functional rRNA element within the large ribosomal subunit (60S), thereby abolishing translation. Whether -sarcin targets the SRL only in mature 60S subunits remains unresolved. Here, we show that, in yeast, -sarcin can cleave SRLs within late 60S pre-ribosomes containing mature 25S rRNA but not nucleolar/nuclear 60S pre-ribosomes containing 27S pre-rRNA in vivo. Conditional expression of -sarcin is lethal, but does not impede early pre-rRNA processing, nuclear export and the cytoplasmic maturation of 60S pre-ribosomes. Thus, SRL-cleaved containing late 60S pre-ribosomes seem to escape cytoplasmic proofreading steps. Polysome analyses revealed that SRL-cleaved 60S ribosomal subunits form 80S initiation complexes, but fail to progress to the step of translation elongation. We suggest that the functional integrity of a -sarcin cleaved SRL might be assessed only during translation.Item Involvement of loops 2 and 3 of alpha-sarcin on its ribotoxic activity(Toxicon, 2015) Castaño Rodríguez, Carlos; Olombrada Sacristán, Miriam; Partida Hanon, Angélica; Lacadena García-Gallo, Francisco Javier; Oñaderra Sánchez, Mercedes; Gavilanes, José G.; García Ortega, Lucía; Martínez Del Pozo, ÁlvaroRibotoxins are a family of fungal ribosome-inactivating proteins displaying highly specific ribonucleolytic activity against the sarcin/ricin loop (SRL) of the larger rRNA, with a-sarcin as its best-characterized member. Their toxicity arises from the combination of this activity with their ability to cross cell membranes. The involvement of a-sarcin's loops 2 and 3 in SRL and ribosomal proteins recognition, as well as in the ribotoxin-lipid interactions involving cell penetration, has been suggested some time ago. In the work presented now different mutants have been prepared in order to study the role of these loops in their ribonucleolytic and lipid-interacting properties. The results obtained confirm that loop 3 residues Lys 111, 112, and 114 are key actors of the specific recognition of the SRL. In addition, it is also shown that Lys 114 and Tyr 48 conform a network of interactions which is essential for the catalysis. Lipid-interaction studies show that this Lys-rich region is indeed involved in the phospholipids recognition needed to cross cell membranes. Loop 2 is shown to be responsible for the conformational change which exposes the region establishing hydrophobic interactions with the membrane inner leaflets and eases penetration of ribotoxins target cells.Item Involvement of loop 5 lysine residues and the N-terminal β- hairpin of the ribotoxin hirsutellin A on its insecticidal activity(Biological Chemistry, 2015) Olombrada, Miriam; García Ortega, Lucía; Lacadena García-Gallo, Francisco Javier; Oñaderra, Mercedes; Gavilanes, José G.; Martínez Del Pozo, ÁlvaroRibotoxins are cytotoxic members of the family of fungal extracellular ribonucleases best represented by RNase T1. They share a high degree of sequence identity and a common structural fold, including the geometric arrangement of their active sites. However,ribotoxins are larger, with a well-defined N-terminal β-hairpin, and display longer and positively charged unstructured loops. These structural differences account for their cytotoxic properties. Unexpectedly, the discovery of hirsutellin A (HtA), a ribotoxin produced by the invertebrate pathogen Hirsutella thompsonii, showed how it was possible to accommodate these features into a shorter amino acid sequence. Examination of HtA Nterminal β-hairpin reveals differences in terms of length, charge, and spatial distribution. Consequently, four different HtA mutants were prepared and characterized. One of them was the result of deleting this hairpin [D(8-15)] while the other three affected single Lys residues in its close spatial proximity (K115E, K118E, and K123E). The results obtained support the general conclusion that HtA active site would show a high degree of plasticity,being able to accommodate electrostatic and structural changes not suitable for the other previously known larger ribotoxins, as the variants described here only presented small differences in terms of ribonucleolytic activity and cytotoxicity against cultured insect cells. .Item Involvement of loop 5 lysine residues and the N-terminal β-hairpin of the ribotoxin hirsutellin A on its insecticidal activity(Biological chemistry, 2016) Olombrada, Miriam; García Ortega, Lucía; Lacadena García-Gallo, Francisco Javier; Oñaderra, Mercedes; Gavilanes, José G.; Martínez Del Pozo, ÁlvaroRibotoxins are cytotoxic members of the family of fungal extracellular ribonucleases best represented by RNase T1. They share a high degree of sequence identity and a common structural fold, including the geometric arrangement of their active sites. However, ribotoxins are larger,with a well-defined N-terminal β-hairpin, and display longer and positively charged unstructured loops. These structural differences account for their cytotoxic properties.Unexpectedly, the discovery of hirsutellin A (HtA), a ribotoxin produced by the invertebrate pathogen Hirsutella thompsonii, showed how it was possible to accommodate these features into a shorter amino acid sequence. Examination of HtA N-terminal β-hairpin reveals differences in terms of length, charge, and spatial distribution. Consequently,four different HtA mutants were prepared and characterized. One of them was the result of deleting this hairpin [Δ(8-15)] while the other three affected single Lys residues in its close spatial proximity (K115E, K118E, and K123E). The results obtained support the general conclusion that HtA active site would show a high degree of plasticity,being able to accommodate electrostatic and structural changes not suitable for the other previously known larger ribotoxins, as the variants described here only presented small differences in terms of ribonucleolytic activity and cytotoxicity against cultured insect cells.