Effects of Sigma-1 Receptor Ligands on Peripheral Nerve Regeneration

Peripheral nerve injuries lead to the loss of motor, sensory and autonomic functions in the territories supplied by the injured nerve. Currently, nerve injuries are managed by surgical repair procedures, and there are no effective drugs in the clinic for improving the capacity of axonal regeneration. Sigma-1 receptor (Sig-1R) is an endoplasmic reticulum chaperon protein involved in many functions, including neuroprotection and neuroplasticity. A few previous studies using Sig-1R ligands reported results that suggest this receptor as a putative target to enhance regeneration. The aim of this study was to evaluate the possible effects of Sig-1R ligands on axonal regeneration in a sciatic nerve section and repair model in mice. To this end, mice were treated either with the Sig-1R agonist PRE-084 or the antagonist BD1063, and a Sig-1R knock-out (KO) mice group was also studied. The electrophysiological and histological data showed that treatment with Sig-1R ligands, or the lack of this protein, did not markedly modify the process of axonal regeneration and target reinnervation after sciatic nerve injury. Nevertheless, the nociceptive tests provided results indicating a role of Sig-1R in sensory perception after nerve injury, and immunohistochemical labeling indicated a regulatory role in inflammatory cell infiltration in the injured nerve

Cryo-EM structure and rRNA modification sites of a plant ribosome

[EN] Protein synthesis in crop plants contributes to the balance of food and fuel on our planet, which influences human metabolic activity and lifespan. Protein synthesis can be regulated with respect to changing environmental cues via the deposition of chemical modifications into rRNA. Here, we present the structure of a plant ribosome from tomato and a quantitative mass spectrometry analysis of its rRNAs. The study reveals fine features of the ribosomal proteins and 71 plant-specific rRNA modifications, and it re-annotates 30 rRNA residues in the available sequence. At the protein level, isoAsp is found in position 137 of uS11, and a zinc finger previously believed to be universal is missing from eL34, suggesting a lower effect of zinc deficiency on protein synthesis in plants. At the rRNA level, the plant ribosome differs markedly from its human counterpart with respect to the spatial distribution of modifications. Thus, it represents an additional layer of gene expression regulation, highlighting the molecular signature of a plant ribosome. The results provide a reference model of a plant ribosome for structural studies and an accurate marker for molecular ecology.This work was supported by the Swedish Foundation for Strategic Research (ARC19:0051), the Knut and Alice Wallenberg Foundation (2018.0080), the EMBO Young Investigator Program, and a NASA award (80NSSC18K1139 to A.S.P.).Cottilli, P.; Itoh, Y.; Nobe, Y.; Petrov, AS.; Lisón, P.; Taoka, M.; Amunts, A. (2022). Cryo-EM structure and rRNA modification sites of a plant ribosome. Plant communications. 3(5):1-9. https://doi.org/10.1016/j.xplc.2022.100342193

Citrus exocortis viroid causes ribosomal stress in tomato plants

[EN] Viroids are naked RNAs that do not code for any known protein and yet are able to infect plants causing severe diseases. Because of their RNA nature, many studies have focused on the involvement of viroids in RNA-mediated gene silencing as being their pathogenesis mechanism. Here, the alterations caused by the Citrus exocortis viroid (CEVd) on the tomato translation machinery were studied as a new aspect of viroid pathogenesis. The presence of viroids in the ribosomal fractions of infected tomato plants was detected. More precisely, CEVd and its derived viroid small RNAs were found to co-sediment with tomato ribosomes in vivo, and to provoke changes in the global polysome profiles, particularly in the 40S ribosomal subunit accumulation. Additionally, the viroid caused alterations in ribosome biogenesis in the infected tomato plants, affecting the 18S rRNA maturation process. A higher expression level of the ribosomal stress mediator NAC082 was also detected in the CEVd-infected tomato leaves. Both the alterations in the rRNA processing and the induction of NAC082 correlate with the degree of viroid symptomatology. Taken together, these results suggest that CEVd is responsible for defective ribosome biogenesis in tomato, thereby interfering with the translation machinery and, therefore, causing ribosomal stress.Spanish Ministry of Science, Innovation and Universities [BIO2009-11818, BIO2015-70483-R to A.F.]; Spanish Ministry of Science, Innovation and Universities [BFU2009-11958]; Generalitat Valenciana (Valencia, Spain) [AICO/2017/048]; Natural Sciences and Engineering Research Council of Canada [155219-17 to J.-P.P.]; The RNA group is supported by a grant from the Universite de Sherbrooke; J.-P.P. holds the Research Chair of the Universite de Sherbrooke in RNA Structure and Genomics, and is a member of the Centre de Recherche du CHUS; B.B.-P. was a recipient of a VALi+d postdoctoral contract of the Generalitat Valenciana [APOSTD/2017/039]; Schleiff group is funded through the Deutsche Forschungsgemeinschaft [SFB 902]. Funding for open access charge: Spanish Ministry of Science, Innovation and Universities.Cottilli, P.; Belda-Palazón, B.; Adkar-Purushothama, CR.; Perreault, J.; Schleiff, E.; Rodrigo Bravo, I.; Ferrando Monleón, AR.... (2019). Citrus exocortis viroid causes ribosomal stress in tomato plants. Nucleic Acids Research. 47(16):8649-8661. https://doi.org/10.1093/nar/gkz679S86498661471

Efecto del viroide de la exocortis de los cítricos sobre el estrés ribosomal en plantas de tomate

[ES] Las ribosomopatías son enfermedades humanas asociadas a defectos en el funcionamiento de los ribosomas. Hasta la fecha no han sido descritas como tales en el reino vegetal. Sin embargo, existen diversos trabajos en los que se describen anomalías en la biogénesis de ribosomas de plantas, asociados a importantes daños en el desarrollo. En el proceso de biogénesis de ribosomas, resulta fundamental el correcto procesamiento del transcrito pre-rRNA para dar lugar a los rRNAs maduros. A pesar de que en plantas no se dispone de un esquema claro de dicho procesamiento, se ha propuesto que puede tener lugar a través de dos vías, que podrían regularse diferencialmente en distintos tejidos o en situaciones de estrés. Los viroides son patógenos de RNA con una elevada estructura secundaria y sin capacidad codificante, por lo que los mecanismos considerados para el estudio de su patogénesis se han centrado en su capacidad para inducir mecanismos de silenciamiento génico. Sin embargo, la relación precisa entre los procesos de silenciamiento activados por viroide y la sintomatología viroidal sigue siendo desconocida. En el presente Trabajo, se describen los resultados presentados en el artículo de Cottilli et al., 2019 (under review en Nucleic Acids Research, ver Anexo) donde exploramos la posibilidad de que las infecciones viroidales puedan producir alteraciones en el funcionamiento ribosomal, considerando así a los viroides como agentes causales de ribosomopatías.[EN] Ribosomopathies are human diseases associated with defects on ribosome function. Up to now, they have not been described in the plant kingdom. However, there are several works that describe anomalies on ribosome biogenesis in plants, associated to important developmental damages. In the process of ribosome biogenesis, the correct processing of the pre-rRNA transcript is fundamental in order to produce mature rRNAs. Despite of the lack of a clear scheme of this process in plants, it has been proposed that it could occur through two pathways, and they could be regulated differentially in diverse tissues or stress situations. Viroids are non-coding RNA pathogens with a high secondary structure, therefore the mechanisms considered to study its pathogenicity have been focused on its capability to induce the gene silencing mechanisms. However, the precise relationship between the silencing processes activated by the viroid and the viroidal symptomatology remain unknown. In this project, we describe the results presented in the article by Cottilli et al., 2019 (under review in Nucleic Acids Research, see Annex) where we hypothesize that the viroid infection could provoke alterations in the ribosomal functioning, thus considering the viroids as ribosomopathogenic agents.Cottilli, P. (2019). Efecto del viroide de la exocortis de los cítricos sobre el estrés ribosomal en plantas de tomate. http://hdl.handle.net/10251/123916TFG

Effects of Sigma-1 Receptor Ligands on Peripheral Nerve Regeneration

Peripheral nerve injuries lead to the loss of motor, sensory and autonomic functions in the territories supplied by the injured nerve. Currently, nerve injuries are managed by surgical repair procedures, and there are no effective drugs in the clinic for improving the capacity of axonal regeneration. Sigma-1 receptor (Sig-1R) is an endoplasmic reticulum chaperon protein involved in many functions, including neuroprotection and neuroplasticity. A few previous studies using Sig-1R ligands reported results that suggest this receptor as a putative target to enhance regeneration. The aim of this study was to evaluate the possible effects of Sig-1R ligands on axonal regeneration in a sciatic nerve section and repair model in mice. To this end, mice were treated either with the Sig-1R agonist PRE-084 or the antagonist BD1063, and a Sig-1R knock-out (KO) mice group was also studied. The electrophysiological and histological data showed that treatment with Sig-1R ligands, or the lack of this protein, did not markedly modify the process of axonal regeneration and target reinnervation after sciatic nerve injury. Nevertheless, the nociceptive tests provided results indicating a role of Sig-1R in sensory perception after nerve injury, and immunohistochemical labeling indicated a regulatory role in inflammatory cell infiltration in the injured nerve

Citrus exocortis viroid causes ribosomal stress in tomato plants

[EN] Viroids are naked RNAs that do not code for any known protein and yet are able to infect plants causing severe diseases. Because of their RNA nature, many studies have focused on the involvement of viroids in RNA-mediated gene silencing as being their pathogenesis mechanism. Here, the alterations caused by the Citrus exocortis viroid (CEVd) on the tomato translation machinery were studied as a new aspect of viroid pathogenesis. The presence of viroids in the ribosomal fractions of infected tomato plants was detected. More precisely, CEVd and its derived viroid small RNAs were found to co-sediment with tomato ribosomes in vivo, and to provoke changes in the global polysome profiles, particularly in the 40S ribosomal subunit accumulation. Additionally, the viroid caused alterations in ribosome biogenesis in the infected tomato plants, affecting the 18S rRNA maturation process. A higher expression level of the ribosomal stress mediator NAC082 was also detected in the CEVd-infected tomato leaves. Both the alterations in the rRNA processing and the induction of NAC082 correlate with the degree of viroid symptomatology. Taken together, these results suggest that CEVd is responsible for defective ribosome biogenesis in tomato, thereby interfering with the translation machinery and, therefore, causing ribosomal stress.Spanish Ministry of Science, Innovation and Universities [BIO2009-11818, BIO2015-70483-R to A.F.]; Spanish Ministry of Science, Innovation and Universities [BFU2009-11958]; Generalitat Valenciana (Valencia, Spain) [AICO/2017/048]; Natural Sciences and Engineering Research Council of Canada [155219-17 to J.-P.P.]; The RNA group is supported by a grant from the Universite de Sherbrooke; J.-P.P. holds the Research Chair of the Universite de Sherbrooke in RNA Structure and Genomics, and is a member of the Centre de Recherche du CHUS; B.B.-P. was a recipient of a VALi+d postdoctoral contract of the Generalitat Valenciana [APOSTD/2017/039]; Schleiff group is funded through the Deutsche Forschungsgemeinschaft [SFB 902]. Funding for open access charge: Spanish Ministry of Science, Innovation and Universities.Cottilli, P.; Belda-Palazón, B.; Adkar-Purushothama, CR.; Perreault, J.; Schleiff, E.; Rodrigo Bravo, I.; Ferrando Monleón, AR.... (2019). Citrus exocortis viroid causes ribosomal stress in tomato plants. Nucleic Acids Research. 47(16):8649-8661. https://doi.org/10.1093/nar/gkz679864986614716Di Serio, F., & Flores, R. (2008). Viroids: Molecular implements for dissecting RNA trafficking in plants. RNA Biology, 5(3), 128-131. doi:10.4161/rna.5.3.6638Flores, R., Owens, R. A., & Taylor, J. (2016). Pathogenesis by subviral agents: viroids and hepatitis delta virus. Current Opinion in Virology, 17, 87-94. doi:10.1016/j.coviro.2016.01.022Di Serio, F., Flores, R., Verhoeven, J. T. J., Li, S.-F., Pallás, V., Randles, J. W., … Owens, R. A. (2014). Current status of viroid taxonomy. 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