Neuronal p38α mediates synaptic and cognitive dysfunction in an Alzheimer’s mouse model by controlling β-amyloid production.

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by a severe and progressive neuronal loss leading to cognitive dysfunctions. Previous reports, based on the use of chemical inhibitors, have connected the stress kinase p38α to neuroinflammation, neuronal death and synaptic dysfunction. To explore the specific role of neuronal p38α signalling in the appearance of pathological symptoms, we have generated mice that combine expression of the 5XFAD transgenes to induce AD symptoms with the downregulation of p38α only in neurons (5XFAD/p38α∆-N). We found that the neuronal-specific deletion of p38α improves the memory loss and long-term potentiation impairment induced by 5XFAD transgenes. Furthermore, 5XFAD/p38α∆-N mice display reduced amyloid-β accumulation, improved neurogenesis, and important changes in brain cytokine expression compared with 5XFAD mice. Our results implicate neuronal p38α signalling in the synaptic plasticity dysfunction and memory impairment observed in 5XFAD mice, by regulating both amyloid-β deposition in the brain and the relay of this accumulation to mount an inflammatory response, which leads to the cognitive deficits.post-print1848 K

Hsp70 and Hsp40 inhibit an inter-domain interaction necessary for transcriptional activity in the androgen receptor.

Molecular chaperones such as Hsp40 and Hsp70 hold the androgen receptor (AR) in an inactive conformation. They are released in the presence of androgens, enabling transactivation and causing the receptor to become aggregation-prone. Here we show that these molecular chaperones recognize a region of the AR N-terminal domain (NTD), including a FQNLF motif, that interacts with the AR ligand-binding domain (LBD) upon activation. This suggests that competition between molecular chaperones and the LBD for the FQNLF motif regulates AR activation. We also show that, while the free NTD oligomerizes, binding to Hsp70 increases its solubility. Stabilizing the NTD-Hsp70 interaction with small molecules reduces AR aggregation and promotes its degradation in cellular and mouse models of the neuromuscular disorder spinal bulbar muscular atrophy. These results help resolve the mechanisms by which molecular chaperones regulate the balance between AR aggregation, activation and quality control

Astrocytic p38α MAPK drives NMDA receptor-dependent long-term depression and modulates long-term memory.

NMDA receptor-dependent long-term depression (LTD) in the hippocampus is a well-known form of synaptic plasticity that has been linked to different cognitive functions. The core mechanism for this form of plasticity is thought to be entirely neuronal. However, we now demonstrate that astrocytic activity drives LTD at CA3-CA1 synapses. We have found that LTD induction enhances astrocyte-to-neuron communication mediated by glutamate, and that Ca2+ signaling and SNARE-dependent vesicular release from the astrocyte are required for LTD expression. In addition, using optogenetic techniques, we show that low-frequency astrocytic activation, in the absence of presynaptic activity, is sufficient to induce postsynaptic AMPA receptor removal and LTD expression. Using cell-type-specific gene deletion, we show that astrocytic p38α MAPK is required for the increased astrocytic glutamate release and astrocyte-to-neuron communication during low-frequency stimulation. Accordingly, removal of astrocytic (but not neuronal) p38α abolishes LTD expression. Finally, this mechanism modulates long-term memory in vivo.post-print5316 K

A new regulatory mechanism of protein phosphatase 2A activity via SET in acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy. Although novel emerging drugs are available, the overall prognosis remains poor and new therapeutic approaches are required. PP2A phosphatase is a key regulator of cell homeostasis and is recurrently inactivated in AML. The anticancer activity of several PP2A-activating drugs (e.g., FTY720) depends on their interaction with the SET oncoprotein, an endogenous PP2A inhibitor that is overexpressed in 30% of AML cases. Elucidation of SET regulatory mechanisms may therefore provide novel targeted therapies for SET-overexpressing AMLs. Here, we show that upregulation of protein kinase p38 beta is a common event in AML. We provide evidence that p38 beta potentiates SET-mediated PP2A inactivation by two mechanisms: facilitating SET cytoplasmic translocation through CK2 phosphorylation, and directly binding to and stabilizing the SET protein. We demonstrate the importance of this new regulatory mechanism in primary AML cells from patients and in zebrafish xenograft models. Accordingly, combination of the CK2 inhibitor CX-4945, which retains SET in the nucleus, and FTY720, which disrupts the SET-PP2A binding in the cytoplasm, significantly reduces the viability and migration of AML cells. In conclusion, we show that the p38 beta/CK2/SET axis represents a new potential therapeutic pathway in AML patients with SET-dependent PP2A inactivation

Author Correction: Hsp70 and Hsp40 inhibit an inter-domain interaction necessary for transcriptional activity in the androgen receptor.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Inventariando la biodiversidad en el Parque Nacional de La Caldera de Taburiente (La Palma, Islas Canarias, España): novedades científicas

This paper is the first result of an agreement between the Organismo Autónomo Parques Nacionales and the Consejo Superior de Investigaciones Científicas, entitled “Inventory and study of the Invertebrate Fauna of the National Park of La Caldera de Taburiente”. A detailed account of the faunistic novelties found up to now among the specimens of terrestrial and freshwater invertebrates collected along the two years of sampling (July 1999 to July 2001), whose number is estimated in ca. 500,000, is given. A brief description of planning and of methodology applied to the inventory of the invertebrate fauna is made and a tabulated summary of novelties is presented. The list shows at present 284 families, 594 genera and 739 species. For the Canary Islands, the present record of new taxa is 29 families, 115 genera (1 of them confirmed as new to Science and 3 awaiting confirmation) and 187 species (24 new to Science). Moreover, 242 genera and 338 species are new to the fauna of La Palma I., being known from other islands of the archipelago. Other 47 taxa, still being studied, could be new to Science as well. These results have been reached with the study of just a minimal part of the whole material, which underlines the need for systematic, continued sampling to evaluate the faunistic richness of poorly explored areas and its possible necessity for protection. Therefore, one should expect more novelties and the inventory may increase significantly when all the material is revised.El presente artículo es el primer resultado de un convenio entre el Organismo Autónomo Parques Nacionales y el Consejo Superior de Investigaciones Científicas, denominado “Inventario y estudio de la Fauna Invertebrada del Parque Nacional de La Caldera de Taburiente”. Se detallan las novedades faunísticas encontradas hasta el momento entre los ejemplares de invertebrados terrestres y dulceacuícolas recogidos durante los dos años de muestreo (julio de 1999 a julio de 2001), cuyo número se estima en unos 500.000. Se hace una breve descripción de la planificación y la metodología aplicadas al inventario de la fauna invertebrada y se tabulan las novedades. En su estado actual el inventario arroja 284 familias, 594 géneros y 739 especies. Para la fauna de las Islas Canarias, el registro actual de táxones nuevos es de 29 familias, 115 géneros (de los cuales 1 género ha sido confirmado como nuevo para la Ciencia y otros 3 están pendientes de confirmación) y 187 especies (de las cuales 24 nuevas para la Ciencia). Además, 242 géneros y 338 especies son nuevas para la fauna de la isla de La Palma, conociéndose con anterioridad de otras islas del archipiélago. Otros 47 táxones aún en estudio, podrían resultar asimismo nuevos para la Ciencia. Estos resultados se han alcanzado tan sólo con el estudio de una parte mínima del material, lo que subraya la necesidad de muestreos continuados y sistemáticos para evaluar la riqueza faunística de áreas poco exploradas y su posible necesidad de protección. Por tanto, cabe esperar más novedades y el inventario puede quedar significativamente incrementado cuando se revise todo el material

Characterization of p38α autophosphorylation inhibitors that target the non-canonical activation pathway

16 pages, 10 figures, supplementary information https://doi.org/10.1038/s41467-023-39051-x.-- Data availability: The diffraction data and coordinates of the p38α complexes bound to NC-p38i compounds have been deposited in the Protein Data Bank under accession codes 7PVU, 7Z6I and 7Z9T. We have also used the following PDB structures: 4LOO, 1A9U, 3COI, 7N8T, 2ZOQ, 1PME, 3GC9, 1CM8, 4UX9. Source data are provided with this paperp38α is a versatile protein kinase that can control numerous processes and plays important roles in the cellular responses to stress. Dysregulation of p38α signaling has been linked to several diseases including inflammation, immune disorders and cancer, suggesting that targeting p38α could be therapeutically beneficial. Over the last two decades, numerous p38α inhibitors have been developed, which showed promising effects in pre-clinical studies but results from clinical trials have been disappointing, fueling the interest in the generation of alternative mechanisms of p38α modulation. Here, we report the in silico identification of compounds that we refer to as non-canonical p38α inhibitors (NC-p38i). By combining biochemical and structural analyses, we show that NC-p38i efficiently inhibit p38α autophosphorylation but weakly affect the activity of the canonical pathway. Our results demonstrate how the structural plasticity of p38α can be leveraged to develop therapeutic opportunities targeting a subset of the functions regulated by this pathwayThis work was supported by grants from the Spanish Ministerio de Ciencia e Innovación (MICINN, PID2019-109521RB-I00 and PID2021-122478NB-I00), the BioMedTec program of IRB-Fundació La Caixa, the European Research Council (Proof of Concept p38_InTh-825763), AGAUR (2016 LLAV 00043 and 2019 PROD 00138 supported by FEDER, and 2017 SGR-557, 2017 SGR-50, 2021 SGR-909, and 2021 SGR-866), BBVA Foundation, and the European Union’s Horizon 2020 research and innovation program (euCanSHare 825903 and BioExcel-3 101093290). L.G. and B.B. were funded by predoctoral contracts from MICINN (BES-2016-077122) and the Marie Skłodowska-Curie COFUND action of IRB Barcelona and the PREBIST Predoc Programme (PREBIST_754558), respectively. F.C. is a Ramon y Cajal Fellow (RYC2019-026768-I). Access to ALBA was granted through the BAG proposals 2018092972 and 2020094472. We gratefully acknowledge institutional funding from IRB Barcelona, the CERCA Programme of the Catalan Government, and the MICINN through the Centres of Excellence Severo Ochoa award. M.J.M. and A.R.N. are supported by the Institució Catalana de Recerca i Estudis Avancats (ICREA)With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe

P38 MAPK: a dual role in hepatocyte proliferation through reactive oxygen species

p38 MAPKs are important mediators of signal transduction that respond to a wide range of extracellular stressors such as UV radiation, osmotic shock, hypoxia, pro-inflammatory cytokines, and oxidative stress. The most abundant family member is p38α, which helps to couple cell proliferation and growth in response to certain damaging stimuli. In fact, increased proliferation and impaired differentiation are hallmarks of p38α-deficient cells. It has been reported that reactive oxygen species (ROS) play a critical role in cytokine-induced p38α activation. Under physiological conditions, p38α can function as a mediator of ROS signaling and either activate or suppress cell cycle progression depending on the activation stimulus. The interplay between cell proliferation, p38 MAPK activation, and ROS production plays an important role in hepatocytes. In fact, low levels of ROS seem to be needed to activate several signaling pathways in response to hepatectomy and to orchestrate liver regeneration. p38 MAPK works as a sensor of oxidative stress and cells that have developed mechanisms to uncouple p38 MAPK activation from oxidative stress are more likely to become tumorigenic. So far, p38α influences the redox balance, determining cell survival, terminal differentiation, proliferation, and senescence. Further studies would be necessary in order to clarify the precise role of p38 MAPK signaling as a redox therapeutical target

A combination of neutral loss and targeted product ion scanning with two enzymatic digestions facilitates the comprehensive mapping of phosphorylation sites

9 p-.5 fig.-2 tab.We propose here a new strategy for the exhaustive mapping of phosphorylation sites in the Xenopus laevis Cdc25 phosphatase, which regulates cell cycle progression in eukaryotic cells. Two different MS analyses in a linear IT were used to identify the phosphorylated residues. First, a data‐dependent neutral loss (DDNL) analysis triggered the fragmentation of peptides that show enhanced neutral loss of phosphoric acid. Second, a targeted product ion scanning (TPIS) mass analysis was carried out in which MS2 events are triggered for specific m/z values. Full coverage of the protein sequence was obtained by combining the two analyses with two enzymatic digestions, trypsin and chymotrypsin, yielding a comprehensive map of the phosphorylation sites. Previous reports have shown Cdc25C to be phosphorylated by Cdc2–cyclin B at four residues (Thr48, Thr67, Thr138 and Ser205). By using this combination of scan modes, we have identified four additional phosphorylation sites (Thr86, Ser99, Thr112 and Ser163) in a recombinant Cdc25C protein containing 198 residues of the NH2‐terminal noncatalytic domain. The sensitivity of this combined approach makes it extremely useful for the comprehensive characterization of phosphorylation sites, virtually permitting complete coverage of the protein sequence with peptides within the mass detection range of the linear IT.Peer reviewe

Aging increases hippocampal DUSP2 by a membrane cholesterol loss-mediated RTK/p38MAPK activation mechanism

Numerous studies suggest that the increased activity of p38MAPK plays an important role in the abnormal immune and inflammatory response observed in the course of neurodegenerative diseases such as Alzheimer's disease. On the other hand, High levels of p38MAPK are present in the brain during normal aging, suggesting the existence of mechanisms that keep the p38MAPK-regulated pro-inflammatory activity within physiological limits. In this study, we show that high p38MAPK activity in the hippocampus of old mice is in part due to the reduction in membrane cholesterol that constitutively occurs in the aging brain. Mechanistically, membrane cholesterol reduction increases p38MAPK activity through the stimulation of a subset of tyrosine kinase receptors (RTKs). In turn, activated p38MAPK increases the expression and activity of the phosphatase DUSP2, which is known to reduce the activity of different MAPKs, including p38MAPK. These results suggest that the loss of membrane cholesterol that constitutively occurs with age takes part in a negative-feedback loop that keeps p38MAPK activity levels within physiological range. Thus, conditions that increase p38MAPK activity such as cellular stressors or that inhibit DUSP2 will amplify inflammatory activity with its consequent deleterious functional changes.Ministry of Economy and Competitiveness grants Consolider CSD2010-00064 and SAF2013-45392 and SAF201676722 to CD. AN was supported by the Consolider grant CSD2010-0045. PF is the recipient of a Ramon y Cajal Award RYC-2014-16410 from the Spanish Ministry of Economy and Competitiveness