Minor intron splicing efficiency increases with the development of lethal prostate cancer

Here we explored the role of minor spliceosome (MiS) function and minor intron-containing gene (MIG) expression in prostate cancer (PCa). We show MIGs are enriched as direct interactors of cancer-causing genes and their expression discriminates PCa progression. Increased expression of MiS U6atac snRNA, including others, and 6x more efficient minor intron splicing was observed in castration-resistant PCa (CRPC) versus primary PCa. Notably, androgen receptor signalling influenced MiS activity. Inhibition of MiS through siU6atac in PCa caused minor intron mis-splicing and aberrant expression of MIG transcripts and encoded proteins, which enriched for MAPK activity, DNA repair and cell cycle. Single cell-RNAseq confirmed cell cycle defects and lineage dependency on the MiS from primary to CRPC and neuroendocrine PCa. siU6atac was ~50% more efficient in lowering tumor burden of CRPC cells and organoids versus current state-of-the-art combination therapy. In all, MiS is a strong therapeutic target for lethal PCa and potentially other cancers.

SARS-CoV-2 hijacks p38β/MAPK11 to promote viral protein translation

SARS-CoV-2, the causative agent of the COVID-19 pandemic, drastically modifies the cells that it infects. One such effect is the activation of the host p38 mitogen-activated protein kinase (MAPK) pathway, which plays a major role in inflammation pathways that are dysregulated in severe COVID-19 cases. Inhibition of p38/MAPK activity in SARS-CoV-2-infected cells reduces both cytokine production and viral replication. Here, we applied a systems biology approach to better understand interactions between the p38/MAPK pathway and SARS-CoV-2 in human lung epithelial cells. We found several components of the p38/MAPK pathway positively and negatively impact SARS-CoV-2 infection and that p38β is a required host factor for SARS-CoV-2 that acts by promoting viral protein translation in a manner that prevents innate immune sensing. Furthermore, we combined chemical and genetic perturbations of p38β with quantitative phosphoproteomics to identify novel, putative p38β substrates in an unbiased manner, with broad relevance beyond SARS-CoV-2 biology.

Protocatechualdehyde Inhibits the Osteoclast Differentiation of RAW264.7 and BMM Cells by Regulating NF-κB and MAPK Activity

Protocatechualdehyde (PCA), an important component of Salvia miltiorrhiza, has many activities, such as anti-inflammatory and antisepsis activities. However, the role of PCA in osteoclasts is not clear. We used RAW264.7 cells (a mouse leukemic monocyte/macrophage cell line) and bone marrow macrophages (BMMs) to probe the role of PCA in osteoclasts and the underlying mechanism. The effects of PCA on cell activity were evaluated with CCK-8 assays. TRAP staining detected mature osteoclasts. Corning Osteo Assay Surface plates were used to examine absorption. The levels of RNA and protein were analyzed, respectively, using RT-PCR and Western blotting. PCA (5 μg/ml) was not toxic to the two cell types but reduced the formation of osteoclasts and bone absorption. Furthermore, PCA restrained the expression of mRNAs encoding proteins associated with osteoclasts and reduced the phosphorylation of proteins in important signaling pathways. The results indicate that PCA inhibits osteoclast differentiation by suppressing NF-κB and MAPK activity.

Phytoestrogen in cowpea (Vigna unguiculata L. Walp) (Fabaceae) extract reduces vaginal oxidative stress and increases proliferation of fibroblast in ovariectomized rats

Purpose: To evaluate the effects of a phytoestrogen extract of cowpea (Vigna unguiculata) on malondialdehyde (MDA) and superoxide dismutase (SOD) levels, mitogen-activated protein kinase (MAPK) activity, as well as proliferation of fibroblasts in ovariectomized rat vagina. This is with a view to identify the optimal dose of a phytoestrogen supplement for use during the menopausal period of women. Methods: Wistar rats (Rattus norvegicus) were divided into five groups: negative control, ovariectomy, and ovariectomy groups treated with 1.25, 2.5, or 5 mg/kg of cowpea extract, respectively. The three doses were used to identify the optimal dose required to reduce vaginal oxidative stress and increase fibroblast proliferation in ovariectomized rats. After treatment, the ovariectomized rat vagina was assessed for SOD and MDA levels, MAPK activity, and fibroblast proliferation. Results: Cowpea extract at a dose of 2.5 and 5 mg/kg caused significant reduction in SOD levels in the vaginal tissue of rats compared with control (p < 0.05). In contrast, cowpea extract at 1.25 mg/kg resulted in MDA levels similar to that of control rats (p < 0.05). Cowpea extract treatment had positive effects on SOD and MDA levels and on fibroblast proliferation. Increase in SOD levels in rat vagina was induced by increased MDA levels, which is characteristic of oxidative stress, while ovariectomy resulted in decreased MAPK activity. Conclusion: Overall, the cowpea extract has no significant effect on MAPK activity or fibroblast proliferation. However, it has a significant effect on SOD and MDA levels and on fibroblast proliferation at a dose of 2.5 mg/kg.

p38-MAPK-mediated translation regulation during early blastocyst development is required for primitive endoderm differentiation in mice

Successful specification of the two mouse blastocyst inner cell mass (ICM) lineages (the primitive endoderm (PrE) and epiblast) is a prerequisite for continued development and requires active fibroblast growth factor 4 (FGF4) signaling. Previously, we identified a role for p38 mitogen-activated protein kinases (p38-MAPKs) during PrE differentiation, but the underlying mechanisms have remained unresolved. Here, we report an early blastocyst window of p38-MAPK activity that is required to regulate ribosome-related gene expression, rRNA precursor processing, polysome formation and protein translation. We show that p38-MAPK inhibition-induced PrE phenotypes can be partially rescued by activating the translational regulator mTOR. However, similar PrE phenotypes associated with extracellular signal-regulated kinase (ERK) pathway inhibition targeting active FGF4 signaling are not affected by mTOR activation. These data indicate a specific role for p38-MAPKs in providing a permissive translational environment during mouse blastocyst PrE differentiation that is distinct from classically reported FGF4-based mechanisms.

A Negative Feedback Loop in Ultraviolet A-Induced Senescence in Human Dermal Fibroblasts Formed by SPCA1 and MAPK

Secretory pathway calcium ATPase 1 (SPCA1) is a calcium pump localized specifically to the Golgi. Its effects on UVA-induced senescence have never been examined. In our study, expression of SPCA1 was increased in UVA-irradiated human dermal fibroblasts (HDFs) by activating mitogen-activated protein kinase (MAPK) and its downstream transcription factor, c-jun. Dual-luciferase reporter and chromatin immunoprecipitation assays revealed that c-jun regulated SPCA1 by binding to its promoter. Furthermore, downregulating SPCA1 with siRNA transfection aggravated UVA-induced senescence due to an elevation of intracellular calcium concentrations and a subsequent increase in reactive oxygen species (ROS) and MAPK activity. In contrast, overexpression of SPCA1 reduced calcium overload, consequently lowering the ROS level and suppressing MAPK activation. This alleviated the cellular senescence caused by UVA irradiation. These results indicated that SPCA1 might exert a protective effect on UVA-induced senescence in HDFs via forming a negative feedback loop. Specifically, activation of MAPK/c-jun triggered by UVA transcriptionally upregulated SPCA1. In turn, the increased SPCA1 lowered the intracellular Ca2+ level, probably through pumping Ca2+ into the Golgi, leading to a reduction of ROS, eventually decreasing MAPK activity and diminishing UVA-induced senescence.

AGO2 localizes to cytokinetic protrusions in a p38-dependent manner and is needed for accurate cell division

Argonaute 2 (AGO2) is an indispensable component of the RNA-induced silencing complex, operating at the translational or posttranscriptional level. It is compartmentalized into structures such as GW- and P-bodies, stress granules and adherens junctions as well as the midbody. Here we show using immunofluorescence, image and bioinformatic analysis and cytogenetics that AGO2 also resides in membrane protrusions such as open- and close-ended tubes. The latter are cytokinetic bridges where AGO2 colocalizes at the midbody arms with cytoskeletal components such as α-Τubulin and Aurora B, and various kinases. AGO2, phosphorylated on serine 387, is located together with Dicer at the midbody ring in a manner dependent on p38 MAPK activity. We further show that AGO2 is stress sensitive and important to ensure the proper chromosome segregation and cytokinetic fidelity. We suggest that AGO2 is part of a regulatory mechanism triggered by cytokinetic stress to generate the appropriate micro-environment for local transcript homeostasis.

Ozone Induced Stomatal Regulations, MAPK and Phytohormone Signaling in Plants

Ozone (O3) is a gaseous environmental pollutant that can enter leaves through stomatal pores and cause damage to foliage. It can induce oxidative stress through the generation of reactive oxygen species (ROS) like hydrogen peroxide (H2O2) that can actively participate in stomatal closing or opening in plants. A number of phytohormones, including abscisic acid (ABA), ethylene (ET), salicylic acid (SA), and jasmonic acid (JA) are involved in stomatal regulation in plants. The effects of ozone on these phytohormones’ ability to regulate the guard cells of stomata have been little studied, however, and the goal of this paper is to explore and understand the effects of ozone on stomatal regulation through guard cell signaling by phytohormones. In this review, we updated the existing knowledge by considering several physiological mechanisms related to stomatal regulation after response to ozone. The collected information should deepen our understanding of the molecular pathways associated with response to ozone stress, in particular, how it influences stomatal regulation, mitogen-activated protein kinase (MAPK) activity, and phytohormone signaling. After summarizing the findings and noting the gaps in the literature, we present some ideas for future research on ozone stress in plants