The SALT OVERLY SENSITIVE 2-CONSTITUTIVE TRIPLE RESPONSE1 module coordinates plant growth and salt tolerance in Arabidopsis.

High salinity stress promotes plant ethylene biosynthesis and triggers the ethylene signalling response. However, the precise mechanism underlying how plants transduce ethylene signalling in response to salt stress remains largely unknown. In this study, we discovered that SALT OVERLY SENSITIVE 2 (SOS2) inhibits the kinase activity of CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) by phosphorylating the 87th serine (S87). This phosphorylation event activates the ethylene signalling response, leading to enhanced plant salt resistance. Furthermore, through genetic analysis, we determined that the loss of CTR1 or the gain of SOS2-mediated CTR1 phosphorylation both contribute to improved plant salt tolerance. Additionally, in the sos2 mutant, we observed compromised proteolytic processing of ETHYLENE INSENSITIVE 2 (EIN2) and reduced nuclear localization of EIN2 C-terminal fragments (EIN2-C), which correlate with decreased accumulation of ETHYLENE INSENSITIVE 3 (EIN3). Collectively, our findings unveil the role of the SOS2-CTR1 regulatory module in promoting the activation of the ethylene signalling pathway and enhancing plant salt tolerance.

The Ca2+ Sensor SCaBP3/CBL7 Modulates Plasma Membrane H+-ATPase Activity and Promotes Alkali Tolerance in Arabidopsis.

Saline-alkali soil is a major environmental constraint impairing plant growth and crop productivity. In this study, we identified a Ca2+ sensor/kinase/plasma membrane (PM) H+-ATPase module as a central component conferring alkali tolerance in Arabidopsis (Arabidopsis thaliana). We report that the SCaBP3 (SOS3-LIKE CALCIUM BINDING PROTEIN3)/CBL7 (CALCINEURIN B-LIKE7) loss-of-function plants exhibit enhanced stress tolerance associated with increased PM H+-ATPase activity and provide fundamental mechanistic insights into the regulation of PM H+-ATPase activity. Consistent with the genetic evidence, interaction analyses, in vivo reconstitution experiments, and determination of H+-ATPase activity indicate that interaction of the Ca2+ sensor SCaBP3 with the C-terminal Region I domain of the PM H+-ATPase AHA2 (Arabidopsis thaliana PLASMA MEMBRANE PROTON ATPASE2) facilitates the intramolecular interaction of the AHA2 C terminus with the Central loop region of the PM H+-ATPase to promote autoinhibition of H+-ATPase activity. Concurrently, direct interaction of SCaPB3 with the kinase PKS5 (PROTEIN KINASE SOS2-LIKE5) stabilizes the kinase-ATPase interaction and thereby fosters the inhibitory phosphorylation of AHA2 by PKS5. Consistently, yeast reconstitution experiments and genetic analysis indicate that SCaBP3 provides a bifurcated pathway for coordinating intramolecular and intermolecular inhibition of PM H+-ATPase. We propose that alkaline stress-triggered Ca2+ signals induce SCaBP3 dissociation from AHA2 to enhance PM H+-ATPase activity. This work illustrates a versatile signaling module that enables the stress-responsive adjustment of plasma membrane proton fluxes.

Protective effect of surface-layer proteins from four Lactobacillus strains on tumor necrosis factor-α-induced intestinal barrier dysfunction.

BACKGROUND: The intestinal epithelium is considered the first defense protection against exogenous harmful substances, playing an indispensable role in regulating intestinal health. The protection offered by surface-layer proteins (Slps) from different Lactobacillus strains on an impaired intestinal barrier was investigated in this study. RESULTS: Four Slps pre-incubated for 6 h significantly prevented the reduced transepithelial electrical resistance value and increased paracellular permeability in tumor necrosis factor (TNF)-α-induced Caco-2 monolayers. TNF-α induced lower protein expression of occludin and zonula occludens-1, and abnormal distributions of occludin and zonula occludens-1 were ameliorated by four Slps as well. Additionally, four Slps weakened TNF-α-evoked interleukin-8 secretion and nuclear factor-κB activation. CONCLUSION: Four Slps from different strains prevent the intestinal barrier from TNF-α-induced dysfunction through blocking the nuclear factor-κB signaling pathway. © 2022 Society of Chemical Industry.

New Drug Candidate Targeting the 4A1 Orphan Nuclear Receptor for Medullary Thyroid Cancer Therapy.

Medullary thyroid cancer (MTC) is a relatively rare thyroid cancer responsible for a substantial fraction of thyroid cancer mortality. More effective therapeutic drugs with low toxicity for MTC are urgently needed. Orphan nuclear receptor 4A1 (NR4A1) plays a pivotal role in regulating the proliferation and apoptosis of a variety of tumor cells. Based on the NR4A1 protein structure, 2-imino-6-methoxy-2H-chromene-3-carbothioamide (IMCA) was identified from the Specs compounds database using the protein structure-guided virtual screening approach. Computationally-based molecular modeling studies suggested that IMCA has a high affinity for the ligand binding pocket of NR4A1. MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide] and apoptosis assays demonstrated that IMCA resulted in significant thyroid cancer cell death. Immunofluorescence assays showed that IMCA induced NR4A1 translocation from the nucleus to the cytoplasm in thyroid cancer cell lines, which may be involved in the cell apoptotic process. In this study, the quantitative polymerase chain reaction results showed that the IMCA-induced upregulation of sestrin1 and sestrin2 was dose-dependent in thyroid cancer cell lines. Western blot showed that IMCA increased phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK) and decreased phosphorylation of ribosomal protein S6 kinase (p70S6K), which is the key enzyme in the mammalian target of rapamycin (mTOR) pathway. The experimental results suggest that IMCA is a drug candidate for MTC therapy and may work by increasing the nuclear export of NR4A1 to the cytoplasm and the tumor protein 53 (p53)-sestrins-AMPK-mTOR signaling pathway.

Surface-layer protein produced by Lactobacillus crispatus JCM 2009 ameliorates lipopolysaccharide-induced inflammation through autophagy cross-talk with the NF-κB signaling pathway.

In recent years, studies on immunomodulation by surface-layer proteins (Slps) have mainly focused on Lactobacillus acidophilus, there is little information on Slp from L. crispatus and its intestinal immunomodulatory mechanisms in macrophages. In our study, the anti-inflammatory actions of Slp derived from L. crispatus JCM 2009 and its related molecular mechanisms were investigated. We initially found that incubation with Slp (5-10 µg/mL) for 4 h significantly inhibited nitric oxide (NO) and prostaglandin E2 (PGE2) production in LPS-stimulated RAW264.7 cells (P < 0.001). We then found that Slp inhibited the inflammatory response by regulating the PI3K/AKT/mTOR signaling pathway and activating autophagy in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Furthermore, ELISA and Western blotting results demonstrated that the NF-κB signaling pathway positively regulated autophagic activity to inhibit the productions of PGE2 and NO during this inflammatory response. And p65 was identified as a potentially important NF-κB signaling pathway molecule mediating the effects of Slp on the LPS-induced inflammatory response in RAW264.7 cells. Our findings provide the novel perspective that Slp exerts its anti-inflammatory effects through the activation of autophagy, making it a promising bioactive ingredient for the development of functional foods.