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Journal of Cell Science Jun 2024Little is known about eukaryotic chemorepulsion. The enzymes Phosphatase and tensin homolog (PTEN) and CnrN dephosphorylate phosphatidylinositol 3,4,5-trisphosphate...
Little is known about eukaryotic chemorepulsion. The enzymes Phosphatase and tensin homolog (PTEN) and CnrN dephosphorylate phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] to phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. Dictyostelium discoideum cells require both PTEN and CnrN to induce chemorepulsion of cells away from the secreted chemorepellent protein AprA. How D. discoideum cells utilize two proteins with redundant phosphatase activities in response to AprA is unclear. Here, we show that D. discoideum cells require both PTEN and CnrN to locally inhibit Ras activation, decrease basal levels of PI(3,4,5)P3, and increase basal numbers of macropinosomes, and AprA prevents this increase. AprA requires both PTEN and CnrN to increase PI(4,5)P2 levels, decrease PI(3,4,5)P3 levels, inhibit proliferation, decrease myosin II phosphorylation, and increase filopod sizes. PTEN, but not CnrN, decreases basal levels of PI(4,5)P2, and AprA requires PTEN, but not CnrN, to induce cell roundness. Together, our results suggest that CnrN and PTEN play unique roles in AprA-induced chemorepulsion.
PubMed: 38940195
DOI: 10.1242/jcs.262054 -
Phytochemistry Jun 2024Five undescribed atranones, namely atranones V-Z (1-5), three undescribed dolabellane-type diterpenoids, namely stachatranones D-F (7-9), together with four known...
Five undescribed atranones, namely atranones V-Z (1-5), three undescribed dolabellane-type diterpenoids, namely stachatranones D-F (7-9), together with four known congeners (6 and 10-12), were obtained from a coral-associated strain of the toxigenic fungus Stachybotrys chartarum. Their structures were elucidated via extensive spectroscopic analyses, mainly including the HRESIMS and NMR data, single-crystal X-ray diffraction analysis, electronic circular dichroism calculation, and [Mo(OAc)] induced circular dichroism spectrum. The cardiomyocyte protective activity assay revealed that compound 9 significantly ameliorated cold ischemic injury at 24 h post cold ischemia (CI) in a dose-dependent manner. Moreover, compound 9 prevented CI induced dephosphorylation of phosphatidylinositol-3-kinase and RAC-α serine/threonine-protein kinase at 12 h post CI in a dose-dependent manner. In this work, the undescribed compound 9 could significantly protect cardiomyocytes against cold ischemic injury, highlighting the promising potential to be designed and developed as a novel cardioprotectant in heart transplant medicine.
PubMed: 38936531
DOI: 10.1016/j.phytochem.2024.114199 -
PLoS Pathogens Jun 2024Stress granules (SGs), formed by untranslated messenger ribonucleoproteins (mRNPs) during cellular stress in eukaryotes, have been linked to flavivirus interference...
Stress granules (SGs), formed by untranslated messenger ribonucleoproteins (mRNPs) during cellular stress in eukaryotes, have been linked to flavivirus interference without clear understanding. This study reveals the role of Zika virus (ZIKV) NS2B as a scaffold protein mediating interaction between protein phosphatase 1α (PP1α) and eukaryotic initiation factor 2α (eIF2α). This interaction promotes eIF2α dephosphorylation by PP1α, inhibiting SG formation. The NS2B-PP1α complex exhibits remarkable stability, resisting ubiquitin-induced degradation and amplifying eIF2α dephosphorylation, thus promoting ZIKV replication. In contrast, the NS2BV35A mutant, interacting exclusively with eIF2α, fails to inhibit SG formation, resulting in reduced viral replication and diminished impact on brain organoid growth. These findings reveal PP1α's dual role in ZIKV infection, inducing interferon production as an antiviral factor and suppressing SG formation as a viral promoter. Moreover, we found that NS2B also serves as a versatile mechanism employed by flaviviruses to counter host antiviral defenses, primarily by broadly inhibiting SG formation. This research advances our comprehension of the complex interplay in flavivirus-host interactions, offering potential for innovative therapeutic strategies against flavivirus infections.
PubMed: 38935808
DOI: 10.1371/journal.ppat.1012355 -
Heliyon Jun 2024This study sheds light on a ground-breaking biochemical mechanotransduction pathway and reveals how Piezo1 channels orchestrate cell migration. We observed an increased...
This study sheds light on a ground-breaking biochemical mechanotransduction pathway and reveals how Piezo1 channels orchestrate cell migration. We observed an increased cell migration rate in HEK293T (HEK) cells treated with Yoda1, a Piezo1 agonist, or in HEK cells overexpressing Piezo1 (HEK + P). Conversely, a significant reduction in cell motility was observed in HEK cells treated with GsMTx4 (a channel inhibitor) or upon silencing Piezo1 (HEK-P). Our findings establish a direct correlation between alterations in cell motility, Piezo1 expression, abnormal F-actin microfilament dynamics, and the regulation of Cofilin1, a protein involved in severing F-actin microfilaments. Here, the conversion of inactive pCofilin1 to active Cofilin1, mediated by the serine/threonine-protein phosphatase 2A catalytic subunit C (PP2AC), resulted in increased severing of F-actin microfilaments and enhanced cell migration in HEK + P cells compared to HEK controls. However, this effect was negligible in HEK-P and HEK cells transfected with hsa-miR-133b, which post-transcriptionally inhibited PP2AC mRNA expression. In summary, our study suggests that Piezo1 regulates cell migration through a biochemical mechanotransduction pathway involving PP2AC-mediated Cofilin1 dephosphorylation, leading to changes in F-actin microfilament dynamics.
PubMed: 38933959
DOI: 10.1016/j.heliyon.2024.e32458 -
International Journal of Molecular... Jun 2024Valosin-containing protein (VCP), an ATPase-associated protein, is emerging as a crucial regulator in cardiac pathologies. However, the pivotal role of VCP in the heart...
Cardiac-Specific Suppression of Valosin-Containing Protein Induces Progressive Heart Failure and Premature Mortality Correlating with Temporal Dysregulations in mTOR Complex 2 and Protein Phosphatase 1.
Valosin-containing protein (VCP), an ATPase-associated protein, is emerging as a crucial regulator in cardiac pathologies. However, the pivotal role of VCP in the heart under physiological conditions remains undetermined. In this study, we tested a hypothesis that sufficient VCP expression is required for cardiac development and physiological cardiac function. Thus, we generated a cardiac-specific VCP knockout (KO) mouse model and assessed the consequences of VCP suppression on the heart through physiological and molecular studies at baseline. Our results reveal that homozygous KO mice are embryonically lethal, whereas heterozygous KO mice with a reduction in VCP by ~40% in the heart are viable at birth but progressively develop heart failure and succumb to mortality at the age of 10 to 12 months. The suppression of VCP induced a selective activation of the mammalian target of rapamycin complex 1 (mTORC1) but not mTORC2 at the early age of 12 weeks. The prolonged suppression of VCP increased the expression (by ~2 folds) and nuclear translocation (by >4 folds) of protein phosphatase 1 (PP1), a key mediator of protein dephosphorylation, accompanied by a remarked reduction (~80%) in AKTSer473 phosphorylation in VCP KO mouse hearts at a later age but not the early stage. These temporal molecular alterations were highly associated with the progressive decline in cardiac function. Overall, our findings shed light on the essential role of VCP in the heart under physiological conditions, providing new insights into molecular mechanisms in the development of heart failure.
Topics: Animals; Heart Failure; Valosin Containing Protein; Mice; Mice, Knockout; Protein Phosphatase 1; Mechanistic Target of Rapamycin Complex 2; Myocardium; Male; Disease Models, Animal
PubMed: 38928151
DOI: 10.3390/ijms25126445 -
Nature Jun 2024Tissue repair, immune defence and cancer progression rely on a vital cellular decision between quiescence and proliferation. Mammalian cells proliferate by triggering a...
Tissue repair, immune defence and cancer progression rely on a vital cellular decision between quiescence and proliferation. Mammalian cells proliferate by triggering a positive feedback mechanism. The transcription factor E2F activates cyclin-dependent kinase 2 (CDK2), which in turn phosphorylates and inactivates the E2F inhibitor protein retinoblastoma (Rb). This action further increases E2F activity to express genes needed for proliferation. Given that positive feedback can inadvertently amplify small signals, understanding how cells keep this positive feedback in check remains a puzzle. Here we measured E2F and CDK2 signal changes in single cells and found that the positive feedback mechanism engages only late in G1 phase. Cells spend variable and often extended times in a reversible state of intermediate E2F activity before committing to proliferate. This intermediate E2F activity is proportional to the amount of phosphorylation of a conserved T373 residue in Rb that is mediated by CDK2 or CDK4/CDK6. Such T373-phosphorylated Rb remains bound on chromatin but dissociates from it once Rb is hyperphosphorylated at many sites, which fully activates E2F. The preferential initial phosphorylation of T373 can be explained by its relatively slower rate of dephosphorylation. Together, our study identifies a primed state of intermediate E2F activation whereby cells sense external and internal signals and decide whether to reverse and exit to quiescence or trigger the positive feedback mechanism that initiates cell proliferation.
PubMed: 38926571
DOI: 10.1038/s41586-024-07554-2 -
Molecular Nutrition & Food Research Jun 2024This study investigates the impact of extracts derived from Antarctic fish species, Trematomus newnesi and Trematomus bernacchii, on the migration of human placental...
The Extracts from Two Antarctic Fish Species, Trematomus newnesi and Trematomus bernacchii, Enhance JEG-3 Cell Migration and Invasion via MMP9 Activation Through Akt/Protein Phosphatase1/β-Catenin Pathway.
SCOPE
This study investigates the impact of extracts derived from Antarctic fish species, Trematomus newnesi and Trematomus bernacchii, on the migration of human placental trophoblast JEG-3 cells, which is a crucial aspect of successful pregnancy.
METHODS AND RESULTS
The extracts, obtained from the muscles of these fish, significantly enhance the migration and invasion of JEG-3 cells in in vitro wound healing, Transwell, and collagen invasion assays. These effects are accompanied by an increase in matrix metalloproteinase (MMP) 9 activity, as demonstrated by zymography. Furthermore, the extracts activated Akt and protein phosphatase 1, resulting in the dephosphorylation of β-catenin at Ser33/37/Thr41, as confirmed by western blot analysis. Consequently, MMP9 is upregulated, while metallopeptidase inhibitor 1/3 is downregulated, as verified by western blot and qRT-PCR analyses. Finally, utilizing ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis, followed by matching with the Global Natural Product Social Molecular Networking library, the study annotates the compound responsible for the observed migratory activity as taurocholic acid. Importantly, the study confirms that taurocholic acid enhances cell migration in JEG-3 cells.
CONCLUSION
The results of this study emphasize the potential of Antarctic fish extracts in promoting extravillous trophoblast migration and invasion, which are critical for successful pregnancy.
PubMed: 38925577
DOI: 10.1002/mnfr.202400028 -
Neurology International Jun 2024The tau protein is a microtubule-associated protein that promotes microtubule stabilization. The phosphorylation of the tau protein has been linked to its dissociation...
The tau protein is a microtubule-associated protein that promotes microtubule stabilization. The phosphorylation of the tau protein has been linked to its dissociation from microtubules. Here, we examined the relationship between neuronal depolarization activity and tau protein phosphorylation by employing model systems in culture as well as in vivo. The KCl-evoked depolarization of cultured neurons has often been used to investigate the effects of neuronal activity. We found dephosphorylation at AT8 sites (S202, T205), T212, AT180 sites (T231, S235), and S396 in KCl-simulated cultured neurons. We also found that the KCl-induced tau protein dephosphorylation increases the level of the tau protein fractionated with stable microtubules. In an in vivo experiment, we demonstrated that the exposure of mice to a new environment activates protein phosphatase 1 in the mouse hippocampus and induces tau protein dephosphorylation. We also found an increased amount of the tau protein in a stable microtubule fraction, suggesting that the dephosphorylation of the tau protein may lead to its increased microtubule association in vivo. These results suggest that the association of microtubules with tau proteins may be regulated by the tau protein phosphorylation status affected by neuronal electrical activity.
PubMed: 38921953
DOI: 10.3390/neurolint16030049 -
Scientific Reports Jun 2024We have reported that an environmental pollutant, cadmium, promotes cell death in the human renal tubular cells (RTCs) through hyperactivation of a serine/threonine...
We have reported that an environmental pollutant, cadmium, promotes cell death in the human renal tubular cells (RTCs) through hyperactivation of a serine/threonine kinase Akt. However, the molecular mechanisms downstream of Akt in this process have not been elucidated. Cadmium has a potential to accumulate misfolded proteins, and proteotoxicity is involved in cadmium toxicity. To clear the roles of Akt in cadmium exposure-induced RTCs death, we investigated the possibility that Akt could regulate proteotoxicity through autophagy in cadmium chloride (CdCl)-exposed HK-2 human renal proximal tubular cells. CdCl exposure promoted the accumulation of misfolded or damaged proteins, the formation of aggresomes (pericentriolar cytoplasmic inclusions), and aggrephagy (selective autophagy to degrade aggresome). Pharmacological inhibition of Akt using MK2206 or Akti-1/2 enhanced aggrephagy by promoting dephosphorylation and nuclear translocation of transcription factor EB (TFEB)/transcription factor E3 (TFE3), lysosomal transcription factors. TFEB or TFE3 knockdown by siRNAs attenuated the protective effects of MK2206 against cadmium toxicity. These results suggested that aberrant activation of Akt attenuates aggrephagy via TFEB or TFE3 to facilitate CdCl-induced cell death. Furthermore, these roles of Akt/TFEB/TFE3 were conserved in CdCl-exposed primary human RTCs. The present study shows the molecular mechanisms underlying Akt activation that promotes cadmium-induced RTCs death.
Topics: Humans; Proto-Oncogene Proteins c-akt; Autophagy; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Cell Line; Cadmium; Kidney Tubules, Proximal; Phosphorylation; Cadmium Chloride; Heterocyclic Compounds, 3-Ring; Kidney Tubules
PubMed: 38914593
DOI: 10.1038/s41598-024-64579-3 -
Journal of Cell Science Jun 2024PTPRK is a receptor tyrosine phosphatase linked to the regulation of growth factor signalling and tumour suppression. It is stabilized at the plasma membrane by trans...
PTPRK is a receptor tyrosine phosphatase linked to the regulation of growth factor signalling and tumour suppression. It is stabilized at the plasma membrane by trans homophilic interactions upon cell-cell contact. It regulates cell-cell adhesion, but is also reported to regulate numerous cancer-associated signalling pathways. However, its signalling mechanism remains to be determined. Here, we find that PTPRK regulates cell adhesion signalling, suppresses invasion and promotes collective, directed migration in colorectal cancer cells. In vivo, PTPRK supports recovery from inflammation-induced colitis. In addition, we confirm that PTPRK functions as a tumour suppressor in the mouse colon and in colorectal cancer xenografts. PTPRK regulates growth factor and adhesion signalling, and suppresses epithelial to mesenchymal transition (EMT). Contrary to the prevailing notion that PTPRK directly dephosphorylates EGFR, we find that PTPRK regulation of both EGFR and EMT is independent of its catalytic function. This suggests that additional adaptor and scaffold functions are important features of PTPRK signalling.
PubMed: 38904097
DOI: 10.1242/jcs.261914