Search Results (55)

In the marine red alga Pyropia yezoensis, filamentous phases of the life cycle, e.g., the conchocelis (sporophyte) and conchosporangium (conchosporophyte), proliferate by tip growth. In this study, we investigated the possible involvement of phosphoinositide turnover and actin polymerization in the spontaneous initiation and tip growth of new branches in isolated single-celled conchocelis cells using pharmacological treatments. Treatment with LY294002 and U73122, specific inhibitors of phosphoinositide-phosphate 3-kinase and phospholipase C, respectively, reduced side-branch formation and inhibited the elongation of branches. In addition, two inhibitors of the actin cytoskeleton, cytochalasin B (CCB) and latrunculin B (LAT-B), had similar effects on tip growth. However, CCB did not alter the branching rate of single-celled conchocelis, whereas LAT-B did. As CCB and LAT-B affect actin polymerization through different mechanisms, this result suggests differences in the contributions of actin polymerization to branch initiation versus tip growth. These findings demonstrate the critical and diverse functional roles played by phosphoinositide turnover and actin polymerization in the regulation of the initiation and maintenance of tip growth in the conchocelis phase of P. yezoensis. Full article

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) have shown clinical activity for patients with EGFR-mutated non-small-cell lung cancer (NSCLC). However, the development of resistance to EGFR-TKIs is almost inevitable, posing a significant barrier to long-term survival. Local ablative therapy (LAT) may facilitate the prolonged survival of patients with oligometastatic NSCLC. Therapeutic combinations of EGFR-TKIs and LAT for residual disease have been suggested to be potentially effective in EGFR-mutated NSCLC with induced oligometastatic disease, wherein a few lesions remain following initial EGFR-TKI treatment. Various resistance pathways for third-generation EGFR-TKIs including osimertinib, current standard of care for patients with EGFR-mutated NSCLC, have also been identified. In addition to resistance mechanisms, the disease-progression pattern may be an essential element for achieving long-term response and survival. Oligo-progressive disease is a state in which only a few lesions become resistant, whereas many lesions remain controlled with effective systemic therapy. Previous studies have shown that LAT for all oligo-progressive lesions could provide survival benefits. This review discusses the current treatment options and potential future therapeutic developments for patients with EGFR-mutated NSCLC who have synchronous oligometastatic disease, oligo-residual disease during treatment with EGFR-TKIs, and oligo-progressive disease following resistance to EGFR-TKIs. Full article

Cervical cancer is the fourth most prevalent cancer among women globally. Protein concentrations of Large Tumor Suppressor Kinase-1 (LATS1) and Nuclear Factor Kappa-B (NF-κB) have been identified as prospective biomarkers of radioresistance in cervical cancer. This preliminary study aimed to investigate the effectiveness of LATS1 and NF-κB levels as a biomarker for radioresistance and evaluate their response to radiation in cervical cancer patients. A comprehensive cross-sectional study was conducted involving 114 subjects diagnosed with advanced stages cervical cancer (stage IIIB and IVA) who underwent definitive radiotherapy. The concentrations of LATS1 and NF-κB were measured using ELISA from biopsy samples taken prior to the initiation of radiotherapy. This study’s finding included 114 subjects, with a median age of 53 years. A total of 85 (74.5%) subjects had stage IIIB, while 29 (25.4%) subjects had stage IVA. The cut-offs for LATS1 and NF-κB were 0.02765 ng/mg and 192.42 pg/mg, respectively. Subjects with a higher expression of LATS1 were found to be unresponsive to radiation therapy (p ≤ 0.001; AUC = 32.7%), and subjects with a lower expression of NF-κB were found to be unresponsive to radiation therapy (p = 0.009; AUC = 61%). This study suggests that elevated LATS1 expression may inversely predict radioresistance, while NF-κB expression shows a weak correlation with resistance to radiation therapy. Full article

Linker for activation of T cells (LAT) is an essential adaptor protein in early T cell receptor (TCR) signaling that propagates multiple signaling pathways. However, how LAT spatial organization facilitates signal initiation and propagation after TCR triggering is not clear. To differentiate de novo assembly in the plasma membrane from pre-existing LAT vesicles and clusters, we developed imaging protocols and analyses to capture the organization and dynamics of single LAT molecules immediately after TCR engagement. We could observe individual LAT molecules in the plasma membrane that assembled into immobile signaling entities requiring LAT phosphorylation. This step-wise assembly process was temporally highly coordinated via the zeta-chain-associated protein kinase 70 (Zap70)-LAT-growth factor receptor-bound protein 2 (Grb2) pathway. While multiple spatial organization co-existed even within the plasma membrane, our data suggest that de novo plasma membrane assemblies facilitated signal propagation. Full article

Phenylalanine (Phe) is a potentially limiting amino acid for lactating cows. The mechanism by which Phe regulates milk protein synthesis remains unclear. The present study elucidates the mechanisms by which phenylalanine affects milk protein synthesis, amino acid utilization, and related signaling pathways in bovine mammary epithelial cells (BMECs). The BMECs were treated with five concentrations (0, 0.22, 0.44, 0.88, 1.76 mM, and serum free). Rapamycin inhibitors and RNA interference (RNAi) were used to inhibit the phosphorylation of the mammalian target of rapamycin (mTOR) signaling pathway and the expression of relevant amino acid transporters, respectively. The results showed that 4×Phe (0.88 mM) significantly increased (p < 0.05) both the mRNA and protein expression of α-casein (CSN1S1), β-casein (CSN2), and κ-casein (CSN3), as well as L-type amino acid transporter-1 (LAT1) mRNA expression. Protein expression and modification assays of mTOR-related proteins showed that 4×Phe could increase (p < 0.05) the expression of α-casein and eukaryotic initiation factor 4E-binding protein-1 (4EBP1) and tended to increase the expression of ribosomal protein S6 protein kinase (S6K1, p = 0.054). The general control nonderepressible 2 (GCN2) signaling pathway factor, eukaryotic initiation factor 2 (eIF2α), was downregulated by 4×Phe treatment (p < 0.05). The rapamycin inhibition test showed that Phe regulated casein synthesis via the mTOR signaling pathway. RNAi experiments showed that LAT1 mediated the entry of Phe into cells. Moreover, 4×Phe treatment tended to decrease (0.05 < p < 0.10) the consumption of valine, leucine, histidine, tyrosine, cysteine, alanine, asparagine, and serine in the medium. Collectively, phenylalanine enhanced α-casein synthesis by regulating the phosphorylation of 4EBP1 and eIF2α and promoting the formation of the mTOR-centered casein translation initiation complex. Full article

Post-translational ubiquitination is an essential mechanism for the regulation of protein stability and function, which contributes to the regulation of the immune system. Cbl, an E3 ubiquitin ligase, is particularly well-characterized in the context of T and NK cell signaling, where it serves as a key regulator of receptor downstream signaling events and as a modulator of cell activation. Cbl promotes the proteasomal degradation of TCR/CD3 subunits as well as the protein kinases Fyn and Lck in T cells. Additionally, the scaffold protein linker for activation of T cells (LAT) is a universal target for Cbl-mediated ubiquitination and degradation in both T and NK cells. Recent findings suggest that CrkII-mediated ubiquitination and degradation of C3G by Cbl during early T cell activation may also be relevant to NK cell signaling. Given its role in modulating immune responses and its manageable impact on autoimmunity, Cbl is being investigated as a target for cancer immunotherapy. This review explores the ubiquitin ligase activity of Cbl and its implications for CAR T and NK cell immunotherapies. Full article

Although antimicrobial peptides (AMPs) exhibit a range of biological functions, reports on AMPs with therapeutic effects in allergic disorders are limited. In this study, we investigated the anti-allergic effects of Pro10-1D, a 10-meric AMP derived from insect defensin protaetiamycine. Our findings demonstrate that Pro10-1D effectively inhibits antigen-induced degranulation of mast cells (MCs) with IC₅₀ values of approximately 11.6 μM for RBL-2H3 cells and 2.7 μM for bone marrow-derived MCs. Furthermore, Pro10-1D suppressed the secretion of cytokines with IC₅₀ values of approximately 2.8 μM for IL-4 and approximately 8.6 μM for TNF-α. Mechanistically, Pro10-1D inhibited the Syk-LAT-PLCγ1 signaling pathway in MCs and decreased the activation of mitogen-activated protein kinases (MAPKs). Pro10-1D demonstrated a dose-dependent reduction in IgE-mediated passive cutaneous anaphylaxis in mice with an ED₅₀ value of approximately 7.6 mg/kg. Further investigation revealed that Pro10-1D significantly reduced the activity of key kinases Fyn and Lyn, which are critical in the initial phase of the FcεRI-mediated signaling pathway, with IC₅₀ values of approximately 22.6 μM for Fyn and approximately 1.5 μM for Lyn. Collectively, these findings suggest that Pro10-1D represents a novel therapeutic candidate for the treatment of IgE-mediated allergic disorders by targeting the Lyn/Fyn Src family kinases in MCs. Full article

Background: Oncogenic mutations in the KRAS gene are detected in >90% of pancreatic cancers (PC). In genetically engineered mouse models of PC, oncogenic KRAS drives the formation of precursor lesions and their progression to invasive PC. The Yes-associated Protein (YAP) is a transcriptional coactivator required for transformation by the RAS oncogenes and the development of PC. In Ras-driven tumors, YAP can also substitute for oncogenic KRAS to drive tumor survival after the repression of the oncogene. Ras oncoproteins exert their transforming properties through their downstream effectors, including the PI3K kinase, Rac1 GTPase, and MAPK pathways. Methods: To identify Ras effectors that regulate YAP, YAP levels were measured in PC cells exposed to inhibitors of oncogenic K-Ras and its effectors. Results: In PC cells, the inhibition of Rac1 leads to a time-dependent decline in YAP protein, which could be blocked by proteosome inhibitor MG132. This YAP degradation after Rac1 inhibition was observed in a range of cell lines using different Rac1 inhibitors, Rac1 siRNA, or expression of dominant negative Rac1^T17N mutant. Several E3 ubiquitin ligases, including SCF^βTrCP, regulate YAP protein stability. To be recognized by this ligase, the βTrCP degron of YAP (amino acid 383–388) requires its phosphorylation by casein kinase 1 at Ser384 and Ser387, but these events must first be primed by the phosphorylation of Ser381 by LATS1/2. Using Flag-tagged mutants of YAP, we show that YAP degradation after Rac1 inhibition requires the integrity of this degron and is blocked by the silencing of βTrCP1/2 and by the inhibition of casein kinase 1. Unexpectedly, YAP degradation after Rac1 inhibition was still observed after the silencing of LATS1/2 or in cells carrying a LATS1/2 double knockout. Conclusions: These results reveal Rac1 as an oncogenic KRAS effector that contributes to YAP stabilization in PC cells. They also show that this regulation of YAP by Rac1 requires the SCF^βTrCP ligase but occurs independently of the LATS1/2 kinases. Full article

Mechanotransduction, the process of how cells sense and convert mechanical stimuli into biochemical response, is crucial in the migration of leukocytes or cancer cells through the endothelium during inflammation or metastasis. Migrating cells exert forces on the endothelium through cell surface adhesion molecules, such as platelet endothelial adhesion molecule PECAM-1, and this is essential for a successful transmigration. To study PECAM-1-mediated mechanotransduction, we applied PECAM-1-antibody-coated magnetic beads and exerted about 40 pN force on the endothelial monolayer. We show that force increases cell–ECM adhesion in the cell center and is accompanied by the opening of cell–cell junctions. Upon depletion of the MEK/ERK kinase, BRAF force increases cell–ECM adhesion both at the cell periphery and in the cell center, but this does not result in the opening of cell–cell junctions. Decreasing cell–ECM adhesion in BRAF-depleted cells through FAK inhibition results in the remodeling of cell–cell junctions. Force-induced increase in cell–ECM adhesion in the cell center correlates with the activation of the transcriptional cofactor Yes-associated protein (YAP). Furthermore, the induced activation of YAP through LATS inhibition prevents junctional remodeling in control cells. Thus, the activation of YAP might determine the strength of cell–cell junctions during PECAM-1-mediated mechanotransduction. Full article

Although Hippo-YAP/TAZ pathway involvement has been extensively studied in the development of certain cancers, the involvement of this cascade in kidney cancer progression is not well-established and, therefore, will be the focus of this review. Renal cell carcinoma (RCC), the most prevalent kidney tumor subtype, has a poor prognosis and a high mortality rate. Core Hippo signaling inactivation (e.g., LATS kinases) leads to the nuclear translocation of YAP/TAZ where they bind to co-transcriptional factors such as TEAD promoting transcription of genes which initiates various fibrotic and neoplastic diseases. Loss of expression of LATS1/2 kinase and activation of YAP/TAZ correlates with poor survival in RCC patients. Renal-specific ablation of LATS1 in mice leads to the spontaneous development of several subtypes of RCC in a YAP/TAZ-dependent manner. Genetic and pharmacological inactivation of YAP/TAZ reverses the oncogenic potential in LATS1-deficient mice, highlighting the therapeutic benefit of network targeting in RCC. Here, we explore the unique upstream controls and downstream consequences of the Hippo-YAP/TAZ pathway deregulation in renal cancer. This review critically evaluates the current literature on the role of the Hippo pathway in RCC progression and highlights the recent scientific evidence designating YAP/TAZ as novel therapeutic targets against kidney cancer. Full article

The Hippo pathway plays crucial roles in governing various biological processes during tumorigenesis and metastasis. Within this pathway, upstream signaling stimuli activate a core kinase cascade, involving MST1/2 and LATS1/2, that subsequently phosphorylates and inhibits the transcriptional co-activators YAP and its paralog TAZ. This inhibition modulates the transcriptional regulation of downstream target genes, impacting cell proliferation, migration, and death. Despite the acknowledged significance of protein kinases in the Hippo pathway, the regulatory influence of protein phosphatases remains largely unexplored. In this study, we conducted the first gain-of-functional screen for protein tyrosine phosphatases (PTPs) regulating the Hippo pathway. Utilizing a LATS kinase biosensor (LATS-BS), a YAP/TAZ activity reporter (STBS-Luc), and a comprehensive PTP library, we identified numerous novel PTPs that play regulatory roles in the Hippo pathway. Subsequent experiments validated PTPN12, a master regulator of oncogenic receptor tyrosine kinases (RTKs), as a previously unrecognized negative regulator of the Hippo pathway effectors, oncogenic YAP/TAZ, influencing breast cancer cell proliferation and migration. In summary, our findings offer valuable insights into the roles of PTPs in the Hippo signaling pathway, significantly contributing to our understanding of breast cancer biology and potential therapeutic strategies. Full article

Originally identified in Drosophila melanogaster in 1995, the Hippo signaling pathway plays a pivotal role in organ size control and tumor suppression by inhibiting proliferation and promoting apoptosis. Large tumor suppressors 1 and 2 (LATS1/2) directly phosphorylate the Yki orthologs YAP (yes-associated protein) and its paralog TAZ (also known as WW domain-containing transcription regulator 1 [WWTR1]), thereby inhibiting their nuclear localization and pairing with transcriptional coactivators TEAD1-4. Earnest efforts from many research laboratories have established the role of mis-regulated Hippo signaling in tumorigenesis, epithelial mesenchymal transition (EMT), oncogenic stemness, and, more recently, development of drug resistances. Hippo signaling components at the heart of oncogenic adaptations fuel the development of drug resistance in many cancers for targeted therapies including KRAS and EGFR mutants. The first U.S. food and drug administration (US FDA) approval of the imatinib tyrosine kinase inhibitor in 2001 paved the way for nearly 100 small-molecule anti-cancer drugs approved by the US FDA and the national medical products administration (NMPA). However, the low response rate and development of drug resistance have posed a major hurdle to improving the progression-free survival (PFS) and overall survival (OS) of cancer patients. Accumulating evidence has enabled scientists and clinicians to strategize the therapeutic approaches of targeting cancer cells and to navigate the development of drug resistance through the continuous monitoring of tumor evolution and oncogenic adaptations. In this review, we highlight the emerging aspects of Hippo signaling in cross-talk with other oncogenic drivers and how this information can be translated into combination therapy to target a broad range of aggressive tumors and the development of drug resistance. Full article

Mouse zygotes undergo multiple rounds of cell division, resulting in the formation of preimplantation blastocysts comprising three lineages: trophectoderm (TE), epiblast (EPI), and primitive endoderm (PrE). Cell fate determination plays a crucial role in establishing a healthy pregnancy. The initial separation of lineages gives rise to TE and inner cell mass (ICM), from which trophoblast stem cells (TSC) and embryonic stem cells (ESC) can be derived in vitro. Studying lineage differentiation is greatly facilitated by the clear functional distinction between TSC and ESC. However, transitioning between these two types of cells naturally poses challenges. In this study, we demonstrate that inhibiting LATS kinase promotes the conversion of ICM to TE and also effectively reprograms ESC into stable, self-renewing TS-like cells (TSLC). Compared to TSC, TSLC exhibits similar molecular properties, including the high expression of marker genes such as Cdx2, Eomes, and Tfap2c, as well as hypomethylation of their promoters. Importantly, TSLC not only displays the ability to differentiate into mature trophoblast cells in vitro but also participates in placenta formation in vivo. These findings highlight the efficient reprogramming of ESCs into TSLCs using a small molecular inducer, which provides a new reference for understanding the regulatory network between ESCs and TSCs. Full article

The Hippo pathway is conserved across species. Key mammalian Hippo pathway kinases, including MST1/2 and LATS1/2, inhibit cellular growth by inactivating the TEAD coactivators, YAP, and TAZ. Extensive research has illuminated the roles of Hippo signaling in cancer, development, and regeneration. Notably, dysregulation of Hippo pathway components not only contributes to tumor growth and metastasis, but also renders tumors resistant to therapies. This review delves into recent research on YAP/TAZ-TEAD-mediated gene regulation and biological processes in cancer. We focus on several key areas: newly identified molecular patterns of YAP/TAZ activation, emerging mechanisms that contribute to metastasis and cancer therapy resistance, unexpected roles in tumor suppression, and advances in therapeutic strategies targeting this pathway. Moreover, we provide an updated view of YAP/TAZ’s biological functions, discuss ongoing controversies, and offer perspectives on specific debated topics in this rapidly evolving field. Full article

The Hippo pathway mediates renal maladaptive repair after acute kidney injury (AKI), which has been considered a driving force in the progression to chronic kidney disease (CKD). LATS2, a core kinase of the Hippo pathway, exerts non-Hippo-dependent functions in the regulation of the cell cycle and cell fate, providing new insights into AKI and further repair. However, its role remains unknown. Here, we utilized a proximal tubular Lats2 conditional knockout mouse strain (Lats2-CKO) to evaluate the effect of LATS2 deficiency on ischemia/reperfusion-induced AKI-to-CKD transition. Lats2-CKO mice presented with more severe tubular maladaptive repair, inflammatory infiltration, interstitial fibrosis, and apoptosis following AKI. Importantly, we discovered that Lats2 ablation caused the activation of p53, with increased levels of cellular apoptotic molecules (p21, Bax, and cleaved caspase-3), and decreased levels of anti-apoptotic molecules (Bcl-2 and Bcl-xL). Pifithirin-α (p53 inhibitor) effectively attenuated renal fibrosis, inflammation, and apoptosis in Lats2-CKO mice after AKI. Consistently, in vitro Lats2 overexpression decreased p53, p21, Bax and cleaved caspase 3 expression after hypoxia/reoxygenation (H/R) treatment. Of note, the phosphorylation of MDM2, which promotes the ubiquitination degradation of p53, at site Ser186 was decreased in Lats2-CKO kidneys, but increased by Lats2 overexpression in vitro. Therefore, LATS2 deficiency aggravated ischemia/reperfusion injury (IRI)-induced maladaptive repair via regulating the tubular MDM2-p53 axis in AKI-to-CKD transition. Full article