Pentabromopseudilin: a myosin V inhibitor suppresses TGF-β activity by recruiting the type II TGF-β receptor to lysosomal degradation

Expanding the Chemical Space of Transforming Growth Factor-β (TGFβ) Receptor Type II Degraders with 3,4-Disubstituted Indole Derivatives

The TGFβ type II receptor (TβRII) is a central player in all TGFβ signaling downstream events, has been linked to cancer progression, and thus, has emerged as an auspicious anti-TGFβ strategy. Especially its targeted degradation presents an excellent goal for effective TGFβ pathway inhibition. Here, cellular structure-activity relationship (SAR) data from the TβRII degrader chemotype 1 was successfully transformed into predictive ligand-based pharmacophore models that allowed scaffold hopping. Two distinct 3,4-disubstituted indoles were identified from virtual screening: tetrahydro-4-oxo-indole 2 and indole-3-acetate 3. Design, synthesis, and screening of focused amide libraries confirmed 2r and 3n as potent TGFβ inhibitors. They were validated to fully recapitulate the ability of 1 to selectively degrade TβRII, without affecting TβRI. Consequently, 2r and 3n efficiently blocked endothelial-to-mesenchymal transition and cell migration in different cancer cell lines while not perturbing the microtubule network. Hence, 2 and 3 present novel TβRII degrader chemotypes that will (1) aid target deconvolution efforts and (2) accelerate proof-of-concept studies for small-molecule-driven TβRII degradation in vivo.

Assessment of the effectiveness of the peptide inhibitor homologous to the transforming growth factor β cytokine blocking the TGFβRI/TGFβRII receptor complex-pilot study

BACKGROUND

A key player in the fibrotic process is the transforming growth factor β (TGF-β) which enhances extracellular matrix production by increasing the transcription of matrix proteins. The cytokine TGF-β first binds to the TGFβRII receptor (dimer), resulting in the recruitment of the TGFβRI receptor (dimer). The complex thus formed leads to the phosphorylation of the kinase domain of TGFβRI, which in turn results in activation of the Smad pathway. This is therefore a targeted pathway for research into the application of peptide inhibitors in blocking the TGF-β-Smad signaling pathway. The aim of this study was to design a peptide inhibitor (homologous to the cytokine TGF-β) which, after binding to the TGFβRI/TGFβRII receptor, would block the cytokine binding and thus prevent the formation of an activating complex.

METHODS

Preliminary work on the design and synthesis of inhibitors for TGFβRI/TGFβRII has allowed us to identify and describe five key regions of the TGF-β-TGFβRI/TGFβRII interface. The following five peptide inhibitors were synthesized for Region 1: 1.1 ALDAAYCFR, 1.2 LDAAYCFRN, 1.3 DAAYCFRNV, 1.4 AAYCFRNVQ, 1.5 AYCFRNVQD. The expression of the SEAP reporter gene, Smad2, Smad3, Smad4, and JNK1 gene was measured using quantitative real-time polymerase chain reaction.

RESULTS

For Region 1 peptide inhibitors tested for TGFβRI/TGFβRII, reduced SEAP (reporter gene) expression was observed in cells of the MFB-F11 line, which suggests inhibited the formation of cytokine-receptor complexes.

CONCLUSIONS

For IP1_2, 1_3 and 1_5 Region 1 peptides tested for TGFβRI/TGFβRII, reduced cytokine-receptor signal by adding newly designed inhibitors. The study revealed an impact of these peptide inhibitors on the reduction of mRNA expression of Smad2, Smad3, Smad4 and JNK1 genes.

Functions of actin-binding proteins in cilia structure remodeling and signaling

Cilia are microtubule-based organelles found on the surfaces of many types of cells, including cardiac fibroblasts, vascular endothelial cells, human retinal pigmented epithelial-1 (RPE-1) cells, and alveolar epithelial cells. These organelles can be classified as immotile cilia, referred to as primary cilia in mammalian cells, and motile cilia. Primary cilia are cellular sensors that detect extracellular signals; this is a critical function associated with ciliopathies, which are characterized by the typical clinical features of developmental disorders. Cilia are extensively studied organelles of the microtubule cytoskeleton. However, the ciliary actin cytoskeleton has rarely been studied. Clear evidence has shown that highly regulated actin cytoskeleton dynamics contribute to normal ciliary function. Actin-binding proteins (ABPs) play vital roles in filamentous actin (F-actin) morphology. Here, we discuss recent progress in understanding the roles of ABPs in ciliary structural remodeling and further downstream ciliary signaling with a focus on the molecular mechanisms underlying actin cytoskeleton-related ciliopathies.

Chemical Investigation of Diketopiperazines and N-Phenethylacetamide Isolated from Aquimarina sp. MC085 and Their Effect on TGF-β-Induced Epithelial–Mesenchymal Transition

Chemical investigations of Aquimarina sp. MC085, which suppressed TGF-β-induced epithelial–mesenchymal transition (EMT) in A549 human lung cancer cells, led to the isolation of compounds 1–3. Structural characterization using spectroscopic data analyses in combination with Marfey’s analysis revealed that they were two diketopiperazines [cyclo(l-Pro-l-Leu) (1) and cyclo(l-Pro-l-Ile) (2)] and one N-phenethylacetamide (3). Cyclo(l-Pro-l-Leu) (1) and N-phenethylactamide (3) inhibited the TGF-β/Smad pathway and suppressed the metastasis of A549 cells by affecting TGF-β-induced EMT. However, cyclo(l-Pro-l-Ile) (2) downregulated mesenchymal factors via a non-Smad-mediated signaling pathway.

Inhibition of A549 Lung Cancer Cell Migration and Invasion by Ent-Caprolactin C via the Suppression of Transforming Growth Factor-β-Induced Epithelial-Mesenchymal Transition

The epithelial–mesenchymal transition (EMT) of cancer cells is a crucial process in cancer cell metastasis. An Aquimarina sp. MC085 extract was found to inhibit A549 human lung cancer cell invasion, and caprolactin C (1), a new natural product, α-amino-ε-caprolactam linked to 3-methyl butanoic acid, was purified through bioactivity-guided isolation of the extract. Furthermore, its enantiomeric compound, ent-caprolactin C (2), was synthesized. Both 1 and 2 inhibited the invasion and γ-irradiation-induced migration of A549 cells. In transforming growth factor-β (TGF-β)-treated A549 cells, 2 inhibited the phosphorylation of Smad2/3 and suppressed the EMT cell marker proteins (N-cadherin, β-catenin, and vimentin), as well as the related messenger ribonucleic acid expression (N-cadherin, matrix metalloproteinase-9, Snail, and vimentin), while compound 1 did not suppress Smad2/3 phosphorylation and the expression of EMT cell markers. Therefore, compound 2 could be a potential candidate for antimetastatic agent development, because it suppresses TGF-β-induced EMT.

Garcimultiflorone K from Garcinia multiflora attenuates hepatocellular carcinoma metastasis by suppressing transforming growth factor-β signaling

BACKGROUND

Transforming growth factor‑β (TGF-β) signaling is a crucial inducer of tissue fibrosis and extracellular matrix accumulation and a vital suppressor of epithelial cell proliferation and cancer metastasis. The nature of this multifunctional cytokine has prompted the development of TGF-β signaling inhibitors as therapeutic agents. Our research group has recently isolated the polyprenylated polycyclic acylphloroglucinol garcimultiflorone K (GMK) from the stems of Garcinia multiflora; GMK exhibits antiangiogenic activity in endothelial cells.

PURPOSE

In the current study, we aimed to explore the antitumor effect and detailed mechanisms of Garcimultiflorone K in hepatocellular carcinoma cells.

METHODS

Cell proliferation and viability were evaluated using the MTT assay. The migratory ability of HepG2 cells was measured using wound healing assays. The inhibitory effect of GMK against the nuclear translocation of Smad by TGF-β was assessed through immunofluorescence staining and Western blotting. To investigate TGF-β-dependent gene expression profiles upon GMK stimulation, RNA transcript levels were determined using reverse transcription polymerase chain reaction. The effects of GMK in Smad2-driven transcriptomic activities were studied using a reporter gene assay. Protein levels were detected using Western blotting.

RESULTS

Our data revealed that GMK inhibited TGF-β-induced cellular responses, including Smad protein phosphorylation, cell migration, and extracellular matrix production, during epithelial-mesenchymal transition (EMT). Mechanistic studies further demonstrated that GMK suppressed TGF-β signaling by downregulating TGF-β receptor II (TβRII).

CONCLUSION

These findings elucidate that TβRII expression in hepatic cells can be specifically suppressed by GMK to attenuate metastasis and the disease-promoting effects of EMT, representing a therapeutic approach.

Actin Cytoskeleton and Regulation of TGFβ Signaling: Exploring Their Links

Human tissues, to maintain their architecture and function, respond to injuries by activating intricate biochemical and physical mechanisms that regulates intercellular communication crucial in maintaining tissue homeostasis. Coordination of the communication occurs through the activity of different actin cytoskeletal regulators, physically connected to extracellular matrix through integrins, generating a platform of biochemical and biomechanical signaling that is deregulated in cancer. Among the major pathways, a controller of cellular functions is the cytokine transforming growth factor β (TGFβ), which remains a complex and central signaling network still to be interpreted and explained in cancer progression. Here, we discuss the link between actin dynamics and TGFβ signaling with the aim of exploring their aberrant interaction in cancer.

Myosin Motors: Novel Regulators and Therapeutic Targets in Colorectal Cancer

Simple Summary

Colorectal cancer (CRC) is a deadly disease that may go undiagnosed until it presents at an advanced metastatic stage for which few interventions are available. The development and metastatic spread of CRC is driven by remodeling of the actin cytoskeleton in cancer cells. Myosins represent a large family of actin motor proteins that play key roles in regulating actin cytoskeleton architecture and dynamics. Different myosins can move and cross-link actin filaments, attach them to the membrane organelles and translocate vesicles along the actin filaments. These diverse activities determine the key roles of myosins in regulating cell proliferation, differentiation and motility. Either mutations or the altered expression of different myosins have been well-documented in CRC; however, the roles of these actin motors in colon cancer development remain poorly understood. The present review aims at summarizing the evidence that implicate myosin motors in regulating CRC growth and metastasis and discusses the mechanisms underlying the oncogenic and tumor-suppressing activities of myosins.

Abstract

Colorectal cancer (CRC) remains the third most common cause of cancer and the second most common cause of cancer deaths worldwide. Clinicians are largely faced with advanced and metastatic disease for which few interventions are available. One poorly understood aspect of CRC involves altered organization of the actin cytoskeleton, especially at the metastatic stage of the disease. Myosin motors are crucial regulators of actin cytoskeletal architecture and remodeling. They act as mechanosensors of the tumor environments and control key cellular processes linked to oncogenesis, including cell division, extracellular matrix adhesion and tissue invasion. Different myosins play either oncogenic or tumor suppressor roles in breast, lung and prostate cancer; however, little is known about their functions in CRC. This review focuses on the functional roles of myosins in colon cancer development. We discuss the most studied class of myosins, class II (conventional) myosins, as well as several classes (I, V, VI, X and XVIII) of unconventional myosins that have been linked to CRC development. Altered expression and mutations of these motors in clinical tumor samples and their roles in CRC growth and metastasis are described. We also evaluate the potential of using small molecular modulators of myosin activity to develop novel anticancer therapies.

Recent progress in TGF-β inhibitors for cancer therapy

Transforming growth factor-β (TGF-β) is a multifunctional cytokine that is involved in proliferation, metastasis, and many other important processes in malignancy. Inhibitors targeting TGF-β have been considered by pharmaceutical companies for cancer therapy, and some of them are in clinical trial now. Unfortunately, several of these programs have recently been relinquished, and most companies that remain in the contest are progressing slowly and cautiously. This review summarizes the TGF-β signal transduction pathway, its roles in oncogenesis and fibrotic diseases, and advancements in antibodies and small-molecule inhibitors of TGF-β.

LINC01980 facilitates esophageal squamous cell carcinoma progression via regulation of miR-190a-5p/MYO5A pathway

Understanding the role of Long non-coding RNAs (lncRNAs) in tumorigenesis in diverse human malignancies would helpful for targeted therapies, containing esophageal squamous cell carcinoma (ESCC). However, the specific role and molecular mechanisms of LINC01980 in ESCC remain unclarified. In this study, we investigated the expression level, function role, and molecular mechanisms of LINC01980 in esophageal cancer cells and ESCC tissues. The high expression of LINC01980 was detected in ESCC tissues and cells, and predicted poor prognosis. LINC01980 promoted the cell proliferation, migration, invasion ability and epithelial-mesenchymal transition (EMT) progress in ESCC cells. In addition, a negative correlation between LINC01980 and miR-190a-5p or miR-190a-5p and MYO5A was observed in ESCC. We found that miR-190a-5p could directly bind with the mRNA of LINC01980 and MYO5A, and it was detected low expression in ESCC. We further demonstrated that the downregulation of MYO5A caused by overexpressing miR-190a-5p was released via upregulation of LINC01980. Functionally, LINC01980 acted as a competitively endogenous RNA (ceRNA) to impact the expression of MYO5A by sponging miR-190a-5p in ESCC. Therefore, these findings suggest that LINC01980 may act as an oncogenic lncRNA in ESCC and LINC01980/miR-190a-5p/MYO5A pathway contributes to the development of ESCC.

Roles of Myosin-Mediated Membrane Trafficking in TGF-β Signaling

Recent findings have revealed the role of membrane traffic in the signaling of transforming growth factor-β (TGF-β). These findings originate from the pivotal function of TGF-β in development, cell proliferation, tumor metastasis, and many other processes essential in malignancy. Actin and unconventional myosin have crucial roles in subcellular trafficking of receptors; research has also revealed a growing number of unconventional myosins that have crucial roles in TGF-β signaling. Unconventional myosins modulate the spatial organization of endocytic trafficking and tether membranes or transport them along the actin cytoskeletons. Current models do not fully explain how membrane traffic forms a bridge between TGF-β and the downstream effectors that produce its functional responsiveness, such as cell migration. In this review, we present a brief overview of the current knowledge of the TGF-β signaling pathway and the molecular components that comprise the core pathway as follows: ligands, receptors, and Smad mediators. Second, we highlight key role(s) of myosin motor-mediated protein trafficking and membrane domain segregation in the modulation of the TGF-β signaling pathway. Finally, we review future challenges and provide future prospects in this field.

The chemical cue tetrabromopyrrole induces rapid cellular stress and mortality in phytoplankton

Eukaryotic phytoplankton contribute to the flow of elements through marine food webs, biogeochemical cycles, and Earth's climate. Therefore, how phytoplankton die is a critical determinate of the flow and fate of nutrients. While heterotroph grazing and viral infection contribute to phytoplankton mortality, recent evidence suggests that bacteria-derived cues also control phytoplankton lysis. Here, we report exposure to nanomolar concentrations of 2,3,4,5-tetrabromopyrrole (TBP), a brominated chemical cue synthesized by marine γ-proteobacteria, resulted in mortality of seven phylogenetically-diverse phytoplankton species. A comparison of nine compounds of marine-origin containing a range of cyclic moieties and halogenation indicated that both a single pyrrole ring and increased bromination were most lethal to the coccolithophore, Emiliania huxleyi. TBP also rapidly induced the production of reactive oxygen species and the release of intracellular calcium stores, both of which can trigger the activation of cellular death pathways. Mining of the Ocean Gene Atlas indicated that TBP biosynthetic machinery is globally distributed throughout the water column in coastal areas. These findings suggest that bacterial cues play multiple functions in regulating phytoplankton communities by inducing biochemical changes associated with cellular death. Chemically-induced lysis by bacterial infochemicals is yet another variable that must be considered when modeling oceanic nutrient dynamics.