Calpain2 mediates Rab5-driven focal adhesion disassembly and cell migration

Tiliroside disrupted iron homeostasis and induced ferroptosis via directly targeting calpain-2 in pancreatic cancer cells

BACKGROUND

Tiliroside (TIL) is a flavonoid compound that exists in a variety of edible plants. These dietary plants are widely used as food and medicine to treat various diseases. However, the effect of TIL on pancreatic cancer (PC) and its underlying mechanisms are unclear.

PURPOSE

This study aims to reveal the anti-PC effect of TIL and clarify its mechanism.

METHODS

The inhibitory effects of TIL on PC growth were studied both in vitro and in vivo. Flow cytometry, transmission electron microscopy, immunofluorescence, biochemical analyses, RT-qPCR, genetic ablation, and western blotting were employed to evaluate ferroptosis, autophagy, and iron regulation. Additionally, RNA sequencing (RNA-seq), biomolecular layer interferometry (BLI), and molecular simulation analysis were combined to identify TIL molecular targets. The clinicopathological significance of Calpain-2 (CAPN2) was determined through immunohistochemistry (IHC) on a PC tissue microarray.

RESULTS

Herein, we showed that TIL was an effective anti-PC drug. CAPN2 was involved in the TIL - induced elevation of the labile iron pool (LIP) in PC cells. TIL directly bound to and inhibited CAPN2 activity, resulting in AKT deactivation and decreased expression of glucose transporters (GLUT1 and GLUT3) in PC cells. Consequently, TIL impaired ATP and NADPH generation, inducing autophagy and ROS production. The accumulation of TIL-induced ROS combined with LIP iron causes the Fenton reaction, leading to lipid peroxidation. Meanwhile, TIL-induced reduction of free iron ions promoted autophagic degradation of ferritin to regulate cellular iron homeostasis, which further exacerbated the death of PC cells by ferroptosis. As an extension of these in vitro findings, our murine xenograft study showed that TIL inhibited the growth of PANC-1 cells. Additionally, we showed that CAPN2 expression levels were related to clinical prognoses in PC patients.

CONCLUSION

We identify TIL as a potent bioactive inhibitor of CAPN2 and an anti-PC candidate of natural origin. These findings also highlight CAPN2 as a potential target for PC treatment.

Regulation of Cell Adhesion and Migration via Microtubule Cytoskeleton Organization, Cell Polarity, and Phosphoinositide Signaling

The capacity for cancer cells to metastasize to distant organs depends on their ability to execute the carefully choreographed processes of cell adhesion and migration. As most human cancers are of epithelial origin (carcinoma), the transcriptional downregulation of adherent/tight junction proteins (e.g., E-cadherin, Claudin and Occludin) with the concomitant gain of adhesive and migratory phenotypes has been extensively studied. Most research and reviews on cell adhesion and migration focus on the actin cytoskeleton and its reorganization. However, metastasizing cancer cells undergo the extensive reorganization of their cytoskeletal system, specifically in originating/nucleation sites of microtubules and their orientation (e.g., from non-centrosomal to centrosomal microtubule organizing centers). The precise mechanisms by which the spatial and temporal reorganization of microtubules are linked functionally with the acquisition of an adhesive and migratory phenotype as epithelial cells reversibly transition into mesenchymal cells during metastasis remains poorly understood. In this Special Issue of "Molecular Mechanisms Underlying Cell Adhesion and Migration", we highlight cell adhesion and migration from the perspectives of microtubule cytoskeletal reorganization, cell polarity and phosphoinositide signaling.

Calpain2 Upregulation Regulates EMT-Mediated Pancreatic Cancer Metastasis via the Wnt/β-Catenin Signaling Pathway

Calpains2 (CAPN2) is a calcium-dependent, non-lysosomal cysteine protease that plays critical roles in normal cellular functions and pathological processes, including tumorigenesis, cancer progression, and metastasis. However, the role and underlying regulatory mechanisms of CAPN2 in pancreatic cancer (PC) are still unknown. We found that CAPN2 is highly expressed in PC tissues and associated with poor PC prognosis by using The Cancer Genome Atlas (TCGA) datasets, Gene Expression Omnibus (GEO) datasets, and PC tissue arrays. CAPN2 downregulation significantly inhibited cell proliferation, migration, and invasion and regulated Wnt/β-catenin signaling pathway-mediated epithelial-mesenchymal transition (EMT) in PC cells. Our findings highlight the significance of CAPN2 in tumor regression and, thus, indicate that CAPN2 could be a promising target for PC treatment.

Endosomal phosphatidylinositol 3-phosphate controls synaptic vesicle cycling and neurotransmission

Neural circuit function requires mechanisms for controlling neurotransmitter release and the activity of neuronal networks, including modulation by synaptic contacts, synaptic plasticity, and homeostatic scaling. However, how neurons intrinsically monitor and feedback control presynaptic neurotransmitter release and synaptic vesicle (SV) recycling to restrict neuronal network activity remains poorly understood at the molecular level. Here, we investigated the reciprocal interplay between neuronal endosomes, organelles of central importance for the function of synapses, and synaptic activity. We show that elevated neuronal activity represses the synthesis of endosomal lipid phosphatidylinositol 3-phosphate [PI(3)P] by the lipid kinase VPS34. Neuronal activity in turn is regulated by endosomal PI(3)P, the depletion of which reduces neurotransmission as a consequence of perturbed SV endocytosis. We find that this mechanism involves Calpain 2-mediated hyperactivation of Cdk5 downstream of receptor- and activity-dependent calcium influx. Our results unravel an unexpected function for PI(3)P-containing neuronal endosomes in the control of presynaptic vesicle cycling and neurotransmission, which may explain the involvement of the PI(3)P-producing VPS34 kinase in neurological disease and neurodegeneration.

Metastasising Fibroblasts Show an HDAC6-Dependent Increase in Migration Speed and Loss of Directionality Linked to Major Changes in the Vimentin Interactome

Metastasising cells express the intermediate filament protein vimentin, which is used to diagnose invasive tumours in the clinic. We aimed to clarify how vimentin regulates the motility of metastasising fibroblasts. STED super-resolution microscopy, live-cell imaging and quantitative proteomics revealed that oncogene-expressing and metastasising fibroblasts show a less-elongated cell shape, reduced cell spreading, increased cell migration speed, reduced directionality, and stronger coupling between these migration parameters compared to normal control cells. In total, we identified and compared 555 proteins in the vimentin interactome. In metastasising cells, the levels of keratin 18 and Rab5C were increased, while those of actin and collagen were decreased. Inhibition of HDAC6 reversed the shape, spreading and migration phenotypes of metastasising cells back to normal. Inhibition of HDAC6 also decreased the levels of talin 1, tropomyosin, Rab GDI β, collagen and emilin 1 in the vimentin interactome, and partially reversed the nanoscale vimentin organisation in oncogene-expressing cells. These findings describe the changes in the vimentin interactome and nanoscale distribution that accompany the defective cell shape, spreading and migration of metastasising cells. These results support the hypothesis that oncogenes can act through HDAC6 to regulate the vimentin binding of the cytoskeletal and cell–extracellular matrix adhesion components that contribute to the defective motility of metastasising cells.

Focal adhesion dynamics in cellular function and disease

Acting as a bridge between the cytoskeleton of the cell and the extra cellular matrix (ECM), the cell-ECM adhesions with integrins at their core, play a major role in cell signalling to direct mechanotransduction, cell migration, cell cycle progression, proliferation, differentiation, growth and repair. Biochemically, these adhesions are composed of diverse, yet an organised group of structural proteins, receptors, adaptors, various enzymes including protein kinases, phosphatases, GTPases, proteases, etc. as well as scaffolding molecules. The major integrin adhesion complexes (IACs) characterised are focal adhesions (FAs), invadosomes (podosomes and invadopodia), hemidesmosomes (HDs) and reticular adhesions (RAs). The varied composition and regulation of the IACs and their signalling, apart from being an integral part of normal cell survival, has been shown to be of paramount importance in various developmental and pathological processes. This review per-illustrates the recent advancements in the research of IACs, their crucial roles in normal as well as diseased states. We have also touched on few of the various methods that have been developed over the years to visualise IACs, measure the forces they exert and study their signalling and molecular composition. Having such pertinent roles in the context of various pathologies, these IACs need to be understood and studied to develop therapeutical targets. We have given an update to the studies done in recent years and described various techniques which have been applied to study these structures, thereby, providing context in furthering research with respect to IAC targeted therapeutics.

Wnt/β-Catenin Signaling in Oral Carcinogenesis

Oral carcinogenesis is a complex and multifactorial process that involves cumulative genetic and molecular alterations, leading to uncontrolled cell proliferation, impaired DNA repair and defective cell death. At the early stages, the onset of potentially malignant lesions in the oral mucosa, or oral dysplasia, is associated with higher rates of malignant progression towards carcinoma in situ and invasive carcinoma. Efforts have been made to get insights about signaling pathways that are deregulated in oral dysplasia, as these could be translated into novel markers and might represent promising therapeutic targets. In this context, recent evidence underscored the relevance of the Wnt/β-catenin signaling pathway in oral dysplasia, as this pathway is progressively "switched on" through the different grades of dysplasia (mild, moderate and severe dysplasia), with the consequent nuclear translocation of β-catenin and expression of target genes associated with the maintenance of representative traits of oral dysplasia, namely cell proliferation and viability. Intriguingly, recent studies provide an unanticipated connection between active β-catenin signaling and deregulated endosome trafficking in oral dysplasia, highlighting the relevance of endocytic components in oral carcinogenesis. This review summarizes evidence about the role of the Wnt/β-catenin signaling pathway and the underlying mechanisms that account for its aberrant activation in oral carcinogenesis.

Focal adhesion kinase-dependent activation of the early endocytic protein Rab5 is associated with cell migration

Focal adhesion kinase (FAK) is a central regulator of integrin-dependent cell adhesion and migration and has recently been shown to co-localize with endosomal proteins. The early endocytic protein Rab5 controls integrin trafficking, focal adhesion disassembly, and cell migration and has been shown to be activated upon integrin engagement by mechanisms that remain unclear. Because FAK is a critical regulator of integrin-dependent signaling and Rab5 recapitulates FAK-mediated effects, we evaluated the possibility that FAK activates Rab5 and contributes to cell migration. Pulldown assays revealed that Rab5-GTP levels are decreased upon treatment with a pharmacological inhibitor of FAK, PF562,271, in resting A549 cells. These events were associated with decreased peripheral Rab5 puncta and a reduced number of early endosome antigen 1 (EEA1)-positive early endosomes. Accordingly, as indicated by FAK inhibition experiments and in FAK-null fibroblasts, adhesion-induced FAK activity increased Rab5-GTP levels. In fact, expression of WT FAK and FAK/Y180A/M183A (open conformation), but not FAK/Arg⁴⁵⁴ (kinase-dead), augmented Rab5-GTP levels in FAK-null fibroblasts and A549 cells. Moreover, expression of a GDP-bound Rab5 mutant (Rab5/S34N) or shRNA-mediated knockdown of endogenous Rab5 prevented FAK-induced A549 cell migration, whereas expression of WT or GTP-bound Rab5 (Rab5/Q79L), but not Rab5/S34N, promoted cell migration in FAK-null fibroblasts. Mechanistically, FAK co-immunoprecipitated with the GTPase-activating protein p85α in a phosphorylation (Tyr³⁹⁷)-dependent manner, preventing Rab5-GTP loading, as shown by knockdown and transfection recovery experiments. Taken together, these results reveal that FAK activates Rab5, leading to cell migration.

RAB38 promotes bladder cancer growth by promoting cell proliferation and motility

BACKGROUND

Bladder cancer is the most common malignancy of urinary system with high morbidity and mortality. In general, the development and progression of bladder cancer are complicated pathological processes, and the treatment methods mainly include surgical resection, radiotherapy, chemotherapy, and combined therapy. In recent years, targeted therapy has made progress in the treatment of bladder cancer. Therefore, to improve survival rates of patients with advanced bladder cancer, novel therapeutic targets are still urgently needed.

METHODS AND RESULTS

In this study, we found that RAB38 expressed in tumor tissues of patients with bladder cancer was linked to clinical features including pTNM stage and tumor recurrence, and positively correlated with the poor prognosis of bladder cancer. Notably, further results indicated that depletion of RAB38 could significantly inhibit the proliferation and motility of two types of human bladder cancer cells, T24 and 5637 cells. In addition, RAB38 ablation obviously blocked tumor growth and development in mice compared with control.

CONCLUSION

In conclusion, this study provides significant evidence that RAB38 promotes the development of bladder cancer and provides a novel therapeutic target of bladder cancer.