A Fresh Look at the Structure, Regulation, and Functions of Fodrin

α-Fodrin-CENP-E interaction is critical for pancreatic cancer progression and drug response

α-Fodrin, a known scaffolding protein for cytoskeleton stabilization, performs various functions including cell adhesion, cell motility, DNA repair and apoptosis. Based on our previous results revealing its role in mitosis in glioblastoma, we have examined its effect in pancreatic cancer, which is often linked to mitotic aberrations including aneuploidy and chromosome instability. Here, we show that the expression of α-Fodrin increases in pancreatic adenocarcinoma tissues compared to its normal counterpart, suggesting its tumor promoting role. shRNA-mediated knock-down of α-Fodrin significantly reduces the xenograft growth in immunocompromised mice underscoring the importance of α-Fodrin in tumor progression. CENP-E (centromere-associated protein E) is a motor protein essential for chromosomal alignment and segregation during mitosis. We have found that α-Fodrin interacts with CENP-E to recruit it to the kinetochore and depletion of α-Fodrin has a crucial role in controlling aneuploidy. As these mitotic defects can lead to apoptosis, we have further evaluated the activation of possible upstream pathways. Paclitaxel, a chemotherapeutic agent that stabilizes microtubules, disrupts mitosis and induces apoptosis. We found that Paclitaxel triggered stronger activation of JNK, ERK, and P38 MAPKs, altered BCL2/BAX ratios, cytochrome C release causing increased apoptosis in α-Fodrin knockdown cells compared to cells with wild-type α-Fodrin. This enhanced sensitivity to paclitaxel is consistent with improved survival in pancreatic cancer patients with low α-Fodrin (SPTAN1) and low CENP-E expression compared to poor prognosis with high expressions of both the genes. Taken together, this study provides the molecular mechanism by which α-Fodrin - CENP-E axis regulates pancreatic cancer progression and drug response.

Endothelial cytoskeleton in mechanotransduction and vascular diseases

The cytoskeleton is an important structural component that regulates various aspects of cell morphology, movement, and intracellular signaling. It plays a pivotal role in the cellular response to biomechanical stimuli, particularly in endothelial cells, which are critical for vascular homeostasis and the pathogenesis of cardiovascular diseases. Mechanical forces, such as shear and tension, activate intracellular signaling cascades that regulate transcription, translation, and cellular behaviors. Despite extensive research into cytoskeletal functions, the precise mechanisms by which the cytoskeleton transduces mechanical signals remain incompletely understood. This review focuses on the role of cytoskeletal components in membrane, cytoplasm, and nucleus in mechanotransduction, with an emphasis on their structure, mechanical and biological behaviors, dynamic interactions, and response to mechanical forces. The collaboration between membrane cytoskeleton, cytoplasmic cytoskeleton, and nucleoskeleton is indispensable for endothelial cells to respond to mechanical stimuli. Understanding their mechanoresponsive mechanisms is essential for advancing therapeutic strategies for cardiovascular diseases.

Interactomic exploration of LRRC8A in volume-regulated anion channels

Ion channels are critical in enabling ion movement into and within cells and are important targets for pharmacological interventions in different human diseases. In addition to their ion transport abilities, ion channels interact with signalling and scaffolding proteins, which affects their function, cellular positioning, and links to intracellular signalling pathways. The study of "channelosomes" within cells has the potential to uncover their involvement in human diseases, although this field of research is still emerging. LRRC8A is the gene that encodes a crucial protein involved in the formation of volume-regulated anion channels (VRACs). Some studies suggest that LRRC8A could be a valuable prognostic tool in different types of cancer, serving as a biomarker for predicting patients' outcomes. LRRC8A expression levels might be linked to tumour progression, metastasis, and treatment response, although its implications in different cancer types can be varied. Here, publicly accessible databases of cancer patients were systematically analysed to determine if a correlation between VRAC channel expression and survival rate exists across distinct cancer types. Moreover, we re-evaluated the impact of LRRC8A on cellular proliferation and migration in colon cancer via HCT116 LRRC8A-KO cells, which is a current topic of debate in the literature. In addition, to investigate the role of LRRC8A in cellular signalling, we conducted biotin proximity-dependent identification (BioID) analysis, revealing a correlation between VRAC channels and cell-cell junctions, mechanisms that govern cellular calcium homeostasis, kinases, and GTPase signalling. Overall, this dataset improves our understanding of LRRC8A/VRAC and explores new research avenues while identifying promising therapeutic targets and promoting inventive methods for disease treatment.

The centrosomal recruitment of γ-tubulin and its microtubule nucleation activity is α-fodrin guided

The regulation and recruitment of γ-TuRCs, the prime nucleator of microtubules, to the centrosome are still thrust areas of research. The interaction of fodrin, a sub-plasmalemmal cytoskeletal protein, with γ-tubulin is a new area of interest. To understand the cellular significance of this interaction, we show that depletion of α-fodrin brings in a significant reduction of γ-tubulin in neural cell centrosomes making it functionally under-efficient. This causes a loss of nucleation ability that cannot efficiently form microtubules in interphase cells and astral microtubules in mitosis. Fluorescence Recovery after Photobleaching (FRAP) experiment implies that α-fodrin is important in the recruitment of γ-tubulin to the centrosome resulting in the aforementioned effects. Further, our experiments indicate that the interaction of α-fodrin with certain pericentriolar matrix proteins such as Pericentrin and CDK5RAP2 are crucial for the recruitment of γ-tubulin to the centrosome. Earlier we reported that α-fodrin limits the nucleation potential of γ-TuRC. In that context, this study suggests that α-fodrin is a γ-tubulin recruiting protein to the centrosome thus preventing cytoplasmic microtubule nucleation and thereby compartmentalizing the process to the centrosome for maximum efficiency. Summary statementα-fodrin is a γ-tubulin interacting protein that controls the process of γ-tubulin recruitment to the centrosome and thereby regulates the microtubule nucleation capacity spatially and temporally.

Mechanical role of the submembrane spectrin scaffold in red blood cells and neurons

Spectrins are large, evolutionarily well-conserved proteins that form highly organized scaffolds on the inner surface of eukaryotic cells. Their organization in different cell types or cellular compartments helps cells withstand mechanical challenges with unique strategies depending on the cell type. This Review discusses our understanding of the mechanical properties of spectrins, their very distinct organization in red blood cells and neurons as two examples, and the contribution of the scaffolds they form to the mechanical properties of these cells.

Neurochemistry evaluated by MR spectroscopy in a patient with SPTAN1-related developmental and epileptic encephalopathy

BACKGROUND

Mutation of the SPTAN1 gene, which encodes α-fodrin (non-erythrocyte α-II spectrin), is one of the causes of developmental and epileptic encephalopathies (DEEs). SPTAN1-related DEE is radiologically characterized by cerebral atrophy, especially due to white matter volume reduction, hypomyelination, pontocerebellar hypoplasia, and a thin corpus callosum, however, no neurochemical analysis has been reported.

CASE REPORT

A Japanese infant female presented with severe psychomotor delay, tonic spasms, and visual impairment. Whole-exome sequencing revealed a de novo variant of the SPTAN1 gene, leading to a diagnosis of SPTAN1-related DEE. MR spectroscopy at ages 5 months, 11 months, and 1 year and 4 months revealed decreased N-acetylaspartate and choline-containing compounds, and increased glutamate or glutamine.

CONCLUSION

The decreased concentrations of N-acetylaspartate and choline-containing compounds may have resulted from neuroaxonal network dysfunction and hypomyelination, respectively. The increased glutamate or glutamine may have reflected a disrupted glutamate-glutamine cycle caused by dysfunction of exocytosis, in which α-fodrin plays an important role. MR spectroscopy revealed neurochemical derangement in SPTAN1-related DEE, which may be a possible pathomechanism and will be useful for its diagnosis.

Proteomic Analysis Reveals Differential Expression Profiles in Idiopathic Pulmonary Fibrosis Cell Lines

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, irreversible lung disorder of unknown cause. This disease is characterized by profibrotic activation of resident pulmonary fibroblasts resulting in aberrant deposition of extracellular matrix (ECM) proteins. However, although much is known about the pathophysiology of IPF, the cellular and molecular processes that occur and allow aberrant fibroblast activation remain an unmet need. To explore the differentially expressed proteins (DEPs) associated with aberrant activation of these fibroblasts, we used the IPF lung fibroblast cell lines LL97A (IPF-1) and LL29 (IPF-2), compared to the normal lung fibroblast cell line CCD19Lu (NL-1). Protein samples were quantified and identified using a label-free quantitative proteomic analysis approach by liquid chromatography-tandem mass spectrometry (LC-MS/MS). DEPs were identified after pairwise comparison, including all experimental groups. Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG), and Protein–Protein Interaction (PPI) network construction were used to interpret the proteomic data. Eighty proteins expressed exclusively in the IPF-1 and IPF-2 clusters were identified. In addition, 19 proteins were identified up-regulated in IPF-1 and 10 in IPF-2; 10 proteins were down-regulated in IPF-1 and 2 in IPF-2 when compared to the NL-1 proteome. Using the search tool for retrieval of interacting genes/proteins (STRING) software, a PPI network was constructed between the DEPs and the 80 proteins expressed exclusively in the IPF-2 and IPF-1 clusters, containing 115 nodes and 136 edges. The 10 hub proteins present in the IPP network were identified using the CytoHubba plugin of the Cytoscape software. GO and KEGG pathway analyses showed that the hub proteins were mainly related to cell adhesion, integrin binding, and hematopoietic cell lineage. Our results provide relevant information on DEPs present in IPF lung fibroblast cell lines when compared to the normal lung fibroblast cell line that could play a key role during IPF pathogenesis.

Spectrins and human diseases

Spectrin, as one of the major components of a plasma membrane-associated cytoskeleton, is a cytoskeletal protein composed of the modular structure of α and β subunits. The spectrin-based skeleton is essential for preserving the integrity and mechanical characteristics of the cell membrane. Moreover, spectrin regulates a variety of cell processes including cell apoptosis, cell adhesion, cell spreading, and cell cycle. Dysfunction of spectrins is implicated in various human diseases including hemolytic anemia, neurodegenerative diseases, ataxia, heart diseases, and cancers. Here, we briefly discuss spectrins function as well as the clinical manifestations and currently known molecular mechanisms of human diseases related to spectrins, highlighting that strategies for targeting regulation of spectrins function may provide new avenues for therapeutic intervention for these diseases.

Cytoskeleton and Associated Proteins: Pleiotropic JNK Substrates and Regulators

This review extensively reports data from the literature concerning the complex relationships between the stress-induced c-Jun N-terminal kinases (JNKs) and the four main cytoskeleton elements, which are actin filaments, microtubules, intermediate filaments, and septins. To a lesser extent, we also focused on the two membrane-associated cytoskeletons spectrin and ESCRT-III. We gather the mechanisms controlling cytoskeleton-associated JNK activation and the known cytoskeleton-related substrates directly phosphorylated by JNK. We also point out specific locations of the JNK upstream regulators at cytoskeletal components. We finally compile available techniques and tools that could allow a better characterization of the interplay between the different types of cytoskeleton filaments upon JNK-mediated stress and during development. This overview may bring new important information for applied medical research.

Serum Biomarkers for the Diagnosis of Glaucoma

Despite the importance of the early detection of glaucoma, most patients with progressive glaucoma show minimal symptoms. We aimed to evaluate biomarkers for glaucoma diagnosis in Korea. Forty-two volunteers with/without open-angle glaucoma were enrolled from January through October 2015—divided into a control or open-angle glaucoma group, which was further divided into normal-tension glaucoma (NTG) and high-tension glaucoma (HTG) groups—and underwent assessments for myelin basic protein (MBP), heat shock protein 60, anti-Sjögren’s-syndrome-related antigen A (SSA) and antigen B (SSB), anti-α-fodrin, and anti-nucleic acid. The glaucoma group showed a higher serum MBP level and lower serum anti-α-fodrin antibody level than the control group (p < 0.05). The NTG group showed higher serum anti-SSA and anti-SSB levels and lower anti-α-fodrin IgG/IgA levels than the HTG group. In the receiver operating characteristic curve analysis, the area under the curve (AUC) for serum MBP level was 0.917 in discriminating between controls and patients with glaucoma. Between the NTG and HTG groups, anti-SSA, anti-SSB, and anti-α-fodrin IgG/IgA levels showed an AUC above 0.8. Thus, these biomarkers were useful for diagnosing glaucoma and discriminating between controls and patients with glaucoma, and patients with NTG and HTG.