Cofilin and Neurodegeneration: New Functions for an Old but Gold Protein

Cofilin(s) and Mitochondria: Function Beyond Actin Dynamics

ADF/cofilins form a family of small, widely expressed actin-binding proteins, regulating actin dynamics in various cellular and physiological processes in all eukaryotes, from yeasts to animals. Changes in the expression of the ADF/cofilin family proteins have been demonstrated under various pathological conditions. The well-established role of cofilin in migration, invasion, epithelial-mesenchymal transition, apoptosis, resistance to radiotherapy and chemotherapy, immune escape, and transcriptional dysregulation in malignant tumors is primarily attributed to its actin-modifying activity. Moreover, drugs targeting this function of cofilin have been developed for cancer treatment. However, its multilevel regulation, highly diverse effects across various pathological conditions, and conflicting data on the functional consequences of altered cofilin expression have prompted us to explore additional roles of cofilin-beyond actin modulation-particularly its involvement in lipid metabolism and mitochondrial homeostasis. Here, we review recent data on the expression of ADF/cofilin family proteins in various pathologies, account for the mutations and post-translational modifications of these proteins and their functional consequences, dwell on the role of K63-type ubiquitination of cofilin for its involvement in lipid metabolism and mitochondrial homeostasis, more specifically, a process of mitochondrial division or mitofission, point out conflicting data in cofilin research, and describe prospects for future studies of cofilin functions.

Inhibition of iron-induced cofilin activation and inflammation in microglia by a novel cofilin inhibitor

Neuroinflammatory conditions linked to iron dysregulation pose significant challenges in neurodegenerative diseases. Iron-loaded microglia are observed in the brains of patients with various neuroinflammatory conditions, yet how iron overload affects microglial function and contributes to various neuroinflammatory processes is poorly understood. This in vitro study elucidates the relationship between excess iron, cofilin activation, and microglial function, shedding light on potential therapeutic avenues. Iron overload was induced in Human Microglial Clone 3 cells using ferrous sulfate, and the expressions of ferritin heavy chain, ferritin light chain, divalent metal transporter 1, cofilin, p-cofilin, nuclear factor-κB (NF-κB), and various inflammatory cytokines were analyzed using real-time quantitative polymerase chain reaction, immunocytochemistry, Western blotting, and enzyme-linked immunosorbent assay. Results revealed a notable increase in cofilin, NF-κB, and inflammatory cytokine expression levels following excess iron exposure. Moreover, treatment with deferoxamine (DFX), a known iron chelator, and a novel cofilin inhibitor (CI) synthesized in our laboratory demonstrate a mitigating effect on iron-induced cofilin expression. Furthermore, both DFX and CI exhibit promising outcomes in mitigating the inflammatory consequences of excess iron, including the expression of pro-inflammatory cytokines and NF-κB activation. These findings suggest that both DFX and CI can potentially alleviate microglia-induced neuroinflammation by targeting both iron dysregulation and cofilin-mediated pathways. Overall, this study provides valuable insights into iron-induced cofilin activation and microglial activation, offering avenues for potential targeted therapies for neuroinflammatory conditions associated with iron and cofilin dysregulation in neurodegenerative diseases.

Research progress of mitochondria and cytoskeleton crosstalk in tumour development

During tumour progression, organelle function undergoes dramatic changes, and crosstalk among organelles plays a significant role. Crosstalk between mitochondria and other organelles such as the endoplasmic reticulum and cytoskeleton has focussed attention on the mechanisms of tumourigenesis. This review demonstrates an overview of the molecular structure of the mitochondrial-cytoskeletal junction and its biological interactions. It also presents a detailed and comprehensive description of mitochondrial-cytoskeletal crosstalk in tumour occurrence and development, including tumour cell proliferation, apoptosis, autophagy, metabolic rearrangement, and metastasis. Finally, the application of crosstalk in tumour therapy, including drug combinations and chemoresistance, is discussed. This review offers a theoretical basis for establishing mitochondrial-cytoskeletal junctions as therapeutic targets, and offers novel insights into the future management of malignant tumours.

The neuroprotective effect of isatin in the rotenone-induced model of parkinonism in rats: the study of delayed effects

Parkinsonism in rats induced by the pesticide rotenone is one of the most adequate models of Parkinson's disease (PD). Isatin (indole-2,3-dione) is an endogenous regulator found in mammals and humans and exhibiting a wide range of biological activities mediated by numerous isatin-binding proteins, including those associated with neurodegenerative pathology. A course of rotenone administration to rats caused behavioral impairments and changes in the profile and relative content of isatin-binding proteins in the brain. In this study, we have investigated the delayed neuroprotective effect of isatin (5 days after completion of the course of rotenone administration) on behavioral reactions and the relative content of isatin-binding proteins in the brain of rats with rotenone-induced experimental parkinsonism. Although during this period the rats retained locomotor dysfunction, the proteomic analysis data (profile of isatin-binding proteins in the brain and changes in their relative content) differed from the results obtained immediately after completion of the course of rotenone administration. Moreover, all isatin-binding proteins with altered relative content changed during this period are associated to varying degrees with neurodegeneration (many with Parkinson's and Alzheimer's diseases).

The Multifaceted Role of Cofilin in Neurodegeneration and Stroke: Insights into Pathogenesis and Targeting as a Therapy

This comprehensive review explores the complex role of cofilin, an actin-binding protein, across various neurodegenerative diseases (Alzheimer's, Parkinson's, schizophrenia, amyotrophic lateral sclerosis (ALS), Huntington's) and stroke. Cofilin is an essential protein in cytoskeletal dynamics, and any dysregulation could lead to potentially serious complications. Cofilin's involvement is underscored by its impact on pathological hallmarks like Aβ plaques and α-synuclein aggregates, triggering synaptic dysfunction, dendritic spine loss, and impaired neuronal plasticity, leading to cognitive decline. In Parkinson's disease, cofilin collaborates with α-synuclein, exacerbating neurotoxicity and impairing mitochondrial and axonal function. ALS and frontotemporal dementia showcase cofilin's association with genetic factors like C9ORF72, affecting actin dynamics and contributing to neurotoxicity. Huntington's disease brings cofilin into focus by impairing microglial migration and influencing synaptic plasticity through AMPA receptor regulation. Alzheimer's, Parkinson's, and schizophrenia exhibit 14-3-3 proteins in cofilin dysregulation as a shared pathological mechanism. In the case of stroke, cofilin takes center stage, mediating neurotoxicity and neuronal cell death. Notably, there is a potential overlap in the pathologies and involvement of cofilin in various diseases. In this context, referencing cofilin dysfunction could provide valuable insights into the common pathologies associated with the aforementioned conditions. Moreover, this review explores promising therapeutic interventions, including cofilin inhibitors and gene therapy, demonstrating efficacy in preclinical models. Challenges in inhibitor development, brain delivery, tissue/cell specificity, and long-term safety are acknowledged, emphasizing the need for precision drug therapy. The call to action involves collaborative research, biomarker identification, and advancing translational efforts. Cofilin emerges as a pivotal player, offering potential as a therapeutic target. However, unraveling its complexities requires concerted multidisciplinary efforts for nuanced and effective interventions across the intricate landscape of neurodegenerative diseases and stroke, presenting a hopeful avenue for improved patient care.

Spatial and temporal mapping of neuron-microglia interaction modes in acute ischemic stroke

Ischemic stroke (IS) is a major cause of morbidity and mortality worldwide, accounting for 75-80% of all strokes. Under conditions of ischemia and hypoxia, neurons suffer damage or death, leading to a series of secondary immune reactions. Microglia, the earliest activated immune cells, can exert neurotoxic or neuroprotective effects on neurons through secretion of factors. There exists a complex interaction between neurons and microglia during this process. Moreover, the interaction between them becomes even more complex due to differences in the infarct area and reperfusion time. This review first elaborates on the differences in neuronal death modes between the ischemic core and penumbra, and then introduces the differences in microglial markers across different infarct areas with varying reperfusion time, indicating distinct functions. Finally, we focus on exploring the interaction modes between neurons and microglia in order to precisely target beneficial interactions and inhibit harmful ones, thus providing new therapeutic strategies for the treatment of IS.

Cofilin Inhibitor Protects against Traumatic Brain Injury-Induced Oxidative Stress and Neuroinflammation

Microglial activation and failure of the antioxidant defense mechanisms are major hallmarks in different brain injuries, particularly traumatic brain injury (TBI). Cofilin is a cytoskeleton-associated protein involved in actin binding and severing. In our previous studies, we identified the putative role of cofilin in mediating microglial activation and apoptosis in ischemic and hemorrhagic conditions. Others have highlighted the involvement of cofilin in ROS production and the resultant neuronal death; however, more studies are needed to delineate the role of cofilin in oxidative stress conditions. The present study aims to investigate the cellular and molecular effects of cofilin in TBI using both in vitro and in vivo models as well as the first-in-class small-molecule cofilin inhibitor (CI). An in vitro H2O2-induced oxidative stress model was used in two different types of cells, human neuroblastoma (SH-SY5Y) and microglia (HMC3), along with an in vivo controlled cortical impact model of TBI. Our results show that treatment with H2O2 increases the expression of cofilin and slingshot-1 (SSH-1), an upstream regulator of cofilin, in microglial cells, which was significantly reduced in the CI-treated group. Cofilin inhibition significantly attenuated H2O2-induced microglial activation by reducing the release of proinflammatory mediators. Furthermore, we demonstrate that CI protects against H2O2-induced ROS accumulation and neuronal cytotoxicity, activates the AKT signaling pathway by increasing its phosphorylation, and modulates mitochondrial-related apoptogenic factors. The expression of NF-E2-related factor 2 (Nrf2) and its associated antioxidant enzymes were also increased in CI-treated SY-SY5Y. In the mice model of TBI, CI significantly activated the Nrf2 and reduced the expression of oxidative/nitrosative stress markers at the protein and gene levels. Together, our data suggest that cofilin inhibition provides a neuroprotective effect in in vitro and in vivo TBI mice models by inhibiting oxidative stress and inflammatory responses, the pivotal mechanisms involved in TBI-induced brain damage.

Visualizing Cofilin-Actin Filaments by Immunofluorescence and CryoEM: Essential Steps for Observing Cofilactin in Cells

Fluorescence microscopy of cytoskeletal proteins in situ using immunolabeling, fluorescent reagents, or expression of tagged proteins has been a common practice for decades but often with too little regard for what might not be visualized. This is especially true for assembled filamentous actin (F-actin), for which binding of fluorescently labeled phalloidin is taken as the gold standard for its quantification even though it is well known that F-actin saturated with cofilin (cofilactin) binds neither fluorescently labeled phalloidin nor genetically encoded F-actin reporters, such as LifeAct. Here, using expressed fluorescent cofilactin reporters, we show that cofilactin is the major component of some actin-containing structures in both normal and stressed neurons and present various fixation, permeabilization, and cryo-preservation methods for optimizing its observation.

Biochemical Pathways of Cellular Mechanosensing/Mechanotransduction and Their Role in Neurodegenerative Diseases Pathogenesis

In this review, we shed light on recent advances regarding the characterization of biochemical pathways of cellular mechanosensing and mechanotransduction with particular attention to their role in neurodegenerative disease pathogenesis. While the mechanistic components of these pathways are mostly uncovered today, the crosstalk between mechanical forces and soluble intracellular signaling is still not fully elucidated. Here, we recapitulate the general concepts of mechanobiology and the mechanisms that govern the mechanosensing and mechanotransduction processes, and we examine the crosstalk between mechanical stimuli and intracellular biochemical response, highlighting their effect on cellular organelles' homeostasis and dysfunction. In particular, we discuss the current knowledge about the translation of mechanosignaling into biochemical signaling, focusing on those diseases that encompass metabolic accumulation of mutant proteins and have as primary characteristics the formation of pathological intracellular aggregates, such as Alzheimer's Disease, Huntington's Disease, Amyotrophic Lateral Sclerosis and Parkinson's Disease. Overall, recent findings elucidate how mechanosensing and mechanotransduction pathways may be crucial to understand the pathogenic mechanisms underlying neurodegenerative diseases and emphasize the importance of these pathways for identifying potential therapeutic targets.

Regulation of Mitochondrial Function by the Actin Cytoskeleton

The regulatory role of actin cytoskeleton on mitochondrial function is a growing research field, but the underlying molecular mechanisms remain poorly understood. Specific actin-binding proteins (ABPs), such as Gelsolin, have also been shown to participate in the pathophysiology of mitochondrial OXPHOS disorders through yet to be defined mechanisms. In this mini-review, we will summarize the experimental evidence supporting the fundamental roles of actin cytoskeleton and ABPs on mitochondrial trafficking, dynamics, biogenesis, metabolism and apoptosis, with a particular focus on Gelsolin involvement in mitochondrial disorders. The functional interplay between the actin cytoskeleton, ABPs and mitochondrial membranes for the regulation of cellular homeostasis thus emerges as a new exciting field for future research and therapeutic approaches.