Tubulin acetylation: responsible enzymes, biological functions and human diseases

Arf6 GTPase deficiency leads to porcine oocyte quality decline during aging

Arf6 is a member of ADP-ribosylation factor (Arf) family, which is widely implicated in the regulation of multiple physiological processes including endocytic recycling, cytoskeletal organization, and membrane trafficking during mitosis. In this study, we investigated the potential relationship between Arf6 and aging-related oocyte quality, and its roles on organelle rearrangement and cytoskeleton dynamics in porcine oocytes. Arf6 expressed in porcine oocytes throughout meiotic maturation, and it decreased in aged oocytes. Disruption of Arf6 led to the failure of cumulus expansion and polar body extrusion. Further analysis indicated that Arf6 modulated ac-tubulin for meiotic spindle organization and microtubule stability. Besides, Arf6 regulated cofilin phosphorylation and fascin for actin assembly, which further affected spindle migration, indicating the roles of Arf6 on cytoskeleton dynamics. Moreover, the lack of Arf6 activity caused the dysfunction of Golgi and ER for protein synthesis and signal transduction. Mitochondrial dysfunction was also observed in Arf6-deficient porcine oocytes, which was supported by the increased ROS level and abnormal membrane potential. In conclusion, our results reported that insufficient Arf6 was related to aging-induced oocyte quality decline through spindle organization, actin assembly, and organelle rearrangement in porcine oocytes.

Endosymbiosis in trypanosomatids: The bacterium division depends on microtubule dynamism

Microtubules are components of the cytoskeleton that perform essential functions in eukaryotes, such as those related to shape change, motility and cell division. In this context some characteristics of these filaments are essential, such as polarity and dynamic instability. In trypanosomatids, microtubules are integral to ultrastructure organization, intracellular transport and mitotic processes. Some species of trypanosomatids co-evolve with a symbiotic bacterium in a mutualistic association that is marked by extensive metabolic exchanges and a coordinated division of the symbiont with other cellular structures, such as the nucleus and the kinetoplast. It is already established that the bacterium division is microtubule-dependent, so in this work, it was investigated whether the dynamism and remodeling of these filaments is capable of affecting the prokaryote division. To this purpose, Angomonas deanei was treated with Trichostatin A (TSA), a deacetylase inhibitor, and mutant cells for histone deacetylase 6 (HDAC6) were obtained by CRISPR-Cas9. A decrease in proliferation, an enhancement in tubulin acetylation, as well as morphological and ultrastructural changes, were observed in TSA-treated protozoa and mutant cells. In both cases, symbiont filamentation occurred, indicating that prokaryote cell division is dependent on microtubule dynamism.

Extracellular signals induce dynamic ER remodeling through αTAT1-dependent microtubule acetylation

Dynamic changes in the endoplasmic reticulum (ER) morphology are central to maintaining cellular homeostasis. Microtubules (MT) facilitate the continuous remodeling of the ER network into sheets and tubules by coordinating with many ER-shaping protein complexes, although how this process is controlled by extracellular signals remains unknown. Here we report that TAK1, a kinase responsive to various growth factors and cytokines including TGF-β and TNF-α, triggers ER tubulation by activating αTAT1, an MT-acetylating enzyme that enhances ER-sliding. We show that this TAK1/αTAT1-dependent ER remodeling promotes cell survival by actively downregulating BOK, an ER membrane-associated proapoptotic effector. While BOK is normally protected from degradation when complexed with IP3R, it is rapidly degraded upon their dissociation during the ER sheets-to-tubules conversion. These findings demonstrate a distinct mechanism of ligand-induced ER remodeling and suggest that the TAK1/αTAT1 pathway may be a key target in ER stress and dysfunction.

Prolonged depletion of profilin 1 or F-actin causes an adaptive response in microtubules

In addition to its well-established role in actin assembly, profilin 1 (PFN1) has been shown to bind to tubulin and alter microtubule growth. However, whether PFN1's predominant control over microtubules in cells occurs through direct regulation of tubulin or indirectly through the polymerization of actin has yet to be determined. Here, we manipulated PFN1 expression, actin filament assembly, and actomyosin contractility and showed that reducing any of these parameters for extended periods of time caused an adaptive response in the microtubule cytoskeleton, with the effect being significantly more pronounced in neuronal processes. All the observed changes to microtubules were reversible if actomyosin was restored, arguing that PFN1's regulation of microtubules occurs principally through actin. Moreover, the cytoskeletal modifications resulting from PFN1 depletion in neuronal processes affected microtubule-based transport and mimicked phenotypes that are linked to neurodegenerative disease. This demonstrates how defects in actin can cause compensatory responses in other cytoskeleton components, which in turn significantly alter cellular function.

Computational drug discovery approaches identify mebendazole as a candidate treatment for autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a rare genetic disorder characterised by numerous renal cysts, the progressive expansion of which can impact kidney function and lead eventually to renal failure. Tolvaptan is the only disease-modifying drug approved for the treatment of ADPKD, however its poor side effect and safety profile necessitates the need for the development of new therapeutics in this area. Using a combination of transcriptomic and machine learning computational drug discovery tools, we predicted that a number of existing drugs could have utility in the treatment of ADPKD, and subsequently validated several of these drug predictions in established models of disease. We determined that the anthelmintic mebendazole was a potent anti-cystic agent in human cellular and in vivo models of ADPKD, and is likely acting through the inhibition of microtubule polymerisation and protein kinase activity. These findings demonstrate the utility of combining computational approaches to identify and understand potential new treatments for traditionally underserved rare diseases.

The role and mechanism of epigenetics in anticancer drug-induced cardiotoxicity

Cardiovascular disease is the main factor contributing to the global burden of diseases, and the cardiotoxicity caused by anticancer drugs is an essential component that cannot be ignored. With the development of anticancer drugs, the survival period of cancer patients is prolonged; however, the cardiotoxicity caused by anticancer drugs is becoming increasingly prominent. Currently, cardiovascular disease has emerged as the second leading cause of mortality among long-term cancer survivors. Anticancer drug-induced cardiotoxicity has become a frontier and hot topic. The discovery of epigenetics has given the possibility of environmental changes in gene expression, protein synthesis, and traits. It has been found that epigenetics plays a pivotal role in promoting cardiovascular diseases, such as heart failure, coronary heart disease, and hypertension. In recent years, increasing studies have underscored the crucial roles played by epigenetics in anticancer drug-induced cardiotoxicity. Here, we provide a comprehensive overview of the role and mechanisms of epigenetics in anticancer drug-induced cardiotoxicity.

ATAT1 deficiency enhances microglia/macrophage-mediated erythrophagocytosis and hematoma absorption following intracerebral hemorrhage

MIcroglia/macrophage-mediated erythrophagocytosis plays a crucial role in hematoma clearance after intracerebral hemorrhage. Dynamic cytoskeletal changes accompany phagocytosis. However, whether and how these changes are associated with microglia/macrophage-mediated erythrophagocytosis remain unclear. In this study, we investigated the function of acetylated α-tubulin, a stabilized microtubule form, in microglia/macrophage erythrophagocytosis after intracerebral hemorrhage both in vitro and in vivo. We first assessed the function of acetylated α-tubulin in erythrophagocytosis using primary DiO GFP-labeled red blood cells co-cultured with the BV2 microglia or RAW264.7 macrophage cell lines. Acetylated α-tubulin expression was significantly decreased in BV2 and RAW264.7 cells during erythrophagocytosis. Moreover, silencing α-tubulin acetyltransferase 1 (ATAT1), a newly discovered α-tubulin acetyltransferase, decreased Ac-α-tub levels and enhanced the erythrophagocytosis by BV2 and RAW264.7 cells. Consistent with these findings, in ATAT1-/- mice, we observed increased ionized calcium binding adapter molecule 1 (Iba1) and Perls-positive microglia/macrophage phagocytes of red blood cells in peri-hematoma and reduced hematoma volume in mice with intracerebral hemorrhage. Additionally, knocking out ATAT1 alleviated neuronal apoptosis and pro-inflammatory cytokines and increased anti-inflammatory cytokines around the hematoma, ultimately improving neurological recovery of mice after intracerebral hemorrhage. These findings suggest that ATAT1 deficiency accelerates erythrophagocytosis by microglia/macrophages and hematoma absorption after intracerebral hemorrhage. These results provide novel insights into the mechanisms of hematoma clearance and suggest ATAT1 as a potential target for the treatment of intracerebral hemorrhage.

Kinesin KIF3A regulates meiotic progression and spindle assembly in oocyte meiosis

Kinesin family member 3A (KIF3A) is a microtubule-oriented motor protein that belongs to the kinesin-2 family for regulating intracellular transport and microtubule movement. In this study, we characterized the critical roles of KIF3A during mouse oocyte meiosis. We found that KIF3A associated with microtubules during meiosis and depletion of KIF3A resulted in oocyte maturation defects. LC-MS data indicated that KIF3A associated with cell cycle regulation, cytoskeleton, mitochondrial function and intracellular transport-related molecules. Depletion of KIF3A activated the spindle assembly checkpoint, leading to metaphase I arrest of the first meiosis. In addition, KIF3A depletion caused aberrant spindle pole organization based on its association with KIFC1 to regulate expression and polar localization of NuMA and γ-tubulin; and KIF3A knockdown also reduced microtubule stability due to the altered microtubule deacetylation by histone deacetylase 6 (HDAC6). Exogenous Kif3a mRNA supplementation rescued the maturation defects caused by KIF3A depletion. Moreover, KIF3A was also essential for the distribution and function of mitochondria, Golgi apparatus and endoplasmic reticulum in oocytes. Conditional knockout of epithelial splicing regulatory protein 1 (ESRP1) disrupted the expression and localization of KIF3A in oocytes. Overall, our results suggest that KIF3A regulates cell cycle progression, spindle assembly and organelle distribution during mouse oocyte meiosis.

Kinesin KIFC3 is essential for microtubule stability and cytokinesis in oocyte meiosis

KIFC3 is a member of Kinesin-14 family motor proteins, which play a variety of roles such as centrosome cohesion, cytokinesis, vesicles transportation and cell proliferation in mitosis. Here, we investigated the functional roles of KIFC3 in meiosis. Our findings demonstrated that KIFC3 exhibited expression and localization at centromeres during metaphase I, followed by translocation to the midbody at telophase I throughout mouse oocyte meiosis. Disruption of KIFC3 activity resulted in defective polar body extrusion. We observed aberrant meiotic spindles and misaligned chromosomes, accompanied by the loss of kinetochore-microtubule attachment, which might be due to the failed recruitment of BubR1/Bub3. Coimmunoprecipitation data revealed that KIFC3 plays a crucial role in maintaining the acetylated tubulin level mediated by Sirt2, thereby influencing microtubule stability. Additionally, our findings demonstrated an interaction between KIFC3 and PRC1 in regulating midbody formation during telophase I, which is involved in cytokinesis regulation. Collectively, these results underscore the essential contribution of KIFC3 to spindle assembly and cytokinesis during mouse oocyte meiosis.

WP1066, a small molecule inhibitor of STAT3, chemosensitizes paclitaxel-resistant ovarian cancer cells to paclitaxel by simultaneously inhibiting the activity of STAT3 and the interaction of STAT3 with Stathmin

Paclitaxel is widely used to treat cancer, however, drug resistance limits its clinical utility. STAT3 is constitutively activated in some cancers, and contributes to chemotherapy resistance. Currently, several STAT3 inhibitors including WP1066 are used in cancer clinical trials. However, whether WP1066 reverses paclitaxel resistance and the mechanismremains unknown. Here, we report that in contrast to paclitaxel-sensitive parental cells, the expressions of several pro-survival BCL2 family members such as BCL-2, BCL-XL and MCL-1 are higher in paclitaxel-resistant ovarian cancer cells. Meanwhile, STAT3 is constitutively activated while stathmin loses its activity in paclitaxel-resistant cells. Importantly, WP1066 amplifies the inhibition of cell proliferation, colony-forming ability and apoptosis of ovarian cancer cells induced by paclitaxel. Mechanistically, WP1066, on the one hand, interferes the STAT3/Stathmin interaction, causing unleash of STAT3/Stathmin from microtubule, thus destroying microtubule stability. This process results in reduction of Ac-α-tubulin, further causing MCL-1 reduction. On the other hand, WP1066 inhibits phosphorylation of STAT3 by JAK2, and blocks its nuclear translocation, therefore repressing the transcription of pro-survival targets such as BCL-2, BCL-XL and MCL-1. Finally, the two pathways jointly promote cell death. Our findings reveal a new mechanism wherein WP1066 reverses paclitaxel-resistance of ovarian cancer cells by dually inhibiting STAT3 activity and STAT3/Stathmin interaction, which may layfoundation for WP1066 combined with paclitaxel in treating paclitaxel-resistant ovarian cancer.

Modulating the acetylation of α-tubulin by LncRNAs and microRNAs helps in the progression of cancer

Malignant tumor cells go through morphological and gene expression alterations, including rearrangement of cytoskeleton proteins that promote invasion and metastasis. Microtubules form a major cytoskeleton component that plays a significant role in regulating multiple cellular activities and function depending on the presence of posttranslational modification (PTM). Acetylation is a type of PTM that generally occurs in the lysine 40 region of α-tubulin and is known to be critically associated with cancer metastasis. Current evidence demonstrates that noncoding RNAs, such as long noncoding RNA (lncRNA) and microRNA (or miRNA), which are correlated with gene regulation modulate the expression of acetylated tubulin in the development and metastasis of cancer. This review provides an overview about the role of lncRNA and miRNA in regulation of tubulin acetylation in various types of cancer.

CCDC66 mutations are associated with high myopia through affected cell mitosis

BACKGROUND

High myopia (HM) refers to an eye refractive error exceeding -5.00 D, significantly elevating blindness risk. The underlying mechanism of HM remains elusive. Given the extensive genetic heterogeneity and vast genetic base opacity, it is imperative to identify more causative genes and explore their pathogenic roles in HM.

METHODS

We employed exome sequencing to pinpoint the causal gene in an HM family. Sanger sequencing was used to confirm and analyse the gene mutations in this family and 200 sporadic HM cases. Single-cell RNA sequencing was conducted to evaluate the gene's expression patterns in developing human and mouse retinas. The CRISPR/Cas9 system facilitated the gene knockout cells, aiding in the exploration of the gene's function and its mutations. Immunofluorescent staining and immunoblot techniques were applied to monitor the functional shifts of the gene mutations at the cellular level.

RESULTS

A suspected nonsense mutation (c.C172T, p.Q58X) in CCDC66 was found to be co-segregated with the HM phenotype in the family. Additionally, six other rare variants were identified among the 200 sporadic patients. CCDC66 was consistently expressed in the embryonic retinas of both humans and mice. Notably, in CCDC66-deficient HEK293 cells, there was a decline in cell proliferation, microtube polymerisation rate and ace-tubulin level. Furthermore, the mutated CCDC66 failed to synchronise with the tubulin system during Hela cell mitosis, unlike its wild type counterpart.

CONCLUSIONS

Our research indicates that the CCDC66 variant c.C172T is associated with HM. A deficiency in CCDC66 might disrupt cell proliferation by influencing the mitotic process during retinal growth, leading to HM.

Arf1 GTPase Regulates Golgi-Dependent G2/M Transition and Spindle Organization in Oocyte Meiosis

ADP-ribosylation factor 1 (Arf1) is a small GTPase belonging to the Arf family. As a molecular switch, Arf1 is found to regulate retrograde and intra-Golgi transport, plasma membrane signaling, and organelle function during mitosis. This study aimed to explore the noncanonical roles of Arf1 in cell cycle regulation and cytoskeleton dynamics in meiosis with a mouse oocyte model. Arf1 accumulated in microtubules during oocyte meiosis, and the depletion of Arf1 led to the failure of polar body extrusion. Unlike mitosis, it finds that Arf1 affected Myt1 activity for cyclin B1/CDK1-based G2/M transition, which disturbed oocyte meiotic resumption. Besides, Arf1 modulated GM130 for the dynamic changes in the Golgi apparatus and Rab35-based vesicle transport during meiosis. Moreover, Arf1 is associated with Ran GTPase for TPX2 expression, further regulating the Aurora A-polo-like kinase 1 pathway for meiotic spindle assembly and microtubule stability in oocytes. Further, exogenous Arf1 mRNA supplementation can significantly rescue these defects. In conclusion, results reported the noncanonical functions of Arf1 in G2/M transition and meiotic spindle organization in mouse oocytes.

Identification and validation of microtubule depolymerizing agent, CYT997, as a potential drug candidate for hepatocellular carcinoma

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) is a typically fatal malignancy with limited treatment options and poor survival rates, despite recent FDA approvals of newer treatment options. We aim to address this unmet need by using a proprietary computational drug discovery platform that identifies drug candidates with the potential to advance rapidly and successfully through preclinical studies.

METHODS

We generated an in silico model of HCC biology to identify the top 10 small molecules with predicted efficacy. The most promising candidate, CYT997, was tested for its in vitro effects on cell viability and cell death, colony formation, cell cycle changes, and cell migration/invasion in HCC cells. We used an HCC patient-derived xenograft (PDX) mouse model to assess its in vivo efficacy.

RESULTS

CYT997 was significantly more cytotoxic against HCC cells than against primary human hepatocytes, and sensitized HCC cells to sorafenib. It arrested cell cycle at the G2/M phase with associated up-regulations of p21, p-MEK1/2, p-ERK, and down-regulation of cyclin B1. Cell apoptosis and senescence-like morphology were also observed. CYT997 inhibited HCC cell migration and invasion, and down-regulated the expressions of acetylated tubulins, β-tubulin, glypican-3 (GPC3), β-catenin, and c-Myc. In vivo, CYT997 (20 mg/kg, three times weekly by oral gavage) significantly inhibited PDX growth, while being non-toxic to mice. Immunohistochemistry confirmed the down-regulation of GPC3, c-Myc, and Ki-67, supporting its anti-proliferative effect.

CONCLUSION

CYT997 is a potentially efficacious and non-toxic drug candidate for HCC therapy. Its ability to down-regulate GPC3, β-catenin, and c-Myc highlights a novel mechanism of action.

Acetylation in pathogenesis: Revealing emerging mechanisms and therapeutic prospects

Protein acetylation modifications play a central and pivotal role in a myriad of biological processes, spanning cellular metabolism, proliferation, differentiation, apoptosis, and beyond, by effectively reshaping protein structure and function. The metabolic state of cells is intricately connected to epigenetic modifications, which in turn influence chromatin status and gene expression patterns. Notably, pathological alterations in protein acetylation modifications are frequently observed in diseases such as metabolic syndrome, cardiovascular disorders, and cancer. Such abnormalities can result in altered protein properties and loss of function, which are closely associated with developing and progressing related diseases. In recent years, the advancement of precision medicine has highlighted the potential value of protein acetylation in disease diagnosis, treatment, and prevention. This review includes provocative and thought-provoking papers outlining recent breakthroughs in acetylation modifications as they relate to cardiovascular disease, mitochondrial metabolic regulation, liver health, neurological health, obesity, diabetes, and cancer. Additionally, it covers the molecular mechanisms and research challenges in understanding the role of acetylation in disease regulation. By summarizing novel targets and prognostic markers for the treatment of related diseases, we aim to contribute to the field. Furthermore, we discuss current hot topics in acetylation research related to health regulation, including N4-acetylcytidine and liquid-liquid phase separation. The primary objective of this review is to provide insights into the functional diversity and underlying mechanisms by which acetylation regulates proteins in disease contexts.

CCDC183 is essential for cytoplasmic invagination around the flagellum during spermiogenesis and male fertility

Sperm flagellum plays a crucial role in male fertility. Here, we generated Ccdc183 knockout mice using the CRISPR/Cas9 system to reveal the protein function of the testis-specific protein CCDC183 in spermiogenesis. We demonstrated that the absence of CCDC183 causes male infertility with morphological and motility defects in spermatozoa. Owing to the lack of CCDC183, centrioles after elongation of axonemal microtubules do not connect the cell surface and nucleus during spermiogenesis, which causes subsequent loss of cytoplasmic invagination around the flagellum. As a result, the flagellar compartment does not form properly and cytosol-exposed axonemal microtubules collapse during spermiogenesis. In addition, ectopic localization of accessory structures, such as the fibrous sheath and outer dense fibers, and abnormal head shape as a result of abnormal sculpting by the manchette are observed in Ccdc183 knockout spermatids. Our results indicate that CCDC183 plays an essential role in cytoplasmic invagination around the flagellum to form functional spermatozoa during spermiogenesis.

Abnormal centriolar biomarker ratios correlate with unexplained bull artificial insemination subfertility: a pilot study

The mechanisms underlying male infertility are poorly understood. Most mammalian spermatozoa have two centrioles: the typical barrel-shaped proximal centriole (PC) and the atypical fan-like distal centriole (DC) connected to the axoneme (Ax). These structures are essential for fertility. However, the relationship between centriole quality and subfertility (reduced fertility) is not well established. Here, we tested the hypothesis that assessing sperm centriole quality can identify cattle subfertility. By comparing sperm from 25 fertile and 6 subfertile bulls, all with normal semen analyses, we found that unexplained subfertility and lower sire conception rates (pregnancy rate from artificial insemination in cattle) correlate with abnormal centriolar biomarker distribution. Fluorescence-based Ratiometric Analysis of Sperm Centrioles (FRAC) found only four fertile bulls (4/25, 16%) had positive FRAC tests (having one or more mean FRAC ratios outside of the distribution range in a group's high-quality sperm population), whereas all of the subfertile bulls (6/6, 100%) had positive FRAC tests (P = 0.00008). The most sensitive biomarker was acetylated tubulin, which had a novel labeling pattern between the DC and Ax. These data suggest that FRAC and acetylated tubulin labeling can identify bull subfertility that remains undetected by current methods and may provide insight into a novel mechanism of subfertility.

Neural deficits in a mouse model of PACS1 syndrome are corrected with PACS1- or HDAC6-targeting therapy

PACS1 syndrome is a neurodevelopmental disorder (NDD) caused by a recurrent de novo missense mutation in PACS1 (p.Arg203Trp (PACS1R203W)). The mechanism by which PACS1R203W causes PACS1 syndrome is unknown, and no curative treatment is available. Here, we use patient cells and PACS1 syndrome mice to show that PACS1 (or PACS-1) is an HDAC6 effector and that the R203W substitution increases the PACS1/HDAC6 interaction, aberrantly potentiating deacetylase activity. Consequently, PACS1R203W reduces acetylation of α-tubulin and cortactin, causing the Golgi ribbon in hippocampal neurons and patient-derived neural progenitor cells (NPCs) to fragment and overpopulate dendrites, increasing their arborization. The dendrites, however, are beset with varicosities, diminished spine density, and fewer functional synapses, characteristic of NDDs. Treatment of PACS1 syndrome mice or patient NPCs with PACS1- or HDAC6-targeting antisense oligonucleotides, or HDAC6 inhibitors, restores neuronal structure and synaptic transmission in prefrontal cortex, suggesting that targeting PACS1R203W/HDAC6 may be an effective therapy for PACS1 syndrome.

Mitochondrial transport in neurons and evidence for its involvement in acute neurological disorders

Ensuring mitochondrial quality is essential for maintaining neuronal homeostasis, and mitochondrial transport plays a vital role in mitochondrial quality control. In this review, we first provide an overview of neuronal mitochondrial transport, followed by a detailed description of the various motors and adaptors associated with the anterograde and retrograde transport of mitochondria. Subsequently, we review the modest evidence involving mitochondrial transport mechanisms that has surfaced in acute neurological disorders, including traumatic brain injury, spinal cord injury, spontaneous intracerebral hemorrhage, and ischemic stroke. An in-depth study of this area will help deepen our understanding of the mechanisms underlying the development of various acute neurological disorders and ultimately improve therapeutic options.

Deciphering the Mysterious Relationship between the Cross-Pathogenetic Mechanisms of Neurodegenerative and Oncological Diseases

The relationship between oncological pathologies and neurodegenerative disorders is extremely complex and is a topic of concern among a growing number of researchers around the world. In recent years, convincing scientific evidence has accumulated that indicates the contribution of a number of etiological factors and pathophysiological processes to the pathogenesis of these two fundamentally different diseases, thus demonstrating an intriguing relationship between oncology and neurodegeneration. In this review, we establish the general links between three intersecting aspects of oncological pathologies and neurodegenerative disorders, i.e., oxidative stress, epigenetic dysregulation, and metabolic dysfunction, examining each process in detail to establish an unusual epidemiological relationship. We also focus on reviewing the current trends in the research and the clinical application of the most promising chemical structures and therapeutic platforms that have a modulating effect on the above processes. Thus, our comprehensive analysis of the set of molecular determinants that have obvious cross-functional pathways in the pathogenesis of oncological and neurodegenerative diseases can help in the creation of advanced diagnostic tools and in the development of innovative pharmacological strategies.

Cytoskeletal adaptation following long-term dysregulation of actomyosin in neuronal processes

Microtubules, intermediate filaments, and actin are cytoskeletal polymer networks found within the cell. While each has unique functions, all the cytoskeletal elements must work together for cellular mechanics to be fully operative. This is achieved through crosstalk mechanisms whereby the different networks influence each other through signaling pathways and direct interactions. Because crosstalk can be complex, it is possible for perturbations in one cytoskeletal element to affect the others in ways that are difficult to predict. Here we investigated how long-term changes to the actin cytoskeleton affect microtubules and intermediate filaments. Reducing F-actin or actomyosin contractility increased acetylated microtubules and intermediate filament expression, with the effect being significantly more pronounced in neuronal processes. Changes to microtubules were completely reversible if F-actin and myosin activity is restored. Moreover, the altered microtubules in neuronal processes resulting from F-actin depletion caused significant changes to microtubule-based transport, mimicking phenotypes that are linked to neurodegenerative disease. Thus, defects in actin dynamics cause a compensatory response in other cytoskeleton components which profoundly alters cellular function.

Acetylated α-Tubulin and α-Synuclein: Physiological Interplay and Contribution to α-Synuclein Oligomerization

Emerging evidence supports that altered α-tubulin acetylation occurs in Parkinson's disease (PD), a neurodegenerative disorder characterized by the deposition of α-synuclein fibrillary aggregates within Lewy bodies and nigrostriatal neuron degeneration. Nevertheless, studies addressing the interplay between α-tubulin acetylation and α-synuclein are lacking. Here, we investigated the relationship between α-synuclein and microtubules in primary midbrain murine neurons and the substantia nigra of post-mortem human brains. Taking advantage of immunofluorescence and Proximity Ligation Assay (PLA), a method allowing us to visualize protein-protein interactions in situ, combined with confocal and super-resolution microscopy, we found that α-synuclein and acetylated α-tubulin colocalized and were in close proximity. Next, we employed an α-synuclein overexpressing cellular model and tested the role of α-tubulin acetylation in α-synuclein oligomer formation. We used the α-tubulin deacetylase HDAC6 inhibitor Tubacin to modulate α-tubulin acetylation, and we evaluated the presence of α-synuclein oligomers by PLA. We found that the increase in acetylated α-tubulin significantly induced α-synuclein oligomerization. In conclusion, we unraveled the link between acetylated α-tubulin and α-synuclein and demonstrated that α-tubulin acetylation could trigger the early step of α-synuclein aggregation. These data suggest that the proper regulation of α-tubulin acetylation might be considered a therapeutic strategy to take on PD.

HDAC6 inhibition: a significant potential regulator and therapeutic option to translate into clinical practice in renal transplantation

Histone deacetylase 6 (HDAC6), an almost exclusively cytoplasmic enzyme, plays an essential role in many biological processes and exerts its deacetylation-dependent/independent effects on a variety of target molecules, which has contributed to the flourishing growth of relatively isoform-specific enzyme inhibitors. Renal transplantation (RT) is one of the alternatively preferred treatments and the most cost-effective treatment approaches for the great majority of patients with end-stage renal disease (ESRD). HDAC6 expression and activity have recently been shown to be increased in kidney disease in a number of studies. To date, a substantial amount of validated studies has identified HDAC6 as a pivotal modulator of innate and adaptive immunity, and HDAC6 inhibitors (HDAC6i) are being developed and investigated for use in arrays of immune-related diseases, making HDAC6i a promising therapeutic candidate for the management of a variety of renal diseases. Based on accumulating evidence, HDAC6i markedly open up new avenues for therapeutic intervention to protect against oxidative stress-induced damage, tip the balance in favor of the generation of tolerance-related immune cells, and attenuate fibrosis by inhibiting multiple activations of cell profibrotic signaling pathways. Taken together, we have a point of view that targeting HDAC6 may be a novel approach for the therapeutic strategy of RT-related complications, including consequences of ischemia-reperfusion injury, induction of immune tolerance in transplantation, equilibrium of rejection, and improvement of chronic renal graft interstitial fibrosis after transplantation in patients. Herein, we will elaborate on the unique function of HDAC6, which focuses on therapeutical mechanism of action related to immunological events with a general account of the tantalizing potential to the clinic.

HDAC6 Deficiency Has Moderate Effects on Behaviors and Parkinson's Disease Pathology in Mice

Histone deacetylase 6 (HDAC6) is involved in the regulation of protein aggregation and neuroinflammation, but its role in Parkinson's disease (PD) remains controversial. In this study, Hdac6^-/- mice were generated by CRISPR-Cas9 technology for exploring the effect of HDAC6 on the pathological progression of PD. We found that male Hdac6^-/- mice exhibit hyperactivity and certain anxiety. In the acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice, though motor injury was slightly alleviated by HDAC6 deficiency, dopamine (DA) depletion in the striatum, the decrease in the number of DA neurons in the substantia nigra (SN) and the reduction in DA neuronal terminals were not affected. In addition, activation of glial cells and the expression of α-synuclein, as well as the levels of apoptosis-related proteins in the nigrostriatal pathway, were not changed in MPTP-injected wild-type and Hdac6^-/- mice. Therefore, HDAC6 deficiency leads to moderate alterations of behaviors and Parkinson's disease pathology in mice.

Structural remodeling of the endoplasmic reticulum in response to extracellular signals requires αTAT1-induced microtubule acetylation

Dynamic changes in the endoplasmic reticulum (ER) morphology are central to maintaining cellular homeostasis. Microtubules (MT) facilitate the continuous remodeling of the ER network into sheets and tubules by coordinating with many ER-shaping protein complexes, although how this process is controlled by extracellular signals remains unknown. Here we report that TAK1, a kinase responsive to numerous growth factors and cytokines including TGF-β and TNF-α, triggers ER tubulation by activating αTAT1, an MT-acetylating enzyme that enhances ER-sliding. We show that this TAK1/αTAT-dependent ER remodeling promotes cell survival by actively downregulating BOK, an ER membrane-associated proapoptotic effector. While BOK is normally protected from degradation when complexed with IP3R, it is rapidly degraded upon their dissociation during the ER sheets-to-tubules conversion. These findings demonstrate a distinct mechanism of ligand-induced ER remodeling and suggest that the TAK1/αTAT pathway may be a key target in ER stress and dysfunction.

Acetylated α-tubulin alleviates injury to the dendritic spines after ischemic stroke in mice

BACKGROUND AND AIM

Functional recovery is associated with the preservation of dendritic spines in the penumbra area after stroke. Previous studies found that polymerized microtubules (MTs) serve a crucial role in regulating dendritic spine formation and plasticity. However, the mechanisms that are involved are poorly understood. This study is designed to understand whether the upregulation of acetylated α-tubulin (α-Ac-Tub, a marker for stable, and polymerized MTs) could alleviate injury to the dendritic spines in the penumbra area and motor dysfunction after ischemic stroke.

METHODS

Ischemic stroke was mimicked both in an in vivo and in vitro setup using middle cerebral artery occlusion and oxygen-glucose deprivation models. Thy1-YFP mice were utilized to observe the morphology of the dendritic spines in the penumbra area. MEC17 is the specific acetyltransferase of α-tubulin. Thy1 Cre^ERT2-eYFP and MEC17^fl/fl mice were mated to produce mice with decreased expression of α-Ac-Tub in dendritic spines of pyramidal neurons in the cerebral cortex. Moreover, AAV-PHP.B-DIO-MEC17 virus and tubastatin A (TBA) were injected into Thy1 Cre^ERT2-eYFP and Thy1-YFP mice to increase α-Ac-Tub expression. Single-pellet retrieval, irregular ladder walking, rotarod, and cylinder tests were performed to test the motor function after the ischemic stroke.

RESULTS

α-Ac-Tub was colocalized with postsynaptic density 95. Although knockout of MEC17 in the pyramidal neurons did not affect the density of the dendritic spines, it significantly aggravated the injury to them in the penumbra area and motor dysfunction after stroke. However, MEC17 upregulation in the pyramidal neurons and TBA treatment could maintain mature dendritic spine density and alleviate motor dysfunction after stroke.

CONCLUSION

Our study demonstrated that α-Ac-Tub plays a crucial role in the maintenance of the structure and functions of mature dendritic spines. Moreover, α-Ac-Tub protected the dendritic spines in the penumbra area and alleviated motor dysfunction after stroke.

Microglia reactivity entails microtubule remodeling from acentrosomal to centrosomal arrays

Microglia reactivity entails a large-scale remodeling of cellular geometry, but the behavior of the microtubule cytoskeleton during these changes remains unexplored. Here we show that activated microglia provide an example of microtubule reorganization from a non-centrosomal array of parallel and stable microtubules to a radial array of more dynamic microtubules. While in the homeostatic state, microglia nucleate microtubules at Golgi outposts, and activating signaling induces recruitment of nucleating material nearby the centrosome, a process inhibited by microtubule stabilization. Our results demonstrate that a hallmark of microglia reactivity is a striking remodeling of the microtubule cytoskeleton and suggest that while pericentrosomal microtubule nucleation may serve as a distinct marker of microglia activation, inhibition of microtubule dynamics may provide a different strategy to reduce microglia reactivity in inflammatory disease.

In silico analysis of TUBA4A mutations in Amyotrophic Lateral Sclerosis to define mechanisms of microtubule disintegration

Amyotrophic lateral sclerosis (ALS) is an inexorably progressive and degenerative disorder of motor neurons with no currently-known cure. Studies to determine the mechanism of neurotoxicity and the impact of ALS-linked mutations (SOD1, FUS, TARDP, C9ORF72, PFN1, TUBA4A and others) have greatly expanded our knowledge of ALS disease mechanisms and have helped to identify potential targets for ALS therapy. Cellular pathologies (e.g., aggregation of mutant forms of SOD1, TDP43, FUS, Ubiqulin2, PFN1, and C9ORF72), mitochondrial dysfunction, neuroinflammation, and oxidative damage are major pathways implicated in ALS. Nevertheless, the selective vulnerability of motor neurons remains unexplained. The importance of tubulins for long-axon infrastructure, and the special morphology and function of motor neurons, underscore the central role of the cytoskeleton. The recent linkage of mutations to the tubulin α chain, TUBA4A, to familial and sporadic cases of ALS provides a new investigative opportunity to shed light on both mechanisms of ALS and the vulnerability of motor neurons. In the current study we investigate TUBA4A, a structural microtubule protein with mutations causal to familial ALS, using molecular-dynamic (MD) modeling of protein structure to predict the effects of each mutation and its overall impact on GTP binding, chain stability, tubulin assembly, and aggregation propensity. These studies predict that each of the reported mutations will cause notable structural changes to the TUBA4A (α chain) tertiary protein structure, adversely affecting its physical properties and functions. Molecular docking and MD simulations indicate certain α chain mutations (e.g. K430N, R215C, and W407X) may cause structural deviations that impair GTP binding, and plausibly prevent or destabilize tubulin polymerization. Furthermore, several mutations (including R320C and K430N) confer a significant increase in predicted aggregation propensity of TUBA4A mutants relative to wild-type. Taken together, these in silico modeling studies predict structural perturbations and disruption of GTP binding, culminating in failure to form a stable tubulin heterocomplex, which may furnish an important pathogenic mechanism to trigger motor neuron degeneration in ALS.

Synthesis and bioactivity evaluation of ferrocene-based hydroxamic acids as selective histone deacetylase 6 inhibitors

Histone deacetylase 6 (HDAC6) is involved in multiple regulatory processes and emerges as a promising target for treating cancer and neurodegenerative diseases. Benefited from the unique sandwich conformation of ferrocene, a series of ferrocene-based hydroxamic acids have been developed as novel HDAC6 inhibitors in this paper, especially the two ansa-ferrocenyl complexes with IC₅₀s at the nanomolar level. [3]-Ferrocenophane hydroxamic acid analog II-5 displays the most potent inhibitory activity on HDAC6 and establishes remarkable selectivity towards other HDAC isoforms. Compound II-5 dose-dependently induces accumulation of acetylated α-tubulin while having a negligible effect on the level of acetylated Histone H3, confirming its isoform selectivity. Further biological evaluation of II-5 on cancer cells corroborates its antiproliferative effect, which mainly contributed to the induction of cellular apoptosis. It is worth noting that compound II-5 demonstrates an optimal profile on human plasma stability. These results strengthen ferrocene's unique role in developing selective protein inhibitors and indicate that compound II-5 may be a suitable lead for further evaluation and development for treating HDAC6-associated disorders and diseases.

Sperm morphological abnormalities in autosomal dominant polycystic kidney disease are associated with the Hippo signaling pathway via PC1

Background

Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary kidney disorder mostly caused by mutations in PKD1 or PKD2 genes. Here, we report thirteen ADPKD males with infertility and investigated the sperm morphological defects associated with PC1 disruption.

Methods

Targeted next-generation sequencing was performed to detect PKD1 variants in patients. Sperm morphology was observed by immunostaining and transmission electron microscopy, and the sperm motility was assessed using the computer-assisted sperm analysis system. The Hippo signaling pathway was analyzed with by quantitative reverse transcription polymerase chain reaction (qPCR) and western blotting in vitro.

Results

The ADPKD patients were infertile and their sperm tails showed morphological abnormalities, including coiled flagella, absent central microtubules, and irregular peripheral doublets. In addition, the length of sperm flagella was shorter in patients than in controls of in in. In vitro, ciliogenesis was impaired in Pkd1-depleted mouse kidney tubule cells. The absence of PC1 resulted in a reduction of MST1 and LATS1, leading to nuclear accumulation of YAP/TAZ and consequently increased transcription of Aurka. which might promote HDAC6-mediated ciliary disassembly.

Conclusion

Our results suggest the dysregulated Hippo signaling significantly contributes to ciliary abnormalities in and may be associated with flagellar defects in spermatozoa from ADPKD patients.

Methods for studying primary cilia in heart tissue after ischemia-reperfusion injury

Cardiovascular diseases are the leading cause of death and disability worldwide. After heart injury triggered by myocardial ischemia or myocardial infarction, extensive zones of tissue are damaged and some of the tissue dies by necrosis and/or apoptosis. The loss of contractile mass activates a series of biochemical mechanisms that allow, through cardiac remodeling, the replacement of the dysfunctional heart tissue by fibrotic material. Our previous studies have shown that primary cilia, non-motile antenna-like structures at the cell surface required for the activation of specific signaling pathways, are present in cardiac fibroblasts and required for cardiac fibrosis induced by ischemia/reperfusion (I/R) in mice. I/R-induced myocardial fibrosis promotes the enrichment of ciliated cardiac fibroblasts where the myocardial injury occurs. Given discussions about the existence of cilia in specific cardiac cell types, as well as the functional relevance of studying cilia-dependent signaling in cardiac fibrosis after I/R, here we describe our methods to evaluate the presence and roles of primary cilia in cardiac fibrosis after I/R in mice.

Actin-microtubule cytoskeletal interplay mediated by MRTF-A/SRF signaling promotes dilated cardiomyopathy caused by LMNA mutations

Mutations in the lamin A/C gene (LMNA) cause dilated cardiomyopathy associated with increased activity of ERK1/2 in the heart. We recently showed that ERK1/2 phosphorylates cofilin-1 on threonine 25 (phospho(T25)-cofilin-1) that in turn disassembles the actin cytoskeleton. Here, we show that in muscle cells carrying a cardiomyopathy-causing LMNA mutation, phospho(T25)-cofilin-1 binds to myocardin-related transcription factor A (MRTF-A) in the cytoplasm, thus preventing the stimulation of serum response factor (SRF) in the nucleus. Inhibiting the MRTF-A/SRF axis leads to decreased α-tubulin acetylation by reducing the expression of ATAT1 gene encoding α-tubulin acetyltransferase 1. Hence, tubulin acetylation is decreased in cardiomyocytes derived from male patients with LMNA mutations and in heart and isolated cardiomyocytes from Lmna^{p.H222P/H222P} male mice. In Atat1 knockout mice, deficient for acetylated α-tubulin, we observe left ventricular dilation and mislocalization of Connexin 43 (Cx43) in heart. Increasing α-tubulin acetylation levels in Lmna^{p.H222P/H222P} mice with tubastatin A treatment restores the proper localization of Cx43 and improves cardiac function. In summary, we show for the first time an actin-microtubule cytoskeletal interplay mediated by cofilin-1 and MRTF-A/SRF, promoting the dilated cardiomyopathy caused by LMNA mutations. Our findings suggest that modulating α-tubulin acetylation levels is a feasible strategy for improving cardiac function.

Tubulin Isotypes and Posttranslational Modifications in Vascular Dementia and Alzheimer's Disease

Background

Vascular dementia (VaD) and Alzheimer's disease (AD) are the two most common forms of dementia. Although these two types of dementia have different etiologies, they share some similarities in their pathophysiology, such as neuronal loss and decreased levels of tau protein. We hypothesize that these can have an impact upon the molecular changes in tubulin, precede the neuronal cell loss, and lead to changes in cytoskeletal associated proteins, as documented in both VaD and AD.

Objective

We characterized different isotypes of tubulin together with their posttranslational modifications, as well as several microtubule associated proteins (MAPs), such as tau protein, MAP2 and MAP6, all together known as the tubulin code.

Methods

We performed western blotting in human brain homogenates of controls and AD and VaD subjects.

Results

We report that the levels of different tubulin isotypes differ depending on the dementia type and the brain area being studied: whereas α-tubulin is increased in the temporal lobe of VaD patients, it is decreased in the frontal lobe of AD patients. In VaD patients, the frontal lobe had a decrease in tyrosinated tubulin, which was accompanied by a decrease in tau protein and a tendency for lower levels of MAP2.

Conclusion

Our findings highlight distinct changes in the tubulin code in VaD and AD, suggesting a therapeutic opportunity for different dementia subtypes in the future.

The interconnections between the microtubules and mitochondrial networks in cardiocerebrovascular diseases: Implications for therapy

Microtubules, a highly dynamic cytoskeleton, participate in many cellular activities including mechanical support, organelles interactions, and intracellular trafficking. Microtubule organization can be regulated by modification of tubulin subunits, microtubule-associated proteins (MAPs) or agents modulating microtubule assembly. Increasing studies demonstrate that microtubule disorganization correlates with various cardiocerebrovascular diseases including heart failure and ischemic stroke. Microtubules also mediate intracellular transport as well as intercellular transfer of mitochondria, a power house in cells which produce ATP for various physiological activities such as cardiac mechanical function. It is known to all that both microtubules and mitochondria participate in the progression of cancer and Parkinson's disease. However, the interconnections between the microtubules and mitochondrial networks in cardiocerebrovascular diseases remain unclear. In this paper, we will focus on the roles of microtubules in cardiocerebrovascular diseases, and discuss the interplay of mitochondria and microtubules in disease development and treatment. Elucidation of these issues might provide significant diagnostic value as well as potential targets for cardiocerebrovascular diseases.

The CD63 homologs, Tsp42Ee and Tsp42Eg, restrict endocytosis and promote neurotransmission through differential regulation of synaptic vesicle pools

The Tetraspanin (Tsp), CD63, is a transmembrane component of late endosomes and facilitates vesicular trafficking through endosomal pathways. Despite being widely expressed in the human brain and localized to late endosomes, CD63's role in regulating endo- and exocytic cycling at the synapse has not been investigated. Synaptic vesicle pools are highly dynamic and disruptions in the mobilization and replenishment of these vesicle pools have adverse neuronal effects. We find that the CD63 homologs, Tsp42Ee and Tsp42Eg, are expressed at the Drosophila neuromuscular junction to regulate synaptic vesicle pools through both shared and unique mechanisms. Tsp42Ee and Tsp42Eg negatively regulate endocytosis and positively regulate neurotransmitter release. Both tsp mutants show impaired locomotion, reduced miniature endplate junctional current frequencies, and increased endocytosis. Expression of human CD63 in Drosophila neurons leads to impaired endocytosis suggesting the role of Tsps in endocytosis is conserved. We further show that Tsps influence the synaptic cytoskeleton and membrane composition by regulating Futsch loop formation and synaptic levels of SCAR and PI(4,5)P2. Finally, Tsp42Ee and Tsp42Eg influence the synaptic localization of several vesicle-associated proteins including Synapsin, Synaptotagmin, and Cysteine String Protein. Together, our results present a novel function for Tsps in the regulation of vesicle pools and provide insight into the molecular mechanisms of Tsp-related synaptic dysfunction.

Combination of microtubule targeting agents with other antineoplastics for cancer treatment

Microtubule targeting agents (MTAs) have attracted extensive attention for cancer treatment. However, their clinical efficacies are limited by intolerable toxicities, inadequate efficacy and acquired multidrug resistance. The combination of MTAs with other antineoplastics has become an efficient strategy to lower the toxicities, overcome resistance and improve the efficacies for cancer treatment. In this article, we review the combinations of MTAs with some other anticancer drugs, such as cytotoxic agents, kinases inhibitors, histone deacetylase inhibitors, immune checkpoints inhibitors, to overcome these obstacles. We strongly believe that this review will provide helpful information for combination therapy based on MTAs.

Insulin-degrading enzyme ablation in mouse pancreatic alpha cells triggers cell proliferation, hyperplasia and glucagon secretion dysregulation

AIMS/HYPOTHESIS

Type 2 diabetes is characterised by hyperglucagonaemia and perturbed function of pancreatic glucagon-secreting alpha cells but the molecular mechanisms contributing to these phenotypes are poorly understood. Insulin-degrading enzyme (IDE) is present within all islet cells, mostly in alpha cells, in both mice and humans. Furthermore, IDE can degrade glucagon as well as insulin, suggesting that IDE may play an important role in alpha cell function in vivo.

METHODS

We have generated and characterised a novel mouse model with alpha cell-specific deletion of Ide, the A-IDE-KO mouse line. Glucose metabolism and glucagon secretion in vivo was characterised; isolated islets were tested for glucagon and insulin secretion; alpha cell mass, alpha cell proliferation and α-synuclein levels were determined in pancreas sections by immunostaining.

RESULTS

Targeted deletion of Ide exclusively in alpha cells triggers hyperglucagonaemia and alpha cell hyperplasia, resulting in elevated constitutive glucagon secretion. The hyperglucagonaemia is attributable in part to dysregulation of glucagon secretion, specifically an impaired ability of IDE-deficient alpha cells to suppress glucagon release in the presence of high glucose or insulin. IDE deficiency also leads to α-synuclein aggregation in alpha cells, which may contribute to impaired glucagon secretion via cytoskeletal dysfunction. We showed further that IDE deficiency triggers impairments in cilia formation, inducing alpha cell hyperplasia and possibly also contributing to dysregulated glucagon secretion and hyperglucagonaemia.

CONCLUSIONS/INTERPRETATION

We propose that loss of IDE function in alpha cells contributes to hyperglucagonaemia in type 2 diabetes.

In vitro effects of the 4-[(10H-phenothiazin-10-yl)methyl]-N-hydroxybenzamide on Giardia intestinalis trophozoites

Giardiasis is an intestinal disease caused by the parasite protozoan Giardia intestinalis. For more than five decades, the treatment of this disease has been based on compounds such as nitroimidazoles and benzimidazoles. The parasite's adverse effects and therapeutic failure are largely recognized. Therefore, it is necessary to develop new forms of chemotherapy treatment against giardiasis. Lysine deacetylases (KDACs), which remove an acetyl group from lysine residues in histone and non-histone proteins as tubulin, are found in the Giardia genome and can become an interesting option for giardiasis treatment. In the present study, we evaluated the effects of 4-[(10H-phenothiazin-10-yl)methyl]-N-hydroxybenzamide, a new class I/II KDAC inhibitor, on G. intestinalis growth, cytoskeleton, and ultrastructure organization. This compound decreased parasite proliferation and viability and displayed an IC₅₀ value of 179 nM. Scanning electron microscopy revealed the presence of protrusions on the cell surface after treatment. In addition, the vacuoles containing concentric membranous lamella and glycogen granules were observed in treated trophozoites. The cell membrane appeared deformed just above these vacuoles. Alterations on the microtubular cytoskeleton of the parasite were not observed after drug exposure. The number of diving cells with incomplete cytokinesis increased after treatment, indicating that the compound can interfere in the late steps of cell division. Our results indicate that 4-[(10H-phenothiazin-10-yl)methyl]-N-hydroxybenzamide should be explored to develop new therapeutic compounds for treating giardiasis.

HDAC6 Inhibition Alleviates Anesthesia and Surgery-Induced Less Medial Prefrontal-Dorsal Hippocampus Connectivity and Cognitive Impairment in Aged Rats

To investigate the underlying mechanisms of postoperative cognitive dysfunction and the impairment of medial prefrontal cortex-hippocampus connectivity. Postoperative cognitive dysfunction frequently affects elderly following surgery. The role of inter-brain-region connectivity abnormality after anesthesia and surgery on postoperative cognitive dysfunction development remains unclear. Medial prefrontal cortex-hippocampus connectivity of aged and adult rats was evaluated by injecting neurotracer biotinylated dextranamine (BDA) into bilateral hippocampus 3 days before partial hepatectomy, and biotinylated dextranamine positive cells of medial prefrontal cortex 2 days after hepatectomy were counted. HDAC6 shRNA was injected into medial prefrontal cortex and hippocampus bilaterally before hepatectomy or an HDAC6 activity inhibitor Tubastatin A was administered systemically after hepatectomy. Neuroinflammation and HDAC6 down-target ac-tubulin in medial prefrontal cortex and hippocampus were detected. Learning and memory of rats were evaluated by Barnes Maze task during 2-5 days after surgery and delayed matching-to-place water maze task during 10-23 days after surgery. Compared to the age-matched normal controls, anesthesia and surgery significantly decreased BDA-positive neurons in medial prefrontal cortex of aged rats, but not young adult rats. Local HDAC6 knockdown and systemic HDAC6 inhibition both increased BDA-positive neurons number of medial prefrontal cortex, alleviated learning and memory impairment in the Barnes Maze task and water maze task, decreased HDAC6 expression, inflammatory cytokines, astrocyte and microglial activation, and increased ac-tubulin expression in aged rats which received surgery. Our data indicated that anesthesia and surgery impaired medial prefrontal cortex-hippocampus connectivity and cognition which was associated with HDAC6 overexpression.

Aromatic patterns: Tryptophan aromaticity as a catalyst for the emergence of life and rise of consciousness

Sunlight held the key to the origin of life on Earth. The earliest life forms, cyanobacteria, captured the sunlight to generate energy through photosynthesis. Life on Earth evolved in accordance with the circadian rhythms tied to sensitivity to sunlight patterns. A unique feature of cyanobacterial photosynthetic proteins and circadian rhythms' molecules, and later of nearly all photon-sensing molecules throughout evolution, is that the aromatic amino acid tryptophan (Trp) resides at the center of light-harvesting active sites. In this perspective, I review the literature and integrate evidence from different scientific fields to explore the role Trp plays in photon-sensing capabilities of living organisms through its resonance delocalization of π-electrons. The observations presented here are the product of apparently unrelated phenomena throughout evolution, but nevertheless share consistent patterns of photon-sensing by Trp-containing and Trp-derived molecules. I posit the unique capacity to transfer electrons during photosynthesis in the earliest life forms is conferred to Trp due to its aromaticity. I propose this ability evolved to assume more complex functions, serving as a host for mechanisms underlying mental aptitudes - a concept which provides a theoretical basis for defining the neural correlates of consciousness. The argument made here is that Trp aromaticity may have allowed for the inception of the mechanistic building blocks used to fabricate complexity in higher forms of life. More specifically, Trp aromatic non-locality may have acted as a catalyst for the emergence of consciousness by instigating long-range synchronization and stabilizing the large-scale coherence of neural networks, which mediate functional brain activity. The concepts proposed in this perspective provide a conceptual foundation that invites further interdisciplinary dialogue aimed at examining and defining the role of aromaticity (beyond Trp) in the emergence of life and consciousness.

The Role of Runx2 in Microtubule Acetylation in Bone Metastatic Breast Cancer Cells

Bone metastasis of breast cancer results in severe bone loss, fractures, and death. Crosstalk between breast cancer cells and bone resident cells promotes osteoclast activity and the release of growth factors from the bone matrix resulting in aggressive tumor growth and bone loss. We and others have shown that Runt-related transcription factor-2 (Runx2) promotes metastatic tumor growth-associated bone loss. Breast cancer cells also induce autophagy to survive metabolic stress at the metastatic site. Recently, we reported a Runx2-dependent increase in autophagy. In this study, to examine the underlying mechanisms of metastasis and tumor resistance to stress, we used a bone metastatic isogenic variant of breast cancer MDA-MB-231 cells isolated from a xenograft tumor mouse model of metastasis. Our results with immunofluorescence and biochemical approaches revealed that Runx2 promotes microtubule (MT) stability to facilitate autophagy. Stable MTs are critical for autophagosome trafficking and display increased acetylation at Lysine 40 of α-tubulin. Runx2 silencing decreases acetylated α-tubulin levels. The expression levels of HDAC6 and αTAT1, which serve to regulate the acetylation of α-tubulin, were not altered with Runx2 silencing. We found that HDAC6 interaction with α-tubulin is inhibited by Runt-related factor-2 (Runx2). We show that the expression of wild-type Runx2 can restore the acetylated polymer of MTs in Runx2 knockdown cells, while the C-terminal deletion mutant fails to rescue the polymer of MTs. Importantly, cellular stress, such as glucose starvation also increases the acetylation of α-tubulin. We found that the loss of Runx2 increases the sensitivity of breast cancer cells to MT-targeting agents. Overall, our results indicate a novel regulatory mechanism of microtubule acetylation and suggest that Runx2 and acetylated microtubules may serve as therapeutic targets for bone metastatic tumors.

Kinesin KIF15 regulates tubulin acetylation and spindle assembly checkpoint in mouse oocyte meiosis

Microtubule dynamics ensure multiple cellular events during oocyte meiosis, which is critical for the fertilization and early embryo development. KIF15 (also termed Hklp2) is a member of kinesin-12 family motor proteins, which participates in Eg5-related bipolar spindle formation in mitosis. In present study, we explored the roles of KIF15 in mouse oocyte meiosis. KIF15 expressed during oocyte maturation and localized with microtubules. Depletion or inhibition of KIF15 disturbed meiotic cell cycle progression, and the oocytes which extruded the first polar body showed a high aneuploidy rate. Further analysis showed that disruption of KIF15 did not affect spindle morphology but resulted in chromosome misalignment. This might be due to the reduced stability of the K-fibers, which further induced the loss of kinetochore-microtubule attachment and activated spindle assembly checkpoint, showing with the failed release of Bub3 and BubR1. Based on mass spectroscopy analysis and coimmunoprecipitation data we showed that KIF15 was responsible for recruiting HDAC6, NAT10 and SIRT2 to maintain the acetylated tubulin level, which further affected tubulin acetylation for microtubule stability. Taken together, these results suggested that KIF15 was essential for the microtubule acetylation and cell cycle control during mouse oocyte meiosis.

Altered cytoskeletal status in the transition from proneural to mesenchymal glioblastoma subtypes

Glioblastoma is a highly aggressive brain tumor with poor patient prognosis. Treatment outcomes remain limited, partly due to intratumoral heterogeneity and the invasive nature of the tumors. Glioblastoma cells invade and spread into the surrounding brain tissue, and even between hemispheres, thus hampering complete surgical resection. This invasive motility can arise through altered properties of the cytoskeleton. We hypothesize that cytoskeletal organization and dynamics can provide important clues to the different malignant states of glioblastoma. In this study, we investigated cytoskeletal organization in glioblastoma cells with different subtype expression profiles, and cytoskeletal dynamics upon subtype transitions. Analysis of the morphological, migratory, and invasive properties of glioblastoma cells identified cytoskeletal components as phenotypic markers that can serve as diagnostic or prognostic tools. We also show that the cytoskeletal function and malignant properties of glioblastoma cells shift during subtype transitions induced by altered expression of the neurodevelopmental transcription factor SOX2. The potential of SOX2 re-expression to reverse the mesenchymal subtype into a more proneural subtype might open up strategies for novel glioblastoma treatments.

LukS-PV inhibits hepatocellular carcinoma cells migration by downregulating HDAC6 expression

BACKGROUND

Hepatocellular carcinoma (HCC) is a clinically common malignant tumor worldwide. LukS-PV is the S component of Panton-Valentine leukocidin secreted by Staphylococcus aureus, which has shown anti-cancer activity. Based on previous findings, this study investigated the effects of LukS-PV on HCC migration and the potential molecular mechanisms involving acetylation pathways.

METHODS

After treating HCC cells with different concentrations of LukS-PV, we used scratch assays to determine the mobility of the cancer cells. Western blots were used to determine the expression levels of migration-related proteins. Quantitative proteomic sequencing was used to evaluate proteomic changes in target proteins. Immunoprecipitation and liquid chromatography coupled with tandem mass spectrometry analyses were used to validate the binding of related target proteins.

RESULTS

LukS-PV inhibited HCC cell migration in a concentration-dependent manner. In addition, LukS-PV attenuated the expression of histone deacetylase (HDAC)6, which is highly expressed in HCC cells. Further studies showed that LukS-PV increased the acetylation level of α-tubulin by down-regulating HDAC6, which resulted in the inhibition of HCC cell migration.

CONCLUSION

Taken together, our data revealed a vital role of LukS-PV in suppressing HCC cell migration by down-regulating HDAC6 and increasing the acetylation level of α-tubulin.

α-Tubulin acetylation on Lysine 40 controls cardiac glucose uptake

Our group previously demonstrated that an excess of nutrients, as observed in diabetes, provokes an increase in cardiac protein acetylation responsible for a reduced insulin-stimulated translocation of the glucose transporter GLUT4 to the plasma membrane. The acetylated proteins involved in this event have yet not been identified. α-Tubulin is a promising candidate as a major cytoskeleton component involved, among other things, in the translocation of GLUT4-containing vesicles from their intracellular pools towards the plasma membrane. Moreover, α-tubulin is known to be acetylated, Lys40 (K40) being its best characterized acetylated residue. The present work sought to evaluate the impact of α-tubulin K40 acetylation on cardiac glucose entry, with a particular interest in GLUT4 translocation. First, we observed that a mouse model of high-fat diet-induced obesity presented an increase in cardiac α-tubulin K40 acetylation level. Next, we showed that treatment of insulin-sensitive primary cultured adult rat cardiomyocytes with tubacin, a specific tubulin acetylation inducer, reduced insulin-stimulated glucose uptake and GLUT4 translocation. Conversely, decreasing α-tubulin K40 acetylation by expressing a non-acetylable dominant form of α-tubulin (mCherry α-tubulin K40A mutant) remarkably intensified insulin-induced glucose transport. Finally, mCherry α-tubulin K40A expression similarly improved glucose transport in insulin-resistant cardiomyocytes or after AMP-activated protein kinase activation. Taken together, our study demonstrates that modulation of α-tubulin K40 acetylation level affects glucose transport in cardiomyocytes, offering new putative therapeutic insights regarding modulation of glucose metabolism in insulin-resistant and diabetic hearts.