Cytoskeleton (Hoboken, N.J.)最新文献

Microtubules are critical components of the cytoskeleton that are extensively involved in various cellular and biological processes. The execution of these functions is intricately linked to post-translational modifications of tubulin. Post-translational modifications of tubulin include acetylation, tyrosination, de-tyrosination, glutamylation, SUMOylation, and so on. These modifications are closely associated with a wide range of biological processes. Accumulating evidence indicates that aberrant microtubule modifications are implicated in various diseases, including cancer, Alzheimer's disease, neurodevelopmental disorders, cardiac atrial hypertrophy, and even infertility. Aneuploid oocytes are a common cause of infertility, spontaneous abortion, trisomy syndrome, and other congenital abnormalities. The occurrence of aneuploidy is often closely associated with defects in spindle assembly, which are influenced by a series of tubulin modifications. In this review, we aimed to summarize the factors that affect tubulin modification and explore the key mechanisms underlying aneuploidy in human oocytes, thereby providing new insights and strategies for the treatment of infertility and prevention of congenital defects in newborns.

Vesicle trafficking is essential for plant cell growth, especially in tip-growing cells, where vesicles are directed to the expanding end of the cell through actin-myosin interactions. This study employs computer simulations to investigate vesicle dynamics in plant cells, specifically examining how myosin and actin filament attachment and polymerization influence vesicle diffusion, clustering, and transport. We utilized Cytosim, a cellular simulation program based on Langevin dynamics, to study vesicle transport by myosin and actin filaments. We analyzed single vesicle diffusion and vesicle-actin complexes with varying filament lengths and numbers. We found that vesicle diffusion decreased significantly with attached filaments, particularly between 200 nm and 2 μm in length. Multiple filaments further reduced diffusion, with their effects being more pronounced than increases in single filament length. When the filaments were simulated as active by allowing polymerization and depolymerization, the vesicle showed super diffusive behavior, with highly directed transport by longer or more abundant filaments. These simulations suggest potentially novel forms for the regulation of vesicle transport in cells. Additionally, simulations of myosin XI-dependent vesicle clustering replicated in vivo observations, supporting a model in which myosin XI, formins, and F-actin play crucial roles in vesicle clustering and directed movement in tip-growing plant cells. These findings provide insights into the mechanisms of vesicle transport and clustering, highlighting the role of myosin and actin dynamics in cellular processes involving vesicle trafficking in plants.

Microtubule cytoskeletal proteins are essential for maintaining cellular functions. In addition to dynamic instability, the organization of the microtubule cytoskeleton is also regulated by microtubule-severing proteins, which play roles in critical processes such as cell division. One of the microtubule-severing proteins, p60-Katanin, localizes to the mitotic spindle, centrosomes, midbody, and contractile ring, thereby facilitating the proper completion of the cell cycle, which requires microtubule remodeling. Here, we identify Meteorin as a novel interaction partner of p60-Katanin in HCT-116 colorectal cancer (CRC) cells. Meteorin is observed to localize at spindle poles during prophase, metaphase, anaphase, and telophase in cell division. Our findings also indicate that Meteorin co-localizes with p60-Katanin during mitosis. Silencing of Meteorin leads to reduced cell proliferation irrespective of TP53 expression in both HCT-116 and HCT-116 p53 (-/-) CRC cells. Upon Meteorin silencing, p60-Katanin expression decreases in both CRC cell types, whereas it increases due to Meteorin overexpression in only HCT-116 CRC cells. Overall, these results indicate that Meteorin localizes to spindle poles and interacts with p60-Katanin, and that depletion of Meteorin inhibits the proliferation of HCT-116 CRC cells regardless of p53 expression.

Current models suggest that MIRO GTPases anchor cytoskeletal motors to the mitochondrial outer membrane (MOM). However, our previous findings indicate that the unconventional myosin, MYO19, interacts with MIRO weakly and that a MIRO-independent MOM-localizing domain interacts more tightly with the MOM. To test the hypothesis that other MIRO interactors may also have MIRO-independent MOM binding, we examined interactions between TRAK proteins (microtubule motor-mitochondria adaptor proteins) and the MOM via quantitative fluorescence microscopy and steady-state kinetic approaches. Using GFP-TRAK truncations expressed in MIRO1-2 double knockout mouse embryonic fibroblasts, we identified a MIRO-independent mitochondrial-binding domain in the C-terminus of TRAK1 and TRAK2, with a MOM localization pattern similar to what we observed for full-length GFP-TRAK proteins. The MIRO-binding domains (MBD) of the TRAK proteins were only able to localize to mitochondria when MIRO is expressed. Importantly, fluorescence recovery after photobleaching (FRAP) demonstrated that the steady-state kinetics of TRAK^MBD/MIRO interactions were faster exchanging than for either full-length TRAK or the TRAK C-terminal MOM-binding domain expressed alone. These data support a model where TRAK/MIRO associations may be serving functions beyond anchoring cytoskeletal motors and their adapters to the MOM.

The unbranched actin filaments in mammalian cells are usually composed of co-polymers of a specific tropomyosin isoform with actin. Genetic manipulation has revealed that the tropomyosins largely define the functional properties of actin filaments in an isoform-specific, non-redundant manner. Tropomyosin isoforms play a role in human diseases including cancers, thrombocytopenia and thrombocythaemia, endometrial decidualisation resistance, and ulcerative colitis. Hence, the development of compounds that target different tropomyosins are potentially valuable tools for cell biology as well as potential therapeutics. We have recently identified compounds that target Tpm1.8/1.9 and now address the isoform specificity of these compounds. Tpm1.8/1.9 is primarily enriched in the lamellipodium of migrating cells but not in stress fibre bundles unlike Tpm3.1/3.2 and Tpm4.2, which are enriched in stress fibres. Human fibroblasts also incorporate Tpm1.8/1.9 into fine filaments emanating from the perinuclear region. Exposure of human fibroblasts and SK-N-SH cells to the compounds 189-1 and 189-3 results in dispersal of Tpm1.8/1.9 from the lamellipodium and fine filaments to a diffuse organisation in the cytoplasm. In contrast, at doses that disperse Tpm1.8/1.9, 189-3 has no impact on the association of either Tpm3.1/3.2 or Tpm4.2 with actin filament bundles, whereas 189-1 also targets Tpm4.2. Tpm1.8/1.9 organisation becomes dispersed between 12- and 18-hour exposure to 189-3, and the organisation of Tpm1.8/1.9 returns within 4 h of drug washout. We conclude that the amino acid sequence differences located at 7 positions in the first 19 residues of these isoforms provide sufficient specificity to generate compounds that target Tpm1.8/1.9 alone.

Cilia are microtubule-based organelles that protrude from the cell surface and are crucial for cellular sensory and motility functions. Defects in cilia are associated with various diseases, collectively known as ciliopathies. Although single-cell transcriptomics and proteomics have identified many proteins linked to cilia, their physiological roles remain largely unclear. In this study, we identify coiled-coil domain-containing 89 (CCDC89) as a new ciliary protein. Super-resolution imaging reveals that CCDC89 localizes to the axonemal lumen in motile cilia of mouse ependymal multiciliated cells. However, no apparent morphological abnormalities are observed in the lung and brain of Ccdc89 knockout mice. While CCDC89 is highly abundant in the testis, Ccdc89 knockout mice appear to have normal male fertility. Overall, our findings suggest that CCDC89 is dispensable for male fertility in mice, providing valuable information for other researchers to avoid unnecessary detailed studies.

Cilia are microtubule-based organelles found on the surface of most eukaryotic cells. These microtubules are composed of α- and β-tubulin heterodimers, and different tubulin isotypes can confer distinct properties to microtubules. Despite their importance, the contribution of individual tubulin isotype to cilia formation and function remains largely unexplored in vertebrates. Here, we identify a critical role for the β-tubulin isotype Tubb6 in the formation of motile cilia in Xenopus epidermal multiciliated cells (MCCs). Tubb6 mRNA is selectively expressed in MCCs, and its protein product localizes to ciliary axonemes. Loss of Tubb6 leads to a marked reduction in cilia number and length, resulting in defective MCC function. In contrast, mono-motile cilia in the gastrocoel roof plate are unaffected by Tubb6 depletion, suggesting a selective requirement for ciliogenesis in MCCs. Together, our findings uncover a cell type-specific role for Tubb6 in motile cilia formation and highlight the functional specialization of tubulin isotypes in vertebrate cilia assembly.

The nexin-dynein regulatory complex (N-DRC) is an essential axonemal structure for ciliary and flagellar motility. Coiled-coil domain containing 153 (CCDC153) has recently been identified as a new N-DRC component in Tetrahymena thermophila. However, the physiological function of its mammalian homolog remains unknown. Here, we generated a Ccdc153 knockout mouse model and explored its functional association with motile cilia. We found that CCDC153 was highly expressed in the motile cilia-abundant tissues and localized to the axonemal lumen in motile cilia. However, Ccdc153 knockout mice were viable and exhibited normal brain ventricles and fertility. Overall, our results suggest that CCDC153 is dispensable for ciliary motility in brain ventricles and sperm movement, indicating that CCDC153 is not a potential causative gene in human ciliopathies.

Joubert syndrome (JBTS) is a group of recessive neurodevelopmental disorders classified as a specific type of ciliopathy with genetic heterogeneity. JBTS23, a subtype of Joubert syndrome, is caused by variations in the KIAA0586 gene. In this study, we report a 9-month-old boy diagnosed with JBTS based on the presence of the molar tooth sign in the midbrain and global developmental delay. Whole-exome sequencing identified two pathogenic variants in KIAA0586 (c.3944 T>G and c.3686 + 3A>G), consistent with an autosomal recessive inheritance pattern. These findings were confirmed through Sanger sequencing of the proband and his parents. This study identifies two novel pathogenic variants in KIAA0586, provides a genetic diagnosis for this patient as JBTS23, and expands the variant spectrum of KIAA0586 associated with JBTS.

Katanin is a microtubule-severing enzyme critical for cellular processes such as cell division, migration, signaling, and cellular homeostasis. Katanin, a heterodimeric protein composed of p60 and p80, exhibits ATPase activity that is stimulated by microtubules and is responsible for removing tubulin subunits during severing. This severing function requires the assembly of katanin into a hexameric complex. Previous studies have demonstrated that katanin has a differential binding affinity towards C-terminal tails (CTTs) of β-tubulin isotypes. However, the interaction dynamics of human katanin hexamer with different β-tubulin isotypes-especially those overexpressed in various carcinomas-remain poorly understood at the atomic level. In this study, we employed homology modeling, docking, and molecular dynamics simulations to examine the binding behavior of the human katanin hexamer with the CTTs of five β-tubulin isotypes, which include βI, βIIa, βIII, βIVb, and βV. Our findings reveal that the katanin hexamer exhibits distinct interaction patterns with each isotype, attributed to their sequence-specific variations in the CTTs. Detailed MD analyses, including radius of gyration, solvent-accessible surface area, hydrogen bonding, principal component analysis, and free energy landscape profiling, further support these isoform-specific differences in the interaction dynamics. Moreover, binding free energy calculations indicate that the hexamer shows the highest affinity for βIIa, followed by βIII, βIVb, and βV, with the weakest interaction observed for βI. These computational insights underscore the mechanism of isoform-specific binding preferences of the human katanin hexamer toward β-tubulin CTTs, highlighting their potential implications for therapeutic targeting in cancer contexts where specific β-tubulin isotypes are upregulated.