Cytoskeleton (Hoboken, N.J.)最新文献

Dyneins were present in the last eukaryotic common ancestor (LECA) and play key roles in eukaryotic biology. Axonemal dyneins form the inner and outer arms that power ciliary beating, and it has long been recognized that outer arms in some organisms contain two different heavy chain motors, whereas those from other species contain a third unit that imparts enhanced motive force during ciliary beating. Previous phylogenetic analyses suggested that this third motor derived from a gene duplication event in the LECA, followed by the subsequent replacement of the N-terminal assembly domain with one formed from kelch and immunoglobulin repeats. Here I revisit the origin and organization of this dynein, combining the increased breadth of sequence information now available, AlphaFold modeling, and the recent recovery of a robustly rooted eukaryotic tree-of-life. This analysis confirms the third outer arm dynein HC arose in a common ancestor of the Diaphoretickes, with a basic N-terminal domain consisting of a β-propeller structure followed by two immunoglobulin folds. However, this region has undergone further diversification in some groups, gaining an additional full or partial β-propeller located immediately adjacent to the AAA motor domain. Thus, three variant forms of this N-terminal segment are discernable in extant eukaryotes.

Skin elasticity is critical for maintaining skin function, yet the molecular mechanisms governing this process remain incompletely understood. Herein, we identify enkurin domain-containing protein 1 (ENKD1) as a key regulator of skin elasticity by modulating microtubule stability in basal keratinocytes. In Enkd1 knockout mice, impaired migration of basal keratinocytes results in reduced epidermal elasticity compared to wild-type controls. Mechanistically, ENKD1 localizes to the centrosome and microtubules, where its expression enhances microtubule stability. Conversely, the absence of ENKD1 destabilizes microtubules, which likely impedes keratinocyte migration and compromises epidermal elasticity. Further investigations suggest that ENKD1 exerts its effects on microtubule stability via EB1. Collectively, these findings establish ENKD1 as a pivotal regulatory factor of mammalian epidermal elasticity, providing new insights into the molecular underpinnings of skin function.

In animal cells, centrosomes function as the microtubule-organizing centers; their presence is essential for mitosis and for assembling various cilia-both primary and motile. Here, we identified coiled-coil domain containing 81 (CCDC81) located at the centrosome through its 301-505 aa. Using bioinformatics approaches, we constructed a Neighbor-Joining phylogenetic tree. We also analyzed the conservation of the CCDC81 protein sequence. The results reveal a high degree of conservation in mammals, implying a potentially vital biological role for CCDC81. Silencing of CCDC81 resulted in a decrease in both the frequency and length of primary cilia, yet it exerted no significant impact on centriole number. Examining CCDC81 tissue distribution in mice revealed markedly elevated Ccdc81 mRNA levels in testis, lung, trachea, and fallopian tubes-tissues characterized by abundant motile cilia. Ccdc81 knockout mice were generated using CRISPR/Cas9 technology. Over a six-week period, body weight measurements of knockout mice showed no significant abnormalities. Our research results suggest that CCDC81 is indispensable for the formation of primary cilia and plays a role in the function of motile cilia.

The homeostatic cortical actin array in plant cells plays important roles in fundamental processes, including intracellular transport, secretion, cell expansion, and cytoplasmic streaming. In response to diverse chemical and mechanical signals, the cortical array can remodel within minutes to assume new configurations or altered filament abundance. The homeostatic cortical actin array of some plant epidermal cells comprises sparsely distributed individual actin filaments and actin bundles, which enable tracking and quantitative analysis of dynamic properties over many minutes at high spatiotemporal resolution. Previous studies using quantitative live-cell imaging, small molecule inhibitors, and genetic mutations reveal the robust dynamic steady state of the cortical actin array, with individual filaments showing a behavior termed stochastic dynamics. Compared to experimental findings, computational efforts focused on the plant actin cytoskeleton are lacking, although computational models have the potential to define underlying mechanisms of actin array homeostasis and remodeling. Here, we used an agent-based computational model to reproduce the stochastic dynamic behavior of individual actin filaments in epidermal cells with consideration of key governing factors, including the nucleation, polymerization, depolymerization, severing, capping, and branching of filaments. Our model was able to reproduce experimental observations with respect to the abundance and length of filaments as well as the rates or frequencies of dynamic events. This model can be used to study the role of myosin motors and other actin-binding proteins, as well as the effects of signaling events and fluxes in cellular second messengers, on actin dynamics in plant cells.

Cancer, a complex and heterogeneous disease, continues to be a major global health concern. Despite advancements in diagnostics and therapeutics, the aggressive nature of certain cancers remain a significant challenge, necessitating a deeper understanding of the underlying molecular mechanisms driving their severity and progression. Cancer severity and progression depend on cellular properties such as cell migration, cell division, cell shape changes, and intracellular transport, all of which are driven by dynamic cellular microtubules. Dynamic properties of microtubules, in turn, are regulated by an array of proteins that influence their stability and growth. Among these regulators, End Binding (EB) proteins stand out as critical orchestrators of microtubule dynamics at their growing plus ends. Beyond their fundamental role in normal cellular functions, recent research has uncovered compelling evidence linking EB proteins to the pathogenesis of various diseases, including cancer progression. As the field of cancer research advances, the clinical implication of EB proteins role in cancer severity and aggressiveness become increasingly evident. This review aims to comprehensively explore the role of microtubule-associated EB proteins in influencing the severity and aggressiveness of cancer. We also discuss the potential significance of EB as a clinical biomarker for cancer diagnosis and prognosis and as a target for therapeutic intervention.

Enteropathogenic Escherichia coli (EPEC) causes diarrheal disease. Once ingested, these extracellular pathogens attach to the intestinal epithelial cells of their host, collapse the localized microvilli, and generate actin-rich structures within the host cells that are located beneath the attached bacteria, called "pedestals." Palladin is an actin-associated protein that cross-links and stabilizes actin filaments. This protein also acts as a scaffolding protein for other actin-binding proteins. Here, we examine the role of Palladin during EPEC infections and show that Palladin is co-opted by EPEC. Depletion of Palladin resulted in shorter pedestals, and when Palladin containing mutations in either its actin- or VASP-binding domains were overexpressed in cells, pedestals decreased in length. Importantly, we show that the overexpression of Palladin in ArpC2 ^-/- (Arp2/3 complex-depleted) cells rescued pedestal length. Together, our results demonstrate that Palladin has the ability to rescue pedestal length during EPEC infections when the function of the Arp2/3 complex is diminished.

We analysed here the dynamic of the kinesin-like Pavarotti (Pav) during male gametogenesis of wild-type and Sas4 mutant flies. Pav localizes to the equatorial region and the inner central spindle of late anaphase wild-type spermatogonia and displays a strong concentration at the midbody during late telophase. At metaphase of the first meiotic division, Pav shows widespread localization on the equatorial region of the spermatocytes. This unusual distribution restricts and enhances during anaphase where antiparallel cortical microtubules overlap. Additional Pav staining is also found in the inner central spindle where the microtubules overlap between the segregating chromosomes. At late telophase, Pav accumulates to the midbody and on a weak ring that surround the cytoplasmic bridges. Pav localizes in an equatorial discontinuous ring of Sas4 spermatogonia where the non-centrosomal microtubules overlap, but the motor protein is absent in the interior central spindle where the inner microtubules are lacking. However, the anastral spindles properly support cell division, suggesting that astral microtubules are dispensable for Pav localization in the Sas4 spermatogonial cell cortex. This function is presumably replaced by the antiparallel cortical microtubules extending from the acentriolar polar regions. In contrast, the majority of the meiotic spindles in Sas4 mutant testes do not progress beyond late anaphase, and only a small fraction of the primary spermatocytes experienced an abnormal division with the assembly of aberrant telophase spindles. Pav accumulates around the chromatin clusters or enhanced at the plus ends of the antiparallel non-centrosomal cortical bundles of microtubules. However, these bundles are not arranged properly in the equatorial region of the cell and cytokinesis is abnormal or fails. Therefore, the observations in Sas4 mutant testes suggest that the spermatogonial mitoses correctly occur in the absence of astral microtubules, whereas meiotic divisions fail.