MTR120/KIAA1383, a novel microtubule-associated protein, promotes microtubule stability and ensures cytokinesis

Transcriptome Analysis Suggests PKD3 Regulates Proliferative Glucose Metabolism, Calcium Homeostasis and Microtubule Dynamics After MEF Spontaneous Immortalization

Cell immortalization corresponds to a biologically relevant clinical feature that allows cells to acquire a high proliferative potential during carcinogenesis. In multiple cancer types, Protein Kinase D3 (PKD3) has often been reported as a dysregulated oncogenic kinase that promotes cell proliferation. Using mouse embryonic fibroblasts (MEFs), in a spontaneous immortalization model, PKD3 has been demonstrated as a critical regulator of cell proliferation after immortalization. However, the mechanisms by which PKD3 regulates proliferation in immortalized MEFs require further elucidation. Using a previously validated Prkd3-deficient MEF model, we performed a poly-A transcriptomic analysis to identify putative Prkd3-regulated biological processes and downstream targets in MEFs after spontaneous immortalization. To this end, differentially expressed genes (DEGs) were identified and further analyzed by gene ontology (GO) enrichment and protein-protein interaction (PPI) network analyses to identify potential hub genes. Our results suggest that Prkd3 modulates proliferation through the regulation of gene expression associated with glucose metabolism (Tnf, Ucp2, Pgam2, Angptl4), calcium homeostasis and transport (Calcr and P2rx7) and microtubule dynamics (Stmn2 and Map10). These candidate processes and associated genes represent potential mechanisms involved in Prkd3-induced proliferation in spontaneously immortalized cells as well as clinical targets in several cancer types.

The Hexosamine Biosynthetic Pathway alters the cytoskeleton to modulate cell proliferation and migration in metastatic prostate cancer

Castration-resistant prostate cancer (CRPC) progresses despite androgen deprivation therapy, as cancer cells adapt to grow without testosterone, becoming more aggressive and prone to metastasis. CRPC biology complicates the development of effective therapies, posing challenges for patient care. Recent gene-expression and metabolomics studies highlight the Hexosamine Biosynthetic Pathway (HBP) as a critical player, with key components like GNPNAT1 and UAP1 being downregulated in metastatic CRPC. GNPNAT1 knockdown has been shown to increase cell proliferation and metastasis in CRPC cell lines, though the mechanisms remain unclear. To investigate the cellular basis of these CRPC phenotypes, we generated a CRISPR-Cas9 knockout model of GNPNAT1 in 22Rv1 CRPC cells, analyzing its impact on metabolomic, glycoproteomic, and transcriptomic profiles of cells. We hypothesize that HBP inhibition disrupts the cytoskeleton, altering mitotic progression and promoting uncontrolled growth. GNPNAT1 KO cells showed reduced levels of cytoskeletal filaments, such as actin and microtubules, leading to cell structure disorganization and chromosomal mis-segregation. GNPNAT1 inhibition also activated PI3K/AKT signaling, promoting proliferation, and impaired cell adhesion by mislocalizing EphB6, enhancing migration via the RhoA pathway and promoting epithelial-to-mesenchymal transition. These findings suggest that HBP plays a critical role in regulating CRPC cell behavior, and targeting this pathway could provide a novel therapeutic approach.

Direct targeting of host microtubule and actin cytoskeletons by a chlamydial pathogenic effector protein

To propagate within a eukaryotic cell, pathogenic bacteria hijack and remodulate host cell functions. The Gram-negative obligate intracellular Chlamydiaceae, which pose a serious threat to human and animal health, attach to host cells and inject effector proteins that reprogram host cell machineries. Members of the conserved chlamydial TarP family have been characterized as major early effectors that bind to and remodel the host actin cytoskeleton. We now describe a new function for the Chlamydia pneumoniae TarP member CPn0572, namely the ability to bind and alter the microtubule cytoskeleton. Thus, CPn0572 is unique in being the only prokaryotic protein that directly modulates both dynamic cytoskeletons of a eukaryotic cell. Ectopically expressed GFP-CPn0572 associates in a dose-independent manner with either cytoskeleton singly or simultaneously. In vitro, CPn0572 binds directly to microtubules. Expression of a microtubule-only CPn0572 variant resulted in the formation of an aberrantly thick, stabilized microtubule network. Intriguingly, during infection, secreted CPn0572 also colocalized with altered microtubules, suggesting that this protein also affects microtubule dynamics during infection. Our analysis points to a crosstalk between actin and microtubule cytoskeletons via chlamydial CPn0572.

Paclitaxel and Caffeine-Taurine, New Colchicine Alternatives for Chromosomes Doubling in Maize Haploid Breeding

The doubled haploid (DH) technology is employed worldwide in various crop-breeding programs, especially maize. Still, restoring tassel fertility is measured as one of the major restrictive factors in producing DH lines. Colchicine, nitrous oxide, oryzalin, and amiprophosmethyl are common chromosome-doubling agents that aid in developing viable diploids (2n) from sterile haploids (n). Although colchicine is the most widely used polyploidy-inducing agent, it is highly toxic to mammals and plants. Therefore, there is a dire need to explore natural, non-toxic, or low-toxic cheaper and accessible substitutes with a higher survival and fertility rate. To the best of our knowledge, the advanced usage of human anticancer drugs "Paclitaxel (PTX)" and "Caffeine-Taurine (CAF-T)" for in vivo maize haploids doubling is being disclosed for the first time. These two antimitotic and antimicrotubular agents (PTX and CAF-T) were assessed under various treatment conditions compared to colchicine. As a result, the maximum actual doubling rates (ADR) for PTX versus colchicine in maize haploid seedlings were 42.1% (400 M, 16 h treatment) versus 31.9% (0.5 mM, 24 h treatment), respectively. In addition, the ADR in maize haploid seeds were CAF-T 20.0% (caffeine 2 g/L + taurine 12 g/L, 16 h), PTX 19.9% (100 μM, 24 h treatment), and colchicine 26.0% (2.0 mM, 8 h treatment). Moreover, the morphological and physiological by-effects in haploid plants by PTX were significantly lower than colchicine. Hence, PTX and CAF-T are better alternatives than the widely used traditional colchicine to improve chromosome-doubling in maize crop.

Regionalized Protein Localization Domains in the Zebrafish Hair Cell Kinocilium

Sensory hair cells are the receptors for auditory, vestibular, and lateral line sensory organs in vertebrates. These cells are distinguished by "hair"-like projections from their apical surface collectively known as the hair bundle. Along with the staircase arrangement of the actin-filled stereocilia, the hair bundle features a single, non-motile, true cilium called the kinocilium. The kinocilium plays an important role in bundle development and the mechanics of sensory detection. To understand more about kinocilial development and structure, we performed a transcriptomic analysis of zebrafish hair cells to identify cilia-associated genes that have yet to be characterized in hair cells. In this study, we focused on three such genes-ankef1a, odf3l2a, and saxo2-because human or mouse orthologs are either associated with sensorineural hearing loss or are located near uncharacterized deafness loci. We made transgenic fish that express fluorescently tagged versions of their proteins, demonstrating their localization to the kinocilia of zebrafish hair cells. Furthermore, we found that Ankef1a, Odf3l2a, and Saxo2 exhibit distinct localization patterns along the length of the kinocilium and within the cell body. Lastly, we have reported a novel overexpression phenotype of Saxo2. Overall, these results suggest that the hair cell kinocilium in zebrafish is regionalized along its proximal-distal axis and set the groundwork to understand more about the roles of these kinocilial proteins in hair cells.

PAK1 Is Involved in the Spindle Assembly during the First Meiotic Division in Porcine Oocytes

P21-activated kinase 1 (PAK1), as a member of the PAK family, has been implicated in various functions during somatic mitosis; however, less is known about its role during oocyte meiosis. Herein, we highlight the indispensable role of PAK1 in regulating spindle assembly and cell cycle progression during the first meiotic division of porcine oocytes. First, we found that the activated PAK1 expressed dynamically, and its subcellular localization was tightly associated with the spindle dynamics during meiosis in porcine oocytes. Specific inhibition of PAK1 activity by inhibitor targeting PAK1 activation-3 (IPA-3) led to impaired extrusion of the first polar body (PB1); with most of the IPA-3-treated oocytes arrested at germinal vesicle breakdown (GVBD) and subjected to failure of bipolar spindle formation. However, the adverse effects caused by IPA-3 on oocytes could be restored by reducing disulfide bonds between PAK1 and IPA-3 with dithiothreitol (DTT) treatment. Furthermore, the co-immunoprecipitation assay revealed that PAK1 interacted directly with Aurora A and transforming acidic coiled coil 3 (TACC3), providing an additional explanation for the similar localization of Aurora A and activated PAK1. Additionally, inhibiting the activity of PAK1 decreased the expression of p-Aurora A and p-TACC3; however, the reduced activity of Aurora A and TACC3 could be restored by DTT. In conclusion, PAK1 plays a crucial role in the proper assembly of the spindle during the first meiotic division of porcine oocytes, and the regulation of PAK1 is associated with its effects on p-Aurora A and p-TACC3 expression.

SPACA9 is a lumenal protein of human ciliary singlet and doublet microtubules

Cilia are cell-surface organelles with cytoskeletons formed by different microtubule types. These microtubules are decorated inside and out by proteins that alter microtubule stability and elasticity and allow cilia to beat. Mutations in these proteins are associated with human ciliopathies such as primary ciliary dyskinesia. Here, we used cryo-EM to reveal the structures of two distinct types of human ciliary microtubule: the doublet microtubules of respiratory tract cilia and the distal singlet microtubules of the sperm tail. Among the microtubule-binding proteins identified is SPACA9, which we show is capable of forming both spirals and striations within human ciliary microtubules. The ability to resolve human ciliary microtubule composition improves our understanding of ciliary complexes and the potential causes of human ciliopathies.

The cilium-centrosome complex contains triplet, doublet, and singlet microtubules. The lumenal surfaces of each microtubule within this diverse array are decorated by microtubule inner proteins (MIPs). Here, we used single-particle cryo-electron microscopy methods to build atomic models of two types of human ciliary microtubule: the doublet microtubules of multiciliated respiratory cells and the distal singlet microtubules of monoflagellated human spermatozoa. We discover that SPACA9 is a polyspecific MIP capable of binding both microtubule types. SPACA9 forms intralumenal striations in the B tubule of respiratory doublet microtubules and noncontinuous spirals in sperm singlet microtubules. By acquiring new and reanalyzing previous cryo-electron tomography data, we show that SPACA9-like intralumenal striations are common features of different microtubule types in animal cilia. Our structures provide detailed references to help rationalize ciliopathy-causing mutations and position cryo-EM as a tool for the analysis of samples obtained directly from ciliopathy patients.

Proteomic profiling reveals neuronal ion channel dysregulation and cellular responses to DNA damage-induced cell cycle arrest and senescence in human neuroblastoma SH-SY5Y cells exposed to cypermethrin

Cypermethrin (CYP), a synthetic pyrethroid of class II, is widely used as a pesticide worldwide. The primary target of cypermethrin is a voltage-gated sodium channel. The neurotoxicity of CYP has been extensively studied in terms of affecting neuronal development, increasing cellular oxidative stress, and apoptosis. However, little is known about how it affects the expression of channel proteins involved in synaptic transmission, as well as the effects of cypermethrin on DNA damage and cell cycle processes. We found that the ligand and voltage-gated calcium channels and proteins involved in synaptic transmission including NMDA 1 receptor subunit, alpha 1A-voltage-dependent calcium channel, synaptotagmin-17, and synaptojanin-2 were downregulated in CYP-treated cells. After 48h of CYP exposure, cell viability was reduced with flattened and enlarged morphology. The levels of 23 proteins regulating cell cycle processes were altered in CYP-treated cells, according to a proteomic study. The cell cycle analysis showed elevated G₀/G₁ cell cycle arrest and DNA fragmentation at the sub-G₀ stage after CYP exposure. CYP treatment also increased senescence-associated β-galactosidase positive cells, DNA damage, and apoptotic markers. Taken together, the current study showed that cypermethrin exposure caused DNA damage and hastened cellular senescence and apoptosis via disrupting cell cycle regulation. In addition, despite its primary target sodium channel, CYP might cause synaptic dysfunction via the downregulation of synaptic proteins and dysregulation of synapse-associated ion channels.

ENKD1 is a centrosomal and ciliary microtubule-associated protein important for primary cilium content regulation

Centrioles and cilia are conserved, microtubule-based structures critical for cell function and development. Their dysfunction causes cancer and developmental disorders. How microtubules are organized into ordered structures by microtubule-associated proteins (MAPs) and tubulin modifications is best understood during mitosis but is largely unexplored for the centrioles and the ciliary axoneme, which are composed of stable microtubules that maintain their length at a steady-state. In particular, we know little about the identity of the centriolar and ciliary MAPs and how they work together during the assembly and maintenance of the cilium and centriole. Here, we identified the Enkurin domain containing 1 (ENKD1) as a component of the centriole wall and the axoneme in mammalian cells and showed that it has extensive proximity interactions with these compartments and MAPs. Using in vitro and cellular assays, we found that ENKD1 is a new MAP that regulates microtubule organization and stability. Consistently, we observed an increase in tubulin polymerization and microtubule stability, as well as disrupted microtubule organization in ENKD1 overexpression. Cells depleted for ENKD1 were defective in ciliary length and content regulation and failed to respond to Hedgehog pathway activation. Together, our results advance our understanding of the functional and regulatory relationship between MAPs and the primary cilium.

Multi-CpG linear regression models to accurately predict paclitaxel and docetaxel activity in cancer cell lines

The microtubule-targeting paclitaxel (PTX) and docetaxel (DTX) are widely used chemotherapeutic agents. However, the dysregulation of apoptotic processes, microtubule-binding proteins, and multi-drug resistance efflux and influx proteins can alter the efficacy of taxane drugs. In this review, we have created multi-CpG linear regression models to predict the activities of PTX and DTX drugs through the integration of publicly available pharmacological and genome-wide molecular profiling datasets generated using hundreds of cancer cell lines of diverse tissue of origin. Our findings indicate that linear regression models based on CpG methylation levels can predict PTX and DTX activities (log-fold change in viability relative to DMSO) with high precision. For example, a 287-CpG model predicts PTX activity at R² of 0.985 among 399 cell lines. Just as precise (R²=0.996) is a 342-CpG model for predicting DTX activity in 390 cell lines. However, our predictive models, which employ a combination of mRNA expression and mutation as input variables, are less accurate compared to the CpG-based models. While a 290 mRNA/mutation model was able to predict PTX activity with R² of 0.830 (for 546 cell lines), a 236 mRNA/mutation model could calculate DTX activity at R² of 0.751 (for 531 cell lines). The CpG-based models restricted to lung cancer cell lines were also highly predictive (R²≥0.980) for PTX (74 CpGs, 88 cell lines) and DTX (58 CpGs, 83 cell lines). The underlying molecular biology behind taxane activity/resistance is evident in these models. Indeed, many of the genes represented in PTX or DTX CpG-based models have functionalities related to apoptosis (e.g., ACIN1, TP73, TNFRSF10B, DNASE1, DFFB, CREB1, BNIP3), and mitosis/microtubules (e.g., MAD1L1, ANAPC2, EML4, PARP3, CCT6A, JAKMIP1). Also represented are genes involved in epigenetic regulation (HDAC4, DNMT3B, and histone demethylases KDM4B, KDM4C, KDM2B, and KDM7A), and those that have never been previously linked to taxane activity (DIP2C, PTPRN2, TTC23, SHANK2). In summary, it is possible to accurately predict taxane activity in cell lines based entirely on methylation at multiple CpG sites.

Evolution and diversification of the nuclear envelope

Eukaryotic cells arose ~1.5 billion years ago, with the endomembrane system a central feature, facilitating evolution of intracellular compartments. Endomembranes include the nuclear envelope (NE) dividing the cytoplasm and nucleoplasm. The NE possesses universal features: a double lipid bilayer membrane, nuclear pore complexes (NPCs), and continuity with the endoplasmic reticulum, indicating common evolutionary origin. However, levels of specialization between lineages remains unclear, despite distinct mechanisms underpinning various nuclear activities. Several distinct modes of molecular evolution facilitate organellar diversification and  to understand which apply to the NE, we exploited proteomic datasets of purified nuclear envelopes from model systems for comparative analysis. We find enrichment of core nuclear functions amongst the widely conserved proteins to be less numerous than lineage-specific cohorts, but enriched in core nuclear functions. This, together with consideration of additional evidence, suggests that, despite a common origin, the NE has evolved as a highly diverse organelle with significant lineage-specific functionality.

Research progress on the source, production, and anti-cancer mechanisms of paclitaxel

Paclitaxel, a tetracyclic diterpenoid compounds, was firstly isolated from the bark of the Pacific yew trees. Currently, as a low toxicity, high efficiency, and broad-spectrum natural anti-cancer drug, paclitaxel has been widely used against ovarian cancer, breast cancer, uterine cancer, and other cancers. As the matter of fact, natural paclitaxel from Taxus species has been proved to be environmentally unsustainable and economically unfeasible. For this reason, researchers from all over the world are devoted to searching for new ways of obtaining paclitaxel. At present, other methods, including artificial cultivation of Taxus plants, microbial fermentation, chemical synthesis, tissue and cell culture have been sought and developed subsequently. Meanwhile, the biosynthesis of paclitaxel is also an extremely attractive method. Unlike other anti-cancer drugs, paclitaxel has its unique anti-cancer mechanisms. Here, the source, production, and anti-cancer mechanisms of paclitaxel were summarized and reviewed, which can provide theoretical basis and reference for further research on the production, anti-cancer mechanisms and utilization of paclitaxel.

Downregulation of lumican enhanced mitotic defects and aneuploidy in lung cancer cells

Lumican is overexpressed in lung cancer cells and has been implicated in the pathogenesis of tumorigenesis and regulation of cancer cell invasion. Lumican is robustly associated with the binding of p120-catenin protein to modulate cell metastasis. However, its role in cancer cell proliferation is still unclear. This study investigated the effect of lumican on the cell division including mitosis and cytokinesis in non-small lung cancer cells. We found that the downregulation of lumican prolonged the doubling time of cells and retarded the cell growth in H460 and A549 cells. Along with tubulin, lumican localized to the mitotic spindle and centrosome during the metaphase-anaphase stage. The cell cycle was retained in the G2/M phase after the downregulation of lumican. Interestingly, lumican was found to play important roles in central spindle and midbody formation during cytokinesis. Lumican interacted with the midbody-associated proteins such as MKLP1, Aurora B, and ECT2. Notably, the downregulation of lumican decreased the level of MKLP1 accompanied by the retention of midbody-residual that resulted in multi-nucleated cells. Downregulation of lumican promoted the chromosome missegregation and the increment of the bi-/multinucleated cells. The results of this study indicated that lumican associated with tubulin is crucial for spindle fiber formation and midbody assembly in cell division. Downregulation of lumican displayed the defects in mitotic spindle assembly/dynamics and improper kinetochore-microtubules attachment that led to increase aneuploidy. This emerging property of lumican is suggested to tightly control chromosome segregation during cell division in lung cancer cells.Abbreviations: ESCRT: endosomal sorting complex required for transport; PRC1: protein regulator of cytokinesis 1; Nci: negative control siRNA; Lumi: lumican siRNAs; MKLP1: mitotic kinesin-like protein 1; H460LD and A549LD: H460 and A549 cell lines with less expressed lumican.

Microtubule-Associated Proteins: Structuring the Cytoskeleton

Microtubule-associated proteins (MAPs) were initially discovered as proteins that bind to and stabilize microtubules. Today, an ever-growing number of MAPs reveals a more complex picture of these proteins as organizers of the microtubule cytoskeleton that have a large variety of functions. MAPs enable microtubules to participate in a plethora of cellular processes such as the assembly of mitotic and meiotic spindles, neuronal development, and the formation of the ciliary axoneme. Although some subgroups of MAPs have been exhaustively characterized, a strikingly large number of MAPs remain barely characterized other than their interactions with microtubules. We provide a comprehensive view on the currently known MAPs in mammals. We discuss their molecular mechanisms and functions, as well as their physiological role and links to pathologies.

Quantitative Proteomic Analysis of Human Airway Cilia Identifies Previously Uncharacterized Proteins of High Abundance

Cilia are essential to many diverse cellular processes. Although many major axonemal components have been identified and studied, how they interact to form a functional axoneme is not completely understood. To further our understanding of the protein composition of human airway cilia, we performed a semiquantitative analysis of ciliary axonemes using label-free LC/MSE, which identified over 400 proteins with high confidence. Tubulins were the most abundant proteins identified, with evidence of 20 different isoforms obtained. Twelve different isoforms of axonemal dynein heavy chain were also identified. Absolute quantification of the nontubulin components demonstrated a greater than 75-fold range of protein abundance (RSPH9;1850 fmol vs CCDC103;24 fmol), adding another level of complexity to axonemal structure. Of the identified proteins, ∼70% are known axonemal proteins. In addition, many previously uncharacterized proteins were identified. Unexpectedly, several of these, including ERICH3, C1orf87, and CCDC181, were present at high relative abundance in the cilia. RT-PCR analysis and immunoblotting confirmed cilia-specific expression for eight uncharacterized proteins, and fluorescence microscopy demonstrated unique axonemal localizations. These studies have provided the first quantitative analysis of the ciliary proteome and have identified and characterized several previously unknown proteins as major constituents of human airway cilia.

Integrative analysis of DNA methylation and gene expression in butyrate-treated CHO cells

The cellular mechanisms responsible for the versatile properties of CHO cells as the major production cell line for biopharmaceutical molecules are not entirely understood yet, although several 'omics' data facilitate the understanding of CHO cells and their reactions to environmental conditions. However, genome-wide studies of epigenetic processes such as DNA methylation are still limited. To prove the applicability and usefulness of integrating DNA methylation and gene expression data in a biotechnological context, we exemplarily analyzed the time course of cellular reactions upon butyrate addition in antibody-producing CHO cells by whole-genome bisulfite sequencing and CHO-specific cDNA microarrays. Gene expression and DNA methylation analyses showed that pathways known to be affected by butyrate, including cell cycle and apoptosis, as well as pathways potentially involved in butyrate-induced hyperproductivity such as central energy metabolism and protein biosynthesis were affected. Differentially methylated regions were furthermore found to contain binding-site motifs of specific transcription factors and were hypothesized to represent regulatory regions closely connected to the cellular response to butyrate. Generally, our experiment underlines the benefit of integrating DNA methylation and gene expression data, as it provided potential novel candidate genes for rational cell line development and allowed for new insights into the butyrate effect on CHO cells.

FOXA1 potentiates lineage-specific enhancer activation through modulating TET1 expression and function

Forkhead box A1 (FOXA1) is an FKHD family protein that plays pioneering roles in lineage-specific enhancer activation and gene transcription. Through genome-wide location analyses, here we show that FOXA1 expression and occupancy are, in turn, required for the maintenance of these epigenetic signatures, namely DNA hypomethylation and histone 3 lysine 4 methylation. Mechanistically, this involves TET1, a 5-methylcytosine dioxygenase. We found that FOXA1 induces TET1 expression via direct binding to its cis-regulatory elements. Further, FOXA1 physically interacts with the TET1 protein through its CXXC domain. TET1 thus co-occupies FOXA1-dependent enhancers and mediates local DNA demethylation and concomitant histone 3 lysine 4 methylation, further potentiating FOXA1 recruitment. Consequently, FOXA1 binding events are markedly reduced following TET1 depletion. Together, our results suggest that FOXA1 is not only able to recognize but also remodel the epigenetic signatures at lineage-specific enhancers, which is mediated, at least in part, by a feed-forward regulatory loop between FOXA1 and TET1.

MAPanalyzer: a novel online tool for analyzing microtubule-associated proteins

The wide functional impacts of microtubules are unleashed and controlled by a battery of microtubule-associated proteins (MAPs). Specialists in the field appreciate the diversity of known MAPs and propel the identifications of novel MAPs. By contrast, there is neither specific database to record known MAPs, nor MAP predictor that can facilitate the discovery of potential MAPs. We here report the establishment of a MAP-centered online analysis tool MAPanalyzer, which consists of a MAP database and a MAP predictor. In the database, a core MAP dataset, which is fully manually curated from the literature, is further enriched by MAP information collected via automated pipeline. The core dataset, on the other hand, enables the building of a novel MAP predictor which combines specialized machine learning classifiers and the BLAST homology searching tool. Benchmarks on the curated testing dataset and the Arabidopsis thaliana whole genome dataset have shown that the proposed predictor outperforms not only its own components (i.e. the machine learning classifiers and BLAST), but also another popular homology searching tool, PSI-BLAST. Therefore, MAPanalyzer will serve as a promising computational resource for the investigations of MAPs.

Database URL:http://systbio.cau.edu.cn/mappred/.

Cortactin-binding protein 2 increases microtubule stability and regulates dendritic arborization

Neurons are characterized by subcellular compartments, such as axons, dendrites and synapses, that have highly specialized morphologies and biochemical specificities. Cortactin-binding protein 2 (CTTNBP2), a neuron-specific F-actin regulator, has been shown to play a role in the regulation of dendritic spine formation and their maintenance. Here, we show that, in addition to F-actin, CTTNBP2 also associates with microtubules before mature dendritic spines form. This association of CTTNBP2 and microtubules induced the formation of microtubule bundles. Although the middle (Mid) region of CTTNBP2 was sufficient for its association with microtubules, for microtubule bundling, the N-terminal region containing the coiled-coil motifs (NCC), which mediates the dimerization or oligomerization of CTTNBP2, was also required. Our study indicates that CTTNBP2 proteins form a dimer or oligomer and brings multiple microtubule filaments together to form bundles. In cultured hippocampal neurons, knockdown of CTTNBP2 or expression of the Mid or NCC domain alone reduced the acetylation levels of microtubules and impaired dendritic arborization. This study suggests that CTTNBP2 influences both the F-actin and microtubule cytoskeletons and regulates dendritic spine formation and dendritic arborization.