Microtubules Research Articles

The microtubule-severing protein UNC-45A preferentially binds to curved microtubules and counteracts the microtubule-straightening effects of Taxol

Uncoordinated protein 45A (UNC-45A) is the only known ATP-independent microtubule (MT)-severing protein. Thus, it severs MTs via a novel mechanism. Invitro and in cells, UNC-45A-mediated MT severing is preceded by the appearance of MT bends. While MTs are stiff biological polymers, in cells, they often curve, and the result of this curving can be breaking off. The contribution of MT-severing proteins on MT lattice curvature is largely undefined. Here, we show that UNC-45A curves MTs. Using invitro biophysical reconstitution and total internal fluorescence microscopy analysis, we show that UNC-45A is enriched in the areas where MTs are curved versus the areas where MTs are straight. In cells, we show that UNC-45A overexpression increases MT curvature and its depletion has the opposite effect. We also show that this effect occurs is independent of actomyosin contractility. Lastly, we show for the first time that in cells, Paclitaxel straightens MTs, and that UNC-45A can counteracts the MT-straightening effects of the drug.

CEP20 promotes invasion and metastasis of non-small cell lung cancer cells by depolymerizing microtubules

Worldwide, Lung cancer is the leading cause of cancer-related death and poses a direct health threat, non-small cell lung cancer (NSCLC) is the most common type. In this study, we demonstrated that centrosomal protein 20 (CEP20) is upregulated in NSCLC tissues and associated with cancer invasion metastasis. Notably, CEP20 depletion inhibited NSCLC cell proliferation, migration, and microtubule polymerization. Mechanistically, we discovered that CEP20 is critical in the development of NSCLC by regulating microtubule dynamics and cell adhesion-related signaling pathways. Furthermore, the knockdown or overexpression of CEP20 affects microtubule polymerization in A549 cell lines. Our research provides a promising therapeutic target for the diagnosis and treatment of lung cancer, as well as a theoretical and experimental basis for clinical application.

Defense against phytopathogens relies on efficient antimicrobial protein secretion mediated by the microtubule-binding protein TGNap1

Plant immunity depends on the secretion of antimicrobial proteins, which occurs through yet-largely unknown mechanisms. The trans-Golgi network (TGN), a hub for intracellular and extracellular trafficking pathways, and the cytoskeleton, which is required for antimicrobial protein secretion, are emerging as pathogen targets to dampen plant immunity. In this work, we demonstrate that tgnap1-2, a loss-of-function mutant of Arabidopsis TGNap1, a TGN-associated and microtubule (MT)-binding protein, is susceptible to Pseudomonas syringae (Pst DC3000). Pst DC3000 infected tgnap1-2 is capable of mobilizing defense pathways, accumulating salicylic acid (SA), and expressing antimicrobial proteins. The susceptibility of tgnap1-2 is due to a failure to efficiently transport antimicrobial proteins to the apoplast in a partially MT-dependent pathway but independent from SA and is additive to the pathogen-antagonizing MIN7, a TGN-associated ARF-GEF protein. Therefore, our data demonstrate that plant immunity relies on TGNap1 for secretion of antimicrobial proteins, and that TGNap1 is a key immunity element that functionally links secretion and cytoskeleton in SA-independent pathogen responses.

Aggregation, Transmission, and Toxicity of the Microtubule-Associated Protein Tau: A Complex Comprehension.

The microtubule-associated protein tau is an intrinsically disordered protein containing a few short and transient secondary structures. Tau physiologically associates with microtubules (MTs) for its stabilization and detaches from MTs to regulate its dynamics. Under pathological conditions, tau is abnormally modified, detaches from MTs, and forms protein aggregates in neuronal and glial cells. Tau protein aggregates can be found in a number of devastating neurodegenerative diseases known as "tauopathies", such as Alzheimer's disease (AD), frontotemporal dementia (FTD), corticobasal degeneration (CBD), etc. However, it is still unclear how the tau protein is compacted into ordered protein aggregates, and the toxicity of the aggregates is still debated. Fortunately, there has been considerable progress in the study of tau in recent years, particularly in the understanding of the intercellular transmission of pathological tau species, the structure of tau aggregates, and the conformational change events in the tau polymerization process. In this review, we summarize the concepts of tau protein aggregation and discuss the views on tau protein transmission and toxicity.

Sliding of antiparallel microtubules drives bipolarization of monoastral spindles.

Time-lapse imaging with liquid crystal polarized light (LC-PolScope) and fluorescent speckle microscopy (FSM) enabled this study of spindle microtubules in monoastral spindles that were produced in crane-fly spermatocytes through flattening-induced centrosome displacement. Monoastral spindles are found in several other contexts: after laser ablation of one of a cell's two centrosomes (in the work of Khodjakov et al.), in Drosophila "urchin" mutants (in the works of Heck et al. and of Wilson et al.), in Sciara males (in the works of Fuge and of Metz), and in RNAi variants of Drosophila S2 cells (in the work of Goshima et al.). In all cases, just one pole has a centrosome (the astral pole); the other lacks a centrosome (the anastral pole). Thus, the question: How is the anastral half-spindle, lacking a centrosome, constructed? We learned that monoastral spindles are assembled in two phases: Phase I assembles the astral half-spindle composed of centrosomal microtubules, and Phase II assembles microtubules of the anastral half through extension of new microtubule polymerization outward from the spindle's equatorial mid-zone. That process uses plus ends of existing centrosomal microtubules as guiding templates to assemble anastral microtubules of opposite polarity. Anastral microtubules slide outward with their minus ends leading, thereby establishing proper bipolarity just like in normal biastral spindles that have two centrosomes.

Drebrin Regulates Collateral Axon Branching in Cortical Layer II/III Somatosensory Neurons.

Proper cortical lamination is essential for cognition, learning, and memory. Within the somatosensory cortex, pyramidal excitatory neurons elaborate axon collateral branches in a laminar-specific manner that dictates synaptic partners and overall circuit organization. Here, we leverage both male and female mouse models, single-cell labeling and imaging approaches to identify intrinsic regulators of laminar-specific collateral, also termed interstitial, axon branching. We developed new approaches for the robust, sparse, labeling of Layer II/III pyramidal neurons to obtain single-cell quantitative assessment of axon branch morphologies. We combined these approaches with cell-autonomous loss-of-function (LOF) and overexpression (OE) manipulations in an in vivo candidate screen to identify regulators of cortical neuron axon branch lamination. We identify a role for the cytoskeletal binding protein drebrin (Dbn1) in regulating Layer II/III cortical projection neuron (CPN) collateral axon branching in vitro LOF experiments show that Dbn1 is necessary to suppress the elongation of Layer II/III CPN collateral axon branches within Layer IV, where axon branching by Layer II/III CPNs is normally absent. Conversely, Dbn1 OE produces excess short axonal protrusions reminiscent of nascent axon collaterals that fail to elongate. Structure-function analyses implicate Dbn1S142 phosphorylation and Dbn1 protein domains known to mediate F-actin bundling and microtubule (MT) coupling as necessary for collateral branch initiation upon Dbn1 OE. Taken together, these results contribute to our understanding of the molecular mechanisms that regulate collateral axon branching in excitatory CPNs, a key process in the elaboration of neocortical circuit formation.SIGNIFICANCE STATEMENT Laminar-specific axon targeting is essential for cortical circuit formation. Here, we show that the cytoskeletal protein drebrin (Dbn1) regulates excitatory Layer II/III cortical projection neuron (CPN) collateral axon branching, lending insight into the molecular mechanisms that underlie neocortical laminar-specific innervation. To identify branching patterns of single cortical neurons in vivo, we have developed tools that allow us to obtain detailed images of individual CPN morphologies throughout postnatal development and to manipulate gene expression in these same neurons. Our results showing that Dbn1 regulates CPN interstitial axon branching both in vivo and in vitro may aid in our understanding of how aberrant cortical neuron morphology contributes to dysfunctions observed in autism spectrum disorder and epilepsy.

Functional plasticity in chromosome-microtubule coupling on the evolutionary time scale.

The Dam1 complex is essential for mitotic progression across evolutionarily divergent fungi. Upon analyzing amino acid (aa) sequences of Dad2, a Dam1 complex subunit, we identified a conserved 10-aa-long Dad2 signature sequence (DSS). An arginine residue (R126) in the DSS is essential for viability in Saccharomyces cerevisiae that possesses point centromeres. The corresponding arginine residues are functionally important but not essential for viability in Candida albicans and Cryptococcus neoformans; both carry several kilobases long regional centromeres. The purified recombinant Dam1 complex containing either Dad2ΔDSS or Dad2R126A failed to bind microtubules (MTs) or form any visible rings like the WT complex. Intriguingly, functional analysis revealed that the requirement of the conserved arginine residue for chromosome biorientation and mitotic progression reduced with increasing centromere length. We propose that plasticity of the invariant arginine of Dad2 in organisms with regional centromeres is achieved by conditional elevation of the kinetochore protein(s) to enable multiple kinetochore MTs to bind to each chromosome. The capacity of a chromosome to bind multiple kinetochore MTs may mask the deleterious effects of such lethal mutations.

The neuroprotective effect of dl-3-n-butylphthalide on the brain with experimental intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the most devastating subtype of stroke, nevertheless specific treatments with conclusive clinical benefit in improving outcomes of ICH remain lacking. The present study applied dl-3-n-butylphthalide (NBP), a compound approved for the treatment of ischemic stroke and rarely studied in ICH, to an experimental animal model of ICH, aiming to evaluate the therapeutic effects of NBP on ICH and the potential mechanisms. The results showed that rats receiving NBP administration exhibited a structural and functional restoration of brain after ICH mainly manifested as alleviation of neuronal apoptosis, suppression of neuroinflammation and oxidative stress, neurovascular remodeling, and eventually improvement of neurological deficits. In addition, several protein targets of NBP were revealed, which mainly play molecular functions of ribonucleoside triphosphate phosphatase activity, pyrophosphatase activity, hydrolase activity and GTPase activity, and participate in the biological process of brain development by regulating the formation of cellular components such as spindles, polymeric cytoskeletal fibers, microtubules and synapses, through mediating pathways such as VEGF signaling pathway, Fc epsilon RI signaling pathway, ECM-receptor interaction, Fc gamma R-mediated phagocytosis, peroxisome and so on, guiding the mechanism exploration of NBP therapy to some extent. Taken together, the study added some new evidence to the application of NBP in ICH treatment.

Exploring Plant Meiosis: Insights from the Kinetochore Perspective.

The central player for chromosome segregation in both mitosis and meiosis is the macromolecular kinetochore structure, which is assembled by >100 structural and regulatory proteins on centromere DNA. Kinetochores play a crucial role in cell division by connecting chromosomal DNA and microtubule polymers. This connection helps in the proper segregation and alignment of chromosomes. Additionally, kinetochores can act as a signaling hub, regulating the start of anaphase through the spindle assembly checkpoint, and controlling the movement of chromosomes during anaphase. However, the role of various kinetochore proteins in plant meiosis has only been recently elucidated, and these proteins differ in their functionality from those found in animals. In this review, our current knowledge of the functioning of plant kinetochore proteins in meiosis will be summarized. In addition, the functional similarities and differences of core kinetochore proteins in meiosis between plants and other species are discussed, and the potential applications of manipulating certain kinetochore genes in meiosis for breeding purposes are explored.

Structural insights into the mechanism of GTP initiation of microtubule assembly

In eukaryotes, the dynamic assembly of microtubules (MT) plays an important role in numerous cellular processes. The underlying mechanism of GTP triggering MT assembly is still unknown. Here, we present cryo-EM structures of tubulin heterodimer at their GTP- and GDP-bound states, intermediate assembly states of GTP-tubulin, and final assembly stages of MT. Both GTP- and GDP-tubulin heterodimers adopt similar curved conformations with subtle flexibility differences. In head-to-tail oligomers of tubulin heterodimers, the inter-dimer interface of GDP-tubulin exhibits greater flexibility, particularly in tangential bending. Cryo-EM of the intermediate assembly states reveals two types of tubulin lateral contacts, “Tube-bond” and “MT-bond”. Further, molecular dynamics (MD) simulations show that GTP triggers lateral contact formation in MT assembly in multiple sequential steps, gradually straightening the curved tubulin heterodimers. Therefore, we propose a flexible model of GTP-initiated MT assembly, including the formation of longitudinal and lateral contacts, to explain the nucleation and assembly of MT.

A Stochastic Model of Cortical Microtubule Anchoring and Mechanics Provides Regulatory Control of Microtubule Shape.

The organization of cortical microtubule arrays play an important role in the development of plant cells. Until recently, the direct mechanical influence of cell geometry on the constrained microtubule (MT) trajectories have been largely ignored in computational models. Modelling MTs as thin elastic rods constrained on a surface, a previous study examined the deflection of MTs using a fixed number of segments and uniform segment lengths between MT anchors. It is known that the resulting MT curves converge to geodesics as the anchor spacing approaches zero. In the case of long MTs on a cylinder, buckling has been found for transverse trajectories. There is a clear interplay between two factors in the problem of deflection: curvature of the membrane and the lengths of MT segments. Here, we examine the latter in detail, in the backdrop of a circular cylinder. In reality, the number of segments are not predetermined and their lengths are not uniform. We present a minimal, realistic model treating the anchor spacing as a stochastic process and examine the net effect on deflection. We find that, by tuning the ratio of growth speed to anchoring rate, it is possible to mitigate MT deflection and even prevent buckling for lengths significantly larger than the previously-derived critical buckling length. We suggest that this mediation of deflection by anchoring might provide cells with a means of preventing arrays from deflecting away from the transverse orientation.

Preliminary PET Imaging of Microtubule-Based PET Radioligand [11C]MPC-6827 in a Nonhuman Primate Model of Alzheimer's Disease.

The microtubule (MT) instability observed in Alzheimer's disease (AD) is commonly attributed to hyperphosphorylation of the MT-associated protein, tau. In vivo PET imaging offers an opportunity to gain critical information about MT changes with the onset and development of AD and related dementia. We developed the first brain-penetrant MT PET ligand, [11C]MPC-6827, and evaluated its in vivo imaging utility in vervet monkeys. Consistent with our previous in vitro cell uptake and in vivo rodent imaging experiments, [11C]MPC-6827 uptake increased with MT destabilization. Radioactive uptake was inversely related to (cerebrospinal fluid) CSF Aβ42 levels and directly related to age in a nonhuman primate (NHP) model of AD. Additionally, in vitro autoradiography studies also corroborated PET imaging results. Here, we report the preliminary results of PET imaging with [11C]MPC-6827 in four female vervet monkeys with high or low CSF Aβ42 levels, which have been shown to correlate with the Aβ plaque burden, similar to humans.

Cep104 is a component of the centriole distal tip complex that regulates centriole growth and contributes to Drosophila spermiogenesis

Proper centrosome number and function relies on the accurate assembly of centrioles, barrel-shaped structures that form the core duplicating elements of the organelle. The growth of centrioles is regulated in a cell cycle-dependent manner; while new daughter centrioles elongate during the S/G2/M phase, mature mother centrioles maintain their length throughout the cell cycle. Centriole length is controlled by the synchronized growth of the microtubules that ensheathe the centriole barrel. Although proteins exist that target the growing distal tips of centrioles, such as CP110 and Cep97, these proteins are generally thought to suppress centriolar microtubule growth, suggesting that distal tips may also contain unidentified counteracting factors that facilitate microtubule polymerization. Currently, a mechanistic understanding of how distal tip proteins balance microtubule growth and shrinkage to either promote daughter centriole elongation or maintain centriole length is lacking. Using a proximity-labeling screen in Drosophila cells, we identified Cep104 as a novel component of a group of evolutionarily conserved proteins that we collectively refer to as the distal tip complex (DTC). We found that Cep104 regulates centriole growth and promotes centriole elongation through its microtubule-binding TOG domain. Furthermore, analysis of Cep104 null flies revealed that Cep104 and Cep97 cooperate during spermiogenesis to align spermatids and coordinate individualization. Lastly, we mapped the complete DTC interactome and showed that Cep97 is the central scaffolding unit required to recruit DTC components to the distal tip of centrioles.

Noscapine alleviates unilateral ureteral obstruction-induced inflammation and fibrosis by regulating the TGFβ1/Smads signaling pathways

Renal fibrosis is a common pathway leading to progressive renal function loss in various forms of chronic kidney disease. Many fibrogenic factors regulate renal fibrosis; two key players are post-injury inflammation and transforming growth factor-β1 (TGF-β1)-induced myofibroblast differentiation. Myofibroblast differentiation is tightly regulated by the microtubule polymerization. Noscapine, an antitussive plant alkaloid, is a potent microtubule-interfering agent previously identified as a potential anticancer compound. Here, we examined how noscapine affects renal fibrogenesis in an in vitro renal fibroblast model and an in vivo unilateral ureteral obstruction (UUO) model. UUO mice were intraperitoneally treated with noscapine at 1 day before UUO surgery and daily thereafter. At 7 days post-surgery, kidneys were collected for further analysis. To analyze whether noscapine inhibits downstream TGF-β1-related signaling, we pre-incubated NRK-49F fibroblasts with noscapine and then performed TGF-β1 stimulation. In UUO mice, noscapine attenuated extracellular matrix protein deposition and the expression levels of type I collagen, type IV collagen, α-smooth muscle actin, and fibronectin. In addition, noscapine decreased tubulointerstitial inflammation in UUO kidneys by reducing TLR2 expression, modulating NLRP3 inflammasome activation, reducing macrophage infiltration, and antagonizing the M2 macrophage phenotype. Furthermore, noscapine pre-incubation suppressed the TGF-β1-induced fibroblast-myofibroblast transformation by downregulating the TGF-β/Smads signaling pathways in NRK-49F cells. These results suggest that noscapine reduces tubulointerstitial inflammation and fibrosis in the kidneys of UUO mice and inhibits the fibroblast-myofibroblast transformation induced by TGF-β1. Noscapine is an over-the-counter antitussive that has been used safely for several decades. Therefore, noscapine is an attractive therapeutic agent for inhibiting renal tubulointerstitial fibrosis.

The dynamic duo of microtubule polymerase Mini spindles/XMAP215 and cytoplasmic dynein is essential for maintaining Drosophila oocyte fate

In many species, only one oocyte is specified among a group of interconnected germline sister cells. In Drosophila melanogaster, 16 interconnected cells form a germline cyst, where one cell differentiates into an oocyte, while the rest become nurse cells that supply the oocyte with mRNAs, proteins, and organelles through intercellular cytoplasmic bridges named ring canals via microtubule-based transport. In this study, we find that a microtubule polymerase Mini spindles (Msps), the Drosophila homolog of XMAP215, is essential for maintenance of the oocyte specification. mRNA encoding Msps is transported and concentrated in the oocyte by dynein-dependent transport along microtubules. Translated Msps stimulates microtubule polymerization in the oocyte, causing more microtubule plus ends to grow from the oocyte through the ring canals into nurse cells, further enhancing nurse cell-to-oocyte transport by dynein. Knockdown of msps blocks the oocyte growth and causes gradual loss of oocyte determinants. Thus, the Msps-dynein duo creates a positive feedback loop, ensuring oocyte fate maintenance by promoting high microtubule polymerization activity in the oocyte, and enhancing dynein-dependent nurse cell-to-oocyte transport.

Microtubule detyrosination by VASH1/SVBP is regulated by the conformational state of tubulin in the lattice

Tubulin, a heterodimer of α- and β-tubulin, is a GTPase that assembles into microtubule (MT) polymers whose dynamic properties are intimately coupled to nucleotide hydrolysis. In cells, the organization and dynamics of MTs are further tuned by post-translational modifications (PTMs), which control the ability of MT-associated proteins (MAPs) and molecular motors to engage MTs. Detyrosination is a PTM of α-tubulin, wherein its C-terminal tyrosine residue is enzymatically removed by either the vasohibin (VASH) or MT-associated tyrosine carboxypeptidase (MATCAP) peptidases. How these enzymes generate specific patterns of MT detyrosination in cells is not known. Here, we use a novel antibody-based probe to visualize the formation of detyrosinated MTs in real time and employ single-molecule imaging of VASH1 bound to its regulatory partner small-vasohibin binding protein (SVBP) to understand the process of MT detyrosination invitro and in cells. We demonstrate that the activity, but not binding, of VASH1/SVBP is much greater on mimics of guanosine triphosphate (GTP)-MTs than on guanosine diphosphate (GDP)-MTs. Given emerging data showing that tubulin subunits in GTP-MTs are in expanded conformation relative to tubulin subunits in GDP-MTs, we reasoned that the lattice conformation of MTs is a key factor that gates the activity of VASH1/SVBP. We show that Taxol, a drug known to expand the MT lattice, promotes MT detyrosination and that CAMSAP2 and CAMSAP3 are two MAPs that spatially regulate detyrosination in cells. Collectively, our work shows that VASH1/SVBP detyrosination is regulated by the conformational state of tubulin in the MT lattice and that this is spatially determined in cells by the activity of MAPs.

Differential regulation of MAP2 by phosphorylation events in proline-rich versus C-terminal domains.

MAP2 is a critical cytoskeletal regulator in neurons. The phosphorylation of MAP2 (MAP2-P) is well known to regulate core functions of MAP2, including microtubule (MT)/actin binding and facilitation of tubulin polymerization. However, site-specific studies of MAP2-P function in regions outside of the MT-binding domain (MTBD) are lacking. We previously identified a set of MAP2 phosphopeptides which are differentially expressed and predominantly increased in the cortex of individuals with schizophrenia relative to nonpsychiatric comparison subjects. The phosphopeptides originated not from the MTBD, but from the flanking proline-rich and C-terminal domains of MAP2. We sought to understand the contribution of MAP2-P at these sites on MAP2 function. To this end, we isolated a series of phosphomimetic MAP2C constructs and subjected them to cell-free tubulin polymerization, MT-binding, actin-binding, and actin polymerization assays. A subset of MAP2-P events significantly impaired these functions, with the two domains displaying different patterns of MAP2 regulation: proline-rich domain mutants T293E and T300E impaired MT assembly and actin-binding affinity but did not affect MT-binding, while C-terminal domain mutants S426E and S439D impaired all three functions. S443D also impaired MT assembly with minimal effects on MT- or actin-binding. Using heterologous cells, we also found that S426E but not T293E had a lower capability for process formation than the wild-type protein. These findings demonstrate the functional utility of MAP2-P in the proline-rich and C-terminal domains and point to distinct, domain-dependent regulations of MAP2 function, which can go on to affect cellular morphology.

Structure challenges in the multivalency of Tau-microtubule interactions.

Structural studies aiming to visualize the interaction of Tau with microtubules (MTs) face several challenges, the main concerning the fact that Tau has multiple MT-interacting regions. In particular, the four (or three) pseudo-repeats of Tau bind to identical elements along the MT lattice but do it through non-identical residues. In addition, any given Tau molecule can use all its repeats or just one for its engagement with MTs. Finally, the binding of one Tau is not necessarily in register with respect to the next one. The mismatch in the MT and Tau repeats, therefore, challenges conventional modes of image analysis when visualizing these samples using cryo-electron microscopy. This commentary is dedicated to those challenges and ways to circumvent them while aiming for an atomic description of the Tau-tubulin interaction.

Why kiss-and-hop explains that tau does not stabilize microtubules and does not interfere with axonal transport (at physiological conditions).

Tau is a microtubule-associated protein that is enriched in the axonal process of neurons. Post-translational modifications of tau have been implicated in the development of tauopathies characterized by defects in axonal transport, neuronal atrophy, and microtubule disassembly. Although tau is almost quantitatively bound to microtubules under physiological conditions, it does not significantly affect axonal transport. Furthermore, acute or chronic tau deficiency does not result in significant destabilization of neuronal microtubules, challenging the classical view that disease-related tau modifications directly cause axonal microtubule collapse. Here, we discuss how the rapid interaction kinetics of the tau-microtubule interaction, which we previously termed the kiss-and-hop interaction, explains why tau does not affect microtubule-dependent axonal transport but still allows tau to modulate microtubule polymerization. In contrast, tau modifications that slow down the kinetics of the tau-microtubule interaction and increase the residence time of tau at a microtubule interaction site can disrupt axonal transport and cause dendritic atrophy. We discuss the consequences of such a gain-of-toxicity mechanism in terms of the development of disease-modulating drugs that target the tau protein.

Design, Synthesis, and Biological Evaluation of SSE1806, a Microtubule Destabilizer That Overcomes Multidrug Resistance.

Microtubules are dynamic structures that form spindle fibers during cell division; pharmacological inhibition of microtubule dynamics arrests cells in mitosis, leading to apoptosis, and they have been extensively used to treat various cancers. However, the efficacy of such drugs is often limited by multidrug resistance. This study synthesized and evaluated 30 novel derivatives of podophyllotoxin, a natural antimitotic compound, for their antiproliferative activities. Compound SSE1806 exhibited the most potent antiproliferative activity with GI50 values ranging from 1.29 ± 0.01 to 21.15 ± 2.1 μM in cancer cell lines of different origins; it directly inhibited microtubule polymerization, causing aberrant mitosis and G2/M arrest. Prolonged treatment with SSE1806 increased p53 expression, induced cell death in monolayer cultures, and reduced the growth of mouse- and patient-derived human colon cancer organoids. Importantly, SSE1806 overcame multidrug resistance in a cell line overexpressing MDR-1. Thus, SSE1806 represents a potential anticancer agent that can overcome multidrug resistance.