The Role of GM130 in Nervous System Diseases

Golgi matrix protein 130 (GM130) is a Golgi-shaping protein located on the cis surface of the Golgi apparatus (GA). It is one of the most studied Golgin proteins so far. Its biological functions are involved in many aspects of life processes, including mitosis, autophagy, apoptosis, cell polarity, and directed migration at the cellular level, as well as intracellular lipid and protein transport, microtubule formation and assembly, lysosome function maintenance, and glycosylation modification. Mutation inactivation or loss of expression of GM130 has been detected in patients with different diseases. GM130 plays an important role in the development of the nervous system, but the studies on it are limited. This article reviewed the current research progress of GM130 in nervous system diseases. It summarized the physiological functions of GM130 in the occurrence and development of Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), microcephaly (MCPH), sepsis associated encephalopathy (SAE), and Ataxia, aiming to provide ideas for the further study of GM130 in nervous system disease detection and treatment.

Loss of kinesin-8 improves the robustness of the self-assembled spindle

Chromosome segregation in female meiosis in many metazoans is mediated by acentrosomal spindles, the existence of which implies that microtubule spindles self-assemble without the participation of the centrosomes. Although it is thought that acentrosomal meiosis is not conserved in fungi, we recently reported the formation of self-assembled microtubule arrays, which were able to segregate chromosomes, in fission yeast mutants where the contribution of the spindle pole body (SPB, the centrosome equivalent in yeast) was specifically blocked during meiosis. Here, we demonstrate that this unexpected microtubule formation represents a bonafide type of acentrosomal spindle. Moreover, a comparative analysis of these self-assembled spindles and the canonical SPB-dependent spindle reveals similarities and differences: for example, both spindles have a similar polarity, but the location of the γ-tubulin complex differs. We also show that the robustness of self-assembled spindles can be reinforced by eliminating kinesin-8 family members, whereas kinesin-8 mutants have an adverse impact on SPB-dependent spindles. Hence, we consider that reinforced self-assembled spindles in yeast will help to clarify the molecular mechanisms behind acentrosomal meiosis, a crucial step towards better understanding gametogenesis.

Crystal structures of taxane-tubulin complexes: Implications for the mechanism of microtubule stabilization by Taxol

Paclitaxel (Taxol) is a first-line chemotherapeutic drug that promotes the curved to straight conformational transition of tubulin, an activation step that is necessary for microtubule formation. Crystallization of Taxol bound to tubulin has been long elusive. We found that baccatin III, the core structure of paclitaxel which lacks the C13 side chain, readily co-crystallizes with curved tubulin. Tailor-made taxanes with alternative side chains also co-crystallized, allowing us to investigate their binding modes. Interestingly, these Taxol derived compounds lost their microtubule stabilizing activity and cytotoxicity but kept their full microtubule binding affinity, and all induced lattice expansion upon binding. Additional nuclear magnetic resonance studies propose that Taxol binds to a small fraction of straight tubulin present in solution. Our results suggest a mode of action of Taxol, where the core structure is responsible for the interacting energy while the bulky hydrophobic C13 side chain enables binding selectively to straight tubulin and promotes stabilization.

α-TubK40me3 is required for neuronal polarization and migration by promoting microtubule formation

Tri-methylation on lysine 40 of α-tubulin (α-TubK40me3) is a recently identified post-translational modification involved in mitosis and cytokinesis. However, knowledge about α-TubK40me3 in microtubule function and post-mitotic cells remains largely incomplete. Here, we report that α-TubK40me3 is required for neuronal polarization and migration by promoting microtubule formation. α-TubK40me3 is enriched in mouse cerebral cortex during embryonic day (E)14 to E16. Knockdown of α-tubulin methyltransferase SETD2 at E14 leads to the defects in neuronal migration, which could be restored by overexpressing either a cytoplasm-localized SETD2 truncation or α-TubK40me3-mimicking mutant. Furthermore, α-TubK40me3 is preferably distributed on polymerized microtubules and potently promotes tubulin nucleation. Downregulation of α-TubK40me3 results in reduced microtubule abundance in neurites and disrupts neuronal polarization, which could be rescued by Taxol. Additionally, α-TubK40me3 is increased after losing α-tubulin K40 acetylation (α-TubK40ac) and largely rescues α-TubK40ac function. This study reveals a critical role of α-TubK40me3 in microtubule formation and neuronal development.

LMBD1 protein participates in cell mitosis by regulating microtubule assembly

LMBD1 was previously demonstrated to regulate the endocytosis of insulin receptor on cell surface and to mediate the export of cobalamin from the lysosomes to cytosol, but little is known about its function in mitosis. In this study, interactome analysis data indicate that LMBD1 is involved in cytoskeleton regulation. Both immunoprecipitation and GST pulldown assays demonstrated association of LMBD1 with tubulin. Immunofluorescence staining also showed the colocalization of LMBD1 with microtubule in both interphase and mitotic cells. LMBD1 specifically accelerates microtubule assembly dynamics in vitro and antagonizes the microtubule-disruptive effect of vinblastine. In addition, LMBRD1-knockdown impairs mitotic spindle formation, inhibits tubulin polymerization, and diminishes the mitosis-associated tubulin acetylation. The reduced acetylation can be reversed by ectopic expression of LMBD1 protein. These results suggest that LMBD1 protein stabilizes microtubule intermediates. Furthermore, embryonic fibroblasts derived from Lmbrd1 heterozygous knockout mice showed abnormality in microtubule formation, mitosis, and cell growth. Taken together, LMBD1 plays a pivotal role in regulating microtubule assembly that is essential for the process of cell mitosis.

Machine learning tools can now help with improving Taxol production in plant cell cultures

Chemotherapeutic intervention for cancer care is an important step. One of the most effective chemotherapy agents in use today is Paclitaxel (PTX), sold under the common name Taxol and Oxanol. Due to its ability to inhibit microtubule formation in cells, PTX is effective at all stages of the cancer and is FDA approved for treatment of many types of cancer (ovarian cancer, esophageal cancer, breast cancer, lung cancer, Kaposi sarcoma, cervical cancer, and pancreatic cancer). PTX is a plant alkaloid in the taxane family of compounds obtained from bark of the Pacific Yew tree (Taxus brevifolia) [1]. Adequate market supply of PTX has remained a challenge, as paclitaxel represents only a minor proportion of the total taxoid content of the Taxus species. Over the years, research into finding an alternate to cutting down Yew trees for PTX harvesting has been on the forefront. It is estimated that up to 60 trees may need to be harvested for the treatment of one patient.

Microtubules form by progressively faster tubulin accretion, not by nucleation–elongation

Microtubules are dynamic polymers that play fundamental roles in all eukaryotes. Despite their importance, how new microtubules form is poorly understood. Textbooks have focused on variations of a nucleation–elongation mechanism in which monomers rapidly equilibrate with an unstable oligomer (nucleus) that limits the rate of polymer formation; once formed, the polymer then elongates efficiently from this nucleus by monomer addition. Such models faithfully describe actin assembly, but they fail to account for how more complex polymers like hollow microtubules assemble. Here, we articulate a new model for microtubule formation that has three key features: (1) microtubules initiate via rectangular, sheet-like structures that grow faster the larger they become; (2) the dominant pathway proceeds via accretion, the stepwise addition of longitudinal or lateral layers; and (3) a “straightening penalty” to account for the energetic cost of tubulin’s curved-to-straight conformational transition. This model can quantitatively fit experimental assembly data, providing new insights into biochemical determinants and assembly pathways for microtubule nucleation.

CAMSAP2 organizes a γ-tubulin-independent microtubule nucleation centre

Microtubules are dynamic polymers consisting of αβ-tubulin heterodimers. The initial polymerization process, called microtubule nucleation, occurs spontaneously via αβ-tubulin. Since a large energy barrier prevents microtubule nucleation in cells, the γ-tubulin ring complex is recruited to the centrosome to overcome the nucleation barrier. However, detachment of a considerable number of microtubules from the centrosome is known to contribute to fundamental processes in cells. Here, we present evidence that minus-end-binding calmodulin-regulated spectrin-associated protein 2 (CAMSAP2) serves as a strong nucleator for microtubule formation from soluble αβ-tubulin independent of γ-tubulin. CAMSAP2 significantly reduces the nucleation barrier close to the critical concentration for microtubule polymerization by stabilizing the longitudinal contacts among αβ-tubulins. CAMSAP2 clusters together with αβ-tubulin to generate nucleation intermediates, from which numerous microtubules radiate, forming aster-like structures. Our findings suggest that CAMSAP2 supports microtubule growth by organizing a nucleation centre as well as by stabilizing microtubule nucleation intermediates.

Two-step generation of mesenchymal stem/stromal cells from human pluripotent stem cells with reinforced efficacy upon osteoarthritis rabbits by HA hydrogel

Background Current studies have enlightened the rosy prospects of human pluripotent stem cell (hPSC)-derived mesenchymal stem/stromal cells (MSCs) in regenerative medicine. However, systematic investigation of their signatures and applications with alternative biomaterials in osteoarthritis (OA) remains indistinct. Methods Herein, we initially took advantage of a small molecule library-mediated programming strategy for hPSC-MSC induction. Then, with the aid of multifaceted analyses such as flow cytometry (FCM), chromosome karyocyte and cell vitality, wound healing and microtubule formation assay and coculturing with T lymphocytes, we systematically evaluated the characterizations of signatures in vitro and the in vivo efficacy of hPSC-MSCs and HA hydrogel composite on rabbit osteoarthritis model. Results We found the combination of LLY-507 and AZD5153 was sufficient for high-efficiency CD73+CD90+CD105+CD31−CD34−CD45−HLA-DR− MSC induction from both hESCs and hiPSCs with stemness (POU5F1/SOX2/NANOG). The programmed hPSC-MSCs revealed conservative transcriptome variations and went through a heterogeneous intermediate-stage with mesenchymal-associated gene expression (NT5E, ENG, VIM and FN1) as well as displayed typical cytomorphology, immunophenotypes and normal karyotyping, multilineage differentiation potential, favorable cell vitality, proangiogenic and immunoregulatory properties in vitro. Meanwhile, the cell population exhibited preferable restorative and ameliorative function on OA rabbits with HA hydrogel in vivo. Conclusions Collectively, we established a rapid and convenient procedure for hPSC-MSC generation without redundant manipulations. The fundamental and clinical studies upon osteoarthritis (OA) treatment would benefit tremendously from the combination of the inexhaustible hPSC-MSCs and advantageous biomaterials.