Expression patterns of LIS1, dynein and their interaction partners dynactin, NudE, NudEL and NudC in human gliomas suggest roles in invasion and proliferation

Spermine Synthase : A Potential Prognostic Marker for Lower-Grade Gliomas

OBJECTIVE

The objective of this study was to assess the relationship between spermine synthase (SMS) expression, tumor occurrence, and prognosis in lower-grade gliomas (LGGs).

METHODS

A total of 523 LGG patients and 1152 normal brain tissues were included as controls. Mann-Whitney U test was performed to evaluate SMS expression in the LGG group. Functional annotation analysis was conducted to explore the biological processes associated with high SMS expression. Immune cell infiltration analysis was performed to examine the correlation between SMS expression and immune cell types. The association between SMS expression and clinical and pathological features was assessed using Spearman correlation analysis. In vitro experiments were conducted to investigate the effects of overexpressing or downregulating SMS on cell proliferation, apoptosis, migration, invasion, and key proteins in the protein kinase B (AKT)/epithelialmesenchymal transition signaling pathway.

RESULTS

The study revealed a significant upregulation of SMS expression in LGGs compared to normal brain tissues. High SMS expression was associated with certain clinical and pathological features, including older age, astrocytoma, higher World Health Organization grade, poor disease-specific survival, disease progression, non-1p/19q codeletion, and wild-type isocitrate dehydrogenase. Cox regression analysis identified SMS as a risk factor for overall survival. Bioinformatics analysis showed enrichment of eosinophils, T cells, and macrophages in LGG samples, while proportions of dendritic (DC) cells, plasmacytoid DC (pDC) cells, and CD8+ T cells were decreased.

CONCLUSION

High SMS expression in LGGs may promote tumor occurrence through cellular proliferation and modulation of immune cell infiltration. These findings suggest the prognostic value of SMS in predicting clinical outcomes for LGG patients.

NUDC Is Critical for Mitosis and Postmitotic Cell Maintenance Through Its Modulation of Dynein and Actin Cytoskeletal Reorganization

Nuclear Distribution Protein C (NUDC) has been studied extensively for its role in mitosis. In addition to its well-established role in dynein-mediated nuclear migration, NUDC also plays a role in postmitotic cells. NUDC affects dynein-mediated protein and organelle trafficking and also stabilizes the actin-modulating protein, cofilin (CFL1), thereby affecting cytoskeletal reorganization. This mini-review will cover the known role of NUDC in mitosis as well as its role in actin cytoskeletal reorganization and in protein and organelle trafficking in nondividing cells, as well as update findings on the effect of a loss of NUDC on rod photoreceptors.

MicroRNA-150-5p-mediated Inhibition of Cell Proliferation, G1/S Transition, and Migration in Bladder Cancer through Targeting NEDD4-binding Protein 2-like 1 Gene

MicroRNA-150-5p (miR-150-5p) has been implicated in the progression of several cancer types, yet its specific functional role and regulatory mechanisms in bladder cancer (BC) remain largely unexplored. Our study revealed significant downregulation of miR-150-5p and upregulation of NEDD4-binding protein 2-like 1 gene (N4BP2L1) in BC tissues compared to controls using quantitative real-time polymerase chain reaction and western blot analysis, respectively. Reduced miR-150-5p expression correlated with advanced tumor stage and lymph node metastasis, while increased N4BP2L1 levels were associated with larger tumor size by the Chi-square test. Functionally, miR-150-5p exerted significant inhibitory effects on BC cell proliferation, migration, inducing G0/G1 phase arrest, and apoptosis. We confirmed N4BP2L1 as a direct target of miR-150-5p in BC cells using luciferase reporter assay. Crucially, N4BP2L1 knockdown mimicked, while overexpression counteracted the inhibitory impacts of miR-150-5p on BC cell proliferation, migration, and invasion. In addition, N4BP2L1 overexpression reversed miR-150-5p-induced alterations in CDK4, Cyclin D1, Bcl-2, PCNA, Ki-67, N-cadherin, Bad, and E-cadherin levels in BC cells. Based on these results, it can be inferred that the miR-150-5p/N4BP2L1 axis might constitute a promising candidate for therapeutic targeting in the treatment of BC.

NUDC is critical for rod photoreceptor function, maintenance, and survival

NUDC (nuclear distribution protein C) is a mitotic protein involved in nuclear migration and cytokinesis across species. Considered a cytoplasmic dynein (henceforth dynein) cofactor, NUDC was shown to associate with the dynein motor complex during neuronal migration. NUDC is also expressed in postmitotic vertebrate rod photoreceptors where its function is unknown. Here, we examined the role of NUDC in postmitotic rod photoreceptors by studying the consequences of a conditional NUDC knockout in mouse rods (rNudC-/- ). Loss of NUDC in rods led to complete photoreceptor cell death at 6 weeks of age. By 3 weeks of age, rNudC-/- function was diminished, and rhodopsin and mitochondria were mislocalized, consistent with dynein inhibition. Levels of outer segment proteins were reduced, but LIS1 (lissencephaly protein 1), a well-characterized dynein cofactor, was unaffected. Transmission electron microscopy revealed ultrastructural defects within the rods of rNudC-/- by 3 weeks of age. We investigated whether NUDC interacts with the actin modulator cofilin 1 (CFL1) and found that in rods, CFL1 is localized in close proximity to NUDC. In addition to its potential role in dynein trafficking within rods, loss of NUDC also resulted in increased levels of phosphorylated CFL1 (pCFL1), which would purportedly prevent depolymerization of actin. The absence of NUDC also induced an inflammatory response in Müller glia and microglia across the neural retina by 3 weeks of age. Taken together, our data illustrate the critical role of NUDC in actin cytoskeletal maintenance and dynein-mediated protein trafficking in a postmitotic rod photoreceptor.

NUDC is critical for rod photoreceptor function, maintenance, and survival

NUDC ( nu clear d istribution protein C) is a mitotic protein involved in nuclear migration and cytokinesis across species. Considered a cytoplasmic dynein (henceforth dynein) cofactor, NUDC was shown to associate with the dynein motor complex during neuronal migration. NUDC is also expressed in postmitotic vertebrate rod photoreceptors where its function is unknown. Here, we examined the role of NUDC in postmitotic rod photoreceptors by studying the consequences of a conditional NUDC knockout in mouse rods (r NudC -/- ). Loss of NUDC in rods led to complete photoreceptor cell death at six weeks of age. By 3 weeks of age, r NudC -/- function was diminished, and rhodopsin and mitochondria were mislocalized, consistent with dynein inhibition. Levels of outer segment proteins were reduced, but LIS1 (lissencephaly protein 1), a well-characterized dynein cofactor, was unaffected. Transmission electron microscopy revealed ultrastructural defects within the rods of r NudC -/- by 3 weeks of age. We investigated whether NUDC interacts with the actin modulator cofilin 1 (CFL1) and found that in rods, CFL1 is localized in close proximity to NUDC. In addition to its potential role in dynein trafficking within rods, loss of NUDC also resulted in increased levels of phosphorylated CFL1 (pCFL1), which would purportedly prevent depolymerization of actin. Absence of NUDC also induced an inflammatory response in Müller glia and microglia across the neural retina by 3 weeks of age. Taken together, our data illustrate the critical role of NUDC in actin cytoskeletal maintenance and dynein-mediated protein trafficking in a postmitotic rod photoreceptor.

Significance Statement

Nuclear distribution protein C (NUDC) has been studied extensively as an essential protein for mitotic cell division. In this study, we discovered its expression and role in the postmitotic rod photoreceptor cell. In the absence of NUDC in mouse rods, we detected functional loss, protein mislocalization, and rapid retinal degeneration consistent with dynein inactivation. In the early phase of retinal degeneration, we observed ultrastructural defects and an upregulation of inflammatory markers suggesting additional, dynein-independent functions of NUDC.

Role of Nesprin-2 and RanBP2 in BICD2-associated brain developmental disorders

Bicaudal D2 (BICD2) is responsible for recruiting cytoplasmic dynein to diverse forms of subcellular cargo for their intracellular transport. Mutations in the human BICD2 gene have been found to cause an autosomal dominant form of spinal muscular atrophy (SMA-LED2), and brain developmental defects. Whether and how the latter mutations are related to roles we and others have identified for BICD2 in brain development remains little understood. BICD2 interacts with the nucleoporin RanBP2 to recruit dynein to the nuclear envelope (NE) of Radial Glial Progenitor cells (RGPs) to mediate their well-known but mysterious cell-cycle-regulated interkinetic nuclear migration (INM) behavior, and their subsequent differentiation to form cortical neurons. We more recently found that BICD2 also mediates NE dynein recruitment in migrating post-mitotic neurons, though via a different interactor, Nesprin-2. Here, we report that Nesprin-2 and RanBP2 compete for BICD2-binding in vitro. To test the physiological implications of this behavior, we examined the effects of known BICD2 mutations using in vitro biochemical and in vivo electroporation-mediated brain developmental assays. We find a clear relationship between the ability of BICD2 to bind RanBP2 vs. Nesprin-2 in controlling of nuclear migration and neuronal migration behavior. We propose that mutually exclusive RanBP2-BICD2 vs. Nesprin-2-BICD2 interactions at the NE play successive, critical roles in INM behavior in RGPs and in post-mitotic neuronal migration and errors in these processes contribute to specific human brain malformations.

LIS1 interacts with CLIP170 to promote tumor growth and metastasis via the Cdc42 signaling pathway in salivary gland adenoid cystic carcinoma

Salivary gland adenoid cystic carcinoma (SACC) is one of the most common malignant tumors, with high aggressive potential in the oral and maxillofacial regions. Lissencephaly 1 (LIS1) is a microtubule-organizing center-associated protein that regulates the polymerization and stability of microtubules by mediating the motor function of dynein. Recent studies have suggested that LIS1 plays a potential role in the malignant development of tumors, such as in mitosis and migration. However, the role of LIS1 in SACC development and its related molecular mechanisms remain unclear. Thus, the effects of LIS1 on the proliferation, apoptosis, invasion and metastasis of SACC were studied, in vivo and in vitro. The results of immunohistochemical staining showed that LIS1 was highly expressed in SACC tissues, and its expression level was associated with malignant progression. In vitro, the results of CCK-8, TUNEL, wound healing and Transwell assays demonstrated that LIS1 promotes proliferation, inhibits apoptosis, and enhances the migration and invasion of SACC-LM cells. In vivo, knockdown of LIS1 effectively suppressed the growth of subcutaneous tumors in a mouse xenograft and distant metastasis of tumor cells in the metastasis model. The co-immunoprecipitation, immunofluorescence and western blot results also revealed that LIS1 binds to cytoplasmic linker protein 170 (CLIP170) to form a protein complex (LIS1/CLIP170), which activates the cell division control protein 42 homolog (Cdc42) signaling pathway to modulate the proliferation and anti-apoptosis of tumor cells, and enhanced invasion and metastasis by regulating the formation of invadopodia and the expression of MMPs in SACC-LM cells. Therefore, the present study demonstrated that LIS1 is a cancer promoter in SACC, and the molecular mechanism of the LIS1/CLIP170/Cdc42 signaling pathway is involved in the malignant progression, which offers a promising strategy for targeted therapy of SACC.

The Interplay of Microtubules with Mitochondria–ER Contact Sites (MERCs) in Glioblastoma

Gliomas are heterogeneous neoplasms, classified into grade I to IV according to their malignancy and the presence of specific histological/molecular hallmarks. The higher grade of glioma is known as glioblastoma (GB). Although progress has been made in surgical and radiation treatments, its clinical outcome is still unfavorable. The invasive properties of GB cells and glioma aggressiveness are linked to the reshaping of the cytoskeleton. Recent works suggest that the different susceptibility of GB cells to antitumor immune response is also associated with the extent and function of mitochondria–ER contact sites (MERCs). The presence of MERCs alterations could also explain the mitochondrial defects observed in GB models, including abnormalities of energy metabolism and disruption of apoptotic and calcium signaling. Based on this evidence, the question arises as to whether a MERCs–cytoskeleton crosstalk exists, and whether GB progression is linked to an altered cytoskeleton–MERCs interaction. To address this possibility, in this review we performed a meta-analysis to compare grade I and grade IV GB patients. From this preliminary analysis, we found that GB samples (grade IV) are characterized by altered expression of cytoskeletal and MERCs related genes. Among them, the cytoskeleton-associated protein 4 (CKAP4 or CLIMP-63) appears particularly interesting as it encodes a MERCs protein controlling the ER anchoring to microtubules (MTs). Although further in-depth analyses remain necessary, this perspective review may provide new hints to better understand GB molecular etiopathogenesis, by suggesting that cytoskeletal and MERCs alterations cooperate to exacerbate the cellular phenotype of high-grade GB and that MERCs players can be exploited as novel biomarkers/targets to enhance the current therapy for GB.

A selective LIS1 requirement for mitotic spindle assembly discriminates distinct T-cell division mechanisms within the T-cell lineage

The ability to proliferate is a common feature of most T-cell populations. However, proliferation follows different cell-cycle dynamics and is coupled to different functional outcomes according to T-cell subsets. Whether the mitotic machineries supporting these qualitatively distinct proliferative responses are identical remains unknown. Here, we show that disruption of the microtubule-associated protein LIS1 in mouse models leads to proliferative defects associated with a blockade of T-cell development after β-selection and of peripheral CD4+ T-cell expansion after antigen priming. In contrast, cell divisions in CD8+ T cells occurred independently of LIS1 following T-cell antigen receptor stimulation, although LIS1 was required for proliferation elicited by pharmacological activation. In thymocytes and CD4+ T cells, LIS1 deficiency did not affect signaling events leading to activation but led to an interruption of proliferation after the initial round of division and to p53-induced cell death. Proliferative defects resulted from a mitotic failure, characterized by the presence of extra-centrosomes and the formation of multipolar spindles, causing abnormal chromosomes congression during metaphase and separation during telophase. LIS1 was required to stabilize dynein/dynactin complexes, which promote chromosome attachment to mitotic spindles and ensure centrosome integrity. Together, these results suggest that proliferative responses are supported by distinct mitotic machineries across T-cell subsets.

Biology of Glioblastoma Multiforme-Exploration of Mitotic Catastrophe as a Potential Treatment Modality

Glioblastoma multiforme (GBM) represents approximately 60% of all brain tumors in adults. This malignancy shows a high biological and genetic heterogeneity associated with exceptional aggressiveness, leading to a poor survival of patients. This review provides a summary of the basic biology of GBM cells with emphasis on cell cycle and cytoskeletal apparatus of these cells, in particular microtubules. Their involvement in the important oncosuppressive process called mitotic catastrophe will next be discussed along with select examples of microtubule-targeting agents, which are currently explored in this respect such as benzimidazole carbamate compounds. Select microtubule-targeting agents, in particular benzimidazole carbamates, induce G₂/M cell cycle arrest and mitotic catastrophe in tumor cells including GBM, resulting in phenotypically variable cell fates such as mitotic death or mitotic slippage with subsequent cell demise or permanent arrest leading to senescence. Their effect is coupled with low toxicity in normal cells and not developed chemoresistance. Given the lack of efficient cytostatics or modern molecular target-specific compounds in the treatment of GBM, drugs inducing mitotic catastrophe might offer a new, efficient alternative to the existing clinical management of this at present incurable malignancy.

Lis1 activates dynein motility by modulating its pairing with dynactin

Lissencephaly-1 (Lis1) is a key cofactor for dynein-mediated intracellular transport towards the minus-ends of microtubules. It remains unclear whether Lis1 serves as an inhibitor or an activator of mammalian dynein motility. Here we use single-molecule imaging and optical trapping to show that Lis1 does not directly alter the stepping and force production of individual dynein motors assembled with dynactin and a cargo adaptor. Instead, Lis1 promotes the formation of an active complex with dynactin. Lis1 also favours the recruitment of two dyneins to dynactin, resulting in increased velocity, higher force production and more effective competition against kinesin in a tug-of-war. Lis1 dissociates from motile complexes, indicating that its primary role is to orchestrate the assembly of the transport machinery. We propose that Lis1 binding releases dynein from its autoinhibited state, which provides a mechanistic explanation for why Lis1 is required for efficient transport of many dynein-associated cargos in cells.

Outer Radial Glia-like Cancer Stem Cells Contribute to Heterogeneity of Glioblastoma

Glioblastoma is a devastating form of brain cancer. To identify aspects of tumor heterogeneity that may illuminate drivers of tumor invasion, we created a glioblastoma tumor cell atlas with single-cell transcriptomics of cancer cells mapped onto a reference framework of the developing and adult human brain. We find that multiple GSC subtypes exist within a single tumor. Within these GSCs, we identify an invasive cell population similar to outer radial glia (oRG), a fetal cell type that expands the stem cell niche in normal human cortex. Using live time-lapse imaging of primary resected tumors, we discover that tumor-derived oRG-like cells undergo characteristic mitotic somal translocation behavior previously only observed in human development, suggesting a reactivation of developmental programs. In addition, we show that PTPRZ1 mediates both mitotic somal translocation and glioblastoma tumor invasion. These data suggest that the presence of heterogeneous GSCs may underlie glioblastoma's rapid progression and invasion.

The Cytoskeleton-A Complex Interacting Meshwork

The cytoskeleton of animal cells is one of the most complicated and functionally versatile structures, involved in processes such as endocytosis, cell division, intra-cellular transport, motility, force transmission, reaction to external forces, adhesion and preservation, and adaptation of cell shape. These functions are mediated by three classical cytoskeletal filament types, as follows: Actin, microtubules, and intermediate filaments. The named filaments form a network that is highly structured and dynamic, responding to external and internal cues with a quick reorganization that is orchestrated on the time scale of minutes and has to be tightly regulated. Especially in brain tumors, the cytoskeleton plays an important role in spreading and migration of tumor cells. As the cytoskeletal organization and regulation is complex and many-faceted, this review aims to summarize the findings about cytoskeletal filament types, including substructures formed by them, such as lamellipodia, stress fibers, and interactions between intermediate filaments, microtubules and actin. Additionally, crucial regulatory aspects of the cytoskeletal filaments and the formed substructures are discussed and integrated into the concepts of cell motility. Even though little is known about the impact of cytoskeletal alterations on the progress of glioma, a final point discussed will be the impact of established cytoskeletal alterations in the cellular behavior and invasion of glioma.

NFAT1-Mediated Regulation of NDEL1 Promotes Growth and Invasion of Glioma Stem-like Cells

Glioma stem-like cells (GSC) promote tumor generation and progression. However, the mechanism of GSC induction or maintenance is largely unknown. We previously demonstrated that the calcium-responsive transcription factor nuclear factor of activated T cells-1 (NFAT1) is activated in glioblastomas and regulates the invasion of tumor cells. In this study, we further explored the role of NFAT1 in GSC. We found that NFAT1 expression was associated with an aggressive phenotype and predicted poor survival in gliomas. Compared with normal glioma cells, NFAT1 was upregulated in GSC. NFAT1 knockdown reduced GSC viability, invasion, and self-renewal in vitro and inhibited tumorigenesis in vivo, whereas NFAT1 overexpression enhanced the growth and invasion of GSCs. RNA sequencing showed that NFAT1 depletion was associated with reduced neurodevelopment protein 1-like 1 (NDEL1, a potential downstream target of NFAT1) expression, whereas NFAT1 overexpression induced NDEL1 expression. In addition, NFAT1 regulated the promoter activities of NDEL1, whereas rescue of NDEL1 in NFAT1-silenced GSC partially restored tumor growth and invasion. Upregulation of NFAT1-NDEL1 signaling elevated Erk activation, increased protein levels of stemness markers in GSC, and resulted in de-differentiation of normal neuronal cells and astrocytes. Our results indicate that NFAT1 controls the growth and invasion of GSC partially through regulation of NDEL1. Targeting the NFAT1-NDEL1 axis therefore might be of potential benefit in the treatment of patients with glioma. SIGNIFICANCE: NFAT1 controls the growth and invasion of GSCs, partially by regulating NDEL1. Targeting the NFAT1-NDEL1 axis might provide opportunities in treating patients with glioma.

Distinct roles for dynein light intermediate chains in neurogenesis, migration, and terminal somal translocation

Cytoplasmic dynein participates in multiple aspects of neocortical development. These include neural progenitor proliferation, morphogenesis, and neuronal migration. The cytoplasmic dynein light intermediate chains (LICs) 1 and 2 are cargo-binding subunits, though their relative roles are not well understood. Here, we used in utero electroporation of shRNAs or LIC functional domains to determine the relative contributions of the two LICs in the developing rat brain. We find that LIC1, through BicD2, is required for apical nuclear migration in neural progenitors. In newborn neurons, we observe specific roles for LIC1 in the multipolar to bipolar transition and glial-guided neuronal migration. In contrast, LIC2 contributes to a novel dynein role in the little-studied mode of migration, terminal somal translocation. Together, our results provide novel insight into the LICs' unique functions during brain development and dynein regulation overall.

Nudel involvement in the high-glucose-induced epithelial-mesenchymal transition of tubular epithelial cells

Nudel is a newly discovered factor related to cell migration. The tubular epithelial-mesenchymal transition (EMT) includes four steps: the loss of the adhesive properties of epithelial cells, the acquisition of a mesenchymal cell phenotype, the destruction of the tubular basal membrane, and the migration into the renal interstitium. The purpose of this study was to investigate the role of Nudel in the high-glucose-induced EMT of tubular epithelial cells. Human renal proximal tubular epithelial cells (HKCs) were treated with Nudel shRNA to clarify the role and mechanism of Nudel in tubular EMT induced by high glucose. We found that Nudel was expressed at a high level in high-glucose-stimulated HKCs, and the expression of Nudel was associated with the activation of signal transducer and activator of transcription 3. After transfection with Nudel shRNA, we detected the expression levels of E-cadherin, α-smooth muscle actin (α-SMA), and the Wiskott-Aldrich syndrome family of proteins (including WASP, N-WASP, WAVE1, WAVE2, and WAVE3) via assay. Cell migration was analyzed by the scratching method. The results showed that high glucose downregulated E-cadherin expression, upregulated α-SMA expression, and promoted the migration of HKCs. The expression levels of N-WASP, WAVE1, and WAVE2 were also elevated in HKCs treated with high glucose. All changes induced by high glucose were ameliorated by Nudel depletion. We conclude that Nudel participates in the transition and the migration of tubular epithelial cells via the regulation of WASP family proteins.

Disrupted in schizophrenia 1 (DISC1) inhibits glioblastoma development by regulating mitochondria dynamics

Glioblastoma(GBM) is one of the most common and aggressive malignant primary tumors of the central nervous system and mitochondria have been proposed to participate in GBM tumorigenesis. Previous studies have identified a potential role of Disrupted in Schizophrenia 1 (DISC1), a multi-compartmentalized protein, in mitochondria. But whether DISC1 could regulate GBM tumorigenesis via mitochondria is still unknown. We determined the expression level of DISC1 by both bioinformatics analysis and tissue analysis, and found that DISC1 was highly expressed in GBM. Knocking down of DISC1 by shRNA in GBM cells significantly inhibited cell proliferation both in vitro and in vivo. In addition, down-regulation of DISC1 decreased cell migration and invasion of GBM and self renewal capacity of glioblastoma stem-like cells. Furthermore, multiple independent rings or spheres could be observed in mitochondria in GBM depleted of DISC1, while normal filamentous morphology was observed in control cells, demonstrating that DISC1 affected the mitochondrial dynamic. Dynamin-related protein 1 (Drp1) was reported to contribute to mitochondrial dynamic regulation and influence glioma cells proliferation and invasion by RHOA/ ROCK1 pathway. Our data showed a significant decrease of Drp1 both in mRNA and protein level in GBM lack of DISC1, indicating that DISC1 maybe affect the mitochondrial dynamic by regulating Drp1. Taken together, our findings reveal that DISC1 affects glioblastoma cell development via mitochondria dynamics partly by down regulation of Drp1.

Molecular and Genetic Determinants of Glioma Cell Invasion

A diffusely invasive nature is a major obstacle in treating a malignant brain tumor, "diffuse glioma", which prevents neurooncologists from surgically removing the tumor cells even in combination with chemotherapy and radiation. Recently updated classification of diffuse gliomas based on distinct genetic and epigenetic features has culminated in a multilayered diagnostic approach to combine histologic phenotypes and molecular genotypes in an integrated diagnosis. However, it is still a work in progress to decipher how the genetic aberrations contribute to the aggressive nature of gliomas including their highly invasive capacity. Here we depict a set of recent discoveries involving molecular genetic determinants of the infiltrating nature of glioma cells, especially focusing on genetic mutations in receptor tyrosine kinase pathways and metabolic reprogramming downstream of common cancer mutations. The specific biology of glioma cell invasion provides an opportunity to explore the genotype-phenotype correlation in cancer and develop novel glioma-specific therapeutic strategies for this devastating disease.

BICD1 expression, as a potential biomarker for prognosis and predicting response to therapy in patients with glioblastomas

There is variation in the survival and therapeutic outcome of patients with glioblastomas (GBMs). Therapy resistance is an important challenge in the treatment of GBM patients. The aim of this study was to identify Temozolomide (TMZ) related genes and confirm their clinical relevance. The TMZ-related genes were discovered by analysis of the gene-expression profiling in our cell-based microarray. Their clinical relevance was verified by in silico meta-analysis of the Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) datasets. Our results demonstrated that BICD1 expression could predict both prognosis and response to therapy in GBM patients. First, high BICD1 expression was correlated with poor prognosis in the TCGA GBM cohort (n=523) and in the CGGA glioma cohort (n=220). Second, high BICD1 expression predicted poor outcome in patients with TMZ treatment (n=301) and radiation therapy (n=405). Third, multivariable Cox regression analysis confirmed BICD1 expression as an independent factor affecting the prognosis and therapeutic response of TMZ and radiation in GBM patients. Additionally, age, MGMT and BICD1 expression were combinedly utilized to stratify GBM patients into more distinct risk groups, which may provide better outcome assessment. Finally, we observed a strong correlation between BICD1 expression and epithelial-mesenchymal transition (EMT) in GBMs, and proposed a possible mechanism of BICD1-associated survival or therapeutic resistance in GBMs accordingly. In conclusion, our study suggests that high BICD1 expression may result in worse prognosis and could be a predictor of poor response to TMZ and radiation therapies in GBM patients.

Protein interaction network of alternatively spliced NudCD1 isoforms

NudCD1, also known as CML66 or OVA66, is a protein initially identified as overexpressed in patients with chronic myelogenous leukemia. The mRNA of NudCD1 is expressed in heart and testis of normal tissues, and is overexpressed in several cancers. Previous studies have shown that the expression level of the protein correlates with tumoral phenotype, possibly interacting upstream of the Insulin Growth Factor - 1 Receptor (IGF-1R). The gene encoding the NudCD1 protein consists of 12 exons that can be alternative spliced, leading to the expression of three different isoforms. These isoforms possess a common region of 492 amino acids in their C-terminus region and have an isoform specific N-terminus. To determine the distinct function of each isoforms, we have localised the isoforms within the cells using immunofluorescence microscopy and used a quantitative proteomics approach (SILAC) to identify specific protein interaction partners for each isoforms. Localization studies showed a different subcellular distribution for the different isoforms, with the first isoform being nuclear, while the other two isoforms have distinct cytoplasmic and nuclear location. We found that the different NudCD1 isoforms have unique interacting partners, with the first isoform binding to a putative RNA helicase named DHX15 involved in mRNA splicing.

Preferential Association of Lissencephaly-1 Gene Expression with CD133+ Glioblastoma Cells

Lissencephaly-1 (Lis1) protein is a dynein-binding protein involved in neural stem cell division, morphogenesis and motility. To determine whether Lis1 is a key factor in glioblastoma, we evaluated its expression and function in CD133+ glioblastoma cells. Global, Lis1 gene expression is similar in glioblastoma and normal samples. Interestingly, immunohistochemistry data indicate increased Lis1 expression colocalized with CD133 in a subset of glioma cells, including the tumor cells with perivascular localization. Lis1 gene expression is increased up to 60-fold in CD133 positive cells isolated from primary cultures of glioblastoma and U87 glioblastoma cell line as compared to CD133 negative cells. To investigate the potential role of Lis1 in CD133+ glioblastoma cells, we silenced Lis1 gene in U87 cell line obtaining shLis1-U87 cells. In shLis1-U87 cell culture we noticed a significant decrease of CD133+ cells fraction as compared with control cells and also, CD133+ cells isolated from shLis1-U87 were two times less adhesive, migratory and proliferative, as compared with control transfected U87 CD133+ cells. Moreover, Lis1 silencing decreased the proliferative capacity of irradiated U87 cells, an effect attributable to the lower percentage of CD133+ cells. This is the first report showing a preferential expression of Lis1 gene in CD133+ glioblastoma cells. Our data suggest a role of Lis1 in regulating CD133+ glioblastoma cells function.

MicroRNA-194 suppresses prostate cancer migration and invasion by downregulating human nuclear distribution protein

Human NudC nuclear distribution protein (hNUDC) is differentially expressed between normal and cancer cells. Based on its marked altered expression and its roles in modulating cell division, cytokineses and migration, a detailed understanding of the mechanisms regulating hNUDC expression in cancer cells is critical. In this study, we identified miR-194 as a downstream target of hNUDC and linked its expression to reduced metastatic capacity and tumorigenicity of prostate cancer (PCa) cells. Using miRNA target prediction programs, hNUDC mRNA was found to contain a potential binding site for miR-194 within its 3'UTR. A Reporter assay confirmed that post-transcriptional regulation of hNUDC was dependent on the miR-194 binding site. Forced expression of miR-194 in PCa cell lines, PC-3 and DU-145, led to a decrease in the mRNA and protein levels of hNUDC. Overexpression of miR-194 in these cells inhibited cell migration and invasion, and induced multinucleated cells. Our data showed that hNUDC knockdown by siRNA significantly reduced the migration and invasion in the PC-3 and DU-145 cells, phenocopying the results of miR-194 overexpression. Furthermore, lentivirus-mediated stable expression of miR-194 in PCa cells reduced the ability of colony formation as detected by a soft agar assay and exhibited significantly less tumorigenic ability in vivo. Our results suggest a novel role for miR-194 in effectively controlling cell metastatic processes in PCa cells via the regulation of hNUDC expression.

Regulation of the actin cytoskeleton by the Ndel1-Tara complex is critical for cell migration

Nuclear distribution element-like 1 (Ndel1) plays pivotal roles in diverse biological processes and is implicated in the pathogenesis of multiple neurodevelopmental disorders. Ndel1 function by regulating microtubules and intermediate filaments; however, its functional link with the actin cytoskeleton is largely unknown. Here, we show that Ndel1 interacts with TRIO-associated repeat on actin (Tara), an actin-bundling protein, to regulate cell movement. In vitro wound healing and Boyden chamber assays revealed that Ndel1- or Tara-deficient cells were defective in cell migration. Moreover, Tara overexpression induced the accumulation of Ndel1 at the cell periphery and resulted in prominent co-localization with F-actin. This redistribution of Ndel1 was abolished by deletion of the Ndel1-interacting domain of Tara, suggesting that the altered peripheral localization of Ndel1 requires a physical interaction with Tara. Furthermore, co-expression of Ndel1 and Tara in SH-SY5Y cells caused a synergistic increase in F-actin levels and filopodia formation, suggesting that Tara facilitates cell movement by sequestering Ndel1 at peripheral structures to regulate actin remodeling. Thus, we demonstrated that Ndel1 interacts with Tara to regulate cell movement. These findings reveal a novel role of the Ndel1-Tara complex in actin reorganization during cell movement.

Unraveling molecular effects of ADAR1 overexpression in HEK293T cells by label-free quantitative proteomics

ADAR1 is a double-stranded RNA (dsRNA) editing enzyme that specifically converts adenosine to inosine. ADAR1 is ubiquitously expressed in eukaryotes and participate in various cellular processes such as differentiation, proliferation and immune responses. We report here a new proteomics study of HEK293T cells with and without ADAR1 overexpression. The up- and down-regulated proteins by ADAR1 overexpression are identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) followed by label-free protein quantification. Totally 1,495 proteins (FDR < 0.01) are identified, among which 211 are up- and 159 are down-regulated for at least 1.5-fold (n = 3, p < 0.05). Gene ontology analysis reveals that these ADAR1-regulated proteins are involved in protein translation and cell cycle regulation. Bioinformatics analysis identifies a closely related network consistent for the protein translation machinery and a tightly connected network through proliferating cell nuclear antigen (PCNA)-interactions. Up-regulation of the proteins in the PCNA-mediated cell proliferation network is confirmed by Western blotting. In addition, ADAR1 overexpression is confirmed to increase cell proliferation in HEK293T cells and A549 cells. We conclude that ADAR1 overexpression modulates the protein translation and cell cycle networks through PCNA-mediated protein-protein interaction to promote cell proliferation in HEK293 cells.

Dynamic Phosphorylation of NudC by Aurora B in Cytokinesis

Nuclear distribution protein C (NudC) is a mitotic regulator that plays a role in cytokinesis. However, how NudC is regulated during cytokinesis remains unclear. Here, we show that NudC is phosphorylated by Aurora B, a kinase critical for cell abscission. NudC is co-localized with Aurora B at the midbody and co-immunoprecipitated with Aurora B in mitosis. Inhibition of Aurora B by ZM447439 reduced NudC phosphorylation, suggesting that NudC is an Aurora B substrate in vivo. We identified T40 on NudC as an Aurora B phosphorylation site. NudC depletion resulted in cytokinesis failure with a dramatic elongation of the intercellular bridge between daughter cells, sustained Aurora B activity at the midbody, and reduced cell abscission. These cytokinetic defects can be rescued by the ectopic expression of wild-type NudC. Reconstitution with T40A phospho-defective NudC was found to rescue the cytokinesis defect. In contrast, reconstitution with the T40D phospho-mimetic NudC was inefficient in supporting the completion of cytokinesis. These results suggest that that dynamic phosphorylation of NudC by Aurora B regulates cytokinesis.

Emerging roles of NudC family: from molecular regulation to clinical implications

Nuclear distribution gene C (NudC) was first found in Aspergillus nidulans as an upstream regulator of NudF, whose mammalian homolog is Lissencephaly 1 (Lis1). NudC is conserved from fungi to mammals. Vertebrate NudC has three homologs: NudC, NudC-like protein (NudCL), and NudC-like protein 2 (NudCL2). All members of the NudC family share a conserved p23 domain, which possesses chaperone activity both in conjunction with and independently of heat shock protein 90 (Hsp90). Our group and the others found that NudC homologs were involved in cell cycle regulation by stabilizing the components of the LIS1/dynein complex. Additionally, NudC plays important roles in cell migration, ciliogenesis, thrombopoiesis, and the inflammatory response. It has been reported that NudCL is essential for the stability of the dynein intermediate chain and ciliogenesis via its interaction with the dynein 2 complex. Our data showed that NudCL2 regulates the LIS1/dynein pathway by stabilizing LIS1 with Hsp90 chaperone. The fourth distantly related member of the NudC family, CML66, a tumor-associated antigen in human leukemia, contains a p23 domain and appears to promote oncogenesis by regulating the IGF-1R-MAPK signaling pathway. In this review, we summarize our current knowledge of the NudC family and highlight its potential clinical relevance.

3-D imaging mass spectrometry of protein distributions in mouse Neurofibromatosis 1 (NF1)-associated optic glioma

Neurofibromatosis type 1 (NF1) is a common neurogenetic disorder, in which affected individuals develop tumors of the nervous system. Children with NF1 are particularly prone to brain tumors (gliomas) involving the optic pathway that can result in impaired vision. Since tumor formation and expansion requires a cooperative tumor microenvironment, it is important to identify the cellular and acellular components associated with glioma development and growth. In this study, we used 3-D matrix assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) to measure the distributions of multiple molecular species throughout optic nerve tissue in mice with and without glioma, and to explore their spatial relationships within the 3-D volume of the optic nerve and chiasm. 3-D IMS studies often involve extensive workflows due to the high volume of sections required to generate high quality 3-D images. Herein, we present a workflow for 3-D data acquisition and volume reconstruction using mouse optic nerve tissue. The resulting 3-D IMS data yield both molecular similarities and differences between glioma-bearing and wild-type (WT) tissues, including protein distributions localizing to different anatomical subregions.

BIOLOGICAL SIGNIFICANCE

The current work addresses a number of challenges in 3-D MALDI IMS, driven by the small size of the mouse optic nerve and the need to maintain consistency across multiple 2-D IMS experiments. The 3-D IMS data yield both molecular similarities and differences between glioma-bearing and wild-type (WT) tissues, including protein distributions localizing to different anatomical subregions, which could then be targeted for identification and related back to the biology observed in gliomas of the optic nerve.

The expression and roles of Nde1 and Ndel1 in the adult mammalian central nervous system

Mental and neurological illnesses affect one in four people. While genetic linkage analyses have shown an association of nuclear distribution factor E (NDE1, or NudE) and its ohnolog NDE-like 1 (NDEL1, or Nudel) with mental disorders, the cellular mechanisms remain unclear. In the present study, we have demonstrated that Nde1 and Ndel1 are differentially localised in the subventricular zone (SVZ) of the forebrain and the subgranular zone (SGZ) of the hippocampus, two regions where neurogenesis actively occurs in the adult brain. Nde1, but not Ndel1, is localized to putative SVZ stem cells, and to actively dividing progenitors of the SGZ. The influence of these proteins on neural stem cell differentiation was investigated by overexpression in a hippocampal neural stem cell line, HCN-A94. Increasing Nde1 expression in this neural stem cell line led to increased neuronal differentiation while decreasing levels of astroglial differentiation. In primary cultured neurons and astrocytes, Nde1 and Ndel1 were found to have different but comparable subcellular localizations. In addition, we have shown for the first time that Nde1 is heterogeneously distributed in cortical astrocytes of human brains. Our data indicate that Nde1 and Ndel1 have distinct but overlapping distribution patterns in mouse brain and cultured nerve cells. They may function differently and therefore their dosage changes may contribute to some aspects of mental disorders.

JNK-interacting protein 3 mediates the retrograde transport of activated c-Jun N-terminal kinase and lysosomes

Retrograde axonal transport requires an intricate interaction between the dynein motor and its cargo. What mediates this interaction is largely unknown. Using forward genetics and a novel in vivo imaging approach, we identified JNK-interacting protein 3 (Jip3) as a direct mediator of dynein-based retrograde transport of activated (phosphorylated) c-Jun N-terminal Kinase (JNK) and lysosomes. Zebrafish jip3 mutants (jip3^nl7) displayed large axon terminal swellings that contained high levels of activated JNK and lysosomes, but not other retrograde cargos such as late endosomes and autophagosomes. Using in vivo analysis of axonal transport, we demonstrated that the terminal accumulations of activated JNK and lysosomes were due to a decreased frequency of retrograde movement of these cargos in jip3^nl7, whereas anterograde transport was largely unaffected. Through rescue experiments with Jip3 engineered to lack the JNK binding domain and exogenous expression of constitutively active JNK, we further showed that loss of Jip3–JNK interaction underlies deficits in pJNK retrograde transport, which subsequently caused axon terminal swellings but not lysosome accumulation. Lysosome accumulation, rather, resulted from loss of lysosome association with dynein light intermediate chain (dynein accessory protein) in jip3^nl7, as demonstrated by our co-transport analyses. Thus, our results demonstrate that Jip3 is necessary for the retrograde transport of two distinct cargos, active JNK and lysosomes. Furthermore, our data provide strong evidence that Jip3 in fact serves as an adapter protein linking these cargos to dynein.

To form and maintain connections, neurons require the active transport of proteins and organelles between the neuronal cell body and axon terminals. Inhibition of this “axonal” transport has been linked to neurodegenerative diseases. Despite the importance of this process, to date there was no vertebrate model system where axonal transport could be studied in an intact animal. Our study introduces zebrafish as such a model and demonstrates its power for the analysis of axonal transport. We used this system to 1) initiate a genetic screen to find novel mediators of axonal transport; 2) develop in vivo imaging strategies to visualize axonal transport in real time in the intact animal; and 3) discover, using these methods, that JNK interacting protein 3 (Jip3) is required for the transport of two cargos, a kinase and lysosomes, from axon terminals to the cell body (retrograde transport). In the absence of Jip3, these cargos accumulate and axon terminals become dysmorphic, though the retrograde transport of other cargos is normal. Interestingly, abnormal localization of these cargos has been linked to axonal disease states, but our work is the first to identify a specific adapter protein necessary for their transport from axon terminals.

Lissencephaly and band heterotopia: LIS1, TUBA1A, and DCX mutations in Hungary

The spectrum of lissencephaly ranges from absent (agyria) or decreased (pachygyria) convolutions to less severe malformation known as subcortical band heterotopia. Mutations involving LIS1 and TUBA1A result in the classic form of lissencephaly, whereas mutations of the DCX gene cause lissencephaly in males and subcortical band heterotopia in females. This report describes the clinical manifestations and imaging and genetic findings in 2 boys with lissencephaly and a girl with subcortical band heterotopia. An ovel mutation (c.83_84delAT, p.Tyr28Phefs*31) was identified in LIS1 in 1 of the boys with lissencephaly and another novel mutation (c.200delG, p.Ile68Leufs*87) was found in DCX in the girl with subcortical band heterotopia. The mutations appeared in the first half of the genes and are predicted to result in truncated proteins. A mutation was found in the TUBA1A gene (c.1205G>A, p.Arg402His) in the other boy. This mutation affects the folding of tubulin heterodimers, changing the interactions with proteins that bind microtubules.

Overexpression of PAFAH1B1 is associated with tumor metastasis and poor survival in non-small cell lung cancer

Our previous array-comparative genomic hybridization study showed that PAFAH1B1 gene locus was amplified in lung cancer patients, suggesting that PAFAH1B1 is a potential oncogene in lung cancer. Here, we investigate the oncogenic mechanisms of PAFAH1B1 in lung cancer. PAFAH1B1 was characterized in cell and animal models of lung cancer by in vitro migration and invasion assays and in vivo metastasis studies. The mRNA and protein expression levels of PAFAH1B1 were further determined and the prognostic effects of PAFAH1B1 overexpression in lung cancer patients were analyzed. Overexpression of PAFAH1B1 enhanced migration and invasion in lung cancer cells, whereas knockdown of PAFAH1B1 decreased cell migration and invasion, and disrupted cell microtubule organization and pericellular poly-fibronectin assemblies. In vivo tumor metastasis assay confirmed that PAFAH1B1 knockdown in lung cancer cells markedly reduced their metastasis capabilities in animals. The frequencies of overexpressed PAFAH1B1 mRNA and protein were 62.4% (63/101) and 57.4% (58/101) in lung cancer patients, respectively. The clinical correlation results showed that overexpression of PAFAH1B1 was significantly associated with late stage (mRNA: P=0.008, protein: P=0.008) and poor survival in lung adenocarcinoma (P=0.020) and male patients (P=0.049). Our results provide the first evidence that PAFAH1B1 overexpression contributes to lung tumorigenesis and poor prognosis. These effects are partly mediated through disruption of microtubule network and pericellular poly-fibronectin assembly to promote migration and invasiveness of lung cancer cells.

BMP activated Smad signaling strongly promotes migration and invasion of hepatocellular carcinoma cells

Several of the different bone morphogenetic proteins (BMPs) are involved in development and progression of specific tumors. For hepatocellular carcinoma (HCC) only BMP4 and BMP6 are described to be important for carcinogenesis. However, up to now neither the influence of other BMPs on tumor progression, nor the responsible signaling pathways to mediate target gene expression in HCC are known. In order to characterize BMP expression pattern in HCC cell lines, we performed RT-PCR analysis and revealed enhanced expression levels of several BMPs (BMP4, 6, 7, 8, 9, 10, 11, 13 and 15) in HCC. Thus, we treated HCC cells with the general BMP inhibitors chordin and noggin to determine the functional relevance of BMP overexpression and observed decreased migration and invasion of HCC cells. A cDNA microarray of noggin treated HCC cells was performed to analyze downstream targets of BMPs mediating these oncogenic functions. Subsequent analysis identified collagen XVI as 'Smad signaling specific' and nidogen-2 as 'MAPK/ERK signaling specific' BMP-target genes. To examine which signaling pathway is mainly responsible for the oncogenic role of BMPs in HCC, we treated HCC cells with dorsomorphin to determine the influence of BMP activated Smad signaling. Interestingly, also migratory and invasive behavior of dorsomorphin treated HCC cells was diminished. In summary, our findings demonstrate enhanced expression levels of several BMPs in HCC supporting enhanced migratory and invasive phenotype of HCC cells mainly via activation of Smad signaling.

Ndel1, Nudel (Noodle): flexible in the cell?

Nuclear distribution element-like 1 (Ndel1 or Nudel) was firstly described as a regulator of the cytoskeleton in microtubule and intermediate filament dynamics and microtubule-based transport. Emerging evidence indicates that Ndel1 also serves as a docking platform for signaling proteins and modulates enzymatic activities (kinase, ATPase, oligopeptidase, GTPase). Through these structural and signaling functions, Ndel1 plays a role in diverse cellular processes (e.g., mitosis, neurogenesis, neurite outgrowth, and neuronal migration). Furthermore, Ndel1 is linked to the etiology of various mental illnesses and neurodegenerative disorders. In the present review, we summarize the physiological and pathological functions associated with Ndel1. We further advance the concept that Ndel1 interfaces GTPases-mediated processes (endocytosis, vesicles morphogenesis/signaling) and cytoskeletal dynamics to impact cell signaling and behaviors. This putative mechanism may affect cellular functionalities and may contribute to shed light into the causes of devastating human diseases.

Structural features and chaperone activity of the NudC protein family

The NudC family consists of four conserved proteins with representatives in all eukaryotes. The archetypal nudC gene from Aspergillus nidulans is a member of the nud gene family that is involved in the maintenance of nuclear migration. This family also includes nudF, whose human orthologue, Lis1, codes for a protein essential for brain cortex development. Three paralogues of NudC are known in vertebrates: NudC, NudC-like (NudCL), and NudC-like 2 (NudCL2). The fourth distantly related member of the family, CML66, contains a NudC-like domain. The three principal NudC proteins have no catalytic activity but appear to play as yet poorly defined roles in proliferating and dividing cells. We present crystallographic and NMR studies of the human NudC protein and discuss the results in the context of structures recently deposited by structural genomics centers (i.e., NudCL and mouse NudCL2). All proteins share the same core CS domain characteristic of proteins acting either as cochaperones of Hsp90 or as independent small heat shock proteins. However, while NudC and NudCL dimerize via an N-terminally located coiled coil, the smaller NudCL2 lacks this motif and instead dimerizes as a result of unique domain swapping. We show that NudC and NudCL, but not NudCL2, inhibit the aggregation of several target proteins, consistent with an Hsp90-independent heat shock protein function. Importantly, and in contrast to several previous reports, none of the three proteins is able to form binary complexes with Lis1. The availability of structural information will be of help in further studies on the cellular functions of the NudC family.

Malignant pleural mesothelioma: genome-wide expression patterns reflecting general resistance mechanisms and a proposal of novel targets

Malignant pleural mesothelioma is an asbestos-related multi-resistant tumour with increasing incidence worldwide. Well-characterized snap-frozen normal parietal, visceral pleura and mesothelioma samples were analysed with Affymetrix Human Genome U133 Plus 2.0 GeneChip oligoarray of 38500 genes. We discovered a close relation between gene profile and resistance towards topoisomerase poisons, alkylating agents, antitubulines, antifolates, platinum compounds and radiation therapy. Target genes of chemo- (e.g. TOP2A, BIRC5/Survivin and proteasome) and radiotherapy (e.g. BRCA2, FANCA, FANCD2, CCNB1 and RAD50) were significantly overexpressed. The Fanconi anemia/BRCA2 pathway, responsible for homologous recombination DNA repair appears as a key pathway in both chemo- and radio-resistance of mesothelioma. Leukocyte trans-endothelial migration gene down-regulation could partly explain resistance against immunological therapies. Gene expression features found in other resistant cancer types related to DNA repair and replication are shared by mesothelioma and could represent general features of tumour resistance. Targeted suppression of some of those key genes and pathways combined with chemotherapy or radiation could improve the outcome of mesothelioma therapy. We propose CHEK1, RAD21, FANCD2 and RAN as new co-targets for mesothelioma treatment. The pro-angiogenic AGGF1 mRNA and protein was highly overexpressed in all tumours and may serve as a target for anti-angiogenic treatment. Overexpression of NQO1 may render mesothelioma sensitive to the novel compound beta-Lapachone.

The mammalian NudC-like genes: a family with functions other than regulating nuclear distribution

Nuclear distribution gene C homolog (NudC) is a highly conserved gene. It has been identified in different species from fungi to mammals. The high degree of conservation, in special in the nudC domain, suggests that they are genes with essential functions. Most of the identified genes in the family have been implicated in cell division through the regulation of cytoplasmic dynein. As for mammalian genes, human NUDC has been implicated in the migration and proliferation of tumor cells and has therefore been considered a possible therapeutic target. There is evidence suggesting that mammalian NudC is also implicated in the regulation of the inflammatory response and in thrombopoiesis. The presence of these other functions not related to the interaction with molecular motors agrees with that these genes and their products are larger in size than their microbial orthologous, indicating that they have evolved to convey additional features.

The effects of dynein inhibition on the autophagic pathway in glioma cells

Autophagy has multiple physiological functions, including protein degradation, organelle turnover and the response of cancer cells to chemotherapy. Because autophagy is implicated in a number of diseases, a better understanding of the molecular mechanisms of autophagy is needed for therapeutic purposes, including rational design of drugs. Autophagy is a process that occurs in several steps as follows: formation of phagophores, formation of mature autophagosomes, targeting and trafficking of autophagosomes to lysosomes, formation of autolysosomes by fusion between autophagosomes and lysosomes, and finally, degradation of the autophagic bodies within the lysosomes. It has been suggested that autophagosome formation is driven by molecular motor machineries, and, once formed, autophagosomes need to reach lysosomes, enriched perinuclearly around the microtubule-organizing centre. While it is recognized that all these steps require the cytoskeletal network, little is known about the mechanisms involved. Here we assessed the role of cytoplasmic dynein in the autophagic process of human glioma cells to determine the part played by dynein in autophagy. We observed that chemical interference with dynein function led to an accumulation of autophagosomes, suggesting impaired autophagosome-lysosome fusion. In contrast, we found that overexpression of dynamitin, which disrupts the dynein complex, reduced the number of autophagosomes, suggesting the requirement of the dynein-dynactin interaction in the early membrane trafficking step in autophagosome formation. These results suggest that dynein plays a variety of crucial roles during the autophagic process in glioma cells.

Molecular and cell biology of brain tumor stem cells: lessons from neural progenitor/stem cells

✓ The results of studies conducted in the past several years have suggested that malignant brain tumors may harbor a small fraction of tumor-initiating cells that are likely to cause tumor recurrence. These cells are known as brain tumor stem cells (BTSCs) because of their multilineage potential and their ability to self-renew in vitro and to recapitulate original tumors in vivo. The understanding of BTSCs has been greatly advanced by knowledge of neural progenitor/stem cells (NPSCs), which are multipotent and self-renewing precursor cells for neurons and glia. In this article, the authors summarize evidence that genetic mutations that deregulate asymmetric cell division by affecting cell polarity, spindle orientation, or cell fate determinants may result in the conversion of NPSCs to BTSCs. In addition, they review evidence that BTSCs and normal NPSCs may reside in similar vascularized microenvironments, where similar evolutionarily conserved signaling pathways control their proliferation. Finally, they discuss preliminary evidence that mechanisms of BTSC-associated infiltrativeness may be similar to those underlying the migration of NPSCs and neurons.

Slit2 involvement in glioma cell migration is mediated by Robo1 receptor

Slit and Robo proteins are evolutionarily conserved molecules whose interaction underlies axon guidance and neuronal precursor cell migration. During development secreted Slit proteins mediate chemorepulsive signals on cells expressing Robo receptors. Because similar molecular mechanisms may be utilized in glioma cell invasion and neuroblast migration, we studied the expression of Slit2 and its transmembrane receptor Robo1 as well as their functional role in migration in glioma cells. qRT-PCR and immunohistochemistry of human specimens revealed that Slit2 was distinctly expressed by non-neoplastic neurons, but at only very low levels in fibrillary astrocytoma and glioblastoma. Robo1 also was mainly restricted to neurons in the normal brain, whereas astrocytic tumor cells in situ as well as glioblastoma cell lines overexpressed Robo1 at mRNA and protein levels. Recombinant human Slit2 in a concentration of 0.45 nM was repulsive for glioma cell lines in a modified Boyden chamber assay. RNAi-mediated knockdown of Robo1 in glioma cell lines neutralized the repulsive effect of Slit2, demonstrating that Robo1 served as the major Slit2 receptor. Our findings suggest that a chemorepulsive effect mediated by interaction of Slit2 and Robo1 participates in glioma cell guidance in the brain.