Adolescent intermittent ethanol exposure decreases perineuronal nets in the hippocampus in a sex dependent manner: Modulation through pharmacological inhibition of RPTPβ/ζ

Adolescence is a critical period for brain maturation in which this organ undergoes critical plasticity mechanisms that increase its vulnerability to the effects of alcohol. Significantly, ethanol-induced disruption of hippocampal neurogenesis has been related to cognitive decline in adulthood. During adolescence, the maturation of perineuronal nets (PNNs), extracellular matrix structures highly affected by ethanol consumption, plays a fundamental role in neurogenesis and plasticity in the hippocampus. Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ is a critical anchor point for PNNs on the cell surface. Using the adolescent intermittent access to ethanol (IAE) model, we previously showed that MY10, a small-molecule inhibitor of RPTPβ/ζ, reduces chronic ethanol consumption in adolescent male mice but not in females and prevents IAE-induced neurogenic loss in the male hippocampus. We have now tested if these effects of MY10 are related to sex-dependent modulatory actions on ethanol-induced effects in PNNs. Our findings suggest a complex interplay between alcohol exposure, neural structures, and sex-related differences in the modulation of PNNs and parvalbumin (PV)-positive cells in the hippocampus. In general, IAE increased the number of PV + cells in the female hippocampus and reduced PNNs intensity in different hippocampal regions, particularly in male mice. Notably, we found that pharmacological inhibition of RPTPβ/ζ with MY10 regulates ethanol-induced alterations of PNNs intensity, which correlates with the protection of hippocampal neurogenesis from ethanol neurotoxic effects and may be related to the capacity of MY10 to increase the gene expression of key components of PNNs.

Challenges in the discovery of tumor-specific alternative splicing-derived cell-surface antigens in glioma

Despite advancements in cancer immunotherapy, solid tumors remain formidable challenges. In glioma, profound inter- and intra-tumoral heterogeneity of antigen landscape hampers therapeutic development. Therefore, it is critical to consider alternative sources to expand the repertoire of targetable (neo-)antigens and improve therapeutic outcomes. Accumulating evidence suggests that tumor-specific alternative splicing (AS) could be an untapped reservoir of antigens. In this study, we investigated tumor-specific AS events in glioma, focusing on those predicted to generate major histocompatibility complex (MHC)-presentation-independent, cell-surface antigens that could be targeted by antibodies and chimeric antigen receptor-T cells. We systematically analyzed bulk RNA-sequencing datasets comparing 429 tumor samples (from The Cancer Genome Atlas) and 9166 normal tissue samples (from the Genotype-Tissue Expression project), and identified 13 AS events in 7 genes predicted to be expressed in more than 10% of the patients, including PTPRZ1 and BCAN, which were corroborated by an external RNA-sequencing dataset. Subsequently, we validated our predictions and elucidated the complexity of the isoforms using full-length transcript amplicon sequencing on patient-derived glioblastoma cells. However, analyses of the RNA-sequencing datasets of spatially mapped and longitudinally collected clinical tumor samples unveiled remarkable spatiotemporal heterogeneity of the candidate AS events. Furthermore, proteomics analysis did not reveal any peptide spectra matching the putative antigens. Our investigation illustrated the diverse characteristics of the tumor-specific AS events and the challenges of antigen exploration due to their notable spatiotemporal heterogeneity and elusive nature at the protein levels. Redirecting future efforts toward intracellular, MHC-presented antigens could offer a more viable avenue.

Clear-cell papillary renal cell tumour: New insights into clinicopathological features and molecular landscape after renaming by 5th WHO classification

OBJECTIVE

Clear cell papillary renal cell tumour (CCPRCT) is a kind of renal epithelial cell tumor, and was renamed by the 5th WHO due to its specific epidemiology and clinicopathological characteristics. However, the biological mechanism and molecular basis of CCPRCT still need to be further clarified. This study aims to comprehensively evaluate clinicopathologic and molecular characteristics of CCPRCC, and particularly compare it with other more prevalent subtypes of renal cell carcinoma.

METHODS

12 cases of CCPRCT were collected for analyzing the clinicopathological characteristics. Then, whole-exome sequencing (WES) was employed to reveal the genetic profiles, followed by comparison with the molecular genetic alterations identified in ccRCC (341) and pRCC (200) datasets obtained from the TCGA database.

RESULTS

Of the 12 CCPRCT cases, the male-to-female ratio was 4:1 with a mean age of 49.5 years (48.5 ± 10.5) at diagnosis. All patients were diagnosed accidentally during routine physical examinations. All tumors (12/12, 100%）had a solid-cystic appearance with a well-defined fibrous capsule. The median size of the tumors was 3 cm (2.98 ± 1.2). Histologically, the cystic papillary structures were considered to be prominent, lined with cuboidal tumor cells away from basement membrane. The tumor cells were moderately atypia equivalent to grade 1 or grade 2 according to the ISUP nuclear grading system. Typically, the tumor cell diffusely positive for CK7 and CAIX in a "cup-like" pattern. The results of WES revealed recurrent gene alterations (mainly missense mutation) of TTN and FLT in 4 cases (4/12, 33.3%), respectively, of which, the alteration of FLT was not observed in ccRCC and pRCC of the TCGA database. Other gene alterations including POTEC (1 cases), PRADC1 (1 cases), ZZZ3 (1 case) and PTPRZ1 (1 case), etc. Moreover, all of the CCPRCT cases displayed a lower tumor mutation burden (TMB) compared to ccRCC and pRCC with median TMB of 1.04 (range: 1.94 ± 2.74). None of the patients experienced tumor metastasis, recurrence, or tumor-related deaths.

CONCLUSION

CCPRCT is a renal epithelial cell tumor characterized by specific clinical and pathological features. Our study provides additional evidence supporting the favorable prognosis of CCPRCT. Furthermore, the potential molecular alterations were uncovered by this study in CCPRCT such as the FLT family and TTN. However, due to the limited sample size, larger studies are required to validate these findings.

[Effect of Naotaifang on microglial polarization and glial scar following cerebral ischemia reperfusion injury]

This study aims to investigate the effect of Naotaifang(NTF) on the proteins associated with microglial polarization and glial scar in the rat model of cerebral ischemia reperfusion injury(CIRI). The CIRI model was established by middle cerebral artery occlusion/reperfusion. The 48 successfully modeled rats were randomized into model 7 d, model 14 d, NTF 7 d, and NTF 14 d groups(n=12). In addition, 12 SD rats were selected as the sham group. The NTF group was administrated with NTF suspension at 27 g·kg~(-1)·d~(-1) by gavage, and the sham, model 7 d, and model 14 d groups were administrated with the same volume of normal saline every day by gavage for 7 and 14 days, respectively. After the intervention, Longa score was evaluated. The infarct volume was measured by 2,3,5-triphenyl-2H-tetrazolium chloride(TTC) staining. Morris water maze and open field tests were carried out to evaluate the spatial learning, memory, cognitive function, and anxiety degree of rats. Hematoxylin-eosin(HE) staining was employed to observe the morphological structure and damage of the brain tissue. The immunofluorescence assay was employed to measure the expression of glial fibrillary acidic protein(GFAP) and glial scar. Western blot was employed to determine the protein levels of GFAP, neurocan, phosphacan, CD206, arginase-1(Arg-1), interleukin(IL)-1β, IL-6, and IL-4. Compared with the sham, model 7 d and model 14 d groups showed cerebral infarction of different degrees, severe pathological injury of cerebral cortex and hippocampus, neurological impairment, reduced spatial learning and memory, cognitive dysfunction, severe anxiety, astrocyte hyperplasia, thickening penumbra glial scar, and up-regulated protein levels of IL-1β, IL-6, GFAP, neurocan, phosphacan, CD206, and Arg-1(P<0.01). Compared with the model group, NTF 7 d and NTF 14 d groups improved spatial learning, memory, and cognitive function, reduced anxiety, improved nerve function, reduced cerebral infarction volume, reduced astrocyte hyperplasia, thinned penumbra glial scar, down-regulated the protein levels of GFAP, neurocan, phosphacan, IL-6, and IL-1β, and up-regulated the protein levels of IL-4, CD206, and Arg-1(P<0.05 or P<0.01). NTF exerts a neuroprotective effect on CIRI by inducing the M2 polarization of microglia, inhibiting inflammatory response, and reducing the formation of glial scar.

MYEF2: an immune infiltration-related prognostic factor in IDH-wild-type glioblastoma

Glioblastoma (GBM) is the most malignant and prevalent primary brain tumor. In this study, weighted gene coexpression network analysis (WGCNA) was performed to analyze RNA binding protein (RBP) expression data from The Cancer Genome Atlas (TCGA) for the IDH-wild type GBM cohort. The CIBERSORT algorithm quantified the cellular composition of immune cells and was used to identify key modules associated with CD8+ T cell infiltration. Coexpression networks analysis and protein-protein interaction (PPI) network analysis was used to filter out central RBP genes. Eleven RBP genes, including MYEF2, MAPT, NOVA1, MAP2, TUBB2B, CDH10, TTYH1, PTPRZ1, SOX2, NOVA2 and SCG3, were identified as candidate CD8+ T cell infiltration-associated central genes. A Cox proportional hazards regression model and Kaplan-Meier analysis were applied to identify candidate biomarkers. MYEF2 was selected as a prognostic biomarker based on the results of prognostic analysis. Flow Cytometric Analysis indicated that MYEF2 expression was negatively correlated with dysfunctional CD8+ T cell markers. Kaplan-Meier survival analysis (based on IHC staining) revealed that GBM patients with elevated MYEF2 expression have a better prognosis. Knockdown of MYEF2 in GBM cells via in vitro assays was observed to promote cell proliferation and migration. Our study suggests that MYEF2 expression negatively correlates with T cell exhaustion and tumor progression, rendering it a potentially valuable prognostic biomarker for GBM.

Identification of Neurocan and Phosphacan as Early Biomarkers for Open Neural Tube Defects

Open neural tube defects (NTDs) such as myelomeningocele (MMC) are debilitating and the most common congenital defects of the central nervous system. Despite their apparent clinical importance, the existing early prenatal diagnostic options for these defects remain limited. Using a well-accepted retinoic-acid-induced model of MMC established in fetal rats, we discovered that neurocan and phosphacan, the secreted chondroitin sulfate proteoglycans of the developing nervous system, are released into the amniotic fluid (AF) of fetal rats displaying spinal cord defects. In contrast to normal controls, elevated AF levels of neurocan and phosphacan were detected in MMC fetuses early in gestation and continued to increase during MMC progression, reaching the highest level in near-term fetuses. The molecular forms of neurocan and phosphacan identified in the AF of MMC fetuses and those found in MMC spinal cords were qualitatively similar. In summary, this is the first report demonstrating the presence of neurocan and phosphacan in the AF of MMC fetuses. The identification of elevated levels of neurocan and phosphacan in the AF of MMC fetuses provides two prospective biomarkers with the potential for early prenatal diagnosis of open NTDs.

Inhibition of RPTPβ/ζ reduces chronic ethanol intake in adolescent mice and modulates ethanol effects on hippocampal neurogenesis and glial responses in a sex-dependent manner

Pleiotrophin (PTN) is a cytokine that modulates ethanol drinking and reward and regulates glial responses in different contexts. PTN is an inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ. Inhibition of RPTPβ/ζ reduces binge-like drinking in adult male mice. Whether inhibition of RPTPβ/ζ is effective in reducing ethanol consumption during adolescence and in both sexes remained to be studied. In this work, male and female adolescent mice underwent an intermittent access to ethanol (IAE) 2-bottle choice protocol. Treatment with MY10 (60 mg/kg, i.g.), a small-molecule RPTPβ/ζ inhibitor, reduced chronic 3-week ethanol consumption only in male mice. We detected an ethanol-induced overall decrease in hippocampal GFAPir and Iba1ir, independently of the treatment received, suggesting that RPTPβ/ζ is not key in the regulation of IAE-induced glial responses. However, we found a significant negative correlation between the size of microglial cells and the number of hippocampal neuronal progenitors only in male mice after IAE. This correlation was disrupted by treatment with MY10 before each drinking session, which may be related to the ability of MY10 to regulate the intensity of the perineuronal nets (PNNs) in the hippocampus in a sex-dependent manner. The data show for the first time that inhibition of RPTPβ/ζ reduces chronic voluntary ethanol consumption in adolescent mice in a sex-dependent manner. In addition, we show evidence for sex-specific differences in the effects of IAE on glial responses and hippocampal neurogenesis, which may be related to different actions of the RPTPβ/ζ signalling pathway in the brains of male and female mice.

Anxiety symptom remission is associated with genetic variation of PTPRZ1 among patients with major depressive disorder treated with escitalopram

OBJECTIVES

Genome-wide analyses of antidepressant response have suggested that genes initially associated with risk for schizophrenia may also serve as promising candidates for selective serotonin reuptake inhibitor (SSRI) efficacy. Protein tyrosine phosphatase, receptor-type, zeta-1 (PTPRZ1) has previously been shown to be associated with schizophrenia, but it has not been investigated as a predictor of antidepressant efficacy. The main objective of the study was to assess whether SSRI-mediated depressive and anxiety symptom remission in Chinese patients with major depressive disorder (MDD) are associated with specific PTPRZ1 variants.

METHODS

Two independent cohorts were investigated, the first sample (N = 344) received an SSRI (i.e. fluoxetine, sertraline, citalopram, escitalopram, fluvoxamine, or paroxetine) for 8 weeks. The second sample (N = 160) only received escitalopram for 8 weeks. Hamilton Depression and Hamilton Anxiety Rating Scale scores at 8-weeks post-baseline in both cohorts were used to determine remission status. Five PTPRZ1 variants (rs12154537, rs6466810, rs6466808, rs6955395, and rs1918031) were genotyped in both cohorts.

RESULTS

Anxiety symptom remission was robustly associated with PTPRZ1 rs12154537 (P = 0.004) and the G-G-G-G haplotype (rs12154537-rs6466810-rs6466808-rs6955395; P = 0.005) in cohort 2 but not cohort 1 (mixed SSRI use). Associations with depressive symptom remission did not survive correction for multiple testing.

CONCLUSIONS

These findings suggest that PTPRZ1 variants may serve as a marker of escitalopram-mediated anxiety symptom remission in MDD.

Co-expression of cancer driver genes: IDH-wildtype glioblastoma-derived tumorspheres

BACKGROUND

Driver genes of GBM may be crucial for the onset of isocitrate dehydrogenase (IDH)-wildtype (WT) glioblastoma (GBM). However, it is still unknown whether the genes are expressed in the identical cluster of cells. Here, we have examined the gene expression patterns of GBM tissues and patient-derived tumorspheres (TSs) and aimed to find a progression-related gene.

METHODS

We retrospectively collected primary IDH-WT GBM tissue samples (n = 58) and tumor-free cortical tissue samples (control, n = 20). TSs are isolated from the IDH-WT GBM tissue with B27 neurobasal medium. Associations among the driver genes were explored in the bulk tissue, bulk cell, and a single cell RNAsequencing techniques (scRNAseq) considering the alteration status of TP53, PTEN, EGFR, and TERT promoter as well as MGMT promoter methylation. Transcriptomic perturbation by temozolomide (TMZ) was examined in the two TSs.

RESULTS

We comprehensively compared the gene expression of the known driver genes as well as MGMT, PTPRZ1, or IDH1. Bulk RNAseq databases of the primary GBM tissue revealed a significant association between TERT and TP53 (p < 0.001, R = 0.28) and its association increased in the recurrent tumor (p  < 0.001, R = 0.86). TSs reflected the tissue-level patterns of association between the two genes (p < 0.01, R = 0.59, n = 20). A scRNAseq data of a TS revealed the TERT and TP53 expressing cells are in a same single cell cluster. The driver-enriched cluster dominantly expressed the glioma-associated long noncoding RNAs. Most of the driver-associated genes were downregulated after TMZ except IGFBP5.

CONCLUSIONS

GBM tissue level expression patterns of EGFR, TERT, PTEN, IDH1, PTPRZ1, and MGMT are observed in the GBM TSs. The driver gene-associated cluster of the GBM single cells were enriched with the glioma-associated long noncoding RNAs.

Synergistic inactivation of AXL: a (cross)road to cure ovarian cancer?

Inhibition of the receptor tyrosine kinase AXL, a key molecular driver of ovarian cancer, has recently been highlighted as promising therapeutic strategy. In this issue of EMBO Reports , Antony et al 1 have identified a novel mechanism of inhibition of AXL, wherein the GPI‐anchored tumour suppressor OPCML sequesters AXL into specialised plasma membrane domains where the phosphatase PTPRG is located, therefore facilitating AXL dephosphorylation. This attenuation of AXL signalling has translational implications for the design of synergistic therapies, to target the kinase for this aggressive malignancy.

Anaplastic lymphoma kinase is activated through the pleiotrophin/receptor protein-tyrosine phosphatase beta/zeta signaling pathway: an alternative mechanism of receptor tyrosine kinase activation

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) first discovered as the constitutively active nucleophosmin-ALK oncoprotein in anaplastic large cell lymphomas (ALCL). Full-length ALK has a critical role in normal development and differentiation. Activated full-length ALK also is found in different malignant cancers. Nevertheless, the ligand to activate ALK remained unknown until recently, when ALK was proposed to be the physiological receptor of the cytokine pleiotrophin (PTN, Ptn). However, earlier studies had demonstrated that receptor protein tyrosine phosphatase (RPTP) beta/zeta is a physiological PTN receptor. We now demonstrate that phosphorylation of ALK in PTN-stimulated cells is mediated through the PTN/RPTPbeta/zeta signaling pathway. ALK is phosphorylated independently of a direct interaction of PTN with ALK. The data thus support a unique model of ALK activation. In cells not stimulated by PTN, RPTPbeta/zeta dephosphorylates ALK at the site(s) in ALK that is undergoing autophosphorylation through autoactivation. In contrast, when RPTPbeta/zeta is inactivated in PTN-stimulated cells, the sites that are autophosphorylated in ALK no longer can be dephosphorylated by RPTPbeta/zeta; thus, autoactivation and tyrosine phosphorylation of ALK rapidly increase. The data indicate that the PTN/RPTPbeta/zeta signaling pathway is a critical regulator of the steady state levels of tyrosine phosphorylation and activation of ALK; the data support the conclusion that ALK phosphorylation and activation in PTN-stimulated cells are increased through a unique "alternative mechanism of RTK activation."

Brevican and phosphacan expression and localization following transient middle cerebral artery occlusion in the rat

The ECM (extracellular matrix) is a complex molecular framework that provides physical support to cells and tissues, while also providing signals for cell growth, migration, differentiation and survival. The ECM of the CNS (central nervous system) is unusual in that it is rich in CSPGs (chondroitin sulfate proteoglycans), hyaluronan and tenascins. The CSPGs are widely expressed throughout the developing and adult CNS and have a role in guiding or limiting neurite outgrowth and cell migration. Alterations in the synthesis or breakdown of the ECM may contribute to disease processes. Here, we examine changes in the brain-specific CSPGs, brevican and phosphacan, following transient middle cerebral artery occlusion, a model of stroke in the rat. We have investigated their expression at various time points as well as their spatial relationship with ADAMTS-4 (adisintegrin and metalloprotease with thrombospondin motifs 4). The co-localization of ADAMTS or its activity may indicate a functional role for this matrix–protease pair in degeneration/regeneration processes that occur in stroke.

The receptor protein tyrosine phosphatase (RPTP)beta/zeta is expressed in different subtypes of human breast cancer

Increasing evidence suggests mutations in human breast cancer cells that induce inappropriate expression of the 18-kDa cytokine pleiotrophin (PTN, Ptn) initiate progression of breast cancers to a more malignant phenotype. Pleiotrophin signals through inactivating its receptor, the receptor protein tyrosine phosphatase (RPTP)beta/zeta, leading to increased tyrosine phosphorylation of different substrate proteins of RPTPbeta/zeta, including beta-catenin, beta-adducin, Fyn, GIT1/Cat-1, and P190RhoGAP. PTN signaling thus has wide impact on different important cellular systems. Recently, PTN was found to activate anaplastic lymphoma kinase (ALK) through the PTN/RPTPbeta/zeta signaling pathway; this discovery potentially is very important, since constitutive ALK activity of nucleophosmin (NPM)-ALK fusion protein is causative of anaplastic large cell lymphomas, and, activated ALK is found in other malignant cancers. Recently ALK was identified in each of 63 human breast cancers from 22 subjects. We now demonstrate that RPTPbeta/zeta is expressed in each of these same 63 human breast cancers that previously were found to express ALK and in 10 additional samples of human breast cancer. RPTPbeta/zeta furthermore was localized not only in its normal association with the cell membrane but also scattered in cytoplasm and in nuclei in different breast cancer cells and, in the case of infiltrating ductal carcinomas, the distribution of RPTPbeta/zeta changes as the breast cancer become more malignant. The data suggest that the PTN/RPTPbeta/zeta signaling pathway may be constitutively activated and potentially function to constitutively activate ALK in human breast cancer.

Expression of transmembrane protein tyrosine phosphatase gamma (PTPgamma) in normal and neoplastic human tissues

AIMS

To establish the conditions for protein tyrosine phosphatase gamma (PTPgamma) detection in paraffin tissues using two antibodies raised against its NH(2)- (anti-P4) and COOH-termini (gammaTL1); to analyse its expression in normal tissues and to perform an initial screening of neoplastic tissues.

METHODS AND RESULTS

Membranous and/or cytoplasmic PTPgamma expression was detected in the majority of epithelial cell types and in endocrine cells, with the highest expression in adrenal medulla, endocrine cells of the gastrointestinal tract and pancreatic islets. Both antibodies stained the thyroid follicular epithelium, but only anti-P4 antibody stained the colloid matrix, suggesting shedding/secretion of the PTPgamma extracellular domain. Marked loss of PTPgamma immunoreactivity was detected in subsets of ovarian (21%), breast (56%) and lung (80%) neoplasms. Conversely, cytoplasmic positivity was found in 37% of lymphomas, mainly of high-grade histotypes, while normal lymphocytes were negative. Brain tissue showed PTPgamma expression in a few neuronal and glial elements and PTPgamma was overexpressed in the majority of high-grade astrocytomas.

CONCLUSIONS

We have analysed PTPgamma expression in archival paraffin-embedded tissues for the first time, demonstrating particularly high expression in endocrine cells and both down- and up-regulation in neoplasia, the latter possibly reflecting the undifferentiated state of the neoplastic cells, suggesting a complex role for this phosphatase.

Anaplastic lymphoma kinase is expressed in different subtypes of human breast cancer

Pleiotrophin (PTN, Ptn) is an 18kDa cytokine expressed in human breast cancers. Since inappropriate expression of Ptn stimulates progression of breast cancer in transgenic mice and a dominant negative PTN reverses the transformed phenotype of human breast cancer cells that inappropriately express Ptn, it is suggested that constitutive PTN signaling in breast cancer cells that inappropriately express Ptn activates pathways that promote a more aggressive breast cancer phenotype. Pleiotrophin signals by inactivating its receptor, the receptor protein tyrosine phosphatase (RPTP)beta/zeta, and, recently, PTN was found to activate anaplastic lymphoma kinase (ALK) through the PTN/RPTPbeta/zeta signaling pathway in PTN-stimulated cells, not through a direct interaction of PTN with ALK and thus not through the PTN-enforced dimerization of ALK. Since full-length ALK is activated in different malignant cancers and activated ALK is a potent oncogenic protein, we examined human breast cancers to test the possibility that ALK may be expressed in breast cancers and potentially activated through the PTN/RPTPbeta/zeta signaling pathway; we now demonstrate that ALK is strongly expressed in different histological subtypes of human breast cancer; furthermore, ALK is expressed in both nuclei and cytoplasm and, in the ;;dotted" pattern characteristic of ALK fusion proteins in anaplastic large cell lymphoma. This study thus supports the possibility that activated ALK may be important in human breast cancers and potentially activated either through the PTN/RPTPbeta/zeta signaling pathway, or, alternatively, as an activated fusion protein to stimulate progression of breast cancer in humans.

DSD-1-Proteoglycan/Phosphacan and Receptor Protein Tyrosine Phosphatase-Beta Isoforms during Development and Regeneration of Neural Tissues

Interactions between neurons and glial cells play important roles in regulating key events of development and regeneration of the CNS. Thus, migrating neurons are partly guided by radial glia to their target, and glial scaffolds direct the growth and directional choice of advancing axons, e.g., at the midline. In the adult, reactive astrocytes and myelin components play a pivotal role in the inhibition of regeneration. The past years have shown that astrocytic functions are mediated on the molecular level by extracellular matrix components, which include various glycoproteins and proteoglycans. One important, developmentally regulated chondroitin sulfate proteoglycan is DSD-1-PG/phosphacan, a glial derived proteoglycan which represents a splice variant of the receptor protein tyrosine phosphatase (RPTP)-beta (also known as PTP-zeta). Current evidence suggests that this proteoglycan influences axon growth in development and regeneration, displaying inhibitory or stimulatory effects dependent on the mode of presentation, and the neuronal lineage. These effects seem to be mediated by neuronal receptors of the Ig-CAM superfamily.

Pleiotrophin disrupts calcium-dependent homophilic cell-cell adhesion and initiates an epithelial-mesenchymal transition

Regulation of the levels of tyrosine phosphorylation is essential to maintain the functions of proteins in different signaling pathways and other cellular systems, but how the steady-state levels of tyrosine phosphorylation are coordinated in different cellular systems to initiate complex cellular functions remains a formidable challenge. The receptor protein tyrosine phosphatase (RPTP)beta/zeta is a transmembrane tyrosine phosphatase whose substrates include proteins important in intracellular and transmembrane protein-signaling pathways, cytoskeletal structure, cell-cell adhesion, endocytosis, and chromatin remodeling. Pleiotrophin (PTN the protein and Ptn the gene) is a ligand for RPTPbeta/zeta; PTN inactivates RPTPbeta/zeta, leaving unchecked the continued endogenous activity of tyrosine kinases that increase phosphorylation of the substrates of RPTPbeta/zeta at sites dephosphorylated by RPTPbeta/zeta in cells not stimulated by PTN. Thus, through the regulation of the tyrosine phosphatase activity of RPTPbeta/zeta, the PTN/RPTPbeta/zeta signaling pathway coordinately regulates the levels of tyrosine phosphorylation of proteins in many cellular systems. We now demonstrate that PTN disrupts cytoskeletal protein complexes, ablates calcium-dependent homophilic cell-cell adhesion, stimulates ubiquitination and degradation of N-cadherin, reorganizes the actin cytoskeleton, and induces a morphological epithelial-mesenchymal transition (EMT) in PTN-stimulated U373 cells. The data suggest that increased tyrosine phosphorylation of the different substrates of RPTPbeta/zeta in PTN-stimulated cells alone is sufficient to coordinately stimulate the different functions needed for an EMT; it is possible that PTN initiates an EMT in cells at sites where PTN is expressed in development and in malignant cells that inappropriately express Ptn.

Clustering of Helicobacter pylori VacA in lipid rafts, mediated by its receptor, receptor-like protein tyrosine phosphatase beta, is required for intoxication in AZ-521 Cells

Helicobacter pylori vacuolating cytotoxin, VacA, induces multiple effects on epithelial cells through different cellular events: one involves pore formation, leading to vacuolation, mitochondrial damage, and apoptosis, and the second involves cell signaling, resulting in stimulation of proinflammatory responses and cell detachment. Our recent data demonstrated that VacA uses receptor-like protein tyrosine phosphatase beta (RPTPbeta) as a receptor, of which five residues (QTTQP) at positions 747 to 751 are involved in binding. In AZ-521 cells, which mainly express RPTPbeta, VacA, after binding to RPTPbeta in non-lipid raft microdomains on the cell surface, is localized with RPTPbeta in lipid rafts in a temperature- and VacA concentration-dependent process. Methyl-beta-cyclodextrin (MCD) did not block binding to RPTPbeta but inhibited translocation of VacA with RPTPbeta to lipid rafts and all subsequent events. On the other hand, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), which disrupts anion channels, did not inhibit translocation of VacA to lipid rafts or VacA-induced activation of p38 mitogen-activated protein (MAP) kinase, but inhibited VacA internalization followed by vacuolation. Thus, p38 MAP kinase activation did not appear to be required for internalization. In contrast, phosphatidylinositol-specific phospholipase C (PI-PLC) inhibited translocation, as well as p38 MAP kinase/ATF-2 activation, internalization, and VacA-induced vacuolation. Neither NPPB nor PI-PLC affected VacA binding to cells and to its receptor, RPTPbeta. Thus, receptor-dependent translocation of VacA to lipid rafts is critical for signaling pathways leading to p38 MAP kinase/ATF-2 activation and vacuolation.

Monoclonal antibody Cat-315 detects a glycoform of receptor protein tyrosine phosphatase beta/phosphacan early in CNS development that localizes to extrasynaptic sites prior to synapse formation

Perineuronal nets (PNs) are lattice-like condensations of the extracellular matrix (ECM) that envelop synapses and decorate the surface of subsets of neurons in the CNS. Previous work has suggested that, despite the fact that PNs themselves are not visualized until later in development, some PN component molecules are expressed in the rodent CNS even before synaptogenesis. In the adult mammalian brain, monoclonal antibody Cat-315 recognizes a glycoform of aggrecan, a major component of PNs. In primary cortical cultures, a Cat-315-reactive chondroitin sulfate proteoglycan (CSPG) is also expressed on neuronal surfaces and is secreted into culture media as early as 24 h after plating. In this study, we show that in primary cortical cultures, the Cat-315 CSPG detected in early neural development is expressed in extrasynaptic sites prior to synapse formation. This suggests that ECM components in the CNS, as in the neuromuscular junction (NMJ), may prepattern neuronal surfaces prior to innervation. We further show that while the Cat-315-reactive carbohydrate decorates aggrecan in the adult, it decorates a different CSPG in the developing CNS. Using receptor protein tyrosine phosphatase beta (RPTPbeta/protein tyrosine phosphatase zeta) knock-out mice and immunoprecipitation techniques, we demonstrate here that in the developing rodent brain Cat-315 recognizes RPTPbeta isoforms. Our further examination of the Cat-315 epitope suggests that it is an O-mannose linked epitope in the HNK-1 family. The presence of the Cat-315 reactive carbohydrate on different PN components--RPTPbeta and aggrecan--at different stages of synapse development suggests a potential role for this neuron-specific carbohydrate motif in synaptogenesis.

RNA interference targeting protein tyrosine phosphatase ζ/receptor-type protein tyrosine phosphatase β suppresses glioblastoma growth in vitro and in vivo

The protein tyrosine phosphatase zeta/receptor-type protein tyrosine phosphatase beta (PTPzeta/RPTPbeta) and its ligand pleiotrophin (PTN) are overexpressed in human glioblastomas. Both molecules are involved in neuronal cell migration during CNS development. In addition, PTN can induce glioma cell migration which is at least in part mediated through binding to PTPzeta/RPTPbeta. To study the relevance of this ligand-receptor pair for glioma growth in vitro and in vivo, we transfected the human glioblastoma cell line U251-MG with small interfering RNA (siRNA) directed against PTPzeta/RPTPbeta. Stable siRNA transfection resulted in strong down-regulation of PTPzeta/RPTPbeta expression. When injected subcutaneously into nude mice, clones that expressed normal levels of PTPzeta/RPTPbeta (PTPzeta + clones) formed exponentially growing tumours, whereas tumour growth was almost completely abrogated for clones that expressed reduced PTPzeta/RPTPbeta levels (PTPzeta - clones). Similar results were obtained using an orthotopic intracerebral model. Proliferation of PTPzeta - cells in vitro was significantly reduced compared with that of control clones. Matrix-immobilized PTN stimulated the proliferation of PTPzeta + cells but not of PTPzeta - cells. Haptotactic migration induced by PTN was reduced for PTPzeta - clones compared with control clones. Our findings suggest that antagonization of PTPzeta/RPTPbeta expression can inhibit glioma growth in vivo and may thus represent a potentially promising treatment strategy.

LRRC4 controls in vitro invasion of glioblastoma cells through inhibiting RPTP-zeta expression

LRRC4 (leucine rich repeat containing 4), a novel member of LRP (Leucine-rich repeat protein) superfamily, contains a conserved leucine-rich repeat (LRR) cassette and an immunoglobulin-like (IgC2) domain in its extracellular region. In the present study, we demonstrated that the N and C terminal LRR (LRRNT and LRRCT) are requisite for membrane and cytoplasm location of LRRC4 in Cos7 cells. We also suggested that RPTP-zeta (receptor-type protein tyrosine phosphatase) receptor is relevant to the invasion ability of gliomas cells, and its expression is inhibited by the reexpression of LRRC4. Our observations indicated that LRRC4 may be a negative regulator of the RPTP-zeta receptor, and contribute to suppressing the invasion ability of gliomas cells.

Receptor-type protein tyrosine phosphatase gamma (PTPgamma), a new identifier for myeloid dendritic cells and specialized macrophages

Protein tyrosine phosphatase (PTPgamma) is a receptor-like molecule with a known role in murine hematopoiesis. We analyzed the regulation of PTPgamma expression in the human hematopoietic system, where it was detected in human peripheral blood monocytes and dendritic cells (DCs) of myeloid and plasmacytoid phenotypes. Its expression was maintained during in vitro monocyte differentiation to dendritic cells (moDC) and was further increased after maturation with bacterial lipopolysaccharide (LPS), CD40L, and TNFalpha. But PTPgamma was absent when monocytes from the same donor were induced to differentiate in macrophages. B and T lymphocytes did not express PTPgamma. Rather, PTPgamma mRNA was expressed in primary and secondary lymphoid tissues, and the highest expression was in the spleen. PTPgamma was detected by immunohistochemistry in subsets of myeloid-derived DCs and specialized macrophages (tingible bodies, sinus and alveolar macrophages). Classic macrophages in infective or reactive granulomatous reactions did not express PTPgamma. Increased PTPgamma expression was associated with a decreased ability to induce proliferation and interferon-gamma secretion in T cells by moDCs from patients with advanced pancreatic cancer. Taken together, these results indicate that PTPgamma is a finely regulated protein in DC and macrophage subsets in vitro and in vivo.

Receptor protein tyrosine phosphatase gamma is a marker for pyramidal cells and sensory neurons in the nervous system and is not necessary for normal development

In order to gain insight into the biological role of receptor protein tyrosine phosphatase gamma (RPTPgamma), we have generated RPTPgamma-null mice. RPTPgamma was disrupted by insertion of the beta-galactosidase gene under the control of the RPTPgamma promoter. As the RPTPgamma-null mice did not exhibit any obvious phenotype, we made use of these mice to study RPTPgamma expression and thus shed light on potential biological functions of this phosphatase. Inspection of mouse embryos shows that RPTPgamma is expressed in a variety of tissues during embryogenesis. RPTPgamma is expressed in both embryonic and adult brains. Specifically, we detected RPTPgamma expression in cortical layers II and V and in the stratum pyramidale of the hippocampus, indicating that RPTPgamma is a marker for pyramidal neurons. Mixed primary culture of glial cells showed a lack of expression of RPTPgamma in astrocytes and a low expression of RPTPgamma in oligodendrocytes and in microglia. Interestingly, RPTPgamma expression was detected in all sensory organs, including the ear, nose, tongue, eye, and vibrissa follicles, suggesting a potential role of RPTPgamma in sensory neurons. An initial behavioral analysis showed minor changes in the RPTPgamma-null mice.

Protein tyrosine phosphatase receptor type Z is inactivated by ligand-induced oligomerization

Receptor-type protein tyrosine phosphatases (RPTPs) are considered to transduce extracellular signals across the membrane through changes in their PTP activity, however, our understanding of the regulatory mechanism is still limited. Here, we show that pleiotrophin (PTN), a natural ligand for protein tyrosine phosphatase receptor type Z (Ptprz) (also called PTPzeta/RPTPbeta), inactivates Ptprz through oligomerization and increases the tyrosine phosphorylation of substrates for Ptprz, G protein-coupled receptor kinase-interactor 1 (Git1) and membrane associated guanylate kinase, WW and PDZ domain containing 1 (Magi1). Oligomerization of Ptprz by an artificial dimerizer or polyclonal antibodies against its extracellular region also leads to inactivation, indicating that Ptprz is active in the monomeric form and inactivated by ligand-induced oligomerization.

Design and synthesis of potent, non-peptidic inhibitors of HPTPbeta

The sulfamic acid phosphotyrosine mimetic was coupled with a previously known malonate template to obtain highly selective and potent inhibitors of HPTPbeta. Potentially hydrolyzable malonate ester functionalities were replaced with 1,2,4-oxadiazoles without a significant effect on HPTPbeta potency.

Keratinocyte growth factor (KGF) induces tamoxifen (Tam) resistance in human breast cancer MCF-7 cells

BACKGROUND

Both estrogen receptor-alpha (ER-alpha) and progesterone receptor (PR) are good prognostic factors and indicators of benefit from endocrine therapy in breast cancer patients. The relationship of the ER-alpha and PR status and the difference in clinical benefit from endocrine therapy in breast cancer is currently unclear. It has been suggested that keratinocyte growth factors (KGFs) are important regulatory factors in breast cancer. Our laboratory has demonstrated that KGF can act as an estromedin for the stimulation of breast cancer cell growth. Also, KGF stimulates aromatase activity in primary cultured human breast cells. This enzyme is a key to the conversion of androgens to estrogens. In the present study, ER-alpha, two estrogen-regulated genes, PR and PTPgamma, KGF and their relationship with endocrine resistance in human breast cancer cells were investigated.

MATERIALS AND METHODS

MCF-7 cells were treated with KGF (1, 5, 10, 20 ng/ml), KGF-13 (0.1, 1, 10 microM) or vehicles as control for 24 hours. KGF-13 is a potential receptor-binding pentapeptide constructed using the KGF peptide residues 101-105 (RTVAV) as a template, located within the beta 4--beta 5 loop. Total RNA were isolated and real-time PCR was employed to identify ER-alpha, PR and PTPgamma gene expressions in response to KGF and KGF-13. Western blot analysis was used to verify the levels of ER-alpha and PR protein, whereas immunohistochemical staining was used to detect PTPgamma expression in MCF-7 cells. To determine the response of MCF-7 cells to endocrine therapy, MCF-7 was treated with either 20 ng/ml KGF or 10 microM KGF-13 combined with 1, 3 and 5 microM of 4-hydroxytamoxifen (4OH-Tam). A non-radioactive cell proliferation assay was applied to determine the growth rate of MCF-7 cells. The results of real-time PCR and the cell proliferation assay were analyzed by Student's t-test and p-values of less than 0.05 were considered statistically significant.

RESULTS

Our data showed that KGF significantly suppressed ER-alpha, PR and PTPgamma expression in MCF-7 cells. KGF suppressed ER-alpha, PR and PTPgamma mRNA to a maximal inhibition at 20 ng/ml by 88%, 57% and 61%, respectively. Western blot analysis and immunohistochemical staining confirmed the down-regulation of ER-alpha, PR and PTPgamma by KGF in protein levels. Ten microM KGF-13 also decreased ER-alpha expression. Ten microM KGF-13 significantly decreased ER-alpha, PR and PTPgamma mRNA expressions by 51%, 57% and 67%, respectively. These KGF-13-mediated mRNA down-regulations were also observed in protein levels. In a cell proliferation assay, 4OH-Tam (3, 5 microM) induced MCF-7 cell death. KGF and KGF-13 alone did not stimulate MCF-7 cell growth. KGF significantly disrupted 4OH-Tam cell killing effects by 1.2- and 1.3-fold at 4OH-Tam concentrations of 3 microM and 5 microM, respectively. KGF-13 significantly disrupted 4OH-Tam cell killing effects by 1.2- and 1.7-fold at 4OH-Tam concentrations of 3 microM and 5 microM, respectively.

CONCLUSION

Our results suggested that not only ER-alpha and PR but also PTPgamma could be potential bio-makers for growth factor-induced endocrine resistant in breast cancer. KGF might increase the endocrine resistance via decreasing ER-alpha, PR and PTPgamma as well. Moreover, the functional analysis of KGF-13 implied possible applications of using short receptor-binding peptides derived from intact KGF as breast cancer therapeutic agents. Thus, our experimental data provided evidence of KGF-induced anti-hormone resistance in human breast cancer and suggested novel strategies for breast cancer via interference with KGF signaling.

Composition of perineuronal net extracellular matrix in rat brain: a different disaccharide composition for the net-associated proteoglycans

We developed a method to extract differentially chondroitin sulfate proteoglycans (CSPGs) that are diffusely present in the central nervous system (CNS) matrix and CSPGs that are present in the condensed matrix of perineuronal nets (PNNs). Adult rat brain was sequentially extracted with Tris-buffered saline (TBS), TBS-containing detergent, 1 m NaCl, and 6 m urea. Extracting tissue sections with these buffers showed that the diffuse and membrane-bound CSPGs were extracted in the first three buffers, but PNN-associated CSPGs remained and were only removed by 6 m urea. Most of the CSPGs were extracted to some degree with all the buffers, with neurocan, brevican, aggrecan, and versican particularly associated with the stable urea-extractable PNNs. The CSPGs in stable complexes only extractable in urea buffer are found from postnatal day 7-14 coinciding with PNN formation. Disaccharide composition analysis indicated a different glycosaminoglycan (GAG) composition for PGs strongly associated with extracellular matrix (ECM). For CS/dermatan sulfate (DS)-GAG the content of nonsulfated, 6-O-sulfated, 2,6-O-disulfated, and 4,6-O-disulfated disaccharides were higher and for heparan sulfate (HS)-GAG, the content of 6-O-sulfated, 2-N-, 6-O-disulfated, 2-O-, 2-N-disulfated, and 2-O-, 2-N-, 6-O-trisulfated disaccharides were higher in urea extract compared with other buffer extracts. Digestions with chondroitinase ABC and hyaluronidase indicated that aggrecan, versican, neurocan, brevican, and phosphacan are retained in PNNs through binding to hyaluronan (HA). A comparison of the brain and spinal cord ECM with respect to CSPGs indicated that the PNNs in both parts of the CNS have the same composition.

Targeting of the receptor protein tyrosine phosphatase beta with a monoclonal antibody delays tumor growth in a glioblastoma model

The receptor protein tyrosine phosphatase beta (RPTPbeta) is a functional biomarker for several solid tumor types. RPTPbeta expression is largely restricted to the central nervous system and overexpressed primarily in astrocytic tumors. RPTPbeta is known to facilitate tumor cell adhesion and migration through interactions with extracellular matrix components and the growth factor pleiotrophin. Here, we show that RPTPbeta is expressed in a variety of solid tumor types with low expression in normal tissue. To assess RPTPbeta as a potential target for treatment of glioblastoma and other cancers, antibodies directed to RPTPbeta have been developed and profiled in vitro and in vivo. The recombinant extracellular domain of human short RPTPbeta was used to immunize mice and generate monoclonal antibodies that selectively recognize RPTPbeta and bind to the antigen with low nanomolar affinities. Moreover, these antibodies recognized the target on living tumor cells as measured by flow cytometry. These antibodies killed glioma cells in vitro when coupled to the cytotoxin saporin either directly or via a secondary antibody. Finally, in vivo studies showed that an anti-RPTPbeta immunotoxin (7E4B11-SAP) could significantly delay human U87 glioma tumors in a mouse xenograft model. Unconjugated 7E4B11 provides a modest but statistically significant tumor growth delay when delivered systemically in mice bearing U87 glioma tumors.

Culture conditions improving the production of jadomycin B

The jadomycins are a unique family of benzoxazolophenanthridine antibiotics produced by Streptomyces venezuelae ISP5230 following heat or ethanol shock or phage infection. We have modified the culture conditions by altering the carbon source, buffer, inoculum size, and timing of ethanol shock, thereby reducing growing times and improving jadomycin B production. Our optimized conditions use glucose as the carbon source, MOPS as buffer, low concentrations of phosphate, a defined inoculum concentration and an immediate ethanol shock to induce jadomycin B production; results that contrast previous studies. The altered media will facilitate the isolation of related jadomycin B congeners.

Protein tyrosine phosphatase receptor type Z is involved in hippocampus-dependent memory formation through dephosphorylation at Y1105 on p190 RhoGAP

Ptprz is a receptor-type protein tyrosine phosphatase predominantly expressed in the brain as a chondroitin sulfate proteoglycan. Ptprz-deficient mice exhibit an age (maturation)-dependent impairment of spatial learning in the Morris water maze test and enhancement of long-term potentiation (LTP) in the CA1 region in hippocampal slices. The enhanced LTP is canceled out by pharmacological inhibition of Rho-associated kinase (ROCK), suggesting that the lack of Ptprz causes learning impairment due to aberrant activation of ROCK. Here, we report that Ptprz-deficient mice exhibit impairments in hippocampus-dependent contextual fear memory because of abnormal tyrosine phosphorylation of p190 RhoGAP, a GTPase-activating protein (GAP) for Rho GTPase. We found that phosphorylation at Y1105, a major tyrosine phosphorylation site on p190 RhoGAP, is decreased 1h after the conditioning in the hippocampus of wild-type mice, but not of Ptprz-deficient mice. Pleiotrophin, a ligand for Ptprz, increased tyrosine phosphorylation of p190 RhoGAP in B103 neuroblastoma cells. Furthermore, Ptprz selectively dephosphorylated pY1105 of p190 RhoGAP in vitro, and the tyrosine phosphorylation at Y1105 controls p190 RhoGAP activity in vivo. These results suggest that Ptprz plays a critical role in memory formation by modulating Rho GTPase activity through dephosphorylation at Y1105 on p190 RhoGAP.

A high throughput messenger RNA differential display screen identifies discrete domains of gene expression and novel patterning processes along the developing neural tube

BACKGROUND

During early development the vertebrate neural tube is broadly organized into the forebrain, midbrain, hindbrain and spinal cord regions. Each of these embryonic zones is patterned by a combination of genetic pathways and the influences of local signaling centres. However, it is clear that much remains to be learned about the complete set of molecular cues that are employed to establish the identity and intrinsic neuronal diversity of these territories. In order to address this, we performed a high-resolution messenger RNA differential display screen to identify molecules whose expression is regionally restricted along the anteroposterior (AP) neuraxis during early chick development, with particular focus on the midbrain and hindbrain vesicles.

RESULTS

This approach identified 44 different genes, with both known and unknown functions, whose transcription is differentially regulated along the AP axis. The identity and ontological classification of these genes is presented. The wide variety of functional classes of transcripts isolated in this screen reflects the diverse spectrum of known influences operating across these embryonic regions. Of these 44 genes, several have been selected for detailed in situ hybridization analysis to validate the screen and accurately define the expression domains. Many of the identified cDNAs showed no identity to the current databases of known or predicted genes or ESTs. Others represent genes whose embryonic expression has not been previously reported. Expression studies confirmed the predictions of the primary differential display data. Moreover, the nature of identified genes, not previously associated with regionalisation of the brain, identifies novel potential mechanisms in that process.

CONCLUSION

This study provides an insight into some of the varied and novel molecular networks that operate during the regionalization of embryonic neural tissue and expands our knowledge of molecular repertoire used during development.

Cytotoxicity and recognition of receptor-like protein tyrosine phosphatases, RPTPalpha and RPTPbeta, by Helicobacter pylori m2VacA

Helicobacter pylori vacuolating cytotoxin, VacA, induces vacuolation in mammalian cell lines. Sequence differences in the middle of VacA molecules define two families, termed m1VacA and m2VacA, which differ in cell specificity. Similar to m1VacA, m2VacA is activated by acid or alkali, which enhances its binding to cells. Immunoprecipitation experiments showed that, in AZ-521 cells, activated m2VacA, similar to m1VacA, binds to two receptor-like protein tyrosine phosphatases, RPTPalpha and RPTPbeta suggesting that activated m2VacA as well as m1VacA may contribute to gastrointestinal disease following H. pylori infection. G401 cells express RPTPalpha, not RPTPbeta, and responded to both m1VacA and m2VacA. HeLa cells likewise expressed RPTPalpha, not RPTPbeta, but, in contrast to other cell lines, responded poorly to m2VacA. m1VacA associated with RPTPalpha of HeLa cells to an extent similar to that in other toxin-sensitive cells, whereas activated m2VacA bound HeLa cell RPTPalpha less well, consistent with its low vacuolating activity against these cells. The molecular mass of RPTPalpha from HeLa cells is less than that of the protein from G401 cells, although their extracellular amino acid sequences are virtually identical, with only two amino acid differences noted. Different post-translational modifications of RPTPalpha in HeLa cells may be responsible for the reduced susceptibility to m2VacA.

The cell-specific phenotype of the polymorphic vacA midregion is independent of the appearance of the cell surface receptor protein tyrosine phosphatase beta

There are two alleles, m1 and m2, of the midregion of the vacuolating cytotoxin gene (vacA) of Helicobacter pylori which code for toxins with different cell specificities. Here we describe the construction of five chimeric strains in which regions of vacA were exchanged between the two genotypes. By analyzing the toxicity of these strains for HeLa and RK13 cells we have confirmed that a 148-amino-acid region determines the phenotypic differences between the two forms of the protein and that this entire region is important for cytotoxicity. Furthermore, we have used our chimeric strains to investigate whether variations in the midregion of VacA have an effect on phorbol 12-myristate 13-acetate (PMA)-induced VacA sensitivity in HL-60 cells. The PMA-induced VacA sensitivity of HL-60 cells has been previously associated with the appearance of the cell surface receptor protein tyrosine phosphatase beta (RPTPbeta). Our data indicate that both the m1 and m2 forms of VacA are able to utilize RPTPbeta, and the cell-specific phenotype of the midregion is independent of the presence of RPTPbeta. It appears that another as-yet-unidentified receptor exists in HL-60 cells that accounts for the m2 phenotype in this cell line. Also, by studying the effect of PMA on levels of RPTPbeta in other cell lines and toxicity of VacA in these cell lines we have shown that RPTPbeta does not play a major role in the vacuolation of HeLa cells.

Conjugated linoleic acid (CLA) up-regulates the estrogen-regulated cancer suppressor gene, protein tyrosine phosphatase gamma (PTPgama), in human breast cells

BACKGROUND

Conjugated linoleic acid (CLA), a naturally occurring compound found in ruminants products, has been shown to possess anticancer properties in vivo and in vitro. There are several CLA isomers in ruminant-produced foods, among which t10, c12-CLA and c9, t11-CLA are the most potent. Protein tyrosine phosphatase gamma (PTPgamma) has been implicated as a tumor suppressor gene in kidney and lung cancers. Our previous results indicated that estradiol-17beta (E2)-induced suppression of PTPgamma may play a role in mammary tumorigenesis.

MATERIALS AND METHODS

The effects of t10, c12-CLA and c9, t11-CLA on PTPgamma mRNA expression in human breast epithelial cells and stromal cells, isolated from surgical specimens of mammoplasty and breast cancer patients, were detected and quantified by RT-PCR RESULTS: The PTPgamma mRNA expression was lower in cancer than in normal breast cells. Both t10, c12-CLA and c9, t11-CLA significantly (p < 0.05) increased the PTPgamma mRNA levels in primary cultured normal breast epithelial cells, normal breast stromal cells and breast cancer epithelial cells, but not in breast cancer stromal cells. t10, c12-CLA appeared to be the most active isomer in estrogen receptor a (ERalpha)-positive human breast cancer epithelial cells.

CONCLUSION

The results indicate that dietary CLA might serve as a chemo-preventive and chemo-therapeutic agent in human breast cancers by up-regulating the estrogen-regulated tumor suppressor gene, PTPgamma expression.

Protein tyrosine-phosphatase expression profiling in gastric cancer tissues

Protein phosphorylation is an important regulatory mechanism involved in signal transduction and cancers. In comparison to the extensive tyrosine-kinase oncogenesis research, there are only relatively few studies of protein tyrosine-phosphatase expression in cancers. The expression profile for tyrosine-phosphatases was investigated in gastric cancers using RT-PCR and molecular cloning. The present study showed a general PTP expression profile in gastric cancer tissues, with the identification of 22 distinct tyrosine-phosphatases. Following the examination of five PTPs (PTPRA, PTPRB, PTPRD, PTPRG and PTPRZ) using immunohistochemistry, strong association was observed between PTPRA/PTPRZ expression and gastric cancer progression including lymphovascular invasion and liver/peritoneal dissemination.

Multiclonal pattern of Jaagsiekte sheep retrovirus integration sites in ovine pulmonary adenocarcinoma

Insertional mutagenesis and envelope (Env)-mediated oncogenesis are hypothesized mechanisms by which Jaagsiekte sheep retrovirus (JSRV) causes ovine pulmonary adenocarcinoma (OPA). Twenty-eight JSRV integration sites in lung tumors (LTs) from four sheep with OPA were cloned and sequenced by a multiple step gene walking technique. Using nested PCR, clonal expansion of these integration sites could be detected, if at all, only in the localized regions of LT from which the integration sites were derived. One sheep had a viral integration site in a sequence with 85 and 81% identity, respectively, over 100 bp to exon 2 of the human and mouse receptor protein tyrosine phosphatase gamma genes. Clonal integration of Jaagsiekte sheep retrovirus in this gene was demonstrated by nested PCR and Southern blot hybridization in the DNA sample from which the integration site was cloned, but not in other LT or kidney DNA samples from the same sheep. OPA may develop from multiple independent oncogenic events and a role for insertional mutagenesis cannot be ruled out.

Synaptic localization of receptor-type protein tyrosine phosphatase zeta/beta in the cerebral and hippocampal neurons of adult rats

Receptor-type protein tyrosine phosphatase (RPTP) zeta/beta is a nervous tissue-specific chondroitin sulfate proteoglycan. In this study, we investigated the immunohistochemical localization of RPTPzeta/beta in adult rat cerebral cortex and hippocampus at light and electron microscopic levels. Double labeling immunofluorescence microscopy revealed that the immunoreactivity of RPTPzeta/beta was observed at MAP2-positive dendrites and PSD-95-positive spines of pyramidal neurons in the cerebral cortex and hippocampus. Electron microscopic observation demonstrated a strong immunoreactivity of RPTPzeta/beta at the postsynaptic membrane of dendritic spines and shafts, and its moderate immunoreactivity at the dendritic membrane. In cultured cortical neurons, the immunoreactivity of RPTPzeta/beta was observed at some of PSD-95-positive spines. These results demonstrate that RPTPzeta/beta is localized mainly at the postsynaptic membrane of pyramidal neurons in adult cerebral cortex and hippocampus.

Chondroitin sulfate proteoglycan phosphacan associates with parallel fibers and modulates axonal extension and fasciculation of cerebellar granule cells

Phosphacan is a nervous system-specific chondroitin sulfate proteoglycan and one of the major components of extracellular matrix in the brain. In the present study, we examined its spatiotemporal expression, ultrastructural localization, binding manner, and in vitro analysis on cell adhesion, axonal extension, and fasciculation in rat cerebellum. The present light microscopic immunohistochemistry showed that phosphacan immunoreactivity was localized mainly at the molecular layer in the cerebellum, but not at the external granular layer. Further double labeling immunohistochemical and immunoelectron microscopic studies revealed that phosphacan was localized around parallel fibers, but not at synapses. The binding of phosphacan to membrane and/or extracellular matrix partly required Ca2+ and was mediated through its core glycoprotein. Phosphacan inhibited adhesion and axonal extension of cerebellar granule cells in dissociated culture, while it promoted axonal fasciculation of their aggregated culture. These results indicate that phosphacan around parallel fibers may be the repulsive substratum for adhesion and extension of granule cells and promote the fasciculation of parallel fibers.

Inhibition of astroglial nuclear factor kappaB reduces inflammation and improves functional recovery after spinal cord injury

In the central nervous system (CNS), the transcription factor nuclear factor (NF)-kappaB is a key regulator of inflammation and secondary injury processes. After trauma or disease, the expression of NF-kappaB-dependent genes is highly activated, leading to both protective and detrimental effects on CNS recovery. We demonstrate that selective inactivation of astroglial NF-kappaB in transgenic mice expressing a dominant negative (dn) form of the inhibitor of kappaB alpha under the control of an astrocyte-specific promoter (glial fibrillary acidic protein [GFAP]-dn mice) leads to a dramatic improvement in functional recovery 8 wk after contusive spinal cord injury (SCI). Histologically, GFAP mice exhibit reduced lesion volume and substantially increased white matter preservation. In parallel, they show reduced expression of proinflammatory chemokines and cytokines, such as CXCL10, CCL2, and transforming growth factor-beta2, and of chondroitin sulfate proteoglycans participating in the formation of the glial scar. We conclude that selective inhibition of NF-kappaB signaling in astrocytes results in protective effects after SCI and propose the NF-kappaB pathway as a possible new target for the development of therapeutic strategies for the treatment of SCI.

Age-dependent enhancement of hippocampal long-term potentiation and impairment of spatial learning through the Rho-associated kinase pathway in protein tyrosine phosphatase receptor type Z-deficient mice

Although protein tyrosine phosphatases (PTPs) are expressed abundantly in the brain, their roles in synaptic plasticity have not been well elucidated. In this study, we have examined the physiological functions of Ptprz, which is a receptor-type PTP expressed predominantly in the brain as a chondroitin sulfate proteoglycan. We have examined phenotypes of mutant mice deficient in Ptprz using electrophysiological, pharmacological, and behavioral approaches. Mutant mice exhibit enhanced long-term potentiation (LTP) in the CA1 region of hippocampal slices and impaired spatial learning abilities in an age-dependent manner: young adult (<10 weeks old) mutant mice show normal LTP and learning abilities in the Morris water maze task, whereas adult (>13 weeks old) mutant mice exhibit enhanced LTP and impairment in the task. The enhanced LTP is specifically canceled out by pharmacological inhibition of Rho-associated kinase (ROCK), a major downstream effector of Rho. These findings suggest that the lack of Ptprz leads to aberrant activation of ROCK and resultantly to enhanced LTP in the slice and learning impairments in the animal.

Pleiotrophin stimulates tyrosine phosphorylation of β-adducin through inactivation of the transmembrane receptor protein tyrosine phosphatase β/ζ

Pleiotrophin (PTN the protein, Ptn the gene) signals through a unique mechanism; it inactivates the tyrosine phosphatase activity of its receptor, the transmembrane receptor protein tyrosine phosphatase (RPTP)beta/zeta, and increases tyrosine phosphorylation of the substrates of RPTPbeta/zeta through the continued activity of a yet to be described protein tyrosine kinase(s) in PTN-stimulated cells. We have now found that the cytoskeletal protein beta-adducin interacts with the intracellular domain of RPTPbeta/zeta in a yeast two-hybrid system, that beta-adducin is a substrate of RPTPbeta/zeta, that beta-adducin is phosphorylated in tyrosine in cells not stimulated by PTN, and that tyrosine phosphorylation of beta-adducin is sharply increased in PTN-stimulated cells, suggesting that beta-adducin is a downstream target of and regulated by the PTN/RPTPbeta/zeta signaling pathway. beta-Catenin was the first downstream target of the PTN/RPTPbeta/zeta signaling pathway to be identified; these data thus also suggest that PTN coordinately regulates steady state levels of tyrosine phosphorylation of the important cytoskeletal proteins beta-adducin and beta-catenin and, through PTN-stimulated tyrosine phosphorylation, beta-adducin may contribute to the disruption of cytoskeletal structure, increased plasticity, and loss of homophilic cell-cell adhesion that are the consequences of PTN stimulation of cells and a characteristic feature of different malignant cells with mutations that activate constitutive expression of the endogenous Ptn gene.

Cortical neurons express PSI, a novel isoform of phosphacan/RPTPbeta

Phosphacan is a chondroitin sulfate proteoglycan representing the secreted extracellular part of a transmembrane receptor protein tyrosine phosphatase (RPTP-beta). These isoforms have been implicated in cell-extracellular matrix signaling events associated with myelination, axon growth, and cell migration in the developing central nervous system and may play critical roles in the context of brain pathologies. Recently, we have reported the identification of a new isoform of phosphacan, the phosphacan short isoform (PSI), the expression of which peaks in the second postnatal week. PSI interacts with the neuronal receptors L1 and F3/contactin and can promote neurite growth of cortical neurons. In this study, we have assessed, by in situ hybridization, the expression profile of PSI in the rat brain at postnatal day 7. PSI is largely expressed in the gray matter of the developing cerebral cortex in which it colocalizes with phosphacan, whereas the expression of RPTPbeta receptor forms is restricted to the ventricular area in which PSI has not been observed. Neurons from all layers of the cortex express PSI. In the cerebellum, on the other hand, no expression of PSI has been detected, although the other phosphacan/RPTP-beta isoforms show strong PSI expression here. Overall, our study suggests that PSI is expressed during the postnatal period in differentiated neurons of the cortex but is absent from structures in which proliferation and migration occur. The significance of these observations is discussed in the context of previous models of phosphacan/RPTP-beta functions.

Pleiotrophin mediates the neurotrophic effect of cyclic AMP on dopaminergic neurons: analysis of suppression-subtracted cDNA libraries and confirmation in vitro

To better understand the particular vulnerability of mesencephalic dopaminergic neurons to toxins or gene mutations causing parkinsonism, we have taken advantage of a primary cell culture system in which these neurons die selectively. Antimitotic agents, such as cytosine arabinoside or cAMP, prevent the death of the neurons by arresting astrocyte proliferation. To identify factors implicated in either the death of the dopaminergic neurons or in the neuroprotective effect of cAMP, we constructed cDNA libraries enriched by subtractive hybridization and suppressive PCR in transcripts that are preferentially expressed in either control or cAMP-treated cultures. Differentially expressed transcripts were identified by hybridization of the enriched cDNAs with a commercially available cDNA expression array. The proteoglycan receptors syndecan-3 and the receptor protein tyrosine phosphatase zeta/beta were found among the transcripts preferentially expressed under control conditions, and their ligand, the cytokine pleiotrophin, was highly represented in the cDNA libraries for both conditions. Since pleiotrophin is expressed during embryonic and perinatal neural development and following lesions in the adult brain, we investigated its role in our cell culture model. Pleiotrophin was not responsible for the death of dopaminergic neurons under control conditions, or for their survival in cAMP-treated cultures. It was, however, implicated in the initial and cAMP-dependent enhancement of the differentiation of the dopaminergic neurons in our cultures. In addition, our experiments have provided evidence for a cAMP-dependent regulatory pathway leading to protease activation, and the identification of pleiotrophin as a target of this pathway.

Fyn is a downstream target of the pleiotrophin/receptor protein tyrosine phosphatase β/ζ-signaling pathway: Regulation of tyrosine phosphorylation of Fyn by pleiotrophin

Pleiotrophin (PTN the protein, Ptn the gene) signals downstream targets through inactivation of its receptor, the transmembrane receptor protein tyrosine phosphatase (RPTP)beta/zeta, disrupting the balanced activity of RPTPbeta/zeta and the activity of a constitutively active tyrosine kinase. As a consequence of the inactivation of RPTPbeta/zeta, PTN stimulates a sharp increase in the levels of tyrosine phosphorylation of the substrates of RPTPbeta/zeta in PTN-stimulated cells. We now report that the Src family member Fyn interacts with the intracellular domain of RPTPbeta/zeta in a yeast two-hybrid system. We further demonstrate that Fyn is a substrate of RPTPbeta/zeta, and that tyrosine phosphorylation of Fyn is sharply increased in PTN-stimulated cells. In previous studies, we demonstrated that beta-catenin and beta-adducin are targets of the PTN/RPTPbeta/zeta-signaling pathway and defined the mechanisms through which tyrosine phosphorylation of beta-catenin and beta-adducin disrupts cytoskeletal protein complexes. We conclude that Fyn is a downstream target of the PTN/RPTPbeta/zeta-signaling pathway and suggest that PTN coordinately regulates tyrosine phosphorylation of beta-catenin, beta-adducin, and Fyn through the PTN/RPTPbeta/zeta-signaling pathway and that together Fyn, beta-adducin, and beta-catenin may be effectors of the previously described PTN-stimulated disruption of cytoskeletal stability, increased cell plasticity, and loss of cell-cell adhesion that are characteristic of PTN-stimulated cells and a feature of many human malignant cells in which mutations have established constitutive expression of the Ptn gene.

Growth-associated gene expression after stroke: evidence for a growth-promoting region in peri-infarct cortex

Stroke induces axonal sprouting in peri-infarct cortex. A set of growth-associated genes important in axonal sprouting in peripheral nervous system regeneration and cortical development has recently been defined. The expression profiles of these growth-associated genes were defined during the post-stroke axonal sprouting response using a model of stroke in barrel field cortex. Stroke induces sequential waves of neuronal growth-promoting genes during the sprouting response: an early expression peak (SPRR1), a mid expression peak (p21, Ta1 tubulin, L1, MARCKS), a late peak (SCG10, SCLIP), and an early/sustained pattern (GAP43, CAP23, c-jun). These expression peaks correspond to specific time points in the sprouting response. The expression of the growth-inhibiting chondroitin sulfate proteoglycans aggrecan, brevican, versican, and phosphacan are induced late in the sprouting process; except neurocan, which is increased during the peak of the growth-promoting gene expression. The developmentally associated growth inhibitors ephrin-A5, ephB1, semaphorin IIIa, and neuropilin 1 are also induced in the early phases of the sprouting response. At the cellular level, chondroitin sulfate proteoglycans, in the form of peri-neuronal nets, are reduced in the region of axonal sprouting, during the peak of growth-promoting gene expression. These results identify a unique profile of growth-promoting gene expression in adult cortex after stroke, the inhibitory molecules that are present during the sprouting response, and a region in which growth-promoting genes are increased, growth-inhibitory proteins are diminished and axonal sprouting occurs. This region may be a growth-promoting zone after stroke.

Functional comparison of long and short splice forms of RPTPbeta: implications for glioblastoma treatment

The receptor protein tyrosine phosphatase beta (RPTPbeta/PTPzeta) is overexpressed in glioblastoma tumors and plays a functional role in tumor cell migration and adhesion. Glioblastomas express at least three splice variants of RPTPbeta, including long and short receptor forms and a secreted chondroitin sulfate proteoglycan called phosphacan. Here we explore the differences in the expression pattern and function of long RPTPbeta and short RPTPbeta. The short form of RPTPbeta lacks exon 12, which encodes 860 amino acids located in the extracellular domain. Until now, functional differences between long and short RPTPbeta have been difficult to elucidate. In this study, antibodies specific to the splice junction, unique to short RPTPbeta, allowed for the discrimination of the two receptors. A study of normal brain tissue and graded astrocytomas indicates that long and short RPTPbeta forms have an overlapping expression pattern. In order to study functional differences between long and short RPTPbeta, we created stable U87 glioblastoma cells that expressed these receptors. U87 stable cell lines overexpressing long or short RPTPbeta migrate faster and adhere more robustly than parental U87 cells. The two forms differ in that long-RPTPbeta-overexpressing cells migrate and adhere better than short-RPTPbeta-overexpressing cells. A study of the extracellular domain of short RPTPbeta indicates that it retains much of the functional capacity of phosphacan. Indeed, the action of recombinant, short-RPTPbeta extracellular domain protein is similar to that of phosphacan as a repulsive substrate for glioblastoma cells. Comparison of the signaling capacity of long RPTPbeta to that of short RPTPbeta reveals very similar abilities to activate transcription pathways. Moreover, transient transfection with either long or short RPTPbeta activates NF-kappaB reporter gene transcription. Because of their tumor-restricted and largely overlapping expression patterns in glioblastoma, both RPTPbeta splice forms are potential therapeutic targets. The involvement of long and short RPTPbeta in glioma tumor cell biology also contributes to the value of RPTPbeta as a cancer target.

Differential induction of glioblastoma migration and growth by two forms of pleiotrophin

Glioblastoma is the most common malignant brain tumor of adults and one of the most lethal cancers. The secreted growth factor pleiotrophin (PTN) promotes glioblastoma migration and proliferation, initiating its oncogenic activities through two cell surface receptors, the protein tyrosine phosphatase receptor zeta (PTPRZ1) and the anaplastic lymphoma kinase (ALK), respectively. Here, we report on the presence and purification of two naturally occurring forms of PTN (18 and 15 kDa) that differentially promote glioblastoma migration and proliferation. Using a panel of glioblastoma cell lines, including low passage patient-derived cultures, we demonstrate that PTN15 promotes glioblastoma proliferation in an ALK-dependent fashion, whereas immobilized PTN18 promotes haptotactic migration of glioblastoma cells in a PTPRZ1-dependent fashion. Mass spectrometric analysis indicated that PTN15 differs from PTN18 by processing of 12 C-terminal amino acids. To demonstrate clinical relevance, we show that PTN15, PTN18, and PTPRZ1 are significantly overexpressed in glioblastoma relative to normal brain at both mRNA and protein levels using microarray, Western blot, and tissue microarray analyses on human tumors. These results indicate that the PTN18-PTPRZ1 and the PTN15-ALK signaling pathways represent potentially important therapeutic targets for glioblastoma invasion and growth.

Epigenetic profiling of cutaneous T-cell lymphoma: promoter hypermethylation of multiple tumor suppressor genes including BCL7a, PTPRG, and p73

PURPOSE

To analyze the occurrence of promoter hypermethylation in primary cutaneous T-cell lymphoma (CTCL) on a genome-wide scale, focusing on epigenetic alterations with pathogenetic significance.

MATERIALS AND METHODS

DNA isolated from biopsy specimens of 28 patients with CTCL, including aggressive CTCL entities (transformed mycosis fungoides and CD30-negative large T-cell lymphoma) and an indolent entity (CD30-positive large T-cell lymphoma), were investigated. For genome-wide DNA methylation screening, differential methylation hybridization using CpG island microarrays was applied, which allows simultaneous detection of the methylation status of 8640 CpG islands. Bisulfite sequence analysis was applied for confirmation and detection of hypermethylation of eight selected tumor suppressor genes.

RESULTS

The DNA methylation patterns of CTCLs emerging from differential methylation hybridization analysis included 35 CpG islands hypermethylated in at least four of the 28 studied CTCL samples when compared with benign T-cell samples. Hypermethylation of the putative tumor suppressor genes BCL7a (in 48% of CTCL samples), PTPRG (27%), and thrombospondin 4 (52%) was confirmed and demonstrated to be associated with transcriptional downregulation. BCL7a was hypermethylated at a higher frequency in aggressive (64%) than in indolent (14%) CTCL entities. In addition, the promoters of the selected tumor suppressor genes p73 (48%), p16 (33%), CHFR (19%), p15 (10%), and TMS1 (10%) were hypermethylated in CTCL.

CONCLUSION

Malignant T cells of patients with CTCL display widespread promoter hypermethylation associated with inactivation of several tumor suppressor genes involved in DNA repair, cell cycle, and apoptosis signaling pathways. In view of this, CTCL may be amenable to treatment with demethylating agents.

Neuronal expression of the chondroitin sulfate proteoglycans receptor-type protein-tyrosine phosphatase beta and phosphacan

Receptor-type protein-tyrosine phosphatase beta (RPTPbeta) and its spliced variant phosphacan are major components of chondroitin sulfate proteoglycans in the CNS. In this study, expression and localization of RPTPbeta and phosphacan were examined in developing neurons by immunological analyses using 6B4, 3F8, and anti-PTP antibodies and reverse transcription-polymerase chain reaction (RT-PCR). Light microscopic immunohistochemistry showed that 6B4 RPTPbeta/phosphacan immunoreactivity was observed around neurons in the cortical plate. Further ultrastructural observation showed that 6B4 RPTPbeta/phosphacan immunoreactivity was observed mainly at the membrane of migrating neurons and radial glia. Immunocytochemical analysis revealed that RPTPbeta immunoreactivity was observed in cultured cerebral, hippocampal, and cerebellar neurons in addition to type-1 and type-2 astrocytes. Western analysis further demonstrated that the shorter receptor form of RPTPbeta (sRPTPbeta) was detected from cell lysate of cortical and hippocampal neurons using 6B4 and anti-PTP antibodies, while sRPTPbeta of cerebellar neurons and type-1 astrocytes was recognized only by anti-PTP antibody. Phosphacan was detected from neuronal culture supernatants of cortical, hippocampal, and cerebellar neurons, but not from type-1 astrocytes using 6B4 and 3F8 antibodies. RT-PCR analysis demonstrated the prominent expression of sRPTPbeta and phosphacan mRNAs in cortical neurons, and that of sRPTPbeta mRNA in type-1 astrocytes. During culture development of cortical neurons, the immunoreactivity of 6B4 sRPTPbeta was observed entirely on the neuronal surface including somata, dendrites, axons, and growth cones at earlier stages of cortical neuronal culture such as stages 2 and 3, while, after longer culture, 6B4 sRPTPbeta immunoreactivity in stages 4 and 5 neurons was detected at dendrites and somata and disappeared from axons, and was not observed over axonal terminals and postsynaptic spines. These results demonstrate that neurons are able to express sRPTPbeta on their cellular surface and to secrete phosphacan, and neuronal expression of sRPTPbeta may modulate neuronal differentiation including neuritogenesis and synaptogenesis.