observation-ciliary-movement-choroid-plexus-epithelial-cells-ex

Observation of the Ciliary Movement of Choroid Plexus Epithelial Cells <em>Ex Vivo</em>

The choroid plexus is located in the ventricular wall of the brain, the main function of which is believed to be production of cerebrospinal fluid. ...

University of Yamanashi

We recently showed that human skin fibroblasts internalize fluorescent analogues of the glycosphingolipids lactosylceramide and globoside almost exclusively by a clathrin-independent mechanism involving caveolae. In contrast, a sphingomyelin analogue is internalized approximately equally via clathrin-dependent and caveolar routes. Here, we further characterized the caveolar pathway for glycosphingolipids, showing that Golgi targeting of sphingolipids internalized via caveolae required microtubules and phosphoinositol 3-kinases and was inhibited in cells expressing dominant-negative Rab7 and Rab9 constructs. In addition, overexpression of wild-type Rab7 or Rab9 (but not Rab11) in Niemann-Pick type C (NP-C) lipid storage disease fibroblasts resulted in correction of lipid trafficking defects, including restoration of Golgi targeting of fluorescent lactosylceramide and endogenous GM(1) ganglioside, and a dramatic reduction in intracellular cholesterol stores. Our results demonstrate a role for Rab7 and Rab9 in the Golgi targeting of glycosphingolipids and suggest a new therapeutic approach for restoring normal lipid trafficking in NP-C cells.

Rab proteins mediate Golgi transport of caveola-internalized glycosphingolipids and correct lipid trafficking in Niemann-Pick C cells.

Glycosphingolipid (GSL) lysosomal storage disorders are a small but challenging group of human diseases to treat. Although these disorders appear to be monogenic in origin, where the catalytic activity of enzymes in GSL catabolism is impaired, the clinical presentation and severity of disease are heterogeneous. Present attitudes to treatment demand individual therapeutics designed to match the specific disease-related gene defect; this is an acceptable approach for those diseases with high frequency, but it lacks viability for extremely rare conditions. An alternative therapeutic approach termed 'substrate deprivation' or 'substrate reduction therapy' (SRT) aims to balance cellular GSL biosynthesis with the impairment in catalytic activity seen in lysosomal storage disorders. The development of N-alkylated iminosugars that have inhibitory activity against the first enzyme in the pathway for glucosylating sphingolipid in eukaryotic cells, ceramide-specific glucosyltransferase, offers a generic therapeutic for the treatment of all glucosphingolipidoses. The successful use of N-alkylated iminosugars to establish SRT as an alternative therapeutic strategy has been demonstrated in in vitro, in vivo and in clinical trials for type 1 Gaucher disease. The implications of these studies and the prospects of improvement to the design of iminosugar compounds for treating Gaucher and other GSL lysosomal storage disorders will be discussed.

Small-molecule therapeutics for the treatment of glycolipid lysosomal storage disorders.

Niemann-Pick disease type C (NPC) is a genetic disorder in which patient cells exhibit lysosomal accumulation of cholesterol and sphingolipids (SLs) caused by defects in either NPC1 or NPC2 proteins. We previously demonstrated that NPC1 human skin fibroblasts overexpressing endosomal Rab proteins (Rab7 or Rab9) showed a correction in the storage disease phenotype. In the current study, we used protein transduction to further investigate Rab9-mediated reduction of stored lipids in NPC cells. Recombinant human Rab9 fused with the herpes simplex virus VP22 protein fragment was overexpressed, purified, and added to culture medium to induce protein transduction. When VP22-Rab9 was transduced into NPC1 fibroblasts, nearly all cells showed significant reduction in cellular free cholesterol levels, with no cytotoxicity up to 5 microM. A fraction of the VP22-Rab9 that was transduced into the cells was shown to bind to rab GDP dissociation inhibitor, suggesting that this pool of VP22-Rab9 had become prenylated. The reduction in cellular free cholesterol was associated with correction of abnormal intracellular trafficking of BODIPY-lactosylceramide and an increase of sterols in the culture media. The clearance of lysosomal free cholesterol was also associated with a decrease in LDL-receptor levels. In addition, we demonstrated reduction of intracellular cholesterol by VP22-Rab9 transduction in NPC2 fibroblasts and in cultured mouse NPC1 neurons. These observations provide important new information about the correction of membrane traffic in NPC cells by Rab9 overexpression and may lead to new therapeutic approaches for treatment of this disease.

Protein transduction of Rab9 in Niemann-Pick C cells reduces cholesterol storage.

We previously identified HSulf-1 as a down-regulated gene in several tumor types including ovarian, breast, and hepatocellular carcinomas. Loss of HSulf-1, which selectively removes 6-O-sulfate from heparan sulfate, up-regulates heparin-binding growth factor signaling and confers resistance to chemotherapy-induced apoptosis. Here we report that HSulf-1 expression in MDA-MB-468 breast carcinoma clonal lines leads to reduced proliferation in vitro and reduced tumor burden in athymic nude mice in vivo. Additionally, xenografts derived from HSulf-1-expressing stable clones of carcinoma cells showed reduced vessel density, marked necrosis, and apoptosis, indicative of inhibition of angiogenesis. Consistent with this observation, HSulf-1-expressing clonal lines showed reduced staining with the endothelial marker CD31 in Matrigel plug assay, indicating that HSulf-1 expression inhibits angiogenesis. More importantly, HSulf-1 expression in the xenografts was associated with a reduced ability of vascular endothelial cell heparan sulfate to participate in a complex with fibroblast growth factor 2 (FGF-2) and its receptor tyrosine kinase FGF receptor 1c. In vitro, short hairpin RNA-mediated down-regulation of HSulf-1 in human umbilical vein endothelial cells (HUVEC) resulted in an increased proliferation mediated by heparan sulfate-dependent FGF-2, hepatocyte growth factor, and vascular endothelial growth factor 165 (VEGF165) but not by heparan sulfate-independent VEGF121. HSulf-1 down-regulation also enhanced downstream signaling through the extracellular signal-regulated kinase pathway compared with untreated cells. Consistent with the role of heparan sulfate glycosaminoglycan sulfation in VEGF-mediated signaling, treatment of HUVEC cells with chlorate, which inhibits heparan sulfate glycosaminoglycan sulfation and therefore mimics HSulf-1 overexpression, led to an attenuated VEGF-mediated signaling. Collectively, these observations provide the first evidence of a novel mechanism by which HSulf-1 modulates the function of heparan sulfate binding VEGF165 in proliferation and angiogenesis.

HSulf-1 inhibits angiogenesis and tumorigenesis in vivo.

Heparan sulfate (HS) glycosaminoglycans are the oligosaccharide chains of heparan sulfate proteoglycans. The sulfation of HS glycosaminoglycan residues is required for its interaction with various heparin-binding growth factors to promote their biological activities to activate their high affinity receptor tyrosine kinases. We have identified HS glycosaminoglycan-6-O-endosulfatase HSulf-1 as a down-regulated gene in ovarian, breast, and several other cancer cell lines. Here we have shown that HSulf-1 inhibits autocrine activation of the EGFR-ERK (epidermal growth factor receptor-extracellular signal-regulated kinase) pathway induced by serum withdrawal in MDA-MB-468 breast cancer cells. Short hairpin RNA-mediated down-regulation of HSulf-1 in HSulf-1 clonal lines of MDA-MB-468 led to a significant increase in autocrine activation of ERK compared with vector only control. The autocrine signaling was also inhibited with neutralization antibodies against amphiregulin and HB-EGF, the heparin-binding growth factor family of the EGF superfamily. Furthermore, HSulf-1-mediated inhibition of autocrine signaling was associated with reduced cyclin D1 levels, leading to decreased S phase fraction and increased G(2)-M fraction, as well as increased cell death. Finally, evaluation of HSulf-1 expression levels in primary invasive breast tumors by RNA in situ hybridization indicated that HSulf-1 is down-regulated in the majority (60%) of tumors, with a predominant association with lobular histology. These data suggest a potential role of HSulf-1 down-regulation in mammary carcinogenesis.

Loss of HSulf-1 expression enhances autocrine signaling mediated by amphiregulin in breast cancer.

Functional defects in cilia are associated with various human diseases including congenital hydrocephalus. Previous studies suggested that defects in cilia not only disrupt the flow of cerebrospinal fluid (CSF) generated by motile cilia in ependyma lining the brain ventricles, but also cause increased CSF production at the choroid plexus. However, the molecular mechanisms of CSF overproduction by ciliary dysfunction remain elusive. To dissect the molecular mechanisms, choroid plexus epithelial cells (CPECs) were isolated from porcine brain. These cells expressed clusters of primary cilia on the apical surface. Deciliation of CPECs elevated the intracellular cyclic AMP (cAMP) levels and stimulated basolateral-to-apical fluid transcytosis, without detrimental effects on other morphological and physiological features. The primary cilia possessed neuropeptide FF (NPFF) receptor 2. In deciliated cells, the responsiveness to NPFF was reduced at nanomolar concentrations. Furthermore, CPECs expressed NPFF precursor along with NPFFR2. An NPFFR antagonist, BIBP3226, increased the fluid transcytosis, suggesting the presence of autocrine NPFF signaling in CPECs for a tonic inhibition of fluid transcytosis. These results suggest that the clusters of primary cilia in CPECs act as a sensitive chemosensor to regulate CSF production.

Multiple primary cilia modulate the fluid transcytosis in choroid plexus epithelium.

Glutamate excitotoxicity is one of the major events that takes place during various neurotoxic injuries such as brain ischemia. We prepared grape seed extracts, from two different varieties, containing high amounts of polyphenols but little resveratrol. Their neuroprotective effects were investigated using primary culture of neonatal mouse hippocampal neurons treated with an excitotoxic concentration of glutamate. Koshu, a white, local variety of V. vinifera, alleviated the acute inactivation of Erk1/2 and dendrite retraction in cultured hippocampal neurons exposed to a toxic concentration of glutamate (1.0 ng/ml). By contrast, Muscat Bailey A, a red, hybrid variety (Muscat Humburg × Bailey), failed to show any neuroprotective effect. Unlike brain-derived neurotrophic factor and other neuroprotective cytokines, Koshu extract did not induce Akt phosphorylation. Koshu extract also augmented neuron survival rate 24 hours after glutamate toxicity. The comparison of polyphenols between the two samples by liquid chromatography/time-of-flight mass spectrometry demonstrated that Koshu had higher amounts of low molecular weight polyphenols along with several Koshu-specific procyanidin oligomers. These data suggest the presence of high affinity molecular targets for polyphenols in hippocampal neurons, which induce neuroprotective effects in a manner different from BDNF, and the importance of low molecular weight polyphenols and/or procyanidin oligomers for neuroprotection.

Differential neuroprotective activity of two different grape seed extracts.

In this review, we propose a new classification of vertebrate cilia/flagella and discuss the evolution and prototype of cilia. Cilia/flagella are evolutionarily well-conserved membranous organelles in eukaryotes and serve a variety of functions, including motility and sensation. Vertebrate cilia have been traditionally classified into conventional motile cilia and sensory primary cilia. However, an avalanche of emerging evidence on the variations of cilia has made it almost impossible to classify them in a simple dichotomic manner. For example, conventional motile cilia are also involved in the sensation of bitter taste to facilitate the beating of cilia as a defense system of the respiratory system. On the other hand, the primary cilium, often regarded as a non-motile sensory organelle, has been revealed to be motile in vertebrate embryonic nodes, where they play a crucial role in the determination of left-right asymmetry of the body. Moreover, choroid plexus epithelial cells in the cerebral ventricular system exhibit multiple primary cilia on a single cell. Considering these lines of evidence on the diversity of cilia, we believe the classification of cilia should be based on their structure and function, and include more detailed criteria. Another intriguing issue is how in the evolution of cilia, their function and morphology are combined. For example, has motility been acquired from originally sensory cilia, or vice versa? Alternatively, were they originally hybrid in nature? These questions are inseparable from the classification of cilia per se. We would like to address these conundrums in this review article, principally from the standpoint of differentiation of the animal cell.

Structure and function of vertebrate cilia, towards a new taxonomy.

Cilia are structurally and functionally diverse organelles, whose malfunction leads to ciliopathies. While recent studies have uncovered common ciliary transport mechanisms, limited information is available on the proteome of cilia, particularly that of sensory subtypes, which could provide insight into their functional and developmental diversities. In the present study, we performed proteomic analysis of unique, multiple 9+0 cilia in choroid plexus epithelial cells (CPECs). The analysis of juvenile swine CPEC cilia identified 868 proteins. Among them, 396 were shared with the proteome of 9+0 photoreceptor cilia (outer segment), whereas only 152 were shared with the proteome of 9+2 cilia and flagella. Various signaling molecules were enriched in a CPEC-specific ciliome subset, implicating multiplicity of sensory functions. The ciliome also included molecules for ciliary motility such as Rsph9. In CPECs from juvenile swine or adult mouse, Rsph9 was localized to a subpopulation of cilia, whereas they were non-motile. Live imaging of mouse choroid plexus revealed that neonatal CPEC cilia could beat vigorously, and the motility waned and was lost within 1-2 weeks. The beating characteristics of neonatal CPEC cilia were variable and different from those of typical 9+2 cilia of ependyma, yet an Efhc1-mediated mechanism to regulate the beating frequency was shared in both types of cilia. Notably, ultrastructural analysis revealed the presence of not only 9+0 but also 9+2 and atypical ciliary subtypes in neonatal CPEC. Overall, these results identified both conserved and variable components of sensory cilia, and demonstrated a novel mode of ciliary development in mammals.

Proteomic analysis of multiple primary cilia reveals a novel mode of ciliary development in mammals.

Cilia have crucial roles in various developmental and physiological events. Previously, we reported that choroid plexus epithelial cells (CPECs) have multiple, nonmotile 9+0 cilia, but the cilia exhibit transient motility with variable axonemal arrangements in the neonatal period. These features make these cilia unique, as they do not fit in to the traditional categories of primary or motile cilia, and their physiological roles remain elusive. To address this issue, we studied ciliary motility on CPECs through development, with particular interest in the embryonic period. In the fetal choroid plexus of the lateral ventricles, the proportion of cells with motile cilia and their beat frequency increased over time. The ciliary motility profiles peaked near the day of birth, and gradually declined in the two weeks thereafter. The dynamic changes in ciliary motility correlated with changes in Dnahc11 expression. We demonstrated previously that the ciliary motility at P2 was insufficient to produce detectable fluid flow; thus it appears that CPEC cilia do not produce fluid flow at any point during development. Together, our results suggest that a temporally regulated, unique function of CPEC cilia may exist during the perinatal period.

Developmental changes in ciliary motility on choroid plexus epithelial cells during the perinatal period.

Visualization of signal transduction in live primary cilia constitutes a technical challenge owing to the organelle's submicrometer dimensions and close proximity to the cell body. Using a genetically encoded calcium indicator targeted to primary cilia, we visualized calcium signaling in cilia of mouse fibroblasts and kidney cells upon chemical or mechanical stimulation with high specificity, high sensitivity and wide dynamic range.

Genetically encoded calcium indicator illuminates calcium dynamics in primary cilia.

The diffusion of materials from systemic circulation to the central nervous system (CNS) is restricted by the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). Choroid plexus epithelial cells (CPECs) of the brain ventricles constitute the BCSFB and regulate the infiltration of plasma proteins as well as immune cells into the interstitium of the CNS. The barrier function is altered in pathologic conditions. However, the regulatory mechanism of BCSFB is not fully understood. Here, we investigated the function of transient receptor potential vanilloid 4 (TRPV4), a polymodally gated divalent cation channel that is highly expressed in CPECs. TRPV4 was localized broadly on the apical membrane in swine CPECs, in contrast with an intense ciliary localization found on other cell types. Treatment with the TRPV4-specific agonist, GSK1016790A (GSK; EC50 34 nM), induced a robust calcium influx and an immediate serine/threonine protein phosphorylation. The agonist treatment induced a marked decrease in the amount of filamentous actin and disintegrated the cell junctions in 10-20 minutes. In contrast, inhibition of the basal TRPV4 activity with the TRPV4-specific antagonist, HC067047 (HC; IC50 74 nM), reduced the basolateral-to-apical transport of α-2-macroglobulin (A2M). Overall, this study demonstrated a novel physiologic function of TRPV4 in the regulation of BCSFB permeability.-Narita, K., Sasamoto, S., Koizumi, S., Okazaki, S., Nakamura, H., Inoue, T., Takeda, S. TRPV4 regulates the integrity of the blood-cerebrospinal fluid barrier and modulates transepithelial protein transport.

TRPV4 regulates the integrity of the blood-cerebrospinal fluid barrier and modulates transepithelial protein transport.

Cilia are whip-like projections that are widely conserved in eukaryotes and function as a motile propeller and/or sensory platform to detect various extracellular stimuli. In vertebrates, cilia are ubiquitously found in most cells, showing structural and functional diversities depending on the cell type. In this review, we focus on the structure and function of cilia in choroid plexus epithelial cells (CPECs). CPECs form one or two dozen non-motile 9+0 cilia, which display transient acquisition of motility during development. Genetic malfunction of cilia can lead to failure of multiple organs including the brain. Especially, several groups have demonstrated that the defects in CPEC cilia cause the communicating form of hydrocephalus. In order to elucidate the molecular mechanisms underlying the hydrocephalus, we have previously demonstrated that the cilia possess an NPFF receptor for autocrine signaling to regulate transepithelial fluid transport. In this perspective, we also discuss the potential involvement of cilia in the other aspects of choroid plexus functions, such as the regulation of brain development and neuroinflammation.

Article	Year
Rab proteins mediate Golgi transport of caveola-internalized glycosphingolipids and correct lipid trafficking in Niemann-Pick C cells. The Journal of clinical investigation\| PubMed ID: 12070301	2002
Small-molecule therapeutics for the treatment of glycolipid lysosomal storage disorders. Philosophical transactions of the Royal Society of London. Series B, Biological sciences\| PubMed ID: 12803927	2003
Protein transduction of Rab9 in Niemann-Pick C cells reduces cholesterol storage. FASEB journal : official publication of the Federation of American Societies for Experimental Biology\| PubMed ID: 15972801	2005
HSulf-1 inhibits angiogenesis and tumorigenesis in vivo. Cancer research\| PubMed ID: 16778174	2006
Loss of HSulf-1 expression enhances autocrine signaling mediated by amphiregulin in breast cancer. The Journal of biological chemistry\| PubMed ID: 17363371	2007
Multiple primary cilia modulate the fluid transcytosis in choroid plexus epithelium. Traffic (Copenhagen, Denmark)\| PubMed ID: 19958467	2010
Differential neuroprotective activity of two different grape seed extracts. PloS one\| PubMed ID: 21283677	2011
Structure and function of vertebrate cilia, towards a new taxonomy. Differentiation; research in biological diversity\| PubMed ID: 22118931	2012
Proteomic analysis of multiple primary cilia reveals a novel mode of ciliary development in mammals. Biology open\| PubMed ID: 23213475	2012
Developmental changes in ciliary motility on choroid plexus epithelial cells during the perinatal period. Cytoskeleton (Hoboken, N.J.)\| PubMed ID: 23959957	2013
Genetically encoded calcium indicator illuminates calcium dynamics in primary cilia. Nature methods\| PubMed ID: 24056873	2013
TRPV4 regulates the integrity of the blood-cerebrospinal fluid barrier and modulates transepithelial protein transport. FASEB journal : official publication of the Federation of American Societies for Experimental Biology\| PubMed ID: 25681460	2015
Cilia in the choroid plexus: their roles in hydrocephalus and beyond. Frontiers in cellular neuroscience\| PubMed ID: 25729351	2015

Keishi Narita

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