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PubMed1979

Distinctive features of cilia in metazoans and their significance for systematics.

A comparative study of epidermal cilia in the Turbellaria and Nemertea has revealed features in these organelles that are specific to certain taxonomic groups. Turbellarians of the order Acoela, in particular, have a characteristic pattern of axonemal filament termination in the distal tips of their cilia and a characteristic ciliary rootlet system that is not seen in other turbellarian orders nor in other metazoans. Each epidermal cilium in acoels has a typical 9 + 2 axonemal pattern through the main part of its length, but near its distal tip there is an abrupt shelf-life narrowing at which filaments 4-7 terminate; filaments 1, 2, 8 and 9 continue into the thinner distal-most part of the shaft along with singlet microtubules from the axonemal center. The rootlet system in acoel cilia involves an interconnecting pattern with lateral connectives. The unique structure of these cilia has systematic and phylogenetic significance for the Acoela, and it is argued that ultrastructural characters in general, including characters of organelles, can be validly applied to the phylogeny and systematics of the Metazoa.

Animals↗
PubMed1985

Cilia in the fetal and neonatal canine retina.

Cilia in the canine retina were examined at 40, 46 and 50 days of gestation and at birth by scanning electron microscopy, transmission electron microscopy, and by the freeze-fracture technique. Cilia were similar in all age groups examined. Scanning electron micrographs showed them to be smooth-surfaced conical to tubular extensions arising from putative photoreceptor inner segments. Cilia when freeze-fractured contained variable numbers of circumferential rows of 10 nm P-face particles: these constitute the ciliary necklace. Transmission electron micrographs showed the ciliary membrane to contain electron-dense beads which corresponded to the ciliary necklace seen in freeze-fracture replicas. The ciliary necklace identified in the developing canine retina was similar to those found in other types of motile and sensory cilia.

Animals↗
PubMed1987

Properties of phospholipase C in isolated olfactory cilia from the channel catfish (Ictalurus punctatus).

1. Cilia were isolated from the olfactory epithelium of the channel catfish (Ictalurus punctatus) with improved yield. The isolated preparations were enriched in cilia as indicated by electron microscopy, tubulin immunoblotting and identification of a ciliary-specific glycoprotein. 2. The isolated cilia preparations exhibited phospholipase C (EC 3.1.4.11) activity. The enzyme was maximally active at pH 6.7. 3. Analysis of inositol phosphates resulting from the hydrolysis of exogenous radiolabeled phosphatidylinositol-4,5-bisphosphate in isolated cilia, indicated that inositol triphosphate was the major (90%) inositol phosphate produced. 4. Three molecular forms of the enzyme, Mr greater than or equal to 100,000, 82,000 and 60,000 were resolved by gel filtration chromatography from a cytosolic fraction from the olfactory epithelium.

Animals↗
PubMed1987

Control of ciliary beat frequency in the gill of Mytilus--II. Effects of saponin and Brij-58 on the lateral cilia.

The effects of saponin and Brij-58 on the beat activation of the lateral cilia on the gill of Mytilus edulis were investigated. The ciliary activation by 5-hydroxytryptamine (5HT) decreased as the saponin-induced permeabilization progressed, increasing the reactivation of the ciliary beat by extracellularly applied ATP (1 mM). The cilia were activated by 5HT even after the treatment with saponin (0.01 and 0.02% w/v) or Brij-58 (0.07%) rendered the preparation capable of the reactivation by ATP. The saponin treatment itself stimulated the beat of the cilia. Theophylline (1 mM) augmented the saponin-induced activation of the cilia.

Adenosine Triphosphate↗
PubMed2004

Mesothelial primary cilia of peritoneal and other serosal surfaces.

The conspicuous presence of primary cilia, a small immotile cilium present on most cell types, left researchers with little doubt of their functional relevance. Recently mechanosensitive functional significance was established and a link with the pathogenesis of polycystic kidney disease. Together these discoveries have raised the profile of this, previously considered "vestigial", organelle. Primary cilia are expressed on the apical surface of serosal mesothelium and display regional variation but are more abundant on biosynthetically active cells. Adult mesothelial cells are highly biosynthetic producing a phospholipid rich surfactant that lubricates and protects the visceral organs. The mesothelium is utilized as a semipermeable membrane during peritoneal dialysis for patients with end stage renal failure. However, little is known about the functional role of primary cilia on this highly specialized cell type. The present review, examines the significance of the primary cilium in serosal mesothelial cell biology with an emphasis on ciliary location, structure, form and function. Future research is identified and discussed in view of the emerging role cilia have in other cells and the established function of the serosal mesothelium in development, normal function, peritoneal dialysis and pathology of the serosal membranes.

Animals↗
PubMed1976

Contractile events in the cilia of Paramecium, Opalina, Mytilus, and Phragmatopoma.

The motion of the abnormal cilia of Opalina and Mytilus can be described by the recently developed model for ciliary motion, provided the activation of the contractility during the effective stroke is reduced by three- to fivefold compared with that in the recovery stroke. The stiffness of the Mytilus cilium during the effective stroke is found several hundred times larger than that predicted by the model, however. The stiffness of the cilia of Paramecium, Opalina, Phragmatopoma, and of Mytilus in the recovery phase, is predicted approximately correctly by the model. The activation of contractility in Mytilus and Phragmatopoma cilia increases with the viscosity of the medium, as the velocity of the ciliary motion slows down. This leads to the equivalent of a force-velocity relation. The velocity of propagation of the bend in the cilia during the recovery stroke is shown to be dependent only on the elastic properties of the ciliary shaft, and to be independent of the contractile activiey.

Animals↗
PubMed1999

Cyclic AMP diffusion coefficient in frog olfactory cilia.

Cyclic AMP (cAMP) is one of the intracellular messengers that mediate odorant signal transduction in vertebrate olfactory cilia. Therefore, the diffusion coefficient of cAMP in olfactory cilia is an important factor in the transduction of the odorous signal. We have employed the excised cilium preparation from the grass frog (Rana pipiens) to measure the cAMP diffusion coefficient. In this preparation an olfactory cilium is drawn into a patch pipette and a gigaseal is formed at the base of the cilium. Subsequently the cilium is excised, allowing bath cAMP to diffuse into the cilium and activate the cyclic nucleotide-gated channels on the plasma membrane. In order to estimate the cAMP diffusion coefficient, we analyzed the kinetics of the currents elicited by step changes in the bath cAMP concentration in the absence of cAMP hydrolysis. Under such conditions, the kinetics of the cAMP-activated currents has a simple dependence on the diffusion coefficient. From the analysis we have obtained a cAMP diffusion coefficient of 2.7 +/- 0.2. 10(-6) cm2 s-1 for frog olfactory cilia. This value is similar to the expected value in aqueous solution, suggesting that there are no significant diffusional barriers inside olfactory cilia. At cAMP concentrations higher than 5 microM, diffusion slowed considerably, suggesting the presence of buffering by immobile cAMP binding sites. A plausible physiological function of such buffering sites would be to prolong the response of the cell to strong stimuli.

Animals↗
PubMed1987

The appearance of compound cilia in the nasal mucosa of normal human subjects following acute, in vivo exposure to sulfur dioxide.

Electron microscopic examination of ultrathin sections of ciliated nasal epithelium obtained from seven normal, healthy human volunteers indicated increases in the prevalence of compound cilia following controlled, acute exposure to 0.75 ppm sulfur dioxide (SO2). Morphometric analyses of the specimens confirmed a statistically significant association between SO2 exposure and compounding of nasal epithelial cilia in four of the seven subjects. Concomitant freeze-fracture replicas prepared from these samples also revealed the occurrence of compound cilia with accompanying evidence of abnormal ciliary membrane ultrastructure in the nasal epithelium. These studies indicate that SO2 may be implicated as a causative agent in ciliary compounding in the upper respiratory tract and that compound cilia represent a form of acquired ciliary defect which may serve as a readily quantifiable marker of epithelial injury.

Cilia↗
PubMed1998

Occurrence of autoantibodies to cilia in lambs with a 'coughing syndrome'.

A respiratory disease of lambs that has been termed the 'coughing syndrome' has been observed in the mid-western region of the United States of America. Mycoplasma ovipneumoniae (M. ovipneumoniae) and Mycoplasma arginini (M. arginini) were routinely isolated from the respiratory tract of lambs with this disease. A high level of antibodies reactive with ovine cilia of the upper respiratory tract was detected in the sera from many of the lambs in affected flocks but not in sera of lambs from unaffected flocks. The reactivity of these antibodies with cilia was demonstrated by ELISA and confirmed by indirect immunofluorescent staining and western immunoblotting. These antibodies were predominantly of the IgG isotype. They were distinct from cold or warm agglutinins and could be absorbed from the sera with cilia but not with antigens of common bacterial pathogens of the sheep respiratory tract including M. ovipneumoniae, M. arginini, Pasteurella haemolytica, Pasteurella multocida or Neisseria ovis. In addition, their occurrence appeared to be independent of the specific antibodies to M. ovipneumoniae and M. arginini. Western immunoblotting indicated that the antibodies were directed primarily against an antigen with apparent molecular weight of 50 kDa. In one flock from which serial serum samples were collected from the same lambs over a 10-month period, antibodies to ovine cilia developed before the onset of the clinical disease and persisted for a period of several months until most of the lambs had apparently recovered. However, colonization of the respiratory tract of the lambs by M. ovipneumoniae preceded the production of these antibodies. Sequential serum samples taken from another flock, with no known history of this coughing, showed no such antibodies throughout the sampling period. It is suggested that an immunopathologic mechanism involving production of autoantibodies directed against a ciliary antigen of the lambs could be a contributing factor to the pathogenesis of this clinical disease.

Animals↗
PubMed1999

Selective targeting of somatostatin receptor 3 to neuronal cilia.

Recently, five members of the somatostatin receptor family have been cloned. However, little is known about their cellular and subcellular localization in the central nervous system. Using specific anti-peptide antisera, we observed somatostatin receptor 3-like immunoreactivity in many brain regions, including the cerebral cortex, hippocampus, hypothalamus, amygdala and cerebellum. In all of these regions (except for the cerebellar cortex), somatostatin receptor 3-like immunoreactivity was selectively targeted to 4-8-microm-long rod-shaped profiles which did not co-localize with axonal or dendritic markers. One immunoreactive profile was always associated with one neuronal cell body. This staining pattern was resistant to colchicine treatment and showed a closely overlapping distribution with somatostatin receptor 3 messenger RNA, suggesting that the receptor protein is not transported over long distances. Electron microscopic analysis revealed that somatostatin receptor 3-like immunoreactivity is localized to the plasma membrane of neuronal cilia which extended into an intercellular pocket and showed a 9+0 filament pattern in their basal body and proximal segments. Thus, somatostatin receptor 3 demonstrates a unique example of a G-protein-coupled receptor not localized to "classical" pre- or postsynaptic sites, but selectively targeted to neuronal cilia. The presence of the somatostatin receptor 3 receptor on neuronal cilia suggests that these presumably non-motile cilia may not merely represent developmental remnants, but rather function as chemical sensors of the immediate milieu.

Amino Acid Sequence↗
PubMed2001

Polarized dendritic transport and the AP-1 mu1 clathrin adaptor UNC-101 localize odorant receptors to olfactory cilia.

Odorant receptors and signaling proteins are localized to sensory cilia on olfactory dendrites. Using a GFP-tagged odorant receptor protein, Caenorhabditis elegans ODR-10, we characterized protein sorting and transport in olfactory neurons in vivo. ODR-10 is transported in rapidly moving dendritic vesicles that shuttle between the cell body and the cilia. Anterograde and retrograde vesicles move at different speeds, suggesting that dendrites have polarized transport mechanisms. Residues immediately after the seventh membrane-spanning domain of ODR-10 are required for localization; these residues are conserved in many G protein-coupled receptors. UNC-101 encodes a mu1 subunit of the AP-1 clathrin adaptor complex. In unc-101 mutants, dendritic vesicles are absent, ODR-10 receptor is evenly distributed over the plasma membrane, and other cilia membrane proteins are also mislocalized, implicating AP-1 in protein sorting to olfactory cilia.

Amino Acid Sequence↗
PubMed2003

Mutations in INVS encoding inversin cause nephronophthisis type 2, linking renal cystic disease to the function of primary cilia and left-right axis determination.

Nephronophthisis (NPHP), an autosomal recessive cystic kidney disease, leads to chronic renal failure in children. The genes mutated in NPHP1 and NPHP4 have been identified, and a gene locus associated with infantile nephronophthisis (NPHP2) was mapped. The kidney phenotype of NPHP2 combines clinical features of NPHP and polycystic kidney disease (PKD). Here, we identify inversin (INVS) as the gene mutated in NPHP2 with and without situs inversus. We show molecular interaction of inversin with nephrocystin, the product of the gene mutated in NPHP1 and interaction of nephrocystin with beta-tubulin, a main component of primary cilia. We show that nephrocystin, inversin and beta-tubulin colocalize to primary cilia of renal tubular cells. Furthermore, we produce a PKD-like renal cystic phenotype and randomization of heart looping by knockdown of invs expression in zebrafish. The interaction and colocalization in cilia of inversin, nephrocystin and beta-tubulin connect pathogenetic aspects of NPHP to PKD, to primary cilia function and to left-right axis determination.

Adaptor Proteins, Signal Transducing↗
PubMed1992

Characterization of a novel inositol 1,4,5-trisphosphate receptor in isolated olfactory cilia.

Inositol 1,4,5-trisphosphate (InsP3), a product of G-protein-mediated receptor activation of phosphoinositide turnover, plays the role of a second messenger when olfactory neurons are stimulated with certain olfactory stimuli. In this paper we examine the specific binding of [3H]InsP3 to isolated olfactory cilia, microsomes and brain membranes from the channel catfish (Ictalurus punctatus) and, by photoaffinity labelling with an InsP3 analogue (125I-labelled 1-[3-(4-azidosalicyloxy)-aminopropyl]inositol 1,4,5-trisphosphate (125I-ASA-InsP3)], we tentatively identify the major InsP3-binding protein in catfish olfactory cilia. InsP3 binding to ciliary membranes is specific and saturable, with a Kd of 1.10 +/- 0.31 microM and a maximum number of binding sites (Bmax) of 17.6 +/- 5.8 pmol/mg. The rank order for potency of inhibition of [3H]InsP3 binding is Ins(1,4)P2 less than Ins(1,3,4)P3 less than Ins(1,3,4,5)P4 = Ins(1,4,5)P3 less than Ins(2,4,5)P3. Exposure of cilia membranes to u.v. light in the presence of 125I-ASA-InsP3 results in the labelling of a protein with apparent Mr 107,000. Labelling is specifically prevented by Ins(1,4,5)P3, Ins(2,4,5)P3 and Ins(1,3,4,5)P4, but not by Ins(1,4)P2 or Ins(1,3,4)P3. Both specific [3H]InsP3 binding and photoaffinity labelling of the Mr-107,000 protein were displaced by heparin. The Kd and the inhibition of [3H]InsP3 binding and of photoaffinity labelling by inositol phosphates and heparin are consistent with the ability of micromolar concentrations of Ins(1,4,5)P3 [but not Ins(1,3,4)P3] to activate the InsP3-gated currents in patch-clamp experiments with olfactory neurons. These results suggest that InsP3 binding to a Mr-107,000 cilia membrane protein may represent binding to the olfactory InsP3-gated cation channel.

Animals↗
PubMed2000

Basic properties of an inositol 1,4,5-trisphosphate-gated channel in carp olfactory cilia.

In addition to the activation of cAMP-dependent pathways, odorant binding to its receptor can lead to inositol 1,4,5-trisphosphate (InsP3) production that may induce the opening of plasma membrane channels. We therefore investigated the presence and nature of such channels in carp olfactory cilia. Functional analysis was performed by reconstitution of the olfactory cilia in planar lipid bilayers (tip-dip method). In the presence of InsP3 (10 microM) and Ca2+ (100 nM), a current of 1.6 +/- 0.1 pA (mean +/- SEM, n = 4) was measured, using Ba2+ as charge carrier. The I/V curve displayed a slope conductance of 45 +/- 5 pS and a reversal potential of -29 mV indicating a higher selectivity for divalent cations. This current was characterized by two mean open times (3.0 +/- 0.4 ms and 42.0 +/- 2.6 ms, n = 4) and was strongly inhibited by ruthenium red (30 microM) or heparin (10 microg/mL). Importantly, the channel activity was closely dependent on the Ca2+ concentration, with the highest open probability (Po) at 100 nM Ca2+ (Po = 0.50 +/- 0.02, n = 4). Po is lower at both higher and lower Ca2+ concentrations. A structural identification of the channel was attempted by using a large panel of antibodies, raised against several InsP3 receptor (InsP3R)/Ca2+ release channel isoforms. The type 1 InsP3R was detected in carp cerebellum and whole brain, while a lower molecular mass InsP3R, which may correspond to type 2 or 3, was detected in heart, whole brain and the soma of the olfactory neurons. None of the antibodies, however, cross-reacted with olfactory cilia. Taken together, these results indicate that in carp olfactory cilia an InsP3-dependent channel is present, distinct from the classical InsP3Rs localized on intracellular membranes.

Animals↗
PubMed1979

Cilia with defective radial spokes: a cause of human respiratory disease.

We studied the fine structure of respiratory-tract cilia in three siblings with chronic respiratory disease, comparing them with those from a patient with Kartagener's syndrome who had dynein-deficient cilia and with control patients who had chronic bronchitis or chronic sinusitis. Electron microscopy of the siblings revealed a new abnormality in the ciliary axoneme--namely, lack of the radial spokes. Their cilia showed an eccentric central pair of tubules but otherwise had a normal central sheath, outer-doublet microtubules, nexin links and dynein arms. The cilia were immotile. Mucociliary clearance was completely lacking in the three siblings and in the patient with Kartagener's syndrome, but was normal in their parents and unaffected siblings. Sperm from the male sibling showed identical structural abnormalities and were immotile. We consider the radial spoke defect to be the congenital anomaly responsible for dysfunction of the mucociliary clearance mechanism in these three patients and of the immotile sperm in one of the them. This defect is apparently another cause of the "immotilecilia syndrome."

Adult↗
PubMed2006

Polycystin-2 cation channel function is under the control of microtubular structures in primary cilia of renal epithelial cells.

Mutations in the gene encoding polycystin-2 (PC2) result in autosomal dominant polycystic kidney disease and defects in left-right asymmetry during embryogenesis. PC2 is a TRP-type Ca(2+)-permeable non-selective cation channel, which is expressed in kidney and other organs. PC2 is present and functional in microtubule-containing primary cilia of renal epithelial cells. However, no information is yet available as to whether PC2 interacts with microtubules. Here, we assessed the role of microtubular dynamics in regulating PC2 channel function in primary cilia. Isolated ciliary membranes from LLC-PK1 epithelial cells were reconstituted in a lipid bilayer system. The acute addition of the microtubular disrupter colchicine (15 mum) rapidly abolished, whereas the addition of the microtubular stabilizer paclitaxel (taxol, 15 mum) increased ciliary PC2 channel activity. The further addition of alpha-tubulin plus GTP also stimulated PC2 channel activity in ciliary membranes. However, alpha-tubulin and GTP had no effect on in vitro translated PC2. Using the yeast two-hybrid assay, we found that PC2 interacts with the microtubule-dependent motor kinesin-2 subunit KIF3A, a protein involved in polycystic kidney disease. The interaction occurred through the carboxyl termini domain of both proteins, which was further confirmed by in vitro glutathione S-transferase pull-down and dot blot overlay assays. Co-immunoprecipitation experiments showed that PC2 and KIF3A are in the same complex in native HEK293, Madin-Darby canine kidney cells (MDCK), and LLC-PK1 cells. Immunofluorescent staining also showed substantial PC2 and KIF3A co-localization in primary cilia of renal epithelial cells. The data indicate that microtubular organization regulates PC2 function, which may explain, among others, the regulatory role of PC2 in the sensory function of primary cilia.

Animals↗
PubMed2004

Primary cilia of human endothelial cells disassemble under laminar shear stress.

We identified primary cilia and centrosomes in cultured human umbilical vein endothelial cells (HUVEC) by antibodies to acetyl-alpha-tubulin and capillary morphogenesis gene-1 product (CMG-1), a human homologue of the intraflagellar transport (IFT) protein IFT-71 in Chlamydomonas. CMG-1 was present in particles along primary cilia of HUVEC at interphase and around the oldest basal body/centriole at interphase and mitosis. To study the response of primary cilia and centrosomes to mechanical stimuli, we exposed cultured HUVEC to laminar shear stress (LSS). Under LSS, all primary cilia disassembled, and centrosomes were deprived of CMG-1. We conclude that the exposure to LSS ends the IFT in cultured endothelial cells.

Amino Acid Sequence↗
PubMed2005

Cilia and the cell cycle?

A recent convergence of data indicating a relationship between cilia and proliferative diseases, such as polycystic kidney disease, has revived the long-standing enigma of the reciprocal regulatory relationship between cilia and the cell cycle. Multiple signaling pathways are localized to cilia in mammalian cells, and some proteins have been shown to act both in the cilium and in cell cycle regulation. Work from the unicellular alga Chlamydomonas is providing novel insights as to how cilia and the cell cycle are coordinately regulated.

Animals↗