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Alhassen W, Alhassen S, Chen J, Monfared RV, Alachkar A. Cilia in the Striatum Mediate Timing-Dependent Functions. Mol Neurobiol 2023; 60:545-565. [PMID: 36322337 PMCID: PMC9849326 DOI: 10.1007/s12035-022-03095-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 10/16/2022] [Indexed: 11/07/2022]
Abstract
Almost all brain cells contain cilia, antennae-like microtubule-based organelles. Yet, the significance of cilia, once considered vestigial organelles, in the higher-order brain functions is unknown. Cilia act as a hub that senses and transduces environmental sensory stimuli to generate an appropriate cellular response. Similarly, the striatum, a brain structure enriched in cilia, functions as a hub that receives and integrates various types of environmental information to drive appropriate motor response. To understand cilia's role in the striatum functions, we used loxP/Cre technology to ablate cilia from the dorsal striatum of male mice and monitored the behavioral consequences. Our results revealed an essential role for striatal cilia in the acquisition and brief storage of information, including learning new motor skills, but not in long-term consolidation of information or maintaining habitual/learned motor skills. A fundamental aspect of all disrupted functions was the "time perception/judgment deficit." Furthermore, the observed behavioral deficits form a cluster pertaining to clinical manifestations overlapping across psychiatric disorders that involve the striatum functions and are known to exhibit timing deficits. Thus, striatal cilia may act as a calibrator of the timing functions of the basal ganglia-cortical circuit by maintaining proper timing perception. Our findings suggest that dysfunctional cilia may contribute to the pathophysiology of neuro-psychiatric disorders, as related to deficits in timing perception.
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Affiliation(s)
- Wedad Alhassen
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California-Irvine, 356A Med Surge II, Irvine, CA 92697-4625 USA
| | - Sammy Alhassen
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California-Irvine, 356A Med Surge II, Irvine, CA 92697-4625 USA
| | - Jiaqi Chen
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California-Irvine, 356A Med Surge II, Irvine, CA 92697-4625 USA
| | - Roudabeh Vakil Monfared
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California-Irvine, 356A Med Surge II, Irvine, CA 92697-4625 USA
| | - Amal Alachkar
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California-Irvine, 356A Med Surge II, Irvine, CA 92697-4625 USA ,UC Irvine Center for the Neurobiology of Learning and Memory, University of California-Irvine, Irvine, CA 92697 USA ,Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA 92697 USA
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2
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Baldi P, Alhassen W, Chen S, Nguyen H, Khoudari M, Alachkar A. Large-scale analysis reveals spatiotemporal circadian patterns of cilia transcriptomes in the primate brain. J Neurosci Res 2021; 99:2610-2624. [PMID: 34310750 DOI: 10.1002/jnr.24919] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 06/08/2021] [Accepted: 06/24/2021] [Indexed: 01/13/2023]
Abstract
Cilia are dynamic subcellular systems, with core structural and functional components operating in a highly coordinated manner. Since many environmental stimuli sensed by cilia are circadian in nature, it is reasonable to speculate that genes encoding cilia structural and functional components follow rhythmic circadian patterns of expression. Using computational methods and the largest spatiotemporal gene expression atlas of primates, we identified and analyzed the circadian rhythmic expression of cilia genes across 22 primate brain areas. We found that around 73% of cilia transcripts exhibited circadian rhythmicity across at least one of 22 brain regions. In 12 brain regions, cilia transcriptomes were significantly enriched with circadian oscillating transcripts, as compared to the rest of the transcriptome. The phase of the cilia circadian transcripts deviated from the phase of the majority of the background circadian transcripts, and transcripts coding for cilia basal body components accounted for the majority of cilia circadian transcripts. In addition, adjacent or functionally connected brain nuclei had large overlapping complements of circadian cilia genes. Most remarkably, cilia circadian transcripts shared across the basal ganglia nuclei and the prefrontal cortex peaked in these structures in sequential fashion that is similar to the sequential order of activation of the basal ganglia-cortical circuitry in connection with movement coordination, albeit on completely different timescales. These findings support a role for the circadian spatiotemporal orchestration of cilia gene expression in the normal physiology of the basal ganglia-cortical circuit and motor control. Studying orchestrated cilia rhythmicity in the basal ganglia-cortical circuits and other brain circuits may help develop better functional models, and shed light on the causal effects cilia functions have on these circuits and on the regulation of movement and other behaviors.
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Affiliation(s)
- Pierre Baldi
- Department of Computer Science, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA, USA.,Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA, USA
| | - Wedad Alhassen
- Department of Pharmaceutical Sciences, School of Pharmacy, University of California-Irvine, Irvine, CA, USA
| | - Siwei Chen
- Department of Computer Science, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA, USA.,Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA, USA
| | - Henry Nguyen
- Department of Pharmaceutical Sciences, School of Pharmacy, University of California-Irvine, Irvine, CA, USA
| | - Mohammad Khoudari
- Department of Pharmaceutical Sciences, School of Pharmacy, University of California-Irvine, Irvine, CA, USA
| | - Amal Alachkar
- Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California-Irvine, Irvine, CA, USA.,Department of Pharmaceutical Sciences, School of Pharmacy, University of California-Irvine, Irvine, CA, USA
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Goldsmith TM, Sakib S, Webster D, Carlson DF, Van der Hoorn F, Dobrinski I. A reduction of primary cilia but not hedgehog signaling disrupts morphogenesis in testicular organoids. Cell Tissue Res 2020; 380:191-200. [PMID: 31900662 PMCID: PMC7815324 DOI: 10.1007/s00441-019-03121-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 10/06/2019] [Indexed: 10/25/2022]
Abstract
Most mammalian cells possess a single, non-motile primary cilium that plays an important role in mediating cellular signaling pathways, such as Hedgehog (Hh) signaling. Primary cilia are present on testicular somatic cells and demonstrate a temporal expression during development; however, their role in testicular morphogenesis is not well characterized. To investigate the role of primary cilia and Hh signaling in Sertoli cells on morphogenesis, we inhibited assembly of primary cilia through CRISPR Cas9-mediated gene editing of ODF2, a structural component of primary cilia and siRNA-mediated gene silencing of IFT88, a functional component of the intraflagellar transport system. Knockdown of ODF2 and IFT88 resulted in a 50% reduction in the number of cells with primary cilia and significant shortening of the remaining cilia. The expression of GLI1, a downstream target of Hh signaling, was significantly reduced when IFT88 but not ODF2, was downregulated. When morphogenesis was examined using tubule formation in vitro and a novel testicular organoid system, loss of cilia after knockdown of both targets affected cellular assembly and organization. While the Hh pathway was found to be active during morphogenesis in vitro, addition of the Hh antagonist cyclopamine did not affect morphogenesis in either in vitro system. These results indicate that primary cilia are important for morphogenesis in vitro but Hh signaling is not the cilia-mediated pathway responsible for orchestrating morphogenic organization.
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Affiliation(s)
- Taylor M Goldsmith
- Faculty of Veterinary Medicine Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada
- Cumming School of Medicine, Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N4N1, Canada
| | - Sadman Sakib
- Faculty of Veterinary Medicine Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada
- Cumming School of Medicine, Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N4N1, Canada
| | - Dennis Webster
- Recombinetics Inc., 1246 University Avenue West, St. Paul, MN, 55104, USA
| | - Daniel F Carlson
- Recombinetics Inc., 1246 University Avenue West, St. Paul, MN, 55104, USA
| | - Frans Van der Hoorn
- Cumming School of Medicine, Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N4N1, Canada
| | - Ina Dobrinski
- Faculty of Veterinary Medicine Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada.
- Cumming School of Medicine, Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N4N1, Canada.
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The Autophagy-Cilia Axis: An Intricate Relationship. Cells 2019; 8:cells8080905. [PMID: 31443299 PMCID: PMC6721705 DOI: 10.3390/cells8080905] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 08/08/2019] [Accepted: 08/12/2019] [Indexed: 01/19/2023] Open
Abstract
Primary cilia are microtubule-based organelles protruding from the surface of almost all vertebrate cells. This organelle represents the cell’s antenna which acts as a communication hub to transfer extracellular signals into intracellular responses during development and in tissue homeostasis. Recently, it has been shown that loss of cilia negatively regulates autophagy, the main catabolic route of the cell, probably utilizing the autophagic machinery localized at the peri-ciliary compartment. On the other side, autophagy influences ciliogenesis in a context-dependent manner, possibly to ensure that the sensing organelle is properly formed in a feedback loop model. In this review we discuss the recent literature and propose that the autophagic machinery and the ciliary proteins are functionally strictly related to control both autophagy and ciliogenesis. Moreover, we report examples of diseases associated with autophagic defects which cause cilia abnormalities, and propose and discuss the hypothesis that, at least some of the clinical manifestations observed in human diseases associated to ciliary disfunction may be the result of a perturbed autophagy.
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Girardet L, Augière C, Asselin MP, Belleannée C. Primary cilia: biosensors of the male reproductive tract. Andrology 2019; 7:588-602. [PMID: 31131532 DOI: 10.1111/andr.12650] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 04/16/2019] [Accepted: 04/17/2019] [Indexed: 12/21/2022]
Abstract
BACKGROUND The primary cilium is a microtubule-based organelle that extends transiently from the apical cell surface to act as a sensory antenna. Initially viewed as a cellular appendage of obscure significance, the primary cilium is now acknowledged as a key coordinator of signaling pathways during development and in tissue homeostasis. OBJECTIVES The aim of this review was to present the structure and function of this overlooked organelle,with an emphasis on its epididymal context and contribution to male infertility issues. MATERIALS AND METHODS A systematic review has been performed in order to include main references relevant to the aforementioned topic. RESULTS Increasing evidence demonstrates that primary cilia dysfunctions are associated with impaired male reproductive system development and male infertility issues. DISCUSSION While a large amount of data exists regarding the role of primary cilia in most organs and tissues, few studies investigated the contribution of these organelles to male reproductive tract development and homeostasis. CONCLUSION Functional studies of primary cilia constitute an emergent and exciting new area in reproductive biology research.
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Affiliation(s)
- Laura Girardet
- Department of Obstetrics, Gynecology and Reproduction, Université Laval, CHU de Québec Research Center (CHUL), Quebec City, QC, Canada
| | - Céline Augière
- Department of Obstetrics, Gynecology and Reproduction, Université Laval, CHU de Québec Research Center (CHUL), Quebec City, QC, Canada
| | - Marie-Pier Asselin
- Department of Obstetrics, Gynecology and Reproduction, Université Laval, CHU de Québec Research Center (CHUL), Quebec City, QC, Canada
| | - Clémence Belleannée
- Department of Obstetrics, Gynecology and Reproduction, Université Laval, CHU de Québec Research Center (CHUL), Quebec City, QC, Canada
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miR-183/96 plays a pivotal regulatory role in mouse photoreceptor maturation and maintenance. Proc Natl Acad Sci U S A 2017; 114:6376-6381. [PMID: 28559309 DOI: 10.1073/pnas.1618757114] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
MicroRNAs (miRNAs) are known to be essential for retinal maturation and functionality; however, the role of the most abundant miRNAs, the miR-183/96/182 cluster (miR-183 cluster), in photoreceptor cells remains unclear. Here we demonstrate that ablation of two components of the miR-183 cluster, miR-183 and miR-96, significantly affects photoreceptor maturation and maintenance in mice. Morphologically, early-onset dislocated cone nuclei, shortened outer segments and thinned outer nuclear layers are observed in the miR-183/96 double-knockout (DKO) mice. Abnormal photoreceptor responses, including abolished photopic electroretinography (ERG) responses and compromised scotopic ERG responses, reflect the functional changes in the degenerated retina. We further identify Slc6a6 as the cotarget of miR-183 and miR-96. The expression level of Slc6a6 is significantly higher in the DKO mice than in the wild-type mice. In contrast, Slc6a6 is down-regulated by adeno-associated virus-mediated overexpression of either miR-183 or miR-96 in wild-type mice. Remarkably, both silencing and overexpression of Slc6a6 in the retina are detrimental to the electrophysiological activity of the photoreceptors in response to dim light stimuli. We demonstrate that miR-183/96-mediated fine-tuning of Slc6a6 expression is indispensable for photoreceptor maturation and maintenance, thereby providing insight into the epigenetic regulation of photoreceptors in mice.
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Lambert IH, Kristensen DM, Holm JB, Mortensen OH. Physiological role of taurine--from organism to organelle. Acta Physiol (Oxf) 2015; 213:191-212. [PMID: 25142161 DOI: 10.1111/apha.12365] [Citation(s) in RCA: 206] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 08/01/2014] [Accepted: 08/13/2014] [Indexed: 12/21/2022]
Abstract
Taurine is often referred to as a semi-essential amino acid as newborn mammals have a limited ability to synthesize taurine and have to rely on dietary supply. Taurine is not thought to be incorporated into proteins as no aminoacyl tRNA synthetase has yet been identified and is not oxidized in mammalian cells. However, taurine contributes significantly to the cellular pool of organic osmolytes and has accordingly been acknowledged for its role in cell volume restoration following osmotic perturbation. This review describes taurine homeostasis in cells and organelles with emphasis on taurine biophysics/membrane dynamics, regulation of transport proteins involved in active taurine uptake and passive taurine release as well as physiological processes, for example, development, lung function, mitochondrial function, antioxidative defence and apoptosis which seem to be affected by a shift in the expression of the taurine transporters and/or the cellular taurine content.
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Affiliation(s)
- I. H. Lambert
- Section of Cellular and Developmental Biology; Department of Biology; University of Copenhagen; Copenhagen Ø Denmark
| | - D. M. Kristensen
- Section of Genomics and Molecular Biomedicine; Department of Biology; University of Copenhagen; Copenhagen Denmark
- Cellular and Metabolic Research Section; Department of Biomedical Sciences; Panum Institute; University of Copenhagen; Copenhagen N Denmark
| | - J. B. Holm
- Section of Genomics and Molecular Biomedicine; Department of Biology; University of Copenhagen; Copenhagen Denmark
| | - O. H. Mortensen
- Cellular and Metabolic Research Section; Department of Biomedical Sciences; Panum Institute; University of Copenhagen; Copenhagen N Denmark
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8
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Affiliation(s)
- Peter Satir
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, 10461 NY, USA.
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9
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Cortellino S, Wang C, Wang B, Bassi MR, Caretti E, Champeval D, Calmont A, Jarnik M, Burch J, Zaret KS, Larue L, Bellacosa A. Defective ciliogenesis, embryonic lethality and severe impairment of the Sonic Hedgehog pathway caused by inactivation of the mouse complex A intraflagellar transport gene Ift122/Wdr10, partially overlapping with the DNA repair gene Med1/Mbd4. Dev Biol 2008; 325:225-37. [PMID: 19000668 DOI: 10.1016/j.ydbio.2008.10.020] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2008] [Revised: 10/16/2008] [Accepted: 10/17/2008] [Indexed: 11/29/2022]
Abstract
Primary cilia are assembled and maintained by evolutionarily conserved intraflagellar transport (IFT) proteins that are involved in the coordinated movement of macromolecular cargo from the basal body to the cilium tip and back. The IFT machinery is organized in two structural complexes named complex A and complex B. Recently, inactivation in the mouse germline of Ift genes belonging to complex B revealed a requirement of ciliogenesis, or proteins involved in ciliogenesis, for Sonic Hedgehog (Shh) signaling in mammals. Here we report on a complex A mutant mouse, defective for the Ift122 gene. Ift122-null embryos show multiple developmental defects (exencephaly, situs viscerum inversus, delay in turning, hemorrhage and defects in limb development) that result in lethality. In the node, primary cilia were absent or malformed in homozygous mutant and heterozygous embryos, respectively. Impairment of the Shh pathway was apparent in both neural tube patterning (expansion of motoneurons and rostro-caudal level-dependent contraction or expansion of the dorso-lateral interneurons), and limb patterning (ectrosyndactyly). These phenotypes are distinct from both complex B IFT mutant embryos and embryos defective for the ciliary protein hennin/Arl13b, and suggest reduced levels of both Gli2/Gli3 activator and Gli3 repressor functions. We conclude that complex A and complex B factors play similar but distinct roles in ciliogenesis and Shh/Gli3 signaling.
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10
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Ahrabi AK, Terryn S, Valenti G, Caron N, Serradeil-Le Gal C, Raufaste D, Nielsen S, Horie S, Verbavatz JM, Devuyst O. PKD1 haploinsufficiency causes a syndrome of inappropriate antidiuresis in mice. J Am Soc Nephrol 2007; 18:1740-53. [PMID: 17475819 DOI: 10.1681/asn.2006010052] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mutations in PKD1 are associated with autosomal dominant polycystic kidney disease. Studies in mouse models suggest that the vasopressin (AVP) V2 receptor (V2R) pathway is involved in renal cyst progression, but potential changes before cystogenesis are unknown. This study used a noncystic mouse model to investigate the effect of Pkd1 haploinsufficiency on water handling and AVP signaling in the collecting duct (CD). In comparison with wild-type littermates, Pkd1(+/-) mice showed inappropriate antidiuresis with higher urine osmolality and lower plasma osmolality at baseline, despite similar renal function and water intake. The Pkd1(+/-) mice had a decreased aquaretic response to both a water load and a selective V2R antagonist, despite similar V2R distribution and affinity. They showed an inappropriate expression of AVP in brain, irrespective of the hypo-osmolality. The cAMP levels in kidney and urine were unchanged, as were the mRNA levels of aquaporin-2 (AQP2), V2R, and cAMP-dependent mediators in kidney. However, the (Ser256) phosphorylated AQP2 was upregulated in Pkd1(+/-) kidneys, with AQP2 recruitment to the apical plasma membrane of CD principal cells. The basal intracellular Ca(2+) concentration was significantly lower in isolated Pkd1(+/-) CD, with downregulated phosphorylated extracellular signal-regulated kinase 1/2 and decreased RhoA activity. Thus, in absence of cystic changes, reduced Pkd1 gene dosage is associated with a syndrome of inappropriate antidiuresis (positive water balance) reflecting decreased intracellular Ca(2+) concentration, decreased activity of RhoA, recruitment of AQP2 in the CD, and inappropriate expression of AVP in the brain. These data give new insights in the potential roles of polycystin-1 in the AVP and Ca(2+) signaling and the trafficking of AQP2 in the CD.
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Affiliation(s)
- Ali K Ahrabi
- Division of Nephrology, UCL Medical School, Université Catholique de Louvain, 10 Avenue Hippocrate, B-1200 Brussels, Belgium
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Abstract
Cilia are membrane-bounded, centriole-derived projections from the cell surface that contain a microtubule cytoskeleton, the ciliary axoneme, surrounded by a ciliary membrane. Axonemes in multiciliated cells of mammalian epithelia are 9 + 2, possess dynein arms, and are motile. In contrast, single nonmotile 9 + 0 primary cilia are found on epithelial cells, such as those of the kidney tubule, but also on nonepithelial cells, such as chondrocytes, fibroblasts, and neurons. The ciliary membranes of all cilia contain specific receptors and ion channel proteins that initiate signaling pathways controlling motility and/or linking mechanical or chemical stimuli, including sonic hedgehog and growth factors, to intracellular transduction cascades regulating differentiation, migration, and cell growth during development and in adulthood. Unique motile 9 + 0 cilia, found during development at the embryonic node, determine left-right asymmetry of the body.
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Affiliation(s)
- Peter Satir
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA.
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Lambert IH, Pedersen SF. Multiple PLA2 isoforms regulate taurine release in NIH3T3 mouse fibroblasts. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 583:99-108. [PMID: 17153593 DOI: 10.1007/978-0-387-33504-9_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- Ian Henry Lambert
- Dept. of Biochemistry, Institute for Molecular Biology and Physiology, The August Krogh Building, 13, Universitetsparken, DK-2100 Copenhagen, Denmark.
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13
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Christensen ST, Pedersen LB, Schneider L, Satir P. Sensory cilia and integration of signal transduction in human health and disease. Traffic 2007; 8:97-109. [PMID: 17241444 DOI: 10.1111/j.1600-0854.2006.00516.x] [Citation(s) in RCA: 193] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The primary cilium is a hallmark of mammalian tissue cells. Recent research has shown that these organelles display unique sets of selected signal transduction modules including receptors, ion channels, effector proteins and transcription factors that relay chemical and physical stimuli from the extracellular environment in order to control basic cellular processes during embryonic and postnatal development, as well as in tissue homeostasis in adulthood. Consequently, defects in building of the cilium or in transport or function of ciliary signal proteins are associated with a series of pathologies, including developmental disorders and cancer. In this review, we highlight recent examples of the mechanisms by which signal components are selectively targeted and transported to the ciliary membrane and we present an overview of the signal transduction pathways associated with primary and motile cilia in vertebrate cells, including platelet-derived growth factor receptor-alpha (PDGFRalpha), hedgehog and Wnt signaling pathways. Finally, we discuss the functions of these cilia-associated signal transduction pathways and their role in human health and development.
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Affiliation(s)
- Søren T Christensen
- Department of Molecular Biology, Section of Biochemistry, The August Krogh Building, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen OE, Denmark.
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Sharp JA, Lefevre C, Brennan AJ, Nicholas KR. The fur seal-a model lactation phenotype to explore molecular factors involved in the initiation of apoptosis at involution. J Mammary Gland Biol Neoplasia 2007; 12:47-58. [PMID: 17431798 DOI: 10.1007/s10911-007-9037-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Mammary gland involution requires co-ordination of milk production, immune responses, apoptosis and remodeling. Initiation and progression of each of these components involves integral control by the mammary gland. Although cell-based culture models and genetically manipulated animals have shed light on these processes, the factors controlling each step in the involution cascade are still poorly understood. The fur seal displays a unique lactation phenotype. During the lactation cycle the mammary gland downregulates milk production and initiates an immune response but fails to initiate the apoptotic phase of involution, allowing the female fur seal to undertake long foraging trips of up to 28 days between suckling bouts. Upon return to shore the female continues feeding her pup following resumption of lactation and milk production. Expression profiling of genes involved in this lactation cycle provides valuable tools for investigation of the factors responsible for the initiation of apoptosis at involution.
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Affiliation(s)
- Julie A Sharp
- CRC for Innovative Dairy Products, Department of Zoology, University of Melbourne, Melbourne, Victoria 3010, Australia.
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15
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Abstract
PURPOSE OF REVIEW Taurine, a free amino acid, is found in millimolar concentrations in most mammalian tissues. Mammals are able to synthesize taurine endogenously, but some species such as humans are more dependent on dietary sources of taurine. A growing body of evidence suggests that taurine plays a preponderant role in many physiological processes, which will be summarized in this review. RECENT FINDINGS Evidence for the requirement of taurine in the human diet has been obtained in many studies involving animal models and a few clinical trials. Recent and past studies suggested that taurine might be a pertinent candidate for use as a nutritional supplement to protect against oxidative stress, neurodegenerative diseases or atherosclerosis. Taurine has demonstrated promising actions in vitro, and as a result clinical trials have begun to investigate its effects on various diseases. SUMMARY Taurine appears to have multiple functions and plays an important role in many physiological processes, such as osmoregulation, immunomodulation and bile salt formation. Taurine analogues/derivatives have recently been reported to have a marked activity on various disorders. Taken together, these observations actualize the old story of taurine.
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Affiliation(s)
- Thomas Bouckenooghe
- Laboratoire de Biologie Cellulaire, Institut des Sciences de la Vie, Université Catholique de Louvain, Bâtiment Carnoy Place, Croix du Sud 5, B-1348 Louvain-la-Neuve, Belgium
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16
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Abstract
Taurine, an important mediator of cellular volume regulation in the central nervous system, is accumulated into neurons and glia by means of a highly specific sodium-dependent membrane transporter. During hyperosmotic cell shrinkage, net cellular taurine content increases as taurine transporter activity is enhanced via elevated gene expression of the transporter protein. In hypo-osmotic conditions, taurine is rapidly lost from cells by means of taurine-conducting membrane channels. We reasoned that changes in taurine transporter activity also might accompany cell swelling to minimize re-accumulation of taurine from the extracellular space. Thus, we determined the kinetic and pharmacological characteristics of neuronal taurine transport and the response to osmotic swelling. Accumulation of radioactive taurine is strongly temperature dependent and occurs via saturable and non-saturable pathways. At concentrations of taurine expected in extracellular fluid in vivo, 98% of taurine accumulation would occur via the saturable pathway. This pathway obeys Michaelis-Menten kinetics with a Km of 30.0 +/- 8.8 microm (mean +/- SE) and Jmax of 2.1 +/- 0.2 nmol/mg protein min. The saturable pathway is dependent on extracellular sodium with an effective binding constant of 80.0 +/- 3.1 mm and a Hill coefficient of 2.1 +/- 0.1. This pathway is inhibited by structural analogues of taurine and by the anion channel inhibitors, 4,4'-diisothiocyanostilbene-2, 2'-disulfonic acid (DIDS) and 5-nitro-2-(3 phenylpropylamino) benzoic acid (NPPB). NPPB, but not DIDS, also reduces the ATP content of the cell cultures. Osmotic swelling at constant extracellular sodium concentration reduces the Jmax of the saturable transport pathway by approximately 48%, increases Kdiff for the non-saturable pathway by 77%, but has no effect on cellular ATP content. These changes in taurine transport occurring in swollen neurons in vivo would contribute to net reduction of taurine content and resulting volume regulation.
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Affiliation(s)
- James E Olson
- Department of Emergency Medicine, Wright State University School of Medicine, Cox Institute, Kettering, Ohio 45429, USA.
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Wang Q, Pan J, Snell WJ. Intraflagellar Transport Particles Participate Directly in Cilium-Generated Signaling in Chlamydomonas. Cell 2006; 125:549-62. [PMID: 16678098 DOI: 10.1016/j.cell.2006.02.044] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 11/18/2005] [Accepted: 02/07/2006] [Indexed: 12/27/2022]
Abstract
Primary cilia are widely used for signal transduction during development and in homeostasis and are assembled and maintained by intraflagellar transport (IFT). Here, we have dissected the role of IFT in signaling within the flagella (structural and functional counterparts of cilia) of the biflagellated green alga Chlamydomonas. Using a conditional IFT mutant enables us to deplete the IFT machinery from intact, existing flagella. We identify a cGMP-dependent protein kinase (CrPKG) within flagella as the substrate of a protein tyrosine kinase activated by flagellar adhesion during fertilization. We demonstrate that flagellar adhesion stimulates association of CrPKG with a new flagellar compartment. Moreover, formation of the compartment requires IFT, and IFT particles themselves are part of the compartment. Our results lead to a model in which the IFT machinery is required not only for assembling cilia and flagella but also for organizing a signaling pathway within the organelles during cilium-generated signaling.
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Affiliation(s)
- Qian Wang
- Department of Cell Biology, University of Texas Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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