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Martinez D, Zhu M, Guidry JJ, Majeste N, Mao H, Yanofsky ST, Tian X, Wu C. Mask, the Drosophila ankyrin repeat and KH domain-containing protein, affects microtubule stability. J Cell Sci 2021; 134:272264. [PMID: 34553767 PMCID: PMC8572007 DOI: 10.1242/jcs.258512] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 09/16/2021] [Indexed: 11/26/2022] Open
Abstract
Proper regulation of microtubule (MT) stability and dynamics is vital for essential cellular processes, including axonal transportation and synaptic growth and remodeling in neurons. In the present study, we demonstrate that the Drosophila ankyrin repeat and KH domain-containing protein Mask negatively affects MT stability in both larval muscles and motor neurons. In larval muscles, loss-of-function of mask increases MT polymer length, and in motor neurons, loss of mask function results in overexpansion of the presynaptic terminal at the larval neuromuscular junctions (NMJs). mask genetically interacts with stathmin (stai), a neuronal modulator of MT stability, in the regulation of axon transportation and synaptic terminal stability. Our structure–function analysis of Mask revealed that its ankyrin repeats domain-containing N-terminal portion is sufficient to mediate Mask's impact on MT stability. Furthermore, we discovered that Mask negatively regulates the abundance of the MT-associated protein Jupiter in motor neuron axons, and that neuronal knocking down of Jupiter partially suppresses mask loss-of-function phenotypes at the larval NMJs. Taken together, our studies demonstrate that Mask is a novel regulator for MT stability, and such a role of Mask requires normal function of Jupiter. Summary: Mask is a novel regulator of MT stability in Drosophila. Mask shows prominent interplay with two important modulators of MT, Tau and Stathmin (Stai), whose mutations are related to human diseases.
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Affiliation(s)
- Daniel Martinez
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Mingwei Zhu
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Jessie J Guidry
- Proteomics Core Facility, and the Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Niles Majeste
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Hui Mao
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Sarah T Yanofsky
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Xiaolin Tian
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Chunlai Wu
- Neuroscience Center of Excellence, Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
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2
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Roubinet C, White IJ, Baum B. Asymmetric nuclear division in neural stem cells generates sibling nuclei that differ in size, envelope composition, and chromatin organization. Curr Biol 2021; 31:3973-3983.e4. [PMID: 34297912 PMCID: PMC8491657 DOI: 10.1016/j.cub.2021.06.063] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 05/12/2021] [Accepted: 06/23/2021] [Indexed: 01/08/2023]
Abstract
Although nuclei are the defining features of eukaryotes, we still do not fully understand how the nuclear compartment is duplicated and partitioned during division. This is especially the case for organisms that do not completely disassemble their nuclear envelope upon entry into mitosis. In studying this process in Drosophila neural stem cells, which undergo asymmetric divisions, we find that the nuclear compartment boundary persists during mitosis thanks to the maintenance of a supporting nuclear lamina. This mitotic nuclear envelope is then asymmetrically remodeled and partitioned to give rise to two daughter nuclei that differ in envelope composition and exhibit a >30-fold difference in volume. The striking difference in nuclear size was found to depend on two consecutive processes: asymmetric nuclear envelope resealing at mitotic exit at sites defined by the central spindle, and differential nuclear growth that appears to depend on the available local reservoir of ER/nuclear membranes, which is asymmetrically partitioned between the two daughter cells. Importantly, these asymmetries in size and composition of the daughter nuclei, and the associated asymmetries in chromatin organization, all become apparent long before the cortical release and the nuclear import of cell fates determinants. Thus, asymmetric nuclear remodeling during stem cell divisions may contribute to the generation of cellular diversity by initiating distinct transcriptional programs in sibling nuclei that contribute to later changes in daughter cell identity and fate.
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Affiliation(s)
- Chantal Roubinet
- MRC Laboratory for Molecular Biology, University College London, London, UK; MRC Laboratory of Molecular Cell Biology, Cambridge, UK.
| | - Ian J White
- MRC Laboratory for Molecular Biology, University College London, London, UK
| | - Buzz Baum
- MRC Laboratory for Molecular Biology, University College London, London, UK; Institute for the Physics of Living Systems, University College London, London, UK; MRC Laboratory of Molecular Cell Biology, Cambridge, UK.
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3
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Dong W, Lu J, Zhang X, Wu Y, Lettieri K, Hammond GR, Hong Y. A polybasic domain in aPKC mediates Par6-dependent control of membrane targeting and kinase activity. J Cell Biol 2021; 219:151883. [PMID: 32580209 PMCID: PMC7337507 DOI: 10.1083/jcb.201903031] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 03/04/2020] [Accepted: 04/19/2020] [Indexed: 12/14/2022] Open
Abstract
Mechanisms coupling the atypical PKC (aPKC) kinase activity to its subcellular localization are essential for cell polarization. Unlike other members of the PKC family, aPKC has no well-defined plasma membrane (PM) or calcium binding domains, leading to the assumption that its subcellular localization relies exclusively on protein–protein interactions. Here we show that in both Drosophila and mammalian cells, the pseudosubstrate region (PSr) of aPKC acts as a polybasic domain capable of targeting aPKC to the PM via electrostatic binding to PM PI4P and PI(4,5)P2. However, physical interaction between aPKC and Par-6 is required for the PM-targeting of aPKC, likely by allosterically exposing the PSr to bind PM. Binding of Par-6 also inhibits aPKC kinase activity, and such inhibition can be relieved through Par-6 interaction with apical polarity protein Crumbs. Our data suggest a potential mechanism in which allosteric regulation of polybasic PSr by Par-6 couples the control of both aPKC subcellular localization and spatial activation of its kinase activity.
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Affiliation(s)
- Wei Dong
- Department of Cell Biology, University of Pittsburgh Medical School, Pittsburgh, PA
| | - Juan Lu
- Department of Cell Biology, University of Pittsburgh Medical School, Pittsburgh, PA
| | - Xuejing Zhang
- Department of Cell Biology, University of Pittsburgh Medical School, Pittsburgh, PA
| | - Yan Wu
- Jiangsu University, Zhengjiang, Jiangsu, People's Republic of China
| | - Kaela Lettieri
- First Experience in Research Program, University of Pittsburgh, Pittsburgh, PA
| | - Gerald R Hammond
- Department of Cell Biology, University of Pittsburgh Medical School, Pittsburgh, PA
| | - Yang Hong
- Department of Cell Biology, University of Pittsburgh Medical School, Pittsburgh, PA
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4
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Martin E, Girardello R, Dittmar G, Ludwig A. New insights into the organization and regulation of the apical polarity network in mammalian epithelial cells. FEBS J 2021; 288:7073-7095. [DOI: 10.1111/febs.15710] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 01/05/2021] [Accepted: 01/11/2021] [Indexed: 12/11/2022]
Affiliation(s)
- Eleanor Martin
- School of Biological Sciences Nanyang Technological University Singapore City Singapore
- Proteomics of Cellular Signaling Luxembourg Institute of Health Strassen Luxembourg
| | - Rossana Girardello
- School of Biological Sciences Nanyang Technological University Singapore City Singapore
- Proteomics of Cellular Signaling Luxembourg Institute of Health Strassen Luxembourg
| | - Gunnar Dittmar
- Proteomics of Cellular Signaling Luxembourg Institute of Health Strassen Luxembourg
- Department of Life Sciences and Medicine University of Luxembourg Luxembourg
| | - Alexander Ludwig
- School of Biological Sciences Nanyang Technological University Singapore City Singapore
- NTU Institute of Structural Biology (NISB) Experimental Medicine Building Nanyang Technological University Singapore City Singapore
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5
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Link N, Chung H, Jolly A, Withers M, Tepe B, Arenkiel BR, Shah PS, Krogan NJ, Aydin H, Geckinli BB, Tos T, Isikay S, Tuysuz B, Mochida GH, Thomas AX, Clark RD, Mirzaa GM, Lupski JR, Bellen HJ. Mutations in ANKLE2, a ZIKA Virus Target, Disrupt an Asymmetric Cell Division Pathway in Drosophila Neuroblasts to Cause Microcephaly. Dev Cell 2019; 51:713-729.e6. [PMID: 31735666 DOI: 10.1016/j.devcel.2019.10.009] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 08/19/2019] [Accepted: 10/14/2019] [Indexed: 12/12/2022]
Abstract
The apical Par complex, which contains atypical protein kinase C (aPKC), Bazooka (Par-3), and Par-6, is required for establishing polarity during asymmetric division of neuroblasts in Drosophila, and its activity depends on L(2)gl. We show that loss of Ankle2, a protein associated with microcephaly in humans and known to interact with Zika protein NS4A, reduces brain volume in flies and impacts the function of the Par complex. Reducing Ankle2 levels disrupts endoplasmic reticulum (ER) and nuclear envelope morphology, releasing the kinase Ballchen-VRK1 into the cytosol. These defects are associated with reduced phosphorylation of aPKC, disruption of Par-complex localization, and spindle alignment defects. Importantly, removal of one copy of ballchen or l(2)gl suppresses Ankle2 mutant phenotypes and restores viability and brain size. Human mutational studies implicate the above-mentioned genes in microcephaly and motor neuron disease. We suggest that NS4A, ANKLE2, VRK1, and LLGL1 define a pathway impinging on asymmetric determinants of neural stem cell division.
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Affiliation(s)
- Nichole Link
- Howard Hughes Medical Institute, BCM, Houston, TX 77030, USA; Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Hyunglok Chung
- Howard Hughes Medical Institute, BCM, Houston, TX 77030, USA; Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Angad Jolly
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; MD/PhD Medical Scientist Training Program and MHG Graduate program, BCM, Houston, TX 77030, USA
| | - Marjorie Withers
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA
| | - Burak Tepe
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA; Program in Developmental Biology, BCM, Houston, TX 77030, USA
| | - Benjamin R Arenkiel
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA; Program in Developmental Biology, BCM, Houston, TX 77030, USA
| | - Priya S Shah
- Department of Chemical Engineering and Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, CA 95616, USA
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; California Institute for Quantitative Biosciences, QB3, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Hatip Aydin
- Center of Genetics Diagnosis, Zeynep Kamil Maternity and Children's Training and Research Hospital, Istanbul, Turkey
| | - Bilgen B Geckinli
- Department of Medical Genetics, Marmara University School of Medicine, Istanbul, Turkey
| | - Tulay Tos
- Department of Medical Genetics, Dr. Sami Ulus Research and Training Hospital of Women's and Children's Health and Diseases, Ankara, Turkey
| | - Sedat Isikay
- Department of Physiotherapy and Rehabilitation, Hasan Kalyoncu University, School of Health Sciences, Gaziantep, Turkey
| | - Beyhan Tuysuz
- Department of Pediatrics, Istanbul University-Cerrahpasa, Medical Faculty, Istanbul, Turkey
| | - Ganesh H Mochida
- Division of Genetics and Genomics, Department of Pediatrics and Manton Center for Orphan Disease Research, Boston Children's Hospital, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA; Pediatric Neurology Unit, Department of Neurology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Ajay X Thomas
- Department of Pediatrics, Section of Neurology and Developmental Neuroscience, BCM, Houston, TX 77030, USA; Section of Child Neurology, Texas Children's Hospital, Houston, TX 77030, USA
| | - Robin D Clark
- Division of Medical Genetics, Department of Pediatrics, Loma Linda University Medical Center, Loma Linda, CA 92354, USA
| | - Ghayda M Mirzaa
- Department of Pediatrics, University of Washington, Seattle, WA 98195, USA; Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98105, USA
| | - James R Lupski
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Department of Pediatrics, BCM, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA; Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA
| | - Hugo J Bellen
- Howard Hughes Medical Institute, BCM, Houston, TX 77030, USA; Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA; MD/PhD Medical Scientist Training Program and MHG Graduate program, BCM, Houston, TX 77030, USA; Program in Developmental Biology, BCM, Houston, TX 77030, USA.
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6
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Abstract
Establishing and maintaining cell polarity are dynamic processes that necessitate complicated but highly regulated protein interactions. Phosphorylation is a powerful mechanism for cells to control the function and subcellular localization of a target protein, and multiple kinases have played critical roles in cell polarity. Among them, atypical protein kinase C (aPKC) is likely the most studied kinase in cell polarity and has the largest number of downstream substrates characterized so far. More than half of the polarity proteins that are essential for regulating cell polarity have been identified as aPKC substrates. This review covers mainly studies of aPKC in regulating anterior-posterior polarity in the worm one-cell embryo and apical-basal polarity in epithelial cells and asymmetrically dividing cells (for example,
Drosophila neuroblasts). We will go through aPKC target proteins in cell polarity and discuss various mechanisms by which aPKC phosphorylation controls their subcellular localizations and biological functions. We will also review the recent progress in determining the detailed molecular mechanisms in spatial and temporal control of aPKC subcellular localization and kinase activity during cell polarization.
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Affiliation(s)
- Yang Hong
- Department of Cell Biology, University of Pittsburgh School of Medicine, S325 BST, 3500 Terrace Street, Pittsburgh, PA 15261, USA
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7
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EGFR/ARF6 regulation of Hh signalling stimulates oncogenic Ras tumour overgrowth. Nat Commun 2017; 8:14688. [PMID: 28281543 PMCID: PMC5353614 DOI: 10.1038/ncomms14688] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 01/20/2017] [Indexed: 12/15/2022] Open
Abstract
Multiple signalling events interact in cancer cells. Oncogenic Ras cooperates with Egfr, which cannot be explained by the canonical signalling paradigm. In turn, Egfr cooperates with Hedgehog signalling. How oncogenic Ras elicits and integrates Egfr and Hedgehog signals to drive overgrowth remains unclear. Using a Drosophila tumour model, we show that Egfr cooperates with oncogenic Ras via Arf6, which functions as a novel regulator of Hh signalling. Oncogenic Ras induces the expression of Egfr ligands. Egfr then signals through Arf6, which regulates Hh transport to promote Hh signalling. Blocking any step of this signalling cascade inhibits Hh signalling and correspondingly suppresses the growth of both, fly and human cancer cells harbouring oncogenic Ras mutations. These findings highlight a non-canonical Egfr signalling mechanism, centered on Arf6 as a novel regulator of Hh signalling. This explains both, the puzzling requirement of Egfr in oncogenic Ras-mediated overgrowth and the cooperation between Egfr and Hedgehog. EGFR signalling is required for oncogenic Ras driven tumorigenesis. In this study, using a Drosophila tumour model the authors demonstrate that depletion of Arf6, a Ras-related GTP-binding protein activated by EGFR, supresses oncogenic Ras driven overgrowth via modulation of Hedgehog signalling.
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8
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Drosophila melanogaster Neuroblasts: A Model for Asymmetric Stem Cell Divisions. Results Probl Cell Differ 2017; 61:183-210. [PMID: 28409305 DOI: 10.1007/978-3-319-53150-2_8] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Asymmetric cell division (ACD) is a fundamental mechanism to generate cell diversity, giving rise to daughter cells with different developmental potentials. ACD is manifested in the asymmetric segregation of proteins or mRNAs, when the two daughter cells differ in size or are endowed with different potentials to differentiate into a particular cell type (Horvitz and Herskowitz, Cell 68:237-255, 1992). Drosophila neuroblasts, the neural stem cells of the developing fly brain, are an ideal system to study ACD since this system encompasses all of these characteristics. Neuroblasts are intrinsically polarized cells, utilizing polarity cues to orient the mitotic spindle, segregate cell fate determinants asymmetrically, and regulate spindle geometry and physical asymmetry. The neuroblast system has contributed significantly to the elucidation of the basic molecular mechanisms underlying ACD. Recent findings also highlight its usefulness to study basic aspects of stem cell biology and tumor formation. In this review, we will focus on what has been learned about the basic mechanisms underlying ACD in fly neuroblasts.
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9
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Jeganathan N, Predescu D, Zhang J, Sha F, Bardita C, Patel M, Wood S, Borgia JA, Balk RA, Predescu S. Rac1-mediated cytoskeleton rearrangements induced by intersectin-1s deficiency promotes lung cancer cell proliferation, migration and metastasis. Mol Cancer 2016; 15:59. [PMID: 27629044 PMCID: PMC5024437 DOI: 10.1186/s12943-016-0543-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 09/06/2016] [Indexed: 12/21/2022] Open
Abstract
Background The mechanisms involved in lung cancer (LC) progression are poorly understood making discovery of successful therapies difficult. Adaptor proteins play a crucial role in cancer as they link cell surface receptors to specific intracellular pathways. Intersectin-1s (ITSN-1s) is an important multidomain adaptor protein implicated in the pathophysiology of numerous pulmonary diseases. To date, the role of ITSN-1s in LC has not been studied. Methods Human LC cells, human LC tissue and A549 LC cells stable transfected with myc-ITSN-1s construct (A549 + ITSN-1s) were used in correlation with biochemical, molecular biology and morphological studies. In addition scratch assay with time lapse microscopy and in vivo xenograft tumor and mouse metastasis assays were performed. Results ITSN-1s, a prevalent protein of lung tissue, is significantly downregulated in human LC cells and LC tissue. Restoring ITSN-1s protein level decreases LC cell proliferation and clonogenic potential. In vivo studies indicate that immunodeficient mice injected with A549 + ITSN-1s cells develop less and smaller metastatic tumors compared to mice injected with A549 cells. Our studies also show that restoring ITSN-1s protein level increases the interaction between Cbl E3 ubiquitin ligase and Eps8 resulting in enhanced ubiquitination of the Eps8 oncoprotein. Subsequently, downstream unproductive assembly of the Eps8-mSos1 complex leads to impaired activation of the small GTPase Rac1. Impaired Rac1 activation mediated by ITSN-1s reorganizes the cytoskeleton (increased thick actin bundles and focal adhesion (FA) complexes as well as collapse of the vimentin filament network) in favor of decreased LC cell migration and metastasis. Conclusion ITSN-1s induced Eps8 ubiquitination and impaired Eps8-mSos1 complex formation, leading to impaired activation of Rac1, is a novel signaling mechanism crucial for abolishing the progression and metastatic potential of LC cells. Electronic supplementary material The online version of this article (doi:10.1186/s12943-016-0543-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Niranjan Jeganathan
- Division of Pulmonary and Critical Care Medicine, Rush University Medical Center and Rush Medical College, 1750 W. Harrison Street, 299 Jelke South Center, Chicago, IL, 60612, USA.
| | - Dan Predescu
- Department of Pharmacology and Division of Pulmonary and Critical Care Medicine, Rush University, 1750 W. Harrison Street, 1415 Jelke, Chicago, IL, 60612, USA
| | - Jin Zhang
- Department of Pharmacology, Rush University, 1750 W. Harrison Street, 1533 Jelke, Chicago, IL, 60612, USA
| | - Fei Sha
- Department of Pharmacology, Rush University, 1750 W. Harrison Street, 1533 Jelke, Chicago, IL, 60612, USA
| | - Cristina Bardita
- Department of Pharmacology, Rush University, 1750 W. Harrison Street, 1537 Jelke, Chicago, IL, 60612, USA
| | - Monal Patel
- Department of Pharmacology, Rush University, 1750 W. Harrison Street, 1533 Jelke, Chicago, IL, 60612, USA
| | - Stephen Wood
- Department of Immunology, Rush University, 1735 W. Harrison Street, 663 Cohn, Chicago, IL, 60612, USA
| | - Jeffrey A Borgia
- Department of Biochemistry, Rush University, 1750 W. Harrison Street, 1415 Jelke, Chicago, IL, 60612, USA
| | - Robert A Balk
- Division of Pulmonary and Critical Care Medicine, Rush University Medical Center and Rush Medical College, 1750 W. Harrison Street, 293 Jelke, Chicago, IL, 60612, USA
| | - Sanda Predescu
- Department of Pharmacology and Division of Pulmonary and Critical Care Medicine, Rush University Medical Center and Rush Medical College, 1750 W. Harrison Street, 1535 Jelke, Chicago, IL, 60612, USA
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10
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Molecular Control of Atypical Protein Kinase C: Tipping the Balance between Self-Renewal and Differentiation. J Mol Biol 2016; 428:1455-64. [PMID: 26992354 DOI: 10.1016/j.jmb.2016.03.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/20/2016] [Accepted: 03/03/2016] [Indexed: 01/05/2023]
Abstract
Complex organisms are faced with the challenge of generating and maintaining diverse cell types, ranging from simple epithelia to neurons and motile immune cells [1-3]. To meet this challenge, a complex set of regulatory pathways controls nearly every aspect of cell growth and function, including genetic and epigenetic programming, cytoskeleton dynamics, and protein trafficking. The far reach of cell fate specification pathways makes it particularly catastrophic when they malfunction, both during development and for tissue homeostasis in adult organisms. Furthermore, the therapeutic promise of stem cells derives from their ability to deftly navigate the multitude of pathways that control cell fate [4]. How the molecular components making up these pathways function to specify cell fate is beginning to become clear. Work from diverse systems suggests that the atypical Protein Kinase C (aPKC) is a key regulator of cell fate decisions in metazoans [5-7]. Here, we examine some of the diverse physiological outcomes of aPKC's function in differentiation, along with the molecular pathways that control aPKC and those that are responsive to changes in its catalytic activity.
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11
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Sabherwal N, Thuret R, Lea R, Stanley P, Papalopulu N. aPKC phosphorylates p27Xic1, providing a mechanistic link between apicobasal polarity and cell-cycle control. Dev Cell 2015; 31:559-71. [PMID: 25490266 PMCID: PMC4262734 DOI: 10.1016/j.devcel.2014.10.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 09/05/2014] [Accepted: 10/29/2014] [Indexed: 11/30/2022]
Abstract
During the development of the nervous system, apicobasally polarized stem cells are characterized by a shorter cell cycle than nonpolar progenitors, leading to a lower differentiation potential of these cells. However, how polarization might be directly linked to the kinetics of the cell cycle is not understood. Here, we report that apicobasally polarized neuroepithelial cells in Xenopus laevis have a shorter cell cycle than nonpolar progenitors, consistent with mammalian systems. We show that the apically localized serine/threonine kinase aPKC directly phosphorylates an N-terminal site of the cell-cycle inhibitor p27Xic1 and reduces its ability to inhibit the cyclin-dependent kinase 2 (Cdk2), leading to shortening of G1 and S phases. Overexpression of activated aPKC blocks the neuronal differentiation-promoting activity of p27Xic1. These findings provide a direct mechanistic link between apicobasal polarity and the cell cycle, which may explain how proliferation is favored over differentiation in polarized neural stem cells. aPKC shortens G1 and S phases of cell cycle by phosphorylating p27Xic1 Phosphorylated p27Xic1 exhibits weaker binding to and inhibition of Cdk2 p27Xic1 promotes neuronal differentiation and elongates cell cycle via G1 phase Effects of p27Xic1 on neuronal differentiation are rescued by activated aPKC
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Affiliation(s)
- Nitin Sabherwal
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
| | - Raphael Thuret
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Robert Lea
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Peter Stanley
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Nancy Papalopulu
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
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12
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Chabu C, Xu T. Oncogenic Ras stimulates Eiger/TNF exocytosis to promote growth. Development 2014; 141:4729-39. [PMID: 25411211 DOI: 10.1242/dev.108092] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Oncogenic mutations in Ras deregulate cell death and proliferation to cause cancer in a significant number of patients. Although normal Ras signaling during development has been well elucidated in multiple organisms, it is less clear how oncogenic Ras exerts its effects. Furthermore, cancers with oncogenic Ras mutations are aggressive and generally resistant to targeted therapies or chemotherapy. We identified the exocytosis component Sec15 as a synthetic suppressor of oncogenic Ras in an in vivo Drosophila mosaic screen. We found that oncogenic Ras elevates exocytosis and promotes the export of the pro-apoptotic ligand Eiger (Drosophila TNF). This blocks tumor cell death and stimulates overgrowth by activating the JNK-JAK-STAT non-autonomous proliferation signal from the neighboring wild-type cells. Inhibition of Eiger/TNF exocytosis or interfering with the JNK-JAK-STAT non-autonomous proliferation signaling at various steps suppresses oncogenic Ras-mediated overgrowth. Our findings highlight important cell-intrinsic and cell-extrinsic roles of exocytosis during oncogenic growth and provide a new class of synthetic suppressors for targeted therapy approaches.
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Affiliation(s)
- Chiswili Chabu
- Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, Boyer Center for Molecular Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
| | - Tian Xu
- Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, Boyer Center for Molecular Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
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13
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Yamamoto S, Jaiswal M, Charng WL, Gambin T, Karaca E, Mirzaa G, Wiszniewski W, Sandoval H, Haelterman NA, Xiong B, Zhang K, Bayat V, David G, Li T, Chen K, Gala U, Harel T, Pehlivan D, Penney S, Vissers LELM, de Ligt J, Jhangiani SN, Xie Y, Tsang SH, Parman Y, Sivaci M, Battaloglu E, Muzny D, Wan YW, Liu Z, Lin-Moore AT, Clark RD, Curry CJ, Link N, Schulze KL, Boerwinkle E, Dobyns WB, Allikmets R, Gibbs RA, Chen R, Lupski JR, Wangler MF, Bellen HJ. A drosophila genetic resource of mutants to study mechanisms underlying human genetic diseases. Cell 2014; 159:200-214. [PMID: 25259927 PMCID: PMC4298142 DOI: 10.1016/j.cell.2014.09.002] [Citation(s) in RCA: 257] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 06/04/2014] [Accepted: 09/02/2014] [Indexed: 12/31/2022]
Abstract
Invertebrate model systems are powerful tools for studying human disease owing to their genetic tractability and ease of screening. We conducted a mosaic genetic screen of lethal mutations on the Drosophila X chromosome to identify genes required for the development, function, and maintenance of the nervous system. We identified 165 genes, most of whose function has not been studied in vivo. In parallel, we investigated rare variant alleles in 1,929 human exomes from families with unsolved Mendelian disease. Genes that are essential in flies and have multiple human homologs were found to be likely to be associated with human diseases. Merging the human data sets with the fly genes allowed us to identify disease-associated mutations in six families and to provide insights into microcephaly associated with brain dysgenesis. This bidirectional synergism between fly genetics and human genomics facilitates the functional annotation of evolutionarily conserved genes involved in human health.
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Affiliation(s)
- Shinya Yamamoto
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA; Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Jan and Dan Duncan Neurological Research Institute, Houston, TX 77030, USA
| | - Manish Jaiswal
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Howard Hughes Medical Institute, Houston, TX 77030, USA
| | - Wu-Lin Charng
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA; Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA
| | - Tomasz Gambin
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Institute of Computer Science, Warsaw University of Technology, 00-661 Warsaw, Poland
| | - Ender Karaca
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA
| | - Ghayda Mirzaa
- Department of Pediatrics, University of Washington, Seattle, WA 98195, USA; Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Wojciech Wiszniewski
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA
| | - Hector Sandoval
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA
| | - Nele A Haelterman
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA
| | - Bo Xiong
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA
| | - Ke Zhang
- Program in Structural and Computational Biology and Molecular Biophysics, BCM, Houston, TX 77030, USA
| | - Vafa Bayat
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA
| | - Gabriela David
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA
| | - Tongchao Li
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA
| | - Kuchuan Chen
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA
| | - Upasana Gala
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA
| | - Tamar Harel
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA
| | - Davut Pehlivan
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA
| | - Samantha Penney
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA
| | - Lisenka E L M Vissers
- Department of Human Genetics, Radboudumc, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Joep de Ligt
- Department of Human Genetics, Radboudumc, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | | | - Yajing Xie
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
| | - Stephen H Tsang
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA; Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
| | - Yesim Parman
- Neurology Department and Neuropathology Laboratory, Istanbul University Medical School, Istanbul 34390, Turkey
| | - Merve Sivaci
- Department of Molecular Biology and Genetics, Bogazici University, Istanbul 34342, Turkey
| | - Esra Battaloglu
- Department of Molecular Biology and Genetics, Bogazici University, Istanbul 34342, Turkey
| | - Donna Muzny
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Human Genome Sequencing Center, BCM, Houston, TX 77030, USA
| | - Ying-Wooi Wan
- Jan and Dan Duncan Neurological Research Institute, Houston, TX 77030, USA; Department of Obstetrics and Gynecology, BCM, Houston, TX 77030, USA
| | - Zhandong Liu
- Jan and Dan Duncan Neurological Research Institute, Houston, TX 77030, USA; Department of Pediatrics, BCM, Houston, TX 77030, USA
| | | | - Robin D Clark
- Division of Medical Genetics, Department of Pediatrics, Loma Linda University Medical Center, Loma Linda, CA 92354, USA
| | - Cynthia J Curry
- Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143, USA; Genetic Medicine Central California, Fresno, CA 93701, USA
| | - Nichole Link
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA
| | - Karen L Schulze
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Howard Hughes Medical Institute, Houston, TX 77030, USA
| | - Eric Boerwinkle
- Human Genome Sequencing Center, BCM, Houston, TX 77030, USA; Human Genetics Center, University of Texas, Health Science Center, Houston, TX 77030, USA
| | - William B Dobyns
- Department of Pediatrics, University of Washington, Seattle, WA 98195, USA; Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA; Department of Neurology, University of Washington, Seattle WA 98195, USA
| | - Rando Allikmets
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA; Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
| | - Richard A Gibbs
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Human Genome Sequencing Center, BCM, Houston, TX 77030, USA
| | - Rui Chen
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA; Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Human Genome Sequencing Center, BCM, Houston, TX 77030, USA
| | - James R Lupski
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA; Human Genome Sequencing Center, BCM, Houston, TX 77030, USA
| | - Michael F Wangler
- Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Texas Children's Hospital, Houston, TX 77030, USA.
| | - Hugo J Bellen
- Program in Developmental Biology, Baylor College of Medicine (BCM), Houston, TX 77030, USA; Department of Molecular and Human Genetics, BCM, Houston, TX 77030, USA; Jan and Dan Duncan Neurological Research Institute, Houston, TX 77030, USA; Howard Hughes Medical Institute, Houston, TX 77030, USA; Program in Structural and Computational Biology and Molecular Biophysics, BCM, Houston, TX 77030, USA; Department of Neuroscience, BCM, Houston, TX 77030, USA.
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14
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Genetic and functional studies implicate synaptic overgrowth and ring gland cAMP/PKA signaling defects in the Drosophila melanogaster neurofibromatosis-1 growth deficiency. PLoS Genet 2013; 9:e1003958. [PMID: 24278035 PMCID: PMC3836801 DOI: 10.1371/journal.pgen.1003958] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 10/01/2013] [Indexed: 12/21/2022] Open
Abstract
Neurofibromatosis type 1 (NF1), a genetic disease that affects 1 in 3,000, is caused by loss of a large evolutionary conserved protein that serves as a GTPase Activating Protein (GAP) for Ras. Among Drosophila melanogaster Nf1 (dNf1) null mutant phenotypes, learning/memory deficits and reduced overall growth resemble human NF1 symptoms. These and other dNf1 defects are relatively insensitive to manipulations that reduce Ras signaling strength but are suppressed by increasing signaling through the 3′-5′ cyclic adenosine monophosphate (cAMP) dependent Protein Kinase A (PKA) pathway, or phenocopied by inhibiting this pathway. However, whether dNf1 affects cAMP/PKA signaling directly or indirectly remains controversial. To shed light on this issue we screened 486 1st and 2nd chromosome deficiencies that uncover >80% of annotated genes for dominant modifiers of the dNf1 pupal size defect, identifying responsible genes in crosses with mutant alleles or by tissue-specific RNA interference (RNAi) knockdown. Validating the screen, identified suppressors include the previously implicated dAlk tyrosine kinase, its activating ligand jelly belly (jeb), two other genes involved in Ras/ERK signal transduction and several involved in cAMP/PKA signaling. Novel modifiers that implicate synaptic defects in the dNf1 growth deficiency include the intersectin-related synaptic scaffold protein Dap160 and the cholecystokinin receptor-related CCKLR-17D1 drosulfakinin receptor. Providing mechanistic clues, we show that dAlk, jeb and CCKLR-17D1 are among mutants that also suppress a recently identified dNf1 neuromuscular junction (NMJ) overgrowth phenotype and that manipulations that increase cAMP/PKA signaling in adipokinetic hormone (AKH)-producing cells at the base of the neuroendocrine ring gland restore the dNf1 growth deficiency. Finally, supporting our previous contention that ALK might be a therapeutic target in NF1, we report that human ALK is expressed in cells that give rise to NF1 tumors and that NF1 regulated ALK/RAS/ERK signaling appears conserved in man. Neurofibromatosis type 1 (NF1) is a genetic disease that affects 1 in 3,000 and that is caused by loss of a protein that inactivates Ras oncoproteins. NF1 is a characteristically variable disease that predisposes patients to several symptoms, the most common of which include benign and malignant tumors, reduced growth and learning problems. We and others previously found that fruit fly mutants that lack a highly conserved dNf1 gene are reduced in size and exhibit impaired learning and memory, and that both defects appear due to abnormal Ras and cyclic-AMP (cAMP) signaling. The former was unremarkable, but how loss of dNf1 affects cAMP signaling remains poorly understood. Here we report results of a genetic screen for dominant modifiers of the dNf1 growth defect. This screen and follow-up functional studies support a model in which synaptic defects and reduced cAMP signaling in specific parts of the neuroendocrine ring gland contribute to the dNf1 growth defect. Beyond these results, we show that human ALK is expressed in cells that give rise to NF1 tumors, and that NF1 regulated ALK/RAS/ERK signaling is evolutionary conserved.
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15
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Emerging roles for intersectin (ITSN) in regulating signaling and disease pathways. Int J Mol Sci 2013; 14:7829-52. [PMID: 23574942 PMCID: PMC3645719 DOI: 10.3390/ijms14047829] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 04/02/2013] [Accepted: 04/03/2013] [Indexed: 01/10/2023] Open
Abstract
Intersectins (ITSNs) represent a family of multi-domain adaptor proteins that regulate endocytosis and cell signaling. ITSN genes are highly conserved and present in all metazoan genomes examined thus far. Lower eukaryotes have only one ITSN gene, whereas higher eukaryotes have two ITSN genes. ITSN was first identified as an endocytic scaffold protein, and numerous studies reveal a conserved role for ITSN in endocytosis. Subsequently, ITSNs were found to regulate multiple signaling pathways including receptor tyrosine kinases (RTKs), GTPases, and phosphatidylinositol 3-kinase Class 2beta (PI3KC2β). ITSN has also been implicated in diseases such as Down Syndrome (DS), Alzheimer Disease (AD), and other neurodegenerative disorders. This review summarizes the evolutionary conservation of ITSN, the latest research on the role of ITSN in endocytosis, the emerging roles of ITSN in regulating cell signaling pathways, and the involvement of ITSN in human diseases such as DS, AD, and cancer.
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16
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Lai SL, Miller MR, Robinson KJ, Doe CQ. The Snail family member Worniu is continuously required in neuroblasts to prevent Elav-induced premature differentiation. Dev Cell 2013; 23:849-57. [PMID: 23079601 DOI: 10.1016/j.devcel.2012.09.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 07/17/2012] [Accepted: 09/12/2012] [Indexed: 11/17/2022]
Abstract
Snail family transcription factors are best known for regulating epithelial-mesenchymal transition (EMT). The Drosophila Snail family member Worniu is specifically transcribed in neural progenitors (neuroblasts) throughout their lifespan, and worniu mutants show defects in neuroblast delamination (a form of EMT). However, the role of Worniu in neuroblasts beyond their formation is unknown. We performed RNA-seq on worniu mutant larval neuroblasts and observed reduced cell-cycle transcripts and increased neural differentiation transcripts. Consistent with these genomic data, worniu mutant neuroblasts showed a striking delay in prophase/metaphase transition by live imaging and increased levels of the conserved neuronal differentiation splicing factor Elav. Reducing Elav levels significantly suppressed the worniu mutant phenotype. We conclude that Worniu is continuously required in neuroblasts to maintain self-renewal by promoting cell-cycle progression and inhibiting premature differentiation.
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Affiliation(s)
- Sen-Lin Lai
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
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17
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Sousa-Nunes R, Somers WG. Mechanisms of asymmetric progenitor divisions in the Drosophila central nervous system. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 786:79-102. [PMID: 23696353 DOI: 10.1007/978-94-007-6621-1_6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The Drosophila central nervous system develops from polarised asymmetric divisions of precursor cells, called neuroblasts. Decades of research on neuroblasts have resulted in a substantial understanding of the factors and molecular events responsible for fate decisions of neuroblasts and their progeny. Furthermore, the cell-cycle dependent mechanisms responsible for asymmetric cortical protein localisation, resulting in the unequal partitioning between daughters, are beginning to be exposed. Disruption to the appropriate partitioning of proteins between neuroblasts and differentiation-committed daughters can lead to supernumerary neuroblast-like cells and the formation of tumours. Many of the factors responsible for regulating asymmetric division of Drosophila neuroblasts are evolutionarily conserved and, in many cases, have been shown to play a functionally conserved role in mammalian neurogenesis. Recent genome-wide studies coupled with advancements in live-imaging technologies have opened further avenues of research into neuroblast biology. We review our current understanding of the molecular mechanisms regulating neuroblast divisions, a powerful system to model mammalian neurogenesis and tumourigenesis.
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Affiliation(s)
- Rita Sousa-Nunes
- MRC Centre for Developmental Neurobiology, King's College London, New Hunt's House, London, SE1 1UL, UK.
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18
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Wong KA, Russo A, Wang X, Chen YJ, Lavie A, O'Bryan JP. A new dimension to Ras function: a novel role for nucleotide-free Ras in Class II phosphatidylinositol 3-kinase beta (PI3KC2β) regulation. PLoS One 2012; 7:e45360. [PMID: 23028960 PMCID: PMC3441633 DOI: 10.1371/journal.pone.0045360] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 08/14/2012] [Indexed: 12/31/2022] Open
Abstract
The intersectin 1 (ITSN1) scaffold stimulates Ras activation on endocytic vesicles without activating classic Ras effectors. The identification of Class II phosphatidylinositol 3-kinase beta, PI3KC2β, as an ITSN1 target on vesicles and the presence of a Ras binding domain (RBD) in PI3KC2β suggests a role for Ras in PI3KC2β activation. Here, we demonstrate that nucleotide-free Ras negatively regulates PI3KC2β activity. PI3KC2β preferentially interacts in vivo with dominant-negative (DN) Ras, which possesses a low affinity for nucleotides. PI3KC2β interaction with DN Ras is disrupted by switch 1 domain mutations in Ras as well as RBD mutations in PI3KC2β. Using purified proteins, we demonstrate that the PI3KC2β-RBD directly binds nucleotide-free Ras in vitro and that this interaction is not disrupted by nucleotide addition. Finally, nucleotide-free Ras but not GTP-loaded Ras inhibits PI3KC2β lipid kinase activity in vitro. Our findings indicate that PI3KC2β interacts with and is regulated by nucleotide-free Ras. These data suggest a novel role for nucleotide-free Ras in cell signaling in which PI3KC2β stabilizes nucleotide-free Ras and that interaction of Ras and PI3KC2β mutually inhibit one another.
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Affiliation(s)
- Katy A. Wong
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Angela Russo
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Xuerong Wang
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Yun-Ju Chen
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - Arnon Lavie
- Cancer Center, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Biochemistry and Molecular Genetics, University of Illinois College of Medicine, Chicago, Illinois, United States of America
| | - John P. O'Bryan
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Cancer Center, University of Illinois College of Medicine, Chicago, Illinois, United States of America
- Center for Cardiovascular Research, University of Illinois College of Medicine, Chicago, Illinois, United States of America
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19
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Abstract
Cell polarization and cell division are two fundamental cellular processes. The mechanisms that establish and maintain cell polarity and the mechanisms by which cells progress through the cell cycle are now fairly well understood following decades of experimental work. There is also increasing evidence that the polarization state of a cell affects its proliferative properties. The challenge now is to understand how these two phenomena are mechanistically connected. The aim of the present chapter is to provide an overview of the evidence of cross-talk between apicobasal polarity and proliferation, and the current state of knowledge of the precise mechanism by which this cross-talk is achieved.
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20
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Chang KC, Wang C, Wang H. Balancing self-renewal and differentiation by asymmetric division: insights from brain tumor suppressors in Drosophila neural stem cells. Bioessays 2012; 34:301-10. [PMID: 22287225 DOI: 10.1002/bies.201100090] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Balancing self-renewal and differentiation of stem cells is an important issue in stem cell and cancer biology. Recently, the Drosophila neuroblast (NB), neural stem cell has emerged as an excellent model for stem cell self-renewal and tumorigenesis. It is of great interest to understand how defects in the asymmetric division of neural stem cells lead to tumor formation. Here, we review recent advances in asymmetric division and the self-renewal control of Drosophila NBs. We summarize molecular mechanisms of asymmetric cell division and discuss how the defects in asymmetric division lead to tumor formation. Gain-of-function or loss-of-function of various proteins in the asymmetric machinery can drive NB overgrowth and tumor formation. These proteins control either the asymmetric protein localization or mitotic spindle orientation of NBs. We also discuss other mechanisms of brain tumor suppression that are beyond the control of asymmetric division.
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Affiliation(s)
- Kai Chen Chang
- Neuroscience & Behavioral Disorder Program, Duke-NUS Graduate Medical School Singapore, Singapore, Singapore
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21
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Carney TD, Miller MR, Robinson KJ, Bayraktar OA, Osterhout JA, Doe CQ. Functional genomics identifies neural stem cell sub-type expression profiles and genes regulating neuroblast homeostasis. Dev Biol 2011; 361:137-46. [PMID: 22061480 DOI: 10.1016/j.ydbio.2011.10.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 10/17/2011] [Accepted: 10/18/2011] [Indexed: 11/18/2022]
Abstract
The Drosophila larval central brain contains about 10,000 differentiated neurons and 200 scattered neural progenitors (neuroblasts), which can be further subdivided into ~95 type I neuroblasts and eight type II neuroblasts per brain lobe. Only type II neuroblasts generate self-renewing intermediate neural progenitors (INPs), and consequently each contributes more neurons to the brain, including much of the central complex. We characterized six different mutant genotypes that lead to expansion of neuroblast numbers; some preferentially expand type II or type I neuroblasts. Transcriptional profiling of larval brains from these mutant genotypes versus wild-type allowed us to identify small clusters of transcripts enriched in type II or type I neuroblasts, and we validated these clusters by gene expression analysis. Unexpectedly, only a few genes were found to be differentially expressed between type I/II neuroblasts, suggesting that these genes play a large role in establishing the different cell types. We also identified a large group of genes predicted to be expressed in all neuroblasts but not in neurons. We performed a neuroblast-specific, RNAi-based functional screen and identified 84 genes that are required to maintain proper neuroblast numbers; all have conserved mammalian orthologs. These genes are excellent candidates for regulating neural progenitor self-renewal in Drosophila and mammals.
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Affiliation(s)
- Travis D Carney
- Institute of Molecular Biology, Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
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22
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Dergai M, Skrypkina I, Dergai O, Tsyba L, Novokhatska O, Filonenko V, Drobot L, Rynditch A. Identification and characterization of a novel mammalian isoform of the endocytic adaptor ITSN1. Gene 2011; 485:120-9. [DOI: 10.1016/j.gene.2011.06.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/09/2011] [Accepted: 06/11/2011] [Indexed: 11/25/2022]
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23
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Halbsgut N, Linnemannstöns K, Zimmermann LI, Wodarz A. Apical-basal polarity in Drosophila neuroblasts is independent of vesicular trafficking. Mol Biol Cell 2011; 22:4373-9. [PMID: 21937725 PMCID: PMC3216662 DOI: 10.1091/mbc.e11-03-0219] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cell polarity in epithelia depends on the PAR proteins, which interact with the machinery for exocytic and endocytic vesicular trafficking. Polarity in Drosophila neural stem cells is independent of vesicular trafficking, although it depends on the PAR proteins, revealing different mechanisms of how polarity is controlled. The possession of apical–basal polarity is a common feature of epithelia and neural stem cells, so-called neuroblasts (NBs). In Drosophila, an evolutionarily conserved protein complex consisting of atypical protein kinase C and the scaffolding proteins Bazooka/PAR-3 and PAR-6 controls the polarity of both cell types. The components of this complex localize to the apical junctional region of epithelial cells and form an apical crescent in NBs. In epithelia, the PAR proteins interact with the cellular machinery for polarized exocytosis and endocytosis, both of which are essential for the establishment of plasma membrane polarity. In NBs, many cortical proteins show a strongly polarized subcellular localization, but there is little evidence for the existence of distinct apical and basolateral plasma membrane domains, raising the question of whether vesicular trafficking is required for polarization of NBs. We analyzed the polarity of NBs mutant for essential regulators of the main exocytic and endocytic pathways. Surprisingly, we found that none of these mutations affected NB polarity, demonstrating that NB cortical polarity is independent of plasma membrane polarity and that the PAR proteins function in a cell type–specific manner.
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Affiliation(s)
- Nils Halbsgut
- Stammzellbiologie, Abteilung Anatomie und Zellbiologie, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
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24
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Intersectin multidomain adaptor proteins: Regulation of functional diversity. Gene 2011; 473:67-75. [DOI: 10.1016/j.gene.2010.11.016] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 11/30/2010] [Accepted: 11/30/2010] [Indexed: 12/17/2022]
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25
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Chang KC, Garcia-Alvarez G, Somers G, Sousa-Nunes R, Rossi F, Lee YY, Soon SB, Gonzalez C, Chia W, Wang H. Interplay between the transcription factor Zif and aPKC regulates neuroblast polarity and self-renewal. Dev Cell 2010; 19:778-85. [PMID: 21074726 DOI: 10.1016/j.devcel.2010.10.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 08/17/2010] [Accepted: 09/14/2010] [Indexed: 12/14/2022]
Abstract
How a cell decides to self-renew or differentiate is a critical issue in stem cell and cancer biology. Atypical protein kinase C (aPKC) promotes self-renewal of Drosophila larval brain neural stem cells, neuroblasts. However, it is unclear how aPKC cortical polarity and protein levels are regulated. Here, we have identified a zinc-finger protein, Zif, which is required for the expression and asymmetric localization of aPKC. aPKC displays ectopic cortical localization with upregulated protein levels in dividing zif mutant neuroblasts, leading to neuroblast overproliferation. We show that Zif is a transcription factor that directly represses aPKC transcription. We further show that Zif is phosphorylated by aPKC both in vitro and in vivo. Phosphorylation of Zif by aPKC excludes it from the nucleus, leading to Zif inactivation in neuroblasts. Thus, reciprocal repression between Zif and aPKC act as a critical regulatory mechanism for establishing cell polarity and controlling neuroblast self-renewal.
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Affiliation(s)
- Kai Chen Chang
- Temasek Life Sciences Laboratory, 1 Research Link, Singapore 117604
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26
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Abstract
The endocytic pathway is involved in activation and inhibition of cellular signaling. Thus, defining the regulatory mechanisms that link endocytosis and cellular signaling is of interest. An emerging link between these processes is a family of proteins called intersectins (ITSNs). These multidomain proteins serve as scaffolds in the assembly of endocytic vesicles and also regulate components of various signaling pathways, including kinases, guanosine triphosphatases, and ubiquitin ligases. This review summarizes research on the role of ITSNs in regulating both endocytic and signal transduction pathways, discusses the link between ITSNs and human disease, and highlights future directions in the study of ITSNs.
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Affiliation(s)
- John P O'Bryan
- Department of Pharmacology, University of Illinois at Chicago, Chicago, IL 60612, USA.
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27
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Dergai O, Novokhatska O, Dergai M, Skrypkina I, Tsyba L, Moreau J, Rynditch A. Intersectin 1 forms complexes with SGIP1 and Reps1 in clathrin-coated pits. Biochem Biophys Res Commun 2010; 402:408-13. [PMID: 20946875 DOI: 10.1016/j.bbrc.2010.10.045] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 10/08/2010] [Indexed: 12/28/2022]
Abstract
Intersectin 1 (ITSN1) is an evolutionarily conserved adaptor protein involved in clathrin-mediated endocytosis, cellular signaling and cytoskeleton rearrangement. ITSN1 gene is located on human chromosome 21 in Down syndrome critical region. Several studies confirmed role of ITSN1 in Down syndrome phenotype. Here we report the identification of novel interconnections in the interaction network of this endocytic adaptor. We show that the membrane-deforming protein SGIP1 (Src homology 3-domain growth factor receptor-bound 2-like (endophilin) interacting protein 1) and the signaling adaptor Reps1 (RalBP associated Eps15-homology domain protein) interact with ITSN1 in vivo. Both interactions are mediated by the SH3 domains of ITSN1 and proline-rich motifs of protein partners. Moreover complexes comprising SGIP1, Reps1 and ITSN1 have been identified. We also identified new interactions between SGIP1, Reps1 and the BAR (Bin/amphiphysin/Rvs) domain-containing protein amphiphysin 1. Immunofluorescent data have demonstrated colocalization of ITSN1 with the newly identified protein partners in clathrin-coated pits. These findings expand the role of ITSN1 as a scaffolding molecule bringing together components of endocytic complexes.
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Affiliation(s)
- Oleksandr Dergai
- Department of Functional Genomics, Institute of Molecular Biology and Genetics, NASU, 150 Zabolotnogo Street, 03680 Kyiv, Ukraine.
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Prehoda KE. Polarization of Drosophila neuroblasts during asymmetric division. Cold Spring Harb Perspect Biol 2010; 1:a001388. [PMID: 20066083 DOI: 10.1101/cshperspect.a001388] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
During Drosophila development, neuroblasts divide to generate progeny with two different fates. One daughter cell self-renews to maintain the neuroblast pool, whereas the other differentiates to populate the central nervous system. The difference in fate arises from the asymmetric distribution of proteins that specify either self-renewal or differentiation, which is brought about by their polarization into separate apical and basal cortical domains during mitosis. Neuroblast symmetry breaking is regulated by numerous proteins, many of which have only recently been discovered. The atypical protein kinase C (aPKC) is a broad regulator of polarity that localizes to the neuroblast apical cortical region and directs the polarization of the basal domain. Recent work suggests that polarity can be explained in large part by the mechanisms that restrict aPKC activity to the apical domain and those that couple asymmetric aPKC activity to the polarization of downstream factors. Polarized aPKC activity is created by a network of regulatory molecules, including Bazooka/Par-3, Cdc42, and the tumor suppressor Lgl, which represses basal recruitment. Direct phosphorylation by aPKC leads to cortical release of basal domain factors, preventing them from occupying the apical domain. In this framework, neuroblast polarity arises from a complex system that orchestrates robust aPKC polarity, which in turn polarizes substrates by coupling phosphorylation to cortical release.
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Affiliation(s)
- Kenneth E Prehoda
- Department of Chemistry and Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, USA.
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29
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McCaffrey LM, Macara IG. Widely conserved signaling pathways in the establishment of cell polarity. Cold Spring Harb Perspect Biol 2010; 1:a001370. [PMID: 20066082 DOI: 10.1101/cshperspect.a001370] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
How are the asymmetric distributions of proteins, lipids, and RNAs established and maintained in various cell types? Studies from diverse organisms show that Par proteins, GTPases, kinases, and phosphoinositides participate in conserved signaling pathways to establish and maintain cell polarity.
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Affiliation(s)
- Luke Martin McCaffrey
- Department of Microbiology, Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, Virginia 22908-5077, USA
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30
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Dergai M, Tsyba L, Dergai O, Zlatskii I, Skrypkina I, Kovalenko V, Rynditch A. Microexon-based regulation of ITSN1 and Src SH3 domains specificity relies on introduction of charged amino acids into the interaction interface. Biochem Biophys Res Commun 2010; 399:307-12. [PMID: 20659428 DOI: 10.1016/j.bbrc.2010.07.080] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 07/22/2010] [Indexed: 11/25/2022]
Abstract
SH3 domains function as protein-protein interaction modules in assembly of signalling and endocytic protein complexes. Here we report investigations of the mechanism of regulation of the binding properties of the SH3 domains of intersectin (ITSN1) and Src kinase by alternative splicing. Comparative sequence analysis of ITSN1 and Src genes revealed the conservation of alternatively spliced microexons affecting the structure of the SH3 domains in vertebrates. We show that neuron-specific ITSN1 transcripts containing the microexon 20 that encodes five amino acid residues within the SH3A domain are expressed in zebrafish from the earliest stages of the development of the nervous system. Models of alternative isoforms of the ITSN1 SH3A domain revealed that the insertion encoded by the microexon is located at the beginning of the n-Src loop of this domain causing a shift of negatively charged amino acids towards the interaction interface. Mutational analysis confirmed the importance of translocation of these negatively charged amino acids for interaction with dynamin 1. We also identified a residue within the microexon-encoded insert in the SH3 domain of brain-specific variant of Src that abolishes interaction of the domain with dynamin 1. Thus microexons provide a mechanism for the control of tissue-specific interactions of ITSN1 and Src with their partners.
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Affiliation(s)
- Mykola Dergai
- Institute of Molecular Biology and Genetics, 150 Zabolotnogo Street, Kyiv 03680, Ukraine.
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31
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Shivas JM, Morrison HA, Bilder D, Skop AR. Polarity and endocytosis: reciprocal regulation. Trends Cell Biol 2010; 20:445-52. [PMID: 20493706 DOI: 10.1016/j.tcb.2010.04.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Revised: 04/09/2010] [Accepted: 04/13/2010] [Indexed: 10/19/2022]
Abstract
The establishment and maintenance of polarized plasma membrane domains is essential for cellular function and proper development of organisms. The molecules and pathways involved in determining cell polarity are remarkably well conserved between animal species. Historically, exocytic mechanisms have received primary emphasis among trafficking routes responsible for cell polarization. Accumulating evidence now reveals that endocytosis plays an equally important role in the proper localization of key polarity proteins. Intriguingly, some polarity proteins can also regulate the endocytic machinery. Here, we review emerging evidence for the reciprocal regulation between polarity proteins and endocytic pathways, and discuss possible models for how these distinct processes could interact to create separate cellular domains.
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Affiliation(s)
- Jessica M Shivas
- Laboratory of Genetics, University of Wisconsin, Madison, WI 53706, USA
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Shen G, Whittington A, Song K, Wang P. Pleiotropic function of intersectin homologue Cin1 in Cryptococcus neoformans. Mol Microbiol 2010; 76:662-76. [PMID: 20345666 DOI: 10.1111/j.1365-2958.2010.07121.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The manifestation of virulence traits in Cryptococcus neoformans is thought to rely on intracellular transport, a process not fully explored in this pathogenic fungus. Through interaction cloning, we identified a multi-modular protein, Cin1 (cryptococcal intersectin 1), whose domain structure is similar to that of the human endocytic protein ITSN1. Cin1 contains an N-terminal EH domain, a central coiled-coil region, a WH2 domain, two SH3 domains and a C-terminal RhoGEF (DH)-PH domain. Interestingly, alternative mRNA splicing resulted in two Cin1 isoforms, and Cin1 homologues are also restricted to basidiomycetous fungi. Disruption of the CIN1 gene had a pleiotropic effect on growth, normal cytokinesis, intracellular transports and the production of several virulence factors. Additionally, Cin1 interacts with cryptococcal Cdc42 and Wsp1 (a WASP homologue) proteins in vitro, suggesting a conserved role in the regulation of the actin cytoskeleton. However, deletion of RhoGEF or SH3 and RhoGEF domains did not result in any phenotypic changes, suggesting that functional redundancy exists in proteins containing similar domains or that the activities by other domains are necessary for Cin1 function. Our study presents the first evidence of a multi-modular protein whose function in intracellular transport underlies the growth, differentiation and virulence of a pathogenic microorganism.
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Affiliation(s)
- Gui Shen
- The Research Institute for Children, Louisiana State University Health Sciences Center, New Orleans, LA 70118, USA
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Cabernard C, Doe CQ. Apical/basal spindle orientation is required for neuroblast homeostasis and neuronal differentiation in Drosophila. Dev Cell 2009; 17:134-41. [PMID: 19619498 DOI: 10.1016/j.devcel.2009.06.009] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Revised: 05/14/2009] [Accepted: 06/18/2009] [Indexed: 12/23/2022]
Abstract
Precise regulation of stem cell self-renewal/differentiation is essential for embryogenesis and tumor suppression. Drosophila neural progenitors (neuroblasts) align their spindle along an apical/basal polarity axis to generate a self-renewed apical neuroblast and a differentiating basal cell. Here, we genetically disrupt spindle orientation without altering cell polarity to test the role of spindle orientation in self-renewal/differentiation. We perform correlative live imaging of polarity markers and spindle orientation over multiple divisions within intact brains, followed by molecular marker analysis of cell fate. We find that spindle alignment orthogonal to apical/basal polarity always segregates apical determinants into both siblings, which invariably assume a neuroblast identity. Basal determinants can all be localized into one sibling without inducing neuronal differentiation, but overexpression of the basal determinant Prospero can deplete neuroblasts. We conclude that the ratio of apical/basal determinants specifies neuroblast/GMC identity, and that apical/basal spindle orientation is required for neuroblast homeostasis and neuronal differentiation.
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Affiliation(s)
- Clemens Cabernard
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon 1254, Eugene OR 97403, USA
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Nakayama Y, Shivas JM, Poole DS, Squirrell JM, Kulkoski JM, Schleede JB, Skop AR. Dynamin participates in the maintenance of anterior polarity in the Caenorhabditis elegans embryo. Dev Cell 2009; 16:889-900. [PMID: 19531359 DOI: 10.1016/j.devcel.2009.04.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2008] [Revised: 03/24/2009] [Accepted: 04/21/2009] [Indexed: 01/10/2023]
Abstract
Cell polarity is crucial for the generation of cell diversity. Recent evidence suggests that the actin cytoskeleton plays a key role in establishment of embryonic polarity, yet the mechanisms that maintain polarity cues in particular membrane domains during development remain unclear. Dynamin, a large GTPase, functions in both endocytosis and actin dynamics. Here, the Caenorhabditis elegans dynamin ortholog, DYN-1, maintains anterior polarity cues. DYN-1-GFP foci are enriched in the anterior cortex in a manner dependent on the anterior polarity proteins, PAR-6 and PKC-3. Membrane internalization and actin comet formation are enriched in the anterior, and are dependent on DYN-1. PAR-6-labeled puncta are also internalized from cortical accumulations of DYN-1-GFP. Our results demonstrate a mechanism for the spatial and temporal regulation of endocytosis in the anterior of the embryo, contributing to the precise localization and maintenance of polarity factors within a dynamic plasma membrane.
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Affiliation(s)
- Yuji Nakayama
- Department of Genetics, University of Wisconsin-Madison, Madison, WI 53706, USA
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Chabu C, Doe CQ. Twins/PP2A regulates aPKC to control neuroblast cell polarity and self-renewal. Dev Biol 2009; 330:399-405. [PMID: 19374896 DOI: 10.1016/j.ydbio.2009.04.014] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 03/25/2009] [Accepted: 04/07/2009] [Indexed: 12/12/2022]
Abstract
Asymmetric cell division is a mechanism for generating cell diversity as well as maintaining stem cell homeostasis in both Drosophila and mammals. In Drosophila, larval neuroblasts are stem cell-like progenitors that divide asymmetrically to generate neurons of the adult brain. Mitotic neuroblasts localize atypical protein kinase C (aPKC) to their apical cortex. Cortical aPKC excludes cortical localization of Miranda and its cargo proteins Prospero and Brain tumor, resulting in their partitioning into the differentiating, smaller ganglion mother cell (GMC) where they are required for neuronal differentiation. In addition to aPKC, the kinases Aurora-A and Polo also regulate neuroblast self-renewal, but the phosphatases involved in neuroblast self-renewal have not been identified. Here we report that aPKC is in a protein complex in vivo with Twins, a Drosophila B-type protein phosphatase 2A (PP2A) subunit, and that Twins and the catalytic subunit of PP2A, called Microtubule star (Mts), are detected in larval neuroblasts. Both Twins and Mts are required to exclude aPKC from the basal neuroblast cortex: twins mutant brains, twins mutant single neuroblast mutant clones, or mts dominant negative single neuroblast clones all show ectopic basal cortical localization of aPKC. Consistent with ectopic basal aPKC is the appearance of supernumerary neuroblasts in twins mutant brains or twins mutant clones. We conclude that Twins/PP2A is required to maintain aPKC at the apical cortex of mitotic neuroblasts, keeping it out of the differentiating GMC, and thereby maintaining neuroblast homeostasis.
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Affiliation(s)
- Chiswili Chabu
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
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Newman RA, Prehoda KE. Intramolecular interactions between the SRC homology 3 and guanylate kinase domains of discs large regulate its function in asymmetric cell division. J Biol Chem 2009; 284:12924-32. [PMID: 19261607 DOI: 10.1074/jbc.m809304200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Membrane-associated guanylate kinases (MAGUKs) regulate the formation and function of molecular assemblies at specialized regions of the membrane. Allosteric regulation of an intramolecular interaction between the Src homology 3 (SH3) and guanylate kinase (GK) domains of MAGUKs is thought to play a central role in regulating MAGUK function. Here we show that a mutant of the Drosophila MAGUK Discs large (Dlg), dlg(sw), encodes a form of Dlg that disrupts the intramolecular association while leaving the SH3 and GK domains intact, providing an excellent model system to assess the role of the SH3-GK intramolecular interaction in MAGUK function. Analysis of asymmetric cell division of maternal-zygotic dlg(sw) embryonic neuroblasts demonstrates that the intramolecular interaction is not required for Dlg localization but is necessary for cell fate determinant segregation to the basal cortex and mitotic spindle alignment with the cortical polarity axis. These defects ultimately result in improper patterning of the embryonic central nervous system. Furthermore, we demonstrate that the sw mutation of Dlg results in unregulated complex assembly as assessed by GukHolder association with the SH3-GK versus PDZ-SH3-GK modules of Dlg(sw). From these studies, we conclude that allosteric regulation of the SH3-GK intramolecular interaction is required for regulation of MAGUK function in asymmetric cell division, possibly through regulation of complex assembly.
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Affiliation(s)
- Rhonda A Newman
- Department of Chemistry and Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
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Abstract
In the past 20 years, the discovery and characterization of the molecular machinery that controls cellular polarization have enabled us to achieve a better understanding of many biological processes. Spatial asymmetry or establishment of cell polarity during embryogenesis, epithelial morphogenesis, neuronal differentiation, and migration of fibroblasts and T cells are thought to rely on a small number of evolutionarily conserved proteins and pathways. Correct polarization is crucial for normal cell physiology and tissue homeostasis, and is lost in cancer. Thus, cell polarity signaling is likely to have an important function in tumor progression. Recent findings have identified a regulator of cell polarity, the Par complex, as an important signaling node in tumorigenesis. In normal cell types, the Par complex is part of the molecular machinery that regulates cell polarity and maintains normal cell homeostasis. As such, the polarity regulators are proposed to have a tumor suppressor function, consistent with the loss of polarity genes associated with hyperproliferation in Drosophila melanogaster. However, recent studies showing that some members of this complex also display pro-oncogenic activities suggest a more complex regulation of the polarity machinery during cellular transformation. Here, we examine the existing data about the different functions of the Par complex. We discuss how spatial restriction, binding partners and substrate specificity determine the signaling properties of Par complex proteins. A better understanding of these processes will very likely shed some light on how the Par complex can switch from a normal polarity regulation function to promotion of transformation downstream of oncogenes.
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Abstract
The neoplastic tumour suppressors, Scribble, Dlg and Lgl, originally discovered in the vinegar fly Drosophila melanogaster, are currently being actively studied for their potential role in mammalian tumourigenesis. In Drosophila, these tumour suppressors function in a common genetic pathway to regulate apicobasal cell polarity and also play important roles in the control of cell proliferation, survival, differentiation and in cell migration/invasion. The precise mechanism by which Scribble, Dlg and Lgl function is not clear; however, they have been implicated in the regulation of signalling pathways, vesicle trafficking and in the Myosin II-actin cytoskeleton. We review the evidence for the involvement of Scribble, Dlg, and Lgl in cancer, and how the various functions ascribed to these tumour suppressors in Drosophila and mammalian systems may impact on the process of tumourigenesis.
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Abstract
A limited number of adult stem cells (SCs) maintain the homoestasis of different tissues through the lifetime of the individual by generating differentiating daughters and renewing themselves. Errors in the SC division rate or in the fine balance between self-renewal and differentiation might result in tissue overgrowth or depletion, two potentially lethal conditions. A few types of SCs have been identified in Drosophila. These include the SCs of the adult intestine and malpighian tubes, (Micchelli and Perrimon, 2006; Ohlstein and Spradling, 2006; Singh et al., 2007), the prohematocytes that maintain the population of cells involved in the immunoresponse (Lanot et al., 2001; Lemaitre and Hoffmann, 2007), the SC of the follicle epithelia in the ovary (Nystul and Spradling, 2007), germ line SCs (GSCs) of both sexes (Fuller and Spradling, 2007) and neuroblasts (NBs), the fly neural SCs (Yu et al., 2006; Chia et al., 2008; Knoblich, 2008). Drosophila SCs have proved a fruitful model system to unveil some aspects of the molecular logic that sustains SC function. This review focuses on results obtained in the last few years from the study of NBs, particularly from the standpoint of the possible functional connection between asymmetric SC division and cancer.
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Affiliation(s)
- J Januschke
- Cell Division Group, IRB-Barcelona, PCB, c/Baldiri Reixac 10-12, Barcelona, Spain
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