1
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Richter Gorey CL, St Louis AP, Chorna T, Brill JA, Dason JS. Differential functions of phosphatidylinositol 4-kinases in neurotransmission and synaptic development. Eur J Neurosci 2024. [PMID: 39267207 DOI: 10.1111/ejn.16526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 08/07/2024] [Accepted: 08/16/2024] [Indexed: 09/14/2024]
Abstract
Phosphoinositides, such as PI(4,5)P2, are known to function as structural components of membranes, signalling molecules, markers of membrane identity, mediators of protein recruitment and regulators of neurotransmission and synaptic development. Phosphatidylinositol 4-kinases (PI4Ks) synthesize PI4P, which are precursors for PI(4,5)P2, but may also have independent functions. The roles of PI4Ks in neurotransmission and synaptic development have not been studied in detail. Previous studies on PI4KII and PI4KIIIβ at the Drosophila larval neuromuscular junction have suggested that PI4KII and PI4KIIIβ enzymes may serve redundant roles, where single PI4K mutants yielded mild or no synaptic phenotypes. However, the precise synaptic functions (neurotransmission and synaptic growth) of these PI4Ks have not been thoroughly studied. Here, we used PI4KII and PI4KIIIβ null mutants and presynaptic-specific knockdowns of these PI4Ks to investigate their roles in neurotransmission and synaptic growth. We found that PI4KII and PI4KIIIβ appear to have non-overlapping functions. Specifically, glial PI4KII functions to restrain synaptic growth, whereas presynaptic PI4KIIIβ promotes synaptic growth. Furthermore, loss of PI4KIIIβ or presynaptic PI4KII impairs neurotransmission. The data presented in this study uncover new roles for PI4K enzymes in neurotransmission and synaptic growth.
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Affiliation(s)
| | | | - Tetyana Chorna
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Jeffrey S Dason
- Department of Biomedical Sciences, University of Windsor, Windsor, Ontario, Canada
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2
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Guo P, Li B, Dong W, Zhou H, Wang L, Su T, Carl C, Zheng Y, Hong Y, Deng H, Pan D. PI4P-mediated solid-like Merlin condensates orchestrate Hippo pathway regulation. Science 2024; 385:eadf4478. [PMID: 39116228 DOI: 10.1126/science.adf4478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 10/11/2023] [Accepted: 06/10/2024] [Indexed: 08/10/2024]
Abstract
Despite recent studies implicating liquid-like biomolecular condensates in diverse cellular processes, many biomolecular condensates exist in a solid-like state, and their function and regulation are less understood. We show that the tumor suppressor Merlin, an upstream regulator of the Hippo pathway, localizes to both cell junctions and medial apical cortex in Drosophila epithelia, with the latter forming solid-like condensates that activate Hippo signaling. Merlin condensation required phosphatidylinositol-4-phosphate (PI4P)-mediated plasma membrane targeting and was antagonistically controlled by Pez and cytoskeletal tension through plasma membrane PI4P regulation. The solid-like material properties of Merlin condensates are essential for physiological function and protect the condensates against external perturbations. Collectively, these findings uncover an essential role for solid-like condensates in normal physiology and reveal regulatory mechanisms for their formation and disassembly.
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Affiliation(s)
- Pengfei Guo
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Bing Li
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Wei Dong
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Huabin Zhou
- Department of Biophysics, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Li Wang
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ting Su
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Christopher Carl
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yonggang Zheng
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yang Hong
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Hua Deng
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Duojia Pan
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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3
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Kim YJ, Pemberton JG, Eisenreichova A, Mandal A, Koukalova A, Rohilla P, Sohn M, Konradi AW, Tang TT, Boura E, Balla T. Non-vesicular phosphatidylinositol transfer plays critical roles in defining organelle lipid composition. EMBO J 2024; 43:2035-2061. [PMID: 38627600 PMCID: PMC11099152 DOI: 10.1038/s44318-024-00096-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 03/12/2024] [Accepted: 03/21/2024] [Indexed: 05/18/2024] Open
Abstract
Phosphatidylinositol (PI) is the precursor lipid for the minor phosphoinositides (PPIns), which are critical for multiple functions in all eukaryotic cells. It is poorly understood how phosphatidylinositol, which is synthesized in the ER, reaches those membranes where PPIns are formed. Here, we used VT01454, a recently identified inhibitor of class I PI transfer proteins (PITPs), to unravel their roles in lipid metabolism, and solved the structure of inhibitor-bound PITPNA to gain insight into the mode of inhibition. We found that class I PITPs not only distribute PI for PPIns production in various organelles such as the plasma membrane (PM) and late endosomes/lysosomes, but that their inhibition also significantly reduced the levels of phosphatidylserine, di- and triacylglycerols, and other lipids, and caused prominent increases in phosphatidic acid. While VT01454 did not inhibit Golgi PI4P formation nor reduce resting PM PI(4,5)P2 levels, the recovery of the PM pool of PI(4,5)P2 after receptor-mediated hydrolysis required both class I and class II PITPs. Overall, these studies show that class I PITPs differentially regulate phosphoinositide pools and affect the overall cellular lipid landscape.
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Affiliation(s)
- Yeun Ju Kim
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Joshua G Pemberton
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Andrea Eisenreichova
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nam. 2., 166 10, Prague 6, Czech Republic
| | - Amrita Mandal
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Alena Koukalova
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Pooja Rohilla
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Mira Sohn
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | | | | | - Evzen Boura
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nam. 2., 166 10, Prague 6, Czech Republic
| | - Tamas Balla
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
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4
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Fujita N, Girada S, Vogler G, Bodmer R, Kiger AA. PI(4,5)P 2 role in Transverse-tubule membrane formation and muscle function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.31.578124. [PMID: 38352484 PMCID: PMC10862868 DOI: 10.1101/2024.01.31.578124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/20/2024]
Abstract
Transverse (T)-tubules - vast, tubulated domains of the muscle plasma membrane - are critical to maintain healthy skeletal and heart contractions. How the intricate T-tubule membranes are formed is not well understood, with challenges to systematically interrogate in muscle. We established the use of intact Drosophila larval body wall muscles as an ideal system to discover mechanisms that sculpt and maintain the T-tubule membrane network. A muscle-targeted genetic screen identified specific phosphoinositide lipid regulators necessary for T-tubule organization and muscle function. We show that a PI4KIIIα - Skittles/PIP5K pathway is needed for T-tubule localized PI(4)P to PI(4,5)P 2 synthesis, T-tubule organization, calcium regulation, and muscle and heart rate functions. Muscles deficient for PI4KIIIα or Amphiphysin , the homolog of human BIN1 , similarly exhibited specific loss of transversal T-tubule membranes and dyad junctions, yet retained longitudinal membranes and the associated dyads. Our results highlight the power of live muscle studies, uncovering distinct mechanisms and functions for sub-compartments of the T-tubule network relevant to human myopathy. Summary T-tubules - vast, tubulated domains of the muscle plasma membrane - are critical to maintain skeletal and heart contractions. Fujita et al . establish genetic screens and assays in intact Drosophila muscles that uncover PI(4,5)P 2 regulation critical for T-tubule maintenance and function. Key Findings PI4KIIIα is required for muscle T-tubule formation and larval mobility. A PI4KIIIα-Sktl pathway promotes PI(4)P and PI(4,5)P 2 function at T-tubules. PI4KIIIα is necessary for calcium dynamics and transversal but not longitudinal dyads. Disruption of PI(4,5)P 2 function in fly heart leads to fragmented T-tubules and abnormal heart rate.
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5
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Hu L, Brichalli W, Li N, Chen S, Cheng Y, Liu Q, Xiong Y, Yu J. Myotubularin functions through actomyosin to interact with the Hippo pathway. EMBO Rep 2022; 23:e55851. [PMID: 36285521 PMCID: PMC9724681 DOI: 10.15252/embr.202255851] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 10/01/2022] [Accepted: 10/07/2022] [Indexed: 12/12/2022] Open
Abstract
The Hippo pathway is an evolutionarily conserved developmental pathway that controls organ size by integrating diverse regulatory inputs, including actomyosin-mediated cytoskeletal tension. Despite established connections between the actomyosin cytoskeleton and the Hippo pathway, the upstream regulation of actomyosin in the Hippo pathway is less defined. Here, we identify the phosphoinositide-3-phosphatase Myotubularin (Mtm) as a novel upstream regulator of actomyosin that functions synergistically with the Hippo pathway during growth control. Mechanistically, Mtm regulates membrane phospholipid PI(3)P dynamics, which, in turn, modulates actomyosin activity through Rab11-mediated vesicular trafficking. We reveal PI(3)P dynamics as a novel mode of upstream regulation of actomyosin and establish Rab11-mediated vesicular trafficking as a functional link between membrane lipid dynamics and actomyosin activation in the context of growth control. Our study also shows that MTMR2, the human counterpart of Drosophila Mtm, has conserved functions in regulating actomyosin activity and tissue growth, providing new insights into the molecular basis of MTMR2-related peripheral nerve myelination and human disorders.
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Affiliation(s)
- Liang Hu
- Department of Physiology and NeurobiologyUniversity of ConnecticutStorrsCTUSA
| | - Wyatt Brichalli
- Department of Anatomy & PhysiologyKansas State University College of Veterinary MedicineManhattanKSUSA
| | - Naren Li
- Department of Physiology and NeurobiologyUniversity of ConnecticutStorrsCTUSA
| | - Shifan Chen
- Department of NeuroscienceUniversity of Connecticut School of MedicineFarmingtonCTUSA
| | - Yaqing Cheng
- Department of Physiology and NeurobiologyUniversity of ConnecticutStorrsCTUSA
| | - Qinfang Liu
- Department of NeuroscienceUniversity of Connecticut School of MedicineFarmingtonCTUSA
| | - Yulan Xiong
- Department of NeuroscienceUniversity of Connecticut School of MedicineFarmingtonCTUSA
| | - Jianzhong Yu
- Department of Physiology and NeurobiologyUniversity of ConnecticutStorrsCTUSA
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6
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Lu J, Dong W, Hammond GR, Hong Y. Hypoxia controls plasma membrane targeting of polarity proteins by dynamic turnover of PI4P and PI(4,5)P2. eLife 2022; 11:79582. [PMID: 35678383 PMCID: PMC9242647 DOI: 10.7554/elife.79582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 06/06/2022] [Indexed: 11/17/2022] Open
Abstract
Phosphatidylinositol 4-phosphate (PI4P) and phosphatidylinositol 4,5-biphosphate (PIP2) are key phosphoinositides that determine the identity of the plasma membrane (PM) and regulate numerous key biological events there. To date, mechanisms regulating the homeostasis and dynamic turnover of PM PI4P and PIP2 in response to various physiological conditions and stresses remain to be fully elucidated. Here, we report that hypoxia in Drosophila induces acute and reversible depletion of PM PI4P and PIP2 that severely disrupts the electrostatic PM targeting of multiple polybasic polarity proteins. Genetically encoded ATP sensors confirmed that hypoxia induces acute and reversible reduction of cellular ATP levels which showed a strong real-time correlation with the levels of PM PI4P and PIP2 in cultured cells. By combining genetic manipulations with quantitative imaging assays we showed that PI4KIIIα, as well as Rbo/EFR3 and TTC7 that are essential for targeting PI4KIIIα to PM, are required for maintaining the homeostasis and dynamic turnover of PM PI4P and PIP2 under normoxia and hypoxia. Our results revealed that in cells challenged by energetic stresses triggered by hypoxia, ATP inhibition and possibly ischemia, dramatic turnover of PM PI4P and PIP2 could have profound impact on many cellular processes including electrostatic PM targeting of numerous polybasic proteins.
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Affiliation(s)
- Juan Lu
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, China [CN]
| | - Wei Dong
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, United States
| | - Gerald R Hammond
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, United States
| | - Yang Hong
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, United States
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7
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Batrouni AG, Bag N, Phan HT, Baird BA, Baskin JM. A palmitoylation code controls PI4KIIIα complex formation and PI(4,5)P2 homeostasis at the plasma membrane. J Cell Sci 2022; 135:272297. [PMID: 34569608 DOI: 10.1242/jcs.259365] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 09/14/2021] [Indexed: 12/12/2022] Open
Abstract
Phosphatidylinositol 4-kinase IIIα (PI4KIIIα) is the major enzyme responsible for generating phosphatidylinositol (4)-phosphate [PI(4)P] at the plasma membrane. This lipid kinase forms two multicomponent complexes, both including a palmitoylated anchor, EFR3. Whereas both PI4KIIIα complexes support production of PI(4)P, the distinct functions of each complex and mechanisms underlying the interplay between them remain unknown. Here, we present roles for differential palmitoylation patterns within a tri-cysteine motif in EFR3B (Cys5, Cys7 and Cys8) in controlling the distribution of PI4KIIIα between these two complexes at the plasma membrane and corresponding functions in phosphoinositide homeostasis. Spacing of palmitoyl groups within three doubly palmitoylated EFR3B 'lipoforms' affects both interactions between EFR3B and TMEM150A, a transmembrane protein governing formation of a PI4KIIIα complex functioning in rapid phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] resynthesis following phospholipase C signaling, and EFR3B partitioning within liquid-ordered and -disordered regions of the plasma membrane. This work identifies a palmitoylation code involved in controlling protein-protein and protein-lipid interactions that affect a plasma membrane-resident lipid biosynthetic pathway.
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Affiliation(s)
- Alex G Batrouni
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.,Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, NY 14853, USA
| | - Nirmalya Bag
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Henry T Phan
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Barbara A Baird
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Jeremy M Baskin
- Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, NY 14853, USA.,Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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8
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Bugda Gwilt K, Thiagarajah JR. Membrane Lipids in Epithelial Polarity: Sorting out the PIPs. Front Cell Dev Biol 2022; 10:893960. [PMID: 35712665 PMCID: PMC9197455 DOI: 10.3389/fcell.2022.893960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 05/04/2022] [Indexed: 11/13/2022] Open
Abstract
The development of cell polarity in epithelia, is critical for tissue morphogenesis and vectorial transport between the environment and the underlying tissue. Epithelial polarity is defined by the development of distinct plasma membrane domains: the apical membrane interfacing with the exterior lumen compartment, and the basolateral membrane directly contacting the underlying tissue. The de novo generation of polarity is a tightly regulated process, both spatially and temporally, involving changes in the distribution of plasma membrane lipids, localization of apical and basolateral membrane proteins, and vesicular trafficking. Historically, the process of epithelial polarity has been primarily described in relation to the localization and function of protein 'polarity complexes.' However, a critical and foundational role is emerging for plasma membrane lipids, and in particular phosphoinositide species. Here, we broadly review the evidence for a primary role for membrane lipids in the generation of epithelial polarity and highlight key areas requiring further research. We discuss the complex interchange that exists between lipid species and briefly examine how major membrane lipid constituents are generated and intersect with vesicular trafficking to be preferentially localized to different membrane domains with a focus on some of the key protein-enzyme complexes involved in these processes.
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Affiliation(s)
- Katlynn Bugda Gwilt
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
| | - Jay R Thiagarajah
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
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9
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Deng H, Yang L, Wen P, Lei H, Blount P, Pan D. Spectrin couples cell shape, cortical tension, and Hippo signaling in retinal epithelial morphogenesis. J Cell Biol 2020; 219:133846. [PMID: 32328630 PMCID: PMC7147103 DOI: 10.1083/jcb.201907018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 11/26/2019] [Accepted: 01/17/2020] [Indexed: 01/05/2023] Open
Abstract
Although extracellular force has a profound effect on cell shape, cytoskeleton tension, and cell proliferation through the Hippo signaling effector Yki/YAP/TAZ, how intracellular force regulates these processes remains poorly understood. Here, we report an essential role for spectrin in specifying cell shape by transmitting intracellular actomyosin force to cell membrane. While activation of myosin II in Drosophila melanogaster pupal retina leads to increased cortical tension, apical constriction, and Yki-mediated hyperplasia, spectrin mutant cells, despite showing myosin II activation and Yki-mediated hyperplasia, paradoxically display decreased cortical tension and expanded apical area. Mechanistically, we show that spectrin is required for tethering cortical F-actin to cell membrane domains outside the adherens junctions (AJs). Thus, in the absence of spectrin, the weakened attachment of cortical F-actin to plasma membrane results in a failure to transmit actomyosin force to cell membrane, causing an expansion of apical surfaces. These results uncover an essential mechanism that couples cell shape, cortical tension, and Hippo signaling and highlight the importance of non–AJ membrane domains in dictating cell shape in tissue morphogenesis.
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Affiliation(s)
- Hua Deng
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX
| | - Limin Yang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Pei Wen
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX
| | - Huiyan Lei
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX
| | - Paul Blount
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Duojia Pan
- Department of Physiology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX
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10
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Trivedi D, CM V, Bisht K, Janardan V, Pandit A, Basak B, H S, Ramesh N, Raghu P. A genome engineering resource to uncover principles of cellular organization and tissue architecture by lipid signaling. eLife 2020; 9:e55793. [PMID: 33320085 PMCID: PMC7771963 DOI: 10.7554/elife.55793] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 12/14/2020] [Indexed: 12/14/2022] Open
Abstract
Phosphoinositides (PI) are key regulators of cellular organization in eukaryotes and genes that tune PI signaling are implicated in human disease mechanisms. Biochemical analyses and studies in cultured cells have identified a large number of proteins that can mediate PI signaling. However, the role of such proteins in regulating cellular processes in vivo and development in metazoans remains to be understood. Here, we describe a set of CRISPR-based genome engineering tools that allow the manipulation of each of these proteins with spatial and temporal control during metazoan development. We demonstrate the use of these reagents to deplete a set of 103 proteins individually in the Drosophila eye and identify several new molecules that control eye development. Our work demonstrates the power of this resource in uncovering the molecular basis of tissue homeostasis during normal development and in human disease biology.
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Affiliation(s)
- Deepti Trivedi
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
| | - Vinitha CM
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
| | - Karishma Bisht
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
| | - Vishnu Janardan
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
| | - Awadhesh Pandit
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
| | - Bishal Basak
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
| | - Shwetha H
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
| | - Navyashree Ramesh
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
| | - Padinjat Raghu
- National Centre for Biological Sciences-TIFR, GKVK CampusBangaloreIndia
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11
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Basu U, Balakrishnan SS, Janardan V, Raghu P. A PI4KIIIα protein complex is required for cell viability during Drosophila wing development. Dev Biol 2020; 462:208-222. [PMID: 32194035 DOI: 10.1016/j.ydbio.2020.03.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 03/06/2020] [Accepted: 03/07/2020] [Indexed: 01/02/2023]
Abstract
Phosphatidylinositol 4 phosphate (PI4P) and phosphatidylinositol 4,5 bisphosphate [PI(4,5)P2] are enriched on the inner leaflet of the plasma membrane and proposed to be key determinants of its function. PI4P is also the biochemical precursor for the synthesis of PI(4,5)P2 but can itself also bind to and regulate protein function. However, the independent function of PI4P at the plasma membrane in supporting cell function in metazoans during development in vivo remains unclear. We find that conserved components of a multi-protein complex composed of phosphatidylinositol 4-kinase IIIα (PI4KIIIα), TTC7 and Efr3 is required for normal vein patterning and wing development. Depletion of each of these three components of the PI4KIIIα complex in developing wing cells results in altered wing morphology. These effects are associated with an increase in apoptosis and can be rescued by expression of an inhibitor of Drosophila caspase. We find that in contrast to previous reports, PI4KIIIα depletion does not alter key outputs of hedgehog signalling in developing wing discs. Depletion of PI4KIIIα results in reduced PI4P levels at the plasma membrane of developing wing disc cells while levels of PI(4,5)P2, the downstream metabolite of PI4P, are not altered. Thus, PI4P itself generated by the activity of the PI4KIIIα complex plays an essential role in supporting cell viability in the developing Drosophila wing disc.
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Affiliation(s)
- Urbashi Basu
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore, 560065, India
| | - Sruthi S Balakrishnan
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore, 560065, India
| | - Vishnu Janardan
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore, 560065, India
| | - Padinjat Raghu
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore, 560065, India.
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12
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Khoury MJ, Bilder D. Distinct activities of Scrib module proteins organize epithelial polarity. Proc Natl Acad Sci U S A 2020; 117:11531-11540. [PMID: 32414916 PMCID: PMC7260944 DOI: 10.1073/pnas.1918462117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
A polarized architecture is central to both epithelial structure and function. In many cells, polarity involves mutual antagonism between the Par complex and the Scribble (Scrib) module. While molecular mechanisms underlying Par-mediated apical determination are well-understood, how Scrib module proteins specify the basolateral domain remains unknown. Here, we demonstrate dependent and independent activities of Scrib, Discs-large (Dlg), and Lethal giant larvae (Lgl) using the Drosophila follicle epithelium. Our data support a linear hierarchy for localization, but rule out previously proposed protein-protein interactions as essential for polarization. Cortical recruitment of Scrib does not require palmitoylation or polar phospholipid binding but instead an independent cortically stabilizing activity of Dlg. Scrib and Dlg do not directly antagonize atypical protein kinase C (aPKC), but may instead restrict aPKC localization by enabling the aPKC-inhibiting activity of Lgl. Importantly, while Scrib, Dlg, and Lgl are each required, all three together are not sufficient to antagonize the Par complex. Our data demonstrate previously unappreciated diversity of function within the Scrib module and begin to define the elusive molecular functions of Scrib and Dlg.
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Affiliation(s)
- Mark J Khoury
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
| | - David Bilder
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
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13
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Griffiths NW, Del Bel LM, Wilk R, Brill JA. Cellular homeostasis in the Drosophila retina requires the lipid phosphatase Sac1. Mol Biol Cell 2020; 31:1183-1199. [PMID: 32186963 PMCID: PMC7353163 DOI: 10.1091/mbc.e20-02-0161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The complex functions of cellular membranes, and thus overall cell physiology, depend on the distribution of crucial lipid species. Sac1 is an essential, conserved, ER-localized phosphatase whose substrate, phosphatidylinositol 4-phosphate (PI4P), coordinates secretory trafficking and plasma membrane function. PI4P from multiple pools is delivered to Sac1 by oxysterol-binding protein and related proteins in exchange for other lipids and sterols, which places Sac1 at the intersection of multiple lipid distribution pathways. However, much remains unknown about the roles of Sac1 in subcellular homeostasis and organismal development. Using a temperature-sensitive allele (Sac1ts), we show that Sac1 is required for structural integrity of the Drosophila retinal floor. The βps-integrin Myospheroid, which is necessary for basal cell adhesion, is mislocalized in Sac1ts retinas. In addition, the adhesion proteins Roughest and Kirre, which coordinate apical retinal cell patterning at an earlier stage, accumulate within Sac1ts retinal cells due to impaired endo-lysosomal degradation. Moreover, Sac1 is required for ER homeostasis in Drosophila retinal cells. Together, our data illustrate the importance of Sac1 in regulating multiple aspects of cellular homeostasis during tissue development.
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Affiliation(s)
- Nigel W Griffiths
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Lauren M Del Bel
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Ronit Wilk
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
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Duhart JC, Raftery LA. Mob Family Proteins: Regulatory Partners in Hippo and Hippo-Like Intracellular Signaling Pathways. Front Cell Dev Biol 2020; 8:161. [PMID: 32266255 DOI: 10.3389/fcell.2020.00161/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Accepted: 02/28/2020] [Indexed: 05/26/2023] Open
Abstract
Studies in yeast first delineated the function of Mob proteins in kinase pathways that regulate cell division and shape; in multicellular eukaryotes Mobs regulate tissue growth and morphogenesis. In animals, Mobs are adaptors in Hippo signaling, an intracellular signal-transduction pathway that restricts growth, impacting the development and homeostasis of animal organs. Central to Hippo signaling are the Nuclear Dbf2-Related (NDR) kinases, Warts and LATS1 and LATS2, in flies and mammals, respectively. A second Hippo-like signaling pathway has been uncovered in animals, which regulates cell and tissue morphogenesis. Central to this emergent pathway are the NDR kinases, Tricornered, STK38, and STK38L. In Hippo signaling, NDR kinase activation is controlled by three activating interactions with a conserved set of proteins. This review focuses on one co-activator family, the highly conserved, non-catalytic Mps1-binder-related (Mob) proteins. In this context, Mobs are allosteric activators of NDR kinases and adaptors that contribute to assembly of multiprotein NDR kinase activation complexes. In multicellular eukaryotes, the Mob family has expanded relative to model unicellular yeasts; accumulating evidence points to Mob functional diversification. A striking example comes from the most sequence-divergent class of Mobs, which are components of the highly conserved Striatin Interacting Phosphatase and Kinase (STRIPAK) complex, that antagonizes Hippo signaling. Mobs stand out for their potential to modulate the output from Hippo and Hippo-like kinases, through their roles both in activating NDR kinases and in antagonizing upstream Hippo or Hippo-like kinase activity. These opposing Mob functions suggest that they coordinate the relative activities of the Tricornered/STK38/STK38L and Warts/LATS kinases, and thus have potential to assemble nodes for pathway signaling output. We survey the different facets of Mob-dependent regulation of Hippo and Hippo-like signaling and highlight open questions that hinge on unresolved aspects of Mob functions.
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Affiliation(s)
- Juan Carlos Duhart
- School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV, United States
| | - Laurel A Raftery
- School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV, United States
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15
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Duhart JC, Raftery LA. Mob Family Proteins: Regulatory Partners in Hippo and Hippo-Like Intracellular Signaling Pathways. Front Cell Dev Biol 2020; 8:161. [PMID: 32266255 PMCID: PMC7096357 DOI: 10.3389/fcell.2020.00161] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Accepted: 02/28/2020] [Indexed: 12/16/2022] Open
Abstract
Studies in yeast first delineated the function of Mob proteins in kinase pathways that regulate cell division and shape; in multicellular eukaryotes Mobs regulate tissue growth and morphogenesis. In animals, Mobs are adaptors in Hippo signaling, an intracellular signal-transduction pathway that restricts growth, impacting the development and homeostasis of animal organs. Central to Hippo signaling are the Nuclear Dbf2-Related (NDR) kinases, Warts and LATS1 and LATS2, in flies and mammals, respectively. A second Hippo-like signaling pathway has been uncovered in animals, which regulates cell and tissue morphogenesis. Central to this emergent pathway are the NDR kinases, Tricornered, STK38, and STK38L. In Hippo signaling, NDR kinase activation is controlled by three activating interactions with a conserved set of proteins. This review focuses on one co-activator family, the highly conserved, non-catalytic Mps1-binder-related (Mob) proteins. In this context, Mobs are allosteric activators of NDR kinases and adaptors that contribute to assembly of multiprotein NDR kinase activation complexes. In multicellular eukaryotes, the Mob family has expanded relative to model unicellular yeasts; accumulating evidence points to Mob functional diversification. A striking example comes from the most sequence-divergent class of Mobs, which are components of the highly conserved Striatin Interacting Phosphatase and Kinase (STRIPAK) complex, that antagonizes Hippo signaling. Mobs stand out for their potential to modulate the output from Hippo and Hippo-like kinases, through their roles both in activating NDR kinases and in antagonizing upstream Hippo or Hippo-like kinase activity. These opposing Mob functions suggest that they coordinate the relative activities of the Tricornered/STK38/STK38L and Warts/LATS kinases, and thus have potential to assemble nodes for pathway signaling output. We survey the different facets of Mob-dependent regulation of Hippo and Hippo-like signaling and highlight open questions that hinge on unresolved aspects of Mob functions.
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Affiliation(s)
| | - Laurel A. Raftery
- School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV, United States
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16
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Verghese S, Moberg K. Roles of Membrane and Vesicular Traffic in Regulation of the Hippo Pathway. Front Cell Dev Biol 2020; 7:384. [PMID: 32010696 PMCID: PMC6971369 DOI: 10.3389/fcell.2019.00384] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 12/19/2019] [Indexed: 12/12/2022] Open
Abstract
The Hippo pathway is a well conserved signaling cascade that modulates cell proliferation and survival in response to external cues such as cell:cell contact, injury, and nutritional status. Models of the Hippo pathway have evolved from a series of genetic interactions defined in the fruit fly Drosophila melanogaster into a complex series of biochemical mechanisms in which transmembrane and cytoskeletal proteins modulate cytoplasmic phosphatase and kinase activities that converge on the serine/threonine kinase Warts (Wts) to regulate nuclear entry of the co-activator protein Yorkie (Yki; vertebrate Yap1). This pathway is well conserved in human cells and broadly implicated in cancer. Progress in understanding biochemical events within the Hippo pathway highlights a need for improved understanding of the cell biological contexts in which these molecular interactions occur. A significant body of data linking Hippo signaling to membranes and proteins involved in intracellular membrane trafficking raise the possibility that some molecular regulatory events occur on the cytoplasmic face of vesicles. In Drosophila, a Yki-vesicle link was solidified by discoveries that cytoplasmic Yki concentrates at late-endosomes and physically interacts with two endosomal adaptor proteins, Myopic (Mop) and Leash. These two proteins are required for Yki to transit the endolysosomal pathway and be turned over in lysosomes. Molecules involved in recruiting and tethering Yki along this endosomal route are not defined but are predicted to play key roles in regulating Yki levels and thus Hippo-responsiveness of cells. As Wts is recruited to the apical membrane by upstream Hippo components, endosomal internalization could also affect complexes involved in Yki phosphorylation events that alter nucleocytoplasmic shuttling. Recent work has revealed an unexpected, non-transcriptional role of membrane-associated Yki in triggering actinomyosin contractility via the myosin-regulatory light chain Spaghetti squash (Sqh). How Yki interacts with the membrane and controls Sqh is unclear, but this mechanism represents a novel regulatory mechanism based on induced localization of Yki to a specific membrane compartment. These and other data will be discussed as we review data linking Yki to membrane and vesicular traffic in development and homeostasis and speculate on missing elements of these membrane-linked Yki regulatory mechanisms.
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Affiliation(s)
- Shilpi Verghese
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Ken Moberg
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
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A Genetic Screen in Drosophila To Identify Novel Regulation of Cell Growth by Phosphoinositide Signaling. G3-GENES GENOMES GENETICS 2020; 10:57-67. [PMID: 31704710 PMCID: PMC6945015 DOI: 10.1534/g3.119.400851] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Phosphoinositides are lipid signaling molecules that regulate several conserved sub-cellular processes in eukaryotes, including cell growth. Phosphoinositides are generated by the enzymatic activity of highly specific lipid kinases and phosphatases. For example, the lipid PIP3, the Class I PI3 kinase that generates it and the phosphatase PTEN that metabolizes it are all established regulators of growth control in metazoans. To identify additional functions for phosphoinositides in growth control, we performed a genetic screen to identify proteins which when depleted result in altered tissue growth. By using RNA-interference mediated depletion coupled with mosaic analysis in developing eyes, we identified and classified additional candidates in the developing Drosophila melanogaster eye that regulate growth either cell autonomously or via cell-cell interactions. We report three genes: Pi3K68D, Vps34 and fwd that are important for growth regulation and suggest that these are likely to act via cell-cell interactions in the developing eye. Our findings define new avenues for the understanding of growth regulation in metazoan tissue development by phosphoinositide metabolizing proteins.
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Abstract
Hippo signaling is an evolutionarily conserved network that has a central role in regulating cell proliferation and cell fate to control organ growth and regeneration. It promotes activation of the LATS kinases, which control gene expression by inhibiting the activity of the transcriptional coactivator proteins YAP and TAZ in mammals and Yorkie in Drosophila. Diverse upstream inputs, including both biochemical cues and biomechanical cues, regulate Hippo signaling and enable it to have a key role as a sensor of cells' physical environment and an integrator of growth control signals. Several components of this pathway localize to cell-cell junctions and contribute to regulation of Hippo signaling by cell polarity, cell contacts, and the cytoskeleton. Downregulation of Hippo signaling promotes uncontrolled cell proliferation, impairs differentiation, and is associated with cancer. We review the current understanding of Hippo signaling and highlight progress in the elucidation of its regulatory mechanisms and biological functions.
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Affiliation(s)
- Jyoti R Misra
- Waksman Institute and Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA;
| | - Kenneth D Irvine
- Waksman Institute and Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA;
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19
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Cantarutti KC, Burgess J, Brill JA, Dason JS. Type II phosphatidylinositol 4-kinase regulates nerve terminal growth and synaptic vesicle recycling. J Neurogenet 2018; 32:230-235. [DOI: 10.1080/01677063.2018.1502762] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
| | - Jason Burgess
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Julie A. Brill
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
- Institute of Medical Science, University of Toronto, Toronto, Canada
| | - Jeffrey S. Dason
- Department of Biological Sciences, University of Windsor, Windsor, Canada
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20
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Balakrishnan SS, Basu U, Shinde D, Thakur R, Jaiswal M, Raghu P. Regulation of PI4P levels by PI4KIIIα during G-protein-coupled PLC signaling in Drosophila photoreceptors. J Cell Sci 2018; 131:jcs.217257. [PMID: 29980590 DOI: 10.1242/jcs.217257] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 06/27/2018] [Indexed: 12/27/2022] Open
Abstract
The activation of phospholipase C (PLC) is a conserved mechanism of receptor-activated cell signaling at the plasma membrane. PLC hydrolyzes the minor membrane lipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], and continued signaling requires the resynthesis and availability of PI(4,5)P2 at the plasma membrane. PI(4,5)P2 is synthesized by the phosphorylation of phosphatidylinositol 4-phosphate (PI4P). Thus, a continuous supply of PI4P is essential to support ongoing PLC signaling. While the enzyme PI4KA has been identified as performing this function in cultured mammalian cells, its function in the context of an in vivo physiological model has not been established. In this study, we show that, in Drosophila photoreceptors, PI4KIIIα activity is required to support signaling during G-protein-coupled PLC activation. Depletion of PI4KIIIα results in impaired electrical responses to light, and reduced plasma membrane levels of PI4P and PI(4,5)P2 Depletion of the conserved proteins Efr3 and TTC7 [also known as StmA and L(2)k14710, respectively, in flies], which assemble PI4KIIIα at the plasma membrane, also results in an impaired light response and reduced plasma membrane PI4P and PI(4,5)P2 levels. Thus, PI4KIIIα activity at the plasma membrane generates PI4P and supports PI(4,5)P2 levels during receptor activated PLC signaling.
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Affiliation(s)
- Sruthi S Balakrishnan
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore 560065, India
| | - Urbashi Basu
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore 560065, India
| | - Dhananjay Shinde
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore 560065, India
| | - Rajan Thakur
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore 560065, India
| | - Manish Jaiswal
- TIFR Center for Interdisciplinary Science, Hyderabad 500107, India
| | - Padinjat Raghu
- National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bangalore 560065, India
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21
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Downregulation of RBO-PI4KIIIα Facilitates Aβ 42 Secretion and Ameliorates Neural Deficits in Aβ 42-Expressing Drosophila. J Neurosci 2017; 37:4928-4941. [PMID: 28424219 DOI: 10.1523/jneurosci.3567-16.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 03/12/2017] [Accepted: 03/31/2017] [Indexed: 12/25/2022] Open
Abstract
Phosphoinositides and their metabolizing enzymes are involved in Aβ42 metabolism and Alzheimer's disease pathogenesis. In yeast and mammals, Eighty-five requiring 3 (EFR3), whose Drosophila homolog is Rolling Blackout (RBO), forms a plasma membrane-localized protein complex with phosphatidylinositol-4-kinase Type IIIα (PI4KIIIα) and a scaffold protein to tightly control the level of plasmalemmal phosphatidylinositol-4-phosphate (PI4P). Here, we report that RBO binds to Drosophila PI4KIIIα, and that in an Aβ42-expressing Drosophila model, separate genetic reduction of PI4KIIIα and RBO, or pharmacological inhibition of PI4KIIIα ameliorated synaptic transmission deficit, climbing ability decline, premature death, and reduced neuronal accumulation of Aβ42 Moreover, we found that RBO-PI4KIIIa downregulation increased neuronal Aβ42 release and that PI4P facilitated the assembly or oligomerization of Aβ42 in/on liposomes. These results indicate that RBO-PI4KIIIa downregulation facilitates neuronal Aβ42 release and consequently reduces neuronal Aβ42 accumulation likely via decreasing Aβ42 assembly in/on plasma membrane. This study suggests the RBO-PI4KIIIα complex as a potential therapeutic target and PI4KIIIα inhibitors as drug candidates for Alzheimer's disease treatment.SIGNIFICANCE STATEMENT Phosphoinositides and their metabolizing enzymes are involved in Aβ42 metabolism and Alzheimer's disease pathogenesis. Here, in an Aβ42-expressing Drosophila model, we discovered and studied the beneficial role of downregulating RBO or its interacting protein PI4KIIIα-a protein that tightly controls the plasmalemmal level of PI4P-against the defects caused by Aβ42 expression. Mechanistically, RBO-PI4KIIIα downregulation reduced neuronal Aβ42 accumulation, and interestingly increased neuronal Aβ42 release. This study suggests the RBO-PI4KIIIα complex as a novel therapeutic target, and PI4KIIIα inhibitors as new drug candidates.
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Duhart JC, Parsons TT, Raftery LA. The repertoire of epithelial morphogenesis on display: Progressive elaboration of Drosophila egg structure. Mech Dev 2017; 148:18-39. [PMID: 28433748 DOI: 10.1016/j.mod.2017.04.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 04/07/2017] [Accepted: 04/12/2017] [Indexed: 12/26/2022]
Abstract
Epithelial structures are foundational for tissue organization in all metazoans. Sheets of epithelial cells form lateral adhesive junctions and acquire apico-basal polarity perpendicular to the surface of the sheet. Genetic analyses in the insect model, Drosophila melanogaster, have greatly advanced our understanding of how epithelial organization is established, and how it is modulated during tissue morphogenesis. Major insights into collective cell migrations have come from analyses of morphogenetic movements within the adult follicular epithelium that cooperates with female germ cells to build a mature egg. Epithelial follicle cells progress through tightly choreographed phases of proliferation, patterning, reorganization and migrations, before they differentiate to form the elaborate structures of the eggshell. Distinct structural domains are organized by differential adhesion, within which lateral junctions are remodeled to further shape the organized epithelia. During collective cell migrations, adhesive interactions mediate supracellular organization of planar polarized macromolecules, and facilitate crawling over the basement membrane or traction against adjacent cell surfaces. Comparative studies with other insects are revealing the diversification of morphogenetic movements for elaboration of epithelial structures. This review surveys the repertoire of follicle cell morphogenesis, to highlight the coordination of epithelial plasticity with progressive differentiation of a secretory epithelium. Technological advances will keep this tissue at the leading edge for interrogating the precise spatiotemporal regulation of normal epithelial reorganization events, and provide a framework for understanding pathological tissue dysplasia.
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Affiliation(s)
- Juan Carlos Duhart
- School of Life Sciences, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154-4004, United States
| | - Travis T Parsons
- School of Life Sciences, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154-4004, United States
| | - Laurel A Raftery
- School of Life Sciences, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154-4004, United States.
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Ye H, Li X, Zheng T, Hu C, Pan Z, Huang J, Li J, Li W, Zheng Y. The Hippo Signaling Pathway Regulates Ovarian Function via the Proliferation of Ovarian Germline Stem Cells. Cell Physiol Biochem 2017; 41:1051-1062. [PMID: 28245464 DOI: 10.1159/000464113] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 12/08/2016] [Indexed: 12/24/2022] Open
Abstract
OBJECTIVE To improve the separation, identification and cultivation of ovarian germline stem cells (OGSCs), to clarify the relationship between the Hippo signaling pathway effector YAP1 and the proliferation and differentiation of OGSCs in vitro and to identify the major contribution of Hippo signaling to ovarian function. METHODS Two-step enzymatic separation processes and magnetic separation were used to isolate and identify OGSCs by determining the expression of Mvh, Oct4, Nanog, Fragilis and Stella markers. Then, YAP1, as the main effector molecule in the Hippo signaling pathway, was chosen as the target gene of the study. Lentivirus containing overexpressed YAP1 or a YAP1-targeted shRNA was transduced into OGSCs. The effects of modulating the Hippo signaling pathway on the proliferation, differentiation, reproduction and endocrine function of ovaries were observed by microinjecting the lentiviral vectors with overexpressed YAP1 or YAP1 shRNA into infertile mouse models or natural mice of reproductive age. RESULTS (1) The specific expression of Mvh, Oct4, Nanog, Fragilis and Stella markers was observed in isolated stem cells. Thus, the isolated cells were preliminarily identified as OGSCs. (2) The co-expression of LATS2, MST1, YAP1 and MVH was observed in isolated OGSCs. Mvh and Oct4 expression levels were significantly increased in OGSCs overexpressing YAP1 compared to GFP controls. Consistently, Mvh and Oct4 levels were significantly decreased in cells expressing YAP1-targeted shRNA. (3) After 14-75 days of YAP1 overexpression in infertile mouse models, we detected follicle regeneration in ovaries, the activation of primordial follicles and increased birth rate, accompanied by increasing levels of E2 and FSH. (4) However, we detected decreasing follicles in ovaries, lower birth rate, and decreasing E2 and FSH in serum from healthy mice of reproductive age following YAP1 shRNA expression. CONCLUSION Methods for the isolation, identification and culture of OGSCs were successfully established. Further results indicate that isolated OGSCs can specifically recognize Hippo signaling molecules and that manipulation of YAP1 expression can be used to regulate the proliferation and differentiation of OGSCs, as well as ovarian function in mice. This study suggests that the Hippo signaling pathway may represent a new molecular target for the regulation of mouse ovarian functional remodeling.
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24
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Multiple Roles for Egalitarian in Polarization of the Drosophila Egg Chamber. Genetics 2016; 203:415-32. [PMID: 27017624 DOI: 10.1534/genetics.115.184622] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 03/20/2016] [Indexed: 01/08/2023] Open
Abstract
The Drosophila egg chamber provides a useful model for examining mechanisms by which cell fates are specified and maintained in the context of a complex tissue. The egg chamber is also an excellent model for understanding the mechanism by which cytoskeletal filaments are organized and the critical interplay between cytoskeletal organization, polarity establishment, and cell fate specification. Previous work has shown that Egalitarian (Egl) is required for specification and maintenance of oocyte fate. Mutants in egl either completely fail to specify an oocyte, or if specified, the oocyte eventually reverts back to nurse cell fate. Due to this very early role for Egl in egg chamber maturation, it is unclear whether later stages of egg chamber development also require Egl function. In this report, we have depleted Egl at specific stages of egg chamber development. We demonstrate that in early-stage egg chambers, Egl has an additional role in organization of oocyte microtubules. In the absence of Egl function, oocyte microtubules completely fail to reorganize. As such, the localization of microtubule motors and their cargo is disrupted. In addition, Egl also appears to function in regulating the translation of critical polarity determining messenger RNAs (mRNAs). Finally, we demonstrate that in midstage egg chambers, Egl does not appear to be required for microtubule organization, but rather for the correct spatial localization of oskar, bicoid, and gurken mRNAs.
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25
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Kabeche R, Madrid M, Cansado J, Moseley JB. Eisosomes Regulate Phosphatidylinositol 4,5-Bisphosphate (PI(4,5)P2) Cortical Clusters and Mitogen-activated Protein (MAP) Kinase Signaling upon Osmotic Stress. J Biol Chem 2015; 290:25960-73. [PMID: 26359496 DOI: 10.1074/jbc.m115.674192] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Indexed: 01/22/2023] Open
Abstract
Eisosomes are multiprotein structures that generate linear invaginations at the plasma membrane of yeast cells. The core component of eisosomes, the BAR domain protein Pil1, generates these invaginations through direct binding to lipids including phosphoinositides. Eisosomes promote hydrolysis of phosphatidylinositol 4,5 bisphosphate (PI(4,5)P2) by functioning with synaptojanin, but the cellular processes regulated by this pathway have been unknown. Here, we found that PI(4,5)P2 regulation by eisosomes inhibits the cell integrity pathway, a conserved MAPK signal transduction cascade. This pathway is activated by multiple environmental conditions including osmotic stress in the fission yeast Schizosaccharomyces pombe. Activation of the MAPK Pmk1 was impaired by mutations in the phosphatidylinositol (PI) 5-kinase Its3, but this defect was suppressed by removal of eisosomes. Using fluorescent biosensors, we found that osmotic stress induced the formation of PI(4,5)P2 clusters that were spatially organized by eisosomes in both fission yeast and budding yeast cells. These cortical clusters contained the PI 5-kinase Its3 and did not assemble in the its3-1 mutant. The GTPase Rho2, an upstream activator of Pmk1, also co-localized with PI(4,5)P2 clusters under osmotic stress, providing a molecular link between these novel clusters and MAPK activation. Our findings have revealed that eisosomes regulate activation of MAPK signal transduction through the organization of cortical lipid-based microdomains.
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Affiliation(s)
- Ruth Kabeche
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
| | - Marisa Madrid
- Yeast Physiology Group, Department of Genetics and Microbiology, Facultad de Biología, Universidad de Murcia, 30071, Murcia, Spain
| | - José Cansado
- Yeast Physiology Group, Department of Genetics and Microbiology, Facultad de Biología, Universidad de Murcia, 30071, Murcia, Spain
| | - James B Moseley
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and
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26
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Wong KKL, Li W, An Y, Duan Y, Li Z, Kang Y, Yan Y. β-Spectrin regulates the hippo signaling pathway and modulates the basal actin network. J Biol Chem 2015; 290:6397-407. [PMID: 25589787 DOI: 10.1074/jbc.m114.629493] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Emerging evidence suggests functional regulation of the Hippo pathway by the actin cytoskeleton, although the detailed molecular mechanism remains incomplete. In a genetic screen, we identified a requirement for β-Spectrin in the posterior follicle cells for the oocyte repolarization process during Drosophila mid-oogenesis. β-spectrin mutations lead to loss of Hippo signaling activity in the follicle cells. A similar reduction of Hippo signaling activity was observed after β-Spectrin knockdown in mammalian cells. We further demonstrated that β-spectrin mutations disrupt the basal actin network in follicle cells. The abnormal stress fiber-like actin structure on the basal side of follicle cells provides a likely link between the β-spectrin mutations and the loss of the Hippo signaling activity phenotype.
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Affiliation(s)
- Kenneth Kin Lam Wong
- From the Division of Life Science and Center of Systems Biology and Human Health, School of Science and Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China and
| | - Wenyang Li
- the Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544
| | - Yanru An
- From the Division of Life Science and Center of Systems Biology and Human Health, School of Science and Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China and
| | | | | | - Yibin Kang
- the Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544
| | - Yan Yan
- From the Division of Life Science and Center of Systems Biology and Human Health, School of Science and Institute for Advanced Study, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China and
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Balakrishnan SS, Basu U, Raghu P. Phosphoinositide signalling in Drosophila. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:770-84. [PMID: 25449646 DOI: 10.1016/j.bbalip.2014.10.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 10/08/2014] [Accepted: 10/22/2014] [Indexed: 01/28/2023]
Abstract
Phosphoinositides (PtdInsPs) are lipids that mediate a range of conserved cellular processes in eukaryotes. These include the transduction of ligand binding to cell surface receptors, vesicular transport and cytoskeletal function. The nature and functions of PtdInsPs were initially elucidated through biochemical experiments in mammalian cells. However, over the years, genetic and cell biological analysis in a range of model organisms including S. cerevisiae, D. melanogaster and C. elegans have contributed to an understanding of the involvement of PtdInsPs in these cellular events. The fruit fly Drosophila is an excellent genetic model for the analysis of cell and developmental biology as well as physiological processes, particularly analysis of the complex relationship between the cell types of a metazoan in mediating animal physiology. PtdInsP signalling pathways are underpinned by enzymes that synthesise and degrade these molecules and also by proteins that bind to these lipids in cells. In this review we provide an overview of the current understanding of PtdInsP signalling in Drosophila. We provide a comparative genomic analysis of the PtdInsP signalling toolkit between Drosophila and mammalian systems. We also review some areas of cell and developmental biology where analysis in Drosophila might provide insights into the role of this lipid-signalling pathway in metazoan biology. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Sruthi S Balakrishnan
- National Centre for Biological Sciences, TIFR-GKVK Campus, Bellary Road, Bangalore 560065, India
| | - Urbashi Basu
- National Centre for Biological Sciences, TIFR-GKVK Campus, Bellary Road, Bangalore 560065, India
| | - Padinjat Raghu
- National Centre for Biological Sciences, TIFR-GKVK Campus, Bellary Road, Bangalore 560065, India.
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Polarized deposition of basement membrane proteins depends on Phosphatidylinositol synthase and the levels of Phosphatidylinositol 4,5-bisphosphate. Proc Natl Acad Sci U S A 2014; 111:7689-94. [PMID: 24828534 DOI: 10.1073/pnas.1407351111] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The basement membrane (BM), a specialized sheet of the extracellular matrix contacting the basal side of epithelial tissues, plays an important role in the control of the polarized structure of epithelial cells. However, little is known about how BM proteins themselves achieve a polarized distribution. Here, we identify phosphatidylinositol 4,5-bisphosphate (PIP2) as a critical regulator of the polarized secretion of BM proteins. A decrease of PIP2 levels, in particular through mutations in Phosphatidylinositol synthase (Pis) and other members of the phosphoinositide pathway, leads to the aberrant accumulation of BM components at the apical side of the cell without primarily affecting the distribution of apical and basolateral polarity proteins. In addition, PIP2 controls the apical and lateral localization of Crag (Calmodulin-binding protein related to a Rab3 GDP/GTP exchange protein), a factor specifically required to prevent aberrant apical secretion of BM. We propose that PIP2, through the control of Crag's subcellular localization, restricts the secretion of BM proteins to the basal side.
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Tan J, Oh K, Burgess J, Hipfner DR, Brill JA. PI4KIIIα is required for cortical integrity and cell polarity during Drosophila oogenesis. J Cell Sci 2014; 127:954-66. [PMID: 24413170 DOI: 10.1242/jcs.129031] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Phosphoinositides regulate myriad cellular processes, acting as potent signaling molecules in conserved signaling pathways and as organelle gatekeepers that recruit effector proteins to membranes. Phosphoinositide-generating enzymes have been studied extensively in yeast and cultured cells, yet their roles in animal development are not well understood. Here, we analyze Drosophila melanogaster phosphatidylinositol 4-kinase IIIα (PI4KIIIα) during oogenesis. We demonstrate that PI4KIIIα is required for production of plasma membrane PtdIns4P and PtdIns(4,5)P2 and is crucial for actin organization, membrane trafficking and cell polarity. Female germ cells mutant for PI4KIIIα exhibit defects in cortical integrity associated with failure to recruit the cytoskeletal-membrane crosslinker Moesin and the exocyst subunit Sec5. These effects reflect a unique requirement for PI4KIIIα, as egg chambers from flies mutant for either of the other Drosophila PI4Ks, fwd or PI4KII, show Golgi but not plasma membrane phenotypes. Thus, PI4KIIIα is a vital regulator of a functionally distinct pool of PtdIns4P that is essential for PtdIns(4,5)P2-dependent processes in Drosophila development.
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Affiliation(s)
- Julie Tan
- Program in Cell Biology, The Hospital for Sick Children, PGCRL, 686 Bay Street, Room 15.9716, Toronto, ON, M5G 0A4, Canada
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Domanitskaya E, Anllo L, Schüpbach T. Phantom, a cytochrome P450 enzyme essential for ecdysone biosynthesis, plays a critical role in the control of border cell migration in Drosophila. Dev Biol 2013; 386:408-18. [PMID: 24373956 DOI: 10.1016/j.ydbio.2013.12.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 12/05/2013] [Accepted: 12/10/2013] [Indexed: 10/25/2022]
Abstract
The border cells of Drosophila are a model system for coordinated cell migration. Ecdysone signaling has been shown to act as the timing signal to initiate the migration process. Here we find that mutations in phantom (phm), encoding an enzyme in the ecdysone biosynthesis pathway, block border cell migration when the entire follicular epithelium of an egg chamber is mutant, even when the associated germline cells (nurse cells and oocyte) are wild-type. Conversely, mutant germline cells survive and do not affect border cell migration, as long as the surrounding follicle cells are wild-type. Interestingly, even small patches of wild-type follicle cells in a mosaic epithelium are sufficient to allow the production of above-threshold levels of ecdysone to promote border cell migration. The same phenotype is observed with mutations in shade (shd), encoding the last enzyme in the pathway that converts ecdysone to the active 20-hydroxyecdysone. Administration of high 20-hydroxyecdysone titers in the medium can also rescue the border cell migration phenotype in cultured egg chambers with an entirely phm mutant follicular epithelium. These results indicate that in normal oogenesis, the follicle cell epithelium of each individual egg chamber must supply sufficient ecdysone precursors, leading ultimately to high enough levels of mature 20-hydroxyecdysone to the border cells to initiate their migration. Neither the germline, nor the neighboring egg chambers, nor the surrounding hemolymph appear to provide threshold amounts of 20-hydroxyecdysone to do so. This "egg chamber autonomous" ecdysone synthesis constitutes a useful way to regulate the individual maturation of the asynchronous egg chambers present in the Drosophila ovary.
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Affiliation(s)
- Elena Domanitskaya
- Howard Hughes Medical Institute, Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States
| | - Lauren Anllo
- Howard Hughes Medical Institute, Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States
| | - Trudi Schüpbach
- Howard Hughes Medical Institute, Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States.
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31
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Tan J, Brill JA. Cinderella story: PI4P goes from precursor to key signaling molecule. Crit Rev Biochem Mol Biol 2013; 49:33-58. [PMID: 24219382 DOI: 10.3109/10409238.2013.853024] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Phosphatidylinositol lipids are signaling molecules involved in nearly all aspects of cellular regulation. Production of phosphatidylinositol 4-phosphate (PI4P) has long been recognized as one of the first steps in generating poly-phosphatidylinositol phosphates involved in actin organization, cell migration, and signal transduction. In addition, progress over the last decade has brought to light independent roles for PI4P in membrane trafficking and lipid homeostasis. Here, we describe recent advances that reveal the breadth of processes regulated by PI4P, the spectrum of PI4P effectors, and the mechanisms of spatiotemporal control that coordinate crosstalk between PI4P and cellular signaling pathways.
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Affiliation(s)
- Julie Tan
- Department of Molecular Genetics, University of Toronto , Toronto, Ontario , Canada and
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Forrest S, Chai A, Sanhueza M, Marescotti M, Parry K, Georgiev A, Sahota V, Mendez-Castro R, Pennetta G. Increased levels of phosphoinositides cause neurodegeneration in a Drosophila model of amyotrophic lateral sclerosis. Hum Mol Genet 2013; 22:2689-704. [PMID: 23492670 PMCID: PMC3674808 DOI: 10.1093/hmg/ddt118] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The Vesicle-associated membrane protein (VAMP)-Associated Protein B (VAPB) is the causative gene of amyotrophic lateral sclerosis 8 (ALS8) in humans. Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by selective death of motor neurons leading to spasticity, muscle atrophy and paralysis. VAP proteins have been implicated in various cellular processes, including intercellular signalling, synaptic remodelling, lipid transport and membrane trafficking and yet, the molecular mechanisms underlying ALS8 pathogenesis remain poorly understood. We identified the conserved phosphoinositide phosphatase Sac1 as a Drosophila VAP (DVAP)-binding partner and showed that DVAP is required to maintain normal levels of phosphoinositides. Downregulating either Sac1 or DVAP disrupts axonal transport, synaptic growth, synaptic microtubule integrity and the localization of several postsynaptic components. Expression of the disease-causing allele (DVAP-P58S) in a fly model for ALS8 induces neurodegeneration, elicits synaptic defects similar to those of DVAP or Sac1 downregulation and increases phosphoinositide levels. Consistent with a role for Sac1-mediated increase of phosphoinositide levels in ALS8 pathogenesis, we found that Sac1 downregulation induces neurodegeneration in a dosage-dependent manner. In addition, we report that Sac1 is sequestered into the DVAP-P58S-induced aggregates and that reducing phosphoinositide levels rescues the neurodegeneration and suppresses the synaptic phenotypes associated with DVAP-P58S transgenic expression. These data underscore the importance of DVAP–Sac1 interaction in controlling phosphoinositide metabolism and provide mechanistic evidence for a crucial role of phosphoinositide levels in VAP-induced ALS.
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Affiliation(s)
- Stuart Forrest
- Center for Integrative Physiology and Euan MacDonald Center for Motor Neuron Disease Research, School of Biomedical Sciences, University of Edinburgh, Edinburgh, UK
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St Johnston D. Using mutants, knockdowns, and transgenesis to investigate gene function in Drosophila. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 2:587-613. [PMID: 24014449 DOI: 10.1002/wdev.101] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The sophisticated genetic techniques available in Drosophila are largely responsible for its success as a model organism. One of the most important of these is the ability to disrupt gene function in vivo and observe the resulting phenotypes. This review considers the ever-increasing repertoire of approaches for perturbing the functions of specific genes in flies, ranging from classical and transposon-mediated mutageneses to newer techniques, such as homologous recombination and RNA interference. Since most genes are used over and over again in different contexts during development, many important advances have depended on being able to interfere with gene function at specific times or places in the developing animal, and a variety of approaches are now available to do this. Most of these techniques rely on being able to create genetically modified strains of Drosophila and the different methods for generating lines carrying single copy transgenic constructs will be described, along with the advantages and disadvantages of each approach.
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Affiliation(s)
- Daniel St Johnston
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Cambridge CB2 1QN, UK.
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Evaluation of phosphatidylinositol-4-kinase IIIα as a hepatitis C virus drug target. J Virol 2012; 86:11595-607. [PMID: 22896614 DOI: 10.1128/jvi.01320-12] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Phosphatidylinositol-4-kinase IIIα (PI4KIIIα) is an essential host cell factor for hepatitis C virus (HCV) replication. An N-terminally truncated 130-kDa form was used to reconstitute an in vitro biochemical lipid kinase assay that was optimized for small-molecule compound screening and identified potent and specific inhibitors. Cell culture studies with PI4KIIIα inhibitors demonstrated that the kinase activity was essential for HCV RNA replication. Two PI4KIIIα inhibitors were used to select cell lines harboring HCV replicon mutants with a 20-fold loss in sensitivity to the compounds. Reverse genetic mapping isolated an NS4B-NS5A segment that rescued HCV RNA replication in PIK4IIIα-deficient cells. HCV RNA replication occurs on specialized membranous webs, and this study with PIK4IIIα inhibitor-resistant mutants provides a genetic link between NS4B/NS5A functions and PI4-phosphate lipid metabolism. A comprehensive assessment of PI4KIIIα as a drug target included its evaluation for pharmacologic intervention in vivo through conditional transgenic murine lines that mimic target-specific inhibition in adult mice. Homozygotes that induce a knockout of the kinase domain or knock in a single amino acid substitution, kinase-defective PI4KIIIα, displayed a lethal phenotype with a fairly widespread mucosal epithelial degeneration of the gastrointestinal tract. This essential host physiologic role raises doubt about the pursuit of PI4KIIIα inhibitors for treatment of chronic HCV infection.
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A screen for round egg mutants in Drosophila identifies tricornered, furry, and misshapen as regulators of egg chamber elongation. G3-GENES GENOMES GENETICS 2012; 2:371-8. [PMID: 22413091 PMCID: PMC3291507 DOI: 10.1534/g3.111.001677] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 01/18/2012] [Indexed: 01/13/2023]
Abstract
The elongation of tissues and organs during embryonic development results from the coordinate polarization of cell behaviors with respect to the elongation axis. Within the Drosophila melanogaster ovary, initially spherical egg chambers lengthen dramatically as they develop to create the elliptical shape of the mature egg. This morphogenesis depends on an unusual form of planar polarity within the egg chamber's outer epithelial cell layer known as the follicle cells. Disruption of follicle cell planar polarity leads to the production of round rather than elongated eggs; however, the molecular mechanisms that control this tissue organization are poorly understood. Starting from a broadly based forward genetic screen, we have isolated 12 new round egg complementation groups, and have identified four of the mutated genes. In mapping the largest complementation group to the fat2 locus, we unexpectedly discovered a high incidence of cryptic fat2 mutations in the backgrounds of publicly available stocks. Three other complementation groups correspond to the genes encoding the cytoplasmic signaling proteins Tricornered (Trc), Furry (Fry), and Misshapen (Msn). Trc and Fry are known members of an NDR kinase signaling pathway, and as a Ste20-like kinase, Msn may function upstream of Trc. We show that all three proteins are required for follicle cell planar polarity at early stages of egg chamber elongation and that Trc shows a planar polarized distribution at the basal follicle cell surface. These results indicate that this new mutant collection is likely to provide novel insight into the molecular mechanisms controlling follicle cell planar polarity and egg chamber elongation.
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Hippo signaling: A hub of growth control, tumor suppression and pluripotency maintenance. J Genet Genomics 2011; 38:471-81. [DOI: 10.1016/j.jgg.2011.09.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 09/02/2011] [Accepted: 09/12/2011] [Indexed: 12/31/2022]
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37
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Staley BK, Irvine KD. Hippo signaling in Drosophila: recent advances and insights. Dev Dyn 2011; 241:3-15. [PMID: 22174083 DOI: 10.1002/dvdy.22723] [Citation(s) in RCA: 205] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/05/2011] [Indexed: 01/08/2023] Open
Abstract
The Hippo signaling pathway emerged from studies of Drosophila tumor suppressor genes, and is now appreciated as a major growth control pathway in vertebrates as well as arthropods. As a recently discovered pathway, key components of the pathway are continually being identified, and new insights into how the pathway is regulated and deployed are arising at a rapid pace. Over the past year and a half, significant advances have been made in our understanding of upstream regulatory inputs into Hippo signaling, key negative regulators of Hippo pathway activity have been identified, and important roles for the pathway in regeneration have been described. This review describes these and other advances, focusing on recent progress in our understanding of Hippo signaling that has come from continued studies in Drosophila.
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Affiliation(s)
- Binnaz Kucuk Staley
- Howard Hughes Medical Institute, Waksman Institute and Department of Molecular Biology and Biochemistry, Rutgers The State University of New Jersey, Piscataway, New Jersey 08854, USA
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