1
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Daly C, Plouffe B. Gα q signalling from endosomes: A new conundrum. Br J Pharmacol 2023. [PMID: 37740273 DOI: 10.1111/bph.16248] [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: 06/29/2023] [Revised: 08/08/2023] [Accepted: 09/13/2023] [Indexed: 09/24/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) constitute the largest family of membrane receptors, and are involved in the transmission of a variety of extracellular stimuli such as hormones, neurotransmitters, light and odorants into intracellular responses. They regulate every aspect of physiology and, for this reason, about one third of all marketed drugs target these receptors. Classically, upon binding to their agonist, GPCRs are thought to activate G-proteins from the plasma membrane and to stop signalling by subsequent desensitisation and endocytosis. However, accumulating evidence indicates that, upon internalisation, some GPCRs can continue to activate G-proteins in endosomes. Importantly, this signalling from endomembranes mediates alternative cellular responses other than signalling at the plasma membrane. Endosomal G-protein signalling and its physiological relevance have been abundantly documented for Gαs - and Gαi -coupled receptors. Recently, some Gαq -coupled receptors have been reported to activate Gαq on endosomes and mediate important cellular processes. However, several questions relative to the series of cellular events required to translate endosomal Gαq activation into cellular responses remain unanswered and constitute a new conundrum. How are these responses in endosomes mediated in the quasi absence of the substrate for the canonical Gαq -activated effector? Is there another effector? Is there another substrate? If so, how does this alternative endosomal effector or substrate produce a downstream signal? This review aims to unravel and discuss these important questions, and proposes possible routes of investigation.
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Affiliation(s)
- Carole Daly
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
| | - Bianca Plouffe
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
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2
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Abstract
Phosphoinositides are signalling lipids derived from phosphatidylinositol, a ubiquitous phospholipid in the cytoplasmic leaflet of eukaryotic membranes. Initially discovered for their roles in cell signalling, phosphoinositides are now widely recognized as key integrators of membrane dynamics that broadly impact on all aspects of cell physiology and on disease. The past decade has witnessed a vast expansion of our knowledge of phosphoinositide biology. On the endocytic and exocytic routes, phosphoinositides direct the inward and outward flow of membrane as vesicular traffic is coupled to the conversion of phosphoinositides. Moreover, recent findings on the roles of phosphoinositides in autophagy and the endolysosomal system challenge our view of lysosome biology. The non-vesicular exchange of lipids, ions and metabolites at membrane contact sites in between organelles has also been found to depend on phosphoinositides. Here we review our current understanding of how phosphoinositides shape and direct membrane dynamics to impact on cell physiology, and provide an overview of emerging concepts in phosphoinositide regulation.
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3
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Jung SR, Jiang Y, Seo JB, Chiu DT, Hille B, Koh DS. β-arrestin-dependent PI(4,5)P 2 synthesis boosts GPCR endocytosis. Proc Natl Acad Sci U S A 2021; 118:e2011023118. [PMID: 33879605 PMCID: PMC8092559 DOI: 10.1073/pnas.2011023118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
β-arrestins regulate many cellular functions including intracellular signaling and desensitization of G protein-coupled receptors (GPCRs). Previous studies show that β-arrestin signaling and receptor endocytosis are modulated by the plasma membrane phosphoinositide lipid phosphatidylinositol-(4, 5)-bisphosphate (PI(4,5)P2). We found that β-arrestin also helped promote synthesis of PI(4,5)P2 and up-regulated GPCR endocytosis. We studied these questions with the Gq-coupled protease-activated receptor 2 (PAR2), which activates phospholipase C, desensitizes quickly, and undergoes extensive endocytosis. Phosphoinositides were monitored and controlled in live cells using lipid-specific fluorescent probes and genetic tools. Applying PAR2 agonist initiated depletion of PI(4,5)P2, which then recovered during rapid receptor desensitization, giving way to endocytosis. This endocytosis could be reduced by various manipulations that depleted phosphoinositides again right after phosphoinositide recovery: PI(4)P, a precusor of PI(4,5)P2, could be depleted at either the Golgi or the plasma membrane (PM) using a recruitable lipid 4-phosphatase enzyme and PI(4,5)P2 could be depleted at the PM using a recruitable 5-phosphatase. Endocytosis required the phosphoinositides. Knock-down of β-arrestin revealed that endogenous β-arrestin normally doubles the rate of PIP5-kinase (PIP5K) after PAR2 desensitization, boosting PI(4,5)P2-dependent formation of clathrin-coated pits (CCPs) at the PM. Desensitized PAR2 receptors were swiftly immobilized when they encountered CCPs, showing a dwell time of ∼90 s, 100 times longer than for unactivated receptors. PAR2/β-arrestin complexes eventually accumulated around the edges or across the surface of CCPs promoting transient binding of PIP5K-Iγ. Taken together, β-arrestins can coordinate potentiation of PIP5K activity at CCPs to induce local PI(4,5)P2 generation that promotes recruitment of PI(4,5)P2-dependent endocytic machinery.
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Affiliation(s)
- Seung-Ryoung Jung
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195;
- Department of Chemistry, University of Washington, Seattle, WA 98195
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Yifei Jiang
- Department of Chemistry, University of Washington, Seattle, WA 98195
| | - Jong Bae Seo
- Department of Biosciences, Mokpo National University, Jeonnam 58554, Republic of Korea
- Department of Biomedicine, Health and Life Convergence Sciences, Mokpo National University, Jeonnam 58554, Republic of Korea
| | - Daniel T Chiu
- Department of Chemistry, University of Washington, Seattle, WA 98195
- Department of Bioengineering, University of Washington, Seattle, WA 98195
| | - Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Duk-Su Koh
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
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4
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Aridor M, Owen DJ. Linton Mark Traub (1962-2020). J Cell Biol 2021; 220:e202011169. [PMID: 33404605 PMCID: PMC7791343 DOI: 10.1083/jcb.202011169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Meir Aridor and David Owen discuss the life and achievements of Linton Traub, who passed away on October 19, 2020.
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Affiliation(s)
- Meir Aridor
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - David J. Owen
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
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5
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Beziau A, Brand D, Piver E. The Role of Phosphatidylinositol Phosphate Kinases during Viral Infection. Viruses 2020; 12:v12101124. [PMID: 33022924 PMCID: PMC7599803 DOI: 10.3390/v12101124] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 09/27/2020] [Accepted: 09/29/2020] [Indexed: 12/11/2022] Open
Abstract
Phosphoinositides account for only a small proportion of cellular phospholipids, but have long been known to play an important role in diverse cellular processes, such as cell signaling, the establishment of organelle identity, and the regulation of cytoskeleton and membrane dynamics. As expected, given their pleiotropic regulatory functions, they have key functions in viral replication. The spatial restriction and steady-state levels of each phosphoinositide depend primarily on the concerted action of specific phosphoinositide kinases and phosphatases. This review focuses on a number of remarkable examples of viral strategies involving phosphoinositide kinases to ensure effective viral replication.
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Affiliation(s)
- Anne Beziau
- INSERM U1259, University of Tours, 37000 Tours, France
| | - Denys Brand
- INSERM U1259, University of Tours, 37000 Tours, France
- Virology Laboratory, Tours University Hospital, 3700 Tours, France
| | - Eric Piver
- INSERM U1259, University of Tours, 37000 Tours, France
- Biochemistry and Molecular Biology, Tours University Hospital, 3700 Tours, France
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6
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The endocytic cargo adaptor complex is required for cell-wall integrity via interacting with the sensor FgWsc2B in Fusarium graminearum. Curr Genet 2019; 65:1071-1080. [DOI: 10.1007/s00294-019-00961-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 03/25/2019] [Accepted: 03/26/2019] [Indexed: 01/09/2023]
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7
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Wallroth A, Haucke V. Phosphoinositide conversion in endocytosis and the endolysosomal system. J Biol Chem 2017; 293:1526-1535. [PMID: 29282290 DOI: 10.1074/jbc.r117.000629] [Citation(s) in RCA: 121] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Phosphoinositides (PIs) are phospholipids that perform crucial cell functions, ranging from cell migration and signaling to membrane trafficking, by serving as signposts of compartmental membrane identity. Although phosphatidylinositol 4,5-bisphosphate, 3-phosphate, and 3,5-bisphosphate are commonly considered as hallmarks of the plasma membrane, endosomes, and lysosomes, these compartments contain other functionally important PIs. Here, we review the roles of PIs in different compartments of the endolysosomal system in mammalian cells and discuss the mechanisms that spatiotemporally control PI conversion in endocytosis and endolysosomal membrane dynamics during endosome maturation and sorting. As defective PI conversion underlies human genetic diseases, including inherited myopathies, neurological disorders, and cancer, PI-converting enzymes represent potential targets for drug-based therapies.
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Affiliation(s)
- Alexander Wallroth
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin and
| | - Volker Haucke
- From the Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin and .,the Faculty of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany
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8
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Chen C, Wang X, Fang J, Xue J, Xiong X, Huang Y, Hu J, Ling K. EGFR-induced phosphorylation of type Iγ phosphatidylinositol phosphate kinase promotes pancreatic cancer progression. Oncotarget 2017; 8:42621-42637. [PMID: 28388589 PMCID: PMC5522093 DOI: 10.18632/oncotarget.16730] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Accepted: 01/24/2017] [Indexed: 01/05/2023] Open
Abstract
Pancreatic cancer is one of the deadliest malignancies and effective treatment has always been lacking. In current study, we investigated how the type Iγ phosphatidylinositol phosphate kinase (PIPKIγ) participates in the progression of pancreatic ductal adenocarcinoma (PDAC) for novel therapeutic potentials against this lethal disease. We found that PIPKIγ is up-regulated in all tested PDAC cell lines. The growth factor (including EGFR)-induced tyrosine phosphorylation of PIPKIγ is significantly elevated in in situ and metastatic PDAC tissues. Loss of PIPKIγ inhibits the aggressiveness of PDAC cells by restraining the activities of AKT and STAT3, as well as MT1-MMP expression. Therefore when planted into the pancreas of nude mice, PIPKIγ-depleted PDAC cells exhibits substantially repressed tumor growth and metastasis comparing to control PDAC cells. Results from further studies showed that the phosphorylation-deficient PIPKIγ mutant, unlike its wild-type counterpart, cannot rescue PDAC progression inhibited by PIPKIγ depletion. These findings indicate that PIPKIγ, functioning downstream of EGFR signaling, is critical to the progression of PDAC, and suggest that PIPKIγ is potentially a valuable therapeutic target for PDAC treatment.
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Affiliation(s)
- Chunhua Chen
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, USA
- These authors have contributed equally to this work
| | - Xiangling Wang
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, USA
- These authors have contributed equally to this work
| | - Juemin Fang
- Shanghai Tenth People’s Hospital, Tongji University, Shanghai, China
- These authors have contributed equally to this work
| | - Junli Xue
- Shanghai East Hospital, Tongji University, Shanghai, China
| | - Xunhao Xiong
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, USA
| | - Yan Huang
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, USA
| | - Jinghua Hu
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, USA
| | - Kun Ling
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, USA
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9
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Yuan Q, Ren C, Xu W, Petri B, Zhang J, Zhang Y, Kubes P, Wu D, Tang W. PKN1 Directs Polarized RAB21 Vesicle Trafficking via RPH3A and Is Important for Neutrophil Adhesion and Ischemia-Reperfusion Injury. Cell Rep 2017; 19:2586-2597. [PMID: 28636945 PMCID: PMC5548392 DOI: 10.1016/j.celrep.2017.05.080] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 04/18/2017] [Accepted: 05/24/2017] [Indexed: 01/08/2023] Open
Abstract
Polarized vesicle transport plays an important role in cell polarization, but the mechanisms underlying this process and its role in innate immune responses are not well understood. Here, we describe a phosphorylation-regulated polarization mechanism that is important for neutrophil adhesion to endothelial cells during inflammatory responses. We show that the protein kinase PKN1 phosphorylates RPH3A, which enhances binding of RPH3A to guanosine triphosphate (GTP)-bound RAB21. These interactions are important for polarized localization of RAB21 and RPH3A in neutrophils, which leads to PIP5K1C90 polarization. Consistent with the roles of PIP5K1C90 polarization, the lack of PKN1 or RPH3A impairs neutrophil integrin activation, adhesion to endothelial cells, and infiltration in inflammatory models. Furthermore, myeloid-specific loss of PKN1 decreases tissue injury in a renal ischemia-reperfusion model. Thus, this study characterizes a mechanism for protein polarization in neutrophils and identifies a potential protein kinase target for therapeutic intervention in reperfusion-related tissue injury.
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Affiliation(s)
- Qianying Yuan
- Department of Pharmacology, Vascular Biology and Therapeutic Program, Yale School of Medicine, New Haven, CT 06520, USA
| | - Chunguang Ren
- Department of Pharmacology, Vascular Biology and Therapeutic Program, Yale School of Medicine, New Haven, CT 06520, USA
| | - Wenwen Xu
- Department of Pharmacology, Vascular Biology and Therapeutic Program, Yale School of Medicine, New Haven, CT 06520, USA
| | - Björn Petri
- Snyder Institute for Chronic Diseases Mouse Phenomics Resource Laboratory, University of Calgary, Calgary, AB T2N 4N1, Canada; Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Jiasheng Zhang
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT 06520, USA
| | - Yong Zhang
- Department of Pharmacology, Vascular Biology and Therapeutic Program, Yale School of Medicine, New Haven, CT 06520, USA
| | - Paul Kubes
- Snyder Institute for Chronic Diseases Mouse Phenomics Resource Laboratory, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Dianqing Wu
- Department of Pharmacology, Vascular Biology and Therapeutic Program, Yale School of Medicine, New Haven, CT 06520, USA.
| | - Wenwen Tang
- Department of Pharmacology, Vascular Biology and Therapeutic Program, Yale School of Medicine, New Haven, CT 06520, USA.
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10
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Martzoukou O, Amillis S, Zervakou A, Christoforidis S, Diallinas G. The AP-2 complex has a specialized clathrin-independent role in apical endocytosis and polar growth in fungi. eLife 2017; 6. [PMID: 28220754 PMCID: PMC5338921 DOI: 10.7554/elife.20083] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 02/07/2017] [Indexed: 12/26/2022] Open
Abstract
Filamentous fungi provide excellent systems for investigating the role of the AP-2 complex in polar growth. Using Aspergillus nidulans, we show that AP-2 has a clathrin-independent essential role in polarity maintenance and growth. This is in line with a sequence analysis showing that the AP-2 β subunit (β2) of higher fungi lacks a clathrin-binding domain, and experiments showing that AP-2 does not co-localize with clathrin. We provide genetic and cellular evidence that AP-2 interacts with endocytic markers SlaBEnd4 and SagAEnd3 and the lipid flippases DnfA and DnfB in the sub-apical collar region of hyphae. The role of AP-2 in the maintenance of proper apical membrane lipid and cell wall composition is further supported by its functional interaction with BasA (sphingolipid biosynthesis) and StoA (apical sterol-rich membrane domains), and its essentiality in polar deposition of chitin. Our findings support that the AP-2 complex of dikarya has acquired, in the course of evolution, a specialized clathrin-independent function necessary for fungal polar growth. DOI:http://dx.doi.org/10.7554/eLife.20083.001
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Affiliation(s)
- Olga Martzoukou
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Sotiris Amillis
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Amalia Zervakou
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Savvas Christoforidis
- Institute of Molecular Biology and Biotechnology-Biomedical Research, Foundation for Research and Technology, Ioannina, Greece.,Laboratory of Biological Chemistry, Department of Medicine, School of Health Sciences, University of Ioannina, Ioannina, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
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11
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Raben DM, Barber CN. Phosphatidic acid and neurotransmission. Adv Biol Regul 2016; 63:15-21. [PMID: 27671966 DOI: 10.1016/j.jbior.2016.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 09/15/2016] [Accepted: 09/19/2016] [Indexed: 12/31/2022]
Abstract
Lipids play a vital role in the health and functioning of neurons and interest in the physiological role of neuronal lipids is certainly increasing. One neuronal function in which neuronal lipids appears to play key roles in neurotransmission. Our understanding of the role of lipids in the synaptic vesicle cycle and neurotransmitter release is becoming increasingly more important. Much of the initial research in this area has highlighted the major roles played by the phosphoinositides (PtdIns), diacylglycerol (DAG), and phosphatidic acid (PtdOH). Of these, PtdOH has not received as much attention as the other lipids although its role and metabolism appears to be extremely important. This lipid has been shown to play a role in modulating both exocytosis and endocytosis although its precise role in either process is not well defined. The currently evidence suggest this lipid likely participates in key processes by altering membrane architecture necessary for membrane fusion, mediating the penetration of membrane proteins, serving as a precursor for other important SV cycling lipids, or activating essential enzymes. In this review, we address the sources of PtdOH, the enzymes involved in its production, the regulation of these enzymes, and its potential roles in neurotransmission in the central nervous system.
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Affiliation(s)
- Daniel M Raben
- The Department of Biological Chemistry, The Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.
| | - Casey N Barber
- The Department of Biological Chemistry, The Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
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12
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Posor Y, Eichhorn-Grünig M, Haucke V. Phosphoinositides in endocytosis. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:794-804. [DOI: 10.1016/j.bbalip.2014.09.014] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Revised: 08/21/2014] [Accepted: 09/17/2014] [Indexed: 02/04/2023]
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13
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Daumke O, Roux A, Haucke V. BAR domain scaffolds in dynamin-mediated membrane fission. Cell 2014; 156:882-92. [PMID: 24581490 DOI: 10.1016/j.cell.2014.02.017] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Indexed: 10/25/2022]
Abstract
Biological membranes undergo constant remodeling by membrane fission and fusion to change their shape and to exchange material between subcellular compartments. During clathrin-mediated endocytosis, the dynamic assembly and disassembly of protein scaffolds comprising members of the bin-amphiphysin-rvs (BAR) domain protein superfamily constrain the membrane into distinct shapes as the pathway progresses toward fission by the GTPase dynamin. In this Review, we discuss how BAR domain protein assembly and disassembly are controlled in space and time and which structural and biochemical features allow the tight regulation of their shape and function to enable dynamin-mediated membrane fission.
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Affiliation(s)
- Oliver Daumke
- Max-Delbrück Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany.
| | - Aurélien Roux
- University of Geneva, Department of Biochemistry, 30 quai Ernest Ansermet, 1211 Geneva 4, Switzerland, and Swiss National Centre for Competence in Research Programme Chemical Biology, 1211 Geneva, Switzerland.
| | - Volker Haucke
- Leibniz Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Strasse 10, 13125 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
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14
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Chakraborty S, Umasankar PK, Preston GM, Khandelwal P, Apodaca G, Watkins SC, Traub LM. A phosphotyrosine switch for cargo sequestration at clathrin-coated buds. J Biol Chem 2014; 289:17497-514. [PMID: 24798335 DOI: 10.1074/jbc.m114.556589] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The AP-2 clathrin adaptor complex oversees endocytic cargo selection in two parallel but independent manners. First, by physically engaging peptide-based endocytic sorting signals, a subset of clathrin-dependent transmembrane cargo is directly collected into assembling buds. Synchronously, by interacting with an assortment of clathrin-associated sorting proteins (CLASPs) that independently select different integral membrane cargo for inclusion within the incipient bud, AP-2 handles additional cargo capture indirectly. The distal platform subdomain of the AP-2 β2 subunit appendage is a privileged CLASP-binding surface that recognizes a cognate, short α-helical interaction motif. This signal, found in the CLASPs β-arrestin and the autosomal recessive hypercholesterolemia (ARH) protein, docks into an elongated groove on the β2 appendage platform. Tyr-888 is a critical constituent of this spatially confined β2 appendage contact interface and is phosphorylated in numerous high-throughput proteomic studies. We find that a phosphomimetic Y888E substitution does not interfere with incorporation of expressed β2-YFP subunit into AP-2 or alter AP-2 deposition at surface clathrin-coated structures. The Y888E mutation does not affect interactions involving the sandwich subdomain of the β2 appendage, indicating that the mutated appendage is folded and operational. However, the Y888E, but not Y888F, switch selectively uncouples interactions with ARH and β-arrestin. Phyogenetic conservation of Tyr-888 suggests that this residue can reversibly control occupancy of the β2 platform-binding site and, hence, cargo sorting.
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Affiliation(s)
| | | | | | - Puneet Khandelwal
- the Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Gerard Apodaca
- the Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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15
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Demmel L, Schmidt K, Lucast L, Havlicek K, Zankel A, Koestler T, Reithofer V, de Camilli P, Warren G. The endocytic activity of the flagellar pocket in Trypanosoma brucei is regulated by an adjacent phosphatidylinositol phosphate kinase. J Cell Sci 2014; 127:2351-64. [PMID: 24639465 DOI: 10.1242/jcs.146894] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Phosphoinositides are spatially restricted membrane signaling molecules. Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]--a phosphoinositide that is highly enriched in, and present throughout, the plasma membrane--has been implicated in endocytosis. Trypanosoma brucei has one of the highest known rates of endocytosis, a process it uses to evade the immune system. To determine whether phosphoinositides play a role in endocytosis in this organism, we have identified and characterized one of the enzymes that is responsible for generating PI(4,5)P2. Surprisingly, this phosphoinositide was found to be highly concentrated in the flagellar pocket, the only site of endocytosis and exocytosis in this organism. The enzyme (designated TbPIPKA, annotated as Tb927.10.1620) was present at the neck of the pocket, towards the anterior-end of the parasite. Depletion of TbPIPKA led to depletion of PI(4,5)P2 and enlargement of the pocket, the result of impaired endocytosis. Taken together, these data suggest that TbPIPKA and its product PI(4,5)P2 are important for endocytosis and, consequently, for homeostasis of the flagellar pocket.
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Affiliation(s)
- Lars Demmel
- Max F. Perutz Laboratories, University of Vienna, Medical University of Vienna, 1030 Vienna, Austria
| | - Katy Schmidt
- Department of Cell Biology and Ultrastructure Research, Center for Anatomy and Cell Biology, Medical University of Vienna, 1090 Vienna, Austria
| | - Louise Lucast
- Department of Cell Biology, Howard Hughes Medical Institute, and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Katharina Havlicek
- Max F. Perutz Laboratories, University of Vienna, Medical University of Vienna, 1030 Vienna, Austria
| | - Armin Zankel
- Institute for Electron Microscopy, Graz University of Technology and Center for Electron Microscopy Graz, 8010 Graz, Austria
| | - Tina Koestler
- Center for Integrative Bioinformatics, Max F. Perutz Laboratories, University of Vienna and Medical University of Vienna, 1030 Vienna, Austria
| | - Viktoria Reithofer
- University of Applied Sciences Wiener Neustadt, Department of Biomedical Analytics, 2700 Wiener Neustadt, Austria
| | - Pietro de Camilli
- Department of Cell Biology, Howard Hughes Medical Institute, and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Graham Warren
- Max F. Perutz Laboratories, University of Vienna, Medical University of Vienna, 1030 Vienna, Austria
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16
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Xu Q, Zhang Y, Xiong X, Huang Y, Salisbury JL, Hu J, Ling K. PIPKIγ targets to the centrosome and restrains centriole duplication. J Cell Sci 2014; 127:1293-305. [PMID: 24434581 DOI: 10.1242/jcs.141465] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Centriole biogenesis depends on the polo-like kinase (PLK4) and a small group of structural proteins. The spatiotemporal regulation of these proteins at pre-existing centrioles is essential to ensure that centriole duplication occurs once per cell cycle. Here, we report that phosphatidylinositol 4-phosphate 5-kinase type-1 gamma (PIP5K1C, hereafter referred to as PIPKIγ) plays an important role in centriole fidelity. PIPKIγ localized in a ring-like pattern in the intermediate pericentriolar materials around the proximal end of the centriole in G1, S and G2 phases, but not in M phase. This localization was dependent upon an association with centrosomal protein of 152 KDa (CEP152). Without detaining cells in S or M phase, the depletion of PIPKIγ led to centriole amplification in a manner that was dependent upon PLK4 and spindle assembly abnormal protein 6 homolog (SAS6). The expression of exogenous PIPKIγ reduced centriole amplification that occurred as a result of endogenous PIPKIγ depletion, hydroxyurea treatment or PLK4 overexpression, suggesting that PIPKIγ is likely to function at the PLK4 level to restrain centriole duplication. Importantly, we found that PIPKIγ bound to the cryptic polo-box domain of PLK4 and that this binding reduced the kinase activity of PLK4. Together, our findings suggest that PIPKIγ is a novel negative regulator of centriole duplication, which acts by modulating the homeostasis of PLK4 activity.
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Affiliation(s)
- Qingwen Xu
- Department of Biochemistry and Molecular Biology, and Division of Hypertension and Nephrology, Mayo Clinic, 200 First Street SW, Rochester, MN 55902, USA
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17
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Puchkov D, Haucke V. Greasing the synaptic vesicle cycle by membrane lipids. Trends Cell Biol 2013; 23:493-503. [DOI: 10.1016/j.tcb.2013.05.002] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 04/30/2013] [Accepted: 05/02/2013] [Indexed: 12/18/2022]
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18
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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19
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Legate KR, Montag D, Böttcher RT, Takahashi S, Fässler R. Comparative phenotypic analysis of the two major splice isoforms of phosphatidylinositol phosphate kinase type Iγ in vivo. J Cell Sci 2012; 125:5636-46. [PMID: 22976293 DOI: 10.1242/jcs.102145] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Localized production of polyphosphoinositides is critical for their signaling function. To examine the biological relevance of specific pools of phosphatidylinositol 4,5-bisphosphate we compared the consequences of genetically ablating all isoforms of phosphatidylinositol phosphate (PIP) kinase type Iγ (PIPKIγ), encoded by the gene Pip5k1c, versus ablation of a specific splice isoform, PIPKIγ_i2, with respect to three reported PIPKIγ functions. Ablation of PIPKIγ_i2 caused a neuron-specific endocytosis defect similar to that found in PIPKIγ(-/-) mice, while agonist-induced calcium signaling was reduced in PIPKIγ(-/-) cells, but was not affected in the absence of PIPKIγ_i2. A reported contribution of PIPKIγ to epithelial integrity was not evident in PIPKIγ(-/-) mice. Given that mice lacking PIPKIγ_i2 live a normal lifespan whereas PIPKIγ(-/-) mice die shortly after birth, we propose that PIPKIγ-mediated metabotropic calcium signaling may represent an essential function of PIPKIγ, whereas functions specific to the PIPKIγ_i2 splice isoform are not essential for survival.
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Affiliation(s)
- Kyle R Legate
- Department of Molecular Medicine, Max Planck Institute of Biochemistry, Martinsried, 82152 Germany
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20
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Abstract
Neurons can sustain high rates of synaptic transmission without exhausting their supply of synaptic vesicles. This property relies on a highly efficient local endocytic recycling of synaptic vesicle membranes, which can be reused for hundreds, possibly thousands, of exo-endocytic cycles. Morphological, physiological, molecular, and genetic studies over the last four decades have provided insight into the membrane traffic reactions that govern this recycling and its regulation. These studies have shown that synaptic vesicle endocytosis capitalizes on fundamental and general endocytic mechanisms but also involves neuron-specific adaptations of such mechanisms. Thus, investigations of these processes have advanced not only the field of synaptic transmission but also, more generally, the field of endocytosis. This article summarizes current information on synaptic vesicle endocytosis with an emphasis on the underlying molecular mechanisms and with a special focus on clathrin-mediated endocytosis, the predominant pathway of synaptic vesicle protein internalization.
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Affiliation(s)
- Yasunori Saheki
- Department of Cell Biology, Howard Hughes Medical Institute and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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21
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Distinct and separable activities of the endocytic clathrin-coat components Fcho1/2 and AP-2 in developmental patterning. Nat Cell Biol 2012; 14:488-501. [PMID: 22484487 PMCID: PMC3354769 DOI: 10.1038/ncb2473] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Accepted: 02/29/2012] [Indexed: 12/13/2022]
Abstract
Clathrin-mediated endocytosis occurs at multiple independent import sites on the plasma membrane, but how these positions are selected and how different cargo is simultaneously recognized is obscure. FCHO1 and FCHO2 are early-arriving proteins at surface clathrin assemblies and are speculated to act as compulsory coat nucleators, preceding the core clathrin adaptor AP-2. Here, we show the μ-homology domain (μHD) of FCHO1/2 represents a novel endocytic interaction hub. Translational silencing of fcho1 in zebrafish embryos causes strong dorsoventral patterning defects analogous to Bmp signal failure. The Fcho1 μHD interacts with the Bmp receptor Alk8, uncovering a new endocytic component that positively modulates Bmp signal transmission. Still, the fcho1 morphant phenotype is distinct from severe embryonic defects apparent when AP-2 is depleted. Our data thus contradict the primacy of FCHO1/2 in coat initiation.
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Thapa N, Sun Y, Schramp M, Choi S, Ling K, Anderson RA. Phosphoinositide signaling regulates the exocyst complex and polarized integrin trafficking in directionally migrating cells. Dev Cell 2012; 22:116-30. [PMID: 22264730 DOI: 10.1016/j.devcel.2011.10.030] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 10/21/2011] [Accepted: 10/29/2011] [Indexed: 10/14/2022]
Abstract
Polarized delivery of signaling and adhesion molecules to the leading edge is required for directional migration of cells. Here, we describe a role for the PIP(2)-synthesizing enzyme, PIPKIγi2, in regulation of exocyst complex control of cell polarity and polarized integrin trafficking during migration. Loss of PIPKIγi2 impaired directional migration, formation of cell polarity, and integrin trafficking to the leading edge. Upon initiation of directional migration, PIPKIγi2 via PIP(2) generation controls the integration of the exocyst complex into an integrin-containing trafficking compartment that requires the talin-binding ability of PIPKIγi2, and talin for integrin recruitment to the leading edge. A PIP(2) requirement is further emphasized by inhibition of PIPKIγi2-regulated directional migration by an Exo70 mutant deficient in PIP(2) binding. These results reveal how phosphoinositide generation orchestrates polarized trafficking of integrin in coordination with talin that links integrins to the actin cytoskeleton, processes that are required for directional migration.
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Affiliation(s)
- Narendra Thapa
- Molecular and Cellular Pharmacology Program, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53706, USA
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23
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Sigismund S, Confalonieri S, Ciliberto A, Polo S, Scita G, Di Fiore PP. Endocytosis and signaling: cell logistics shape the eukaryotic cell plan. Physiol Rev 2012; 92:273-366. [PMID: 22298658 DOI: 10.1152/physrev.00005.2011] [Citation(s) in RCA: 236] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our understanding of endocytosis has evolved remarkably in little more than a decade. This is the result not only of advances in our knowledge of its molecular and biological workings, but also of a true paradigm shift in our understanding of what really constitutes endocytosis and of its role in homeostasis. Although endocytosis was initially discovered and studied as a relatively simple process to transport molecules across the plasma membrane, it was subsequently found to be inextricably linked with almost all aspects of cellular signaling. This led to the notion that endocytosis is actually the master organizer of cellular signaling, providing the cell with understandable messages that have been resolved in space and time. In essence, endocytosis provides the communications and supply routes (the logistics) of the cell. Although this may seem revolutionary, it is still likely to be only a small part of the entire story. A wealth of new evidence is uncovering the surprisingly pervasive nature of endocytosis in essentially all aspects of cellular regulation. In addition, many newly discovered functions of endocytic proteins are not immediately interpretable within the classical view of endocytosis. A possible framework, to rationalize all this new knowledge, requires us to "upgrade" our vision of endocytosis. By combining the analysis of biochemical, biological, and evolutionary evidence, we propose herein that endocytosis constitutes one of the major enabling conditions that in the history of life permitted the development of a higher level of organization, leading to the actuation of the eukaryotic cell plan.
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Affiliation(s)
- Sara Sigismund
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milan, Italy
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Jha A, Watkins SC, Traub LM. The apoptotic engulfment protein Ced-6 participates in clathrin-mediated yolk uptake in Drosophila egg chambers. Mol Biol Cell 2012; 23:1742-64. [PMID: 22398720 PMCID: PMC3338440 DOI: 10.1091/mbc.e11-11-0939] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
During oogenesis in Drosophila, the phagocytic engulfment protein Ced-6 recognizes the atypical endocytic sorting signal within the vitellogenin receptor Yolkless. Because Ced-6 displays all of the features of an authentic clathrin adaptor, an unrecognized clathrin dependence for Ced-6/Gulp operation during phagocytosis is possible. Clathrin-mediated endocytosis and phagocytosis are both selective surface internalization processes but have little known mechanistic similarity or interdependence. Here we show that the phosphotyrosine-binding (PTB) domain protein Ced-6, a well-established phagocytosis component that operates as a transducer of so-called “eat-me” signals during engulfment of apoptotic cells and microorganisms, is expressed in the female Drosophila germline and that Ced-6 expression correlates with ovarian follicle development. Ced-6 exhibits all the known biochemical properties of a clathrin-associated sorting protein, yet ced-6–null flies are semifertile despite massive accumulation of soluble yolk precursors in the hemolymph. This is because redundant sorting signals within the cytosolic domain of the Drosophila vitellogenin receptor Yolkless, a low density lipoprotein receptor superfamily member, occur; a functional atypical dileucine signal binds to the endocytic AP-2 clathrin adaptor directly. Nonetheless, the Ced-6 PTB domain specifically recognizes the noncanonical Yolkless FXNPXA sorting sequence and in HeLa cells promotes the rapid, clathrin-dependent uptake of a Yolkless chimera lacking the distal dileucine signal. Ced-6 thus operates in vivo as a clathrin adaptor. Because the human Ced-6 orthologue GULP similarly binds to clathrin machinery, localizes to cell surface clathrin-coated structures, and is enriched in placental clathrin-coated vesicles, new possibilities for Ced-6/Gulp operation during phagocytosis must be considered.
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Affiliation(s)
- Anupma Jha
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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25
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Pirruccello M, De Camilli P. Inositol 5-phosphatases: insights from the Lowe syndrome protein OCRL. Trends Biochem Sci 2012; 37:134-43. [PMID: 22381590 DOI: 10.1016/j.tibs.2012.01.002] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/13/2012] [Accepted: 01/24/2012] [Indexed: 12/01/2022]
Abstract
The precise regulation of phosphoinositide lipids in cellular membranes is crucial for cellular survival and function. Inositol 5-phosphatases have been implicated in a variety of disorders, including various cancers, obesity, type 2 diabetes, neurodegenerative diseases and rare genetic conditions. Despite the obvious impact on human health, relatively little structural and biochemical information is available for this family. Here, we review recent structural and mechanistic work on the 5-phosphatases with a focus on OCRL, whose loss of function results in oculocerebrorenal syndrome of Lowe and Dent 2 disease. Studies of OCRL emphasize how the actions of 5-phosphatases rely on both intrinsic and extrinsic membrane recognition properties for full catalytic function. Additionally, structural analysis of missense mutations in the catalytic domain of OCRL provides insight into the phenotypic heterogeneity observed in Lowe syndrome and Dent disease.
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Affiliation(s)
- Michelle Pirruccello
- Department of Cell Biology, HHMI and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
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26
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Tóth DJ, Tóth JT, Gulyás G, Balla A, Balla T, Hunyady L, Várnai P. Acute depletion of plasma membrane phosphatidylinositol 4,5-bisphosphate impairs specific steps in endocytosis of the G-protein-coupled receptor. J Cell Sci 2012; 125:2185-97. [PMID: 22357943 DOI: 10.1242/jcs.097279] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Receptor endocytosis plays an important role in regulating the responsiveness of cells to specific ligands. Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] has been shown to be crucial for endocytosis of some cell surface receptors, such as EGF and transferrin receptors, but its role in G-protein-coupled receptor internalization has not been investigated. By using luciferase-labeled type 1 angiotensin II (AT1R), type 2C serotonin (5HT2CR) or β(2) adrenergic (β2AR) receptors and fluorescently tagged proteins (β-arrestin-2, plasma-membrane-targeted Venus, Rab5) we were able to follow the sequence of molecular interactions along the endocytic route of the receptors in HEK293 cells using the highly sensitive method of bioluminescence resonance energy transfer and confocal microscopy. To study the role of plasma membrane PtdIns(4,5)P(2) in receptor endocytosis, we used our previously developed rapamycin-inducible heterodimerization system, in which the recruitment of a 5-phosphatase domain to the plasma membrane degrades PtdIns(4,5)P(2). Here we show that ligand-induced interaction of AT1, 5HT2C and β(2)A receptors with β-arrestin-2 was unaffected by PtdIns(4,5)P(2) depletion. However, trafficking of the receptors to Rab5-positive early endosomes was completely abolished in the absence of PtdIns(4,5)P(2). Remarkably, removal of the receptors from the plasma membrane was reduced but not eliminated after PtdIns(4,5)P(2) depletion. Under these conditions, stimulated AT1 receptors clustered along the plasma membrane, but did not enter the cells. Our data suggest that in the absence of PtdIns(4,5)P(2), these receptors move into clathrin-coated membrane structures, but these are not cleaved efficiently and hence cannot reach the early endosomal compartment.
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Affiliation(s)
- Dániel J Tóth
- Department of Physiology, Semmelweis University, Faculty of Medicine, Budapest, Hungary
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27
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Wu M, De Camilli P. Supported native plasma membranes as platforms for the reconstitution and visualization of endocytic membrane budding. Methods Cell Biol 2012; 108:3-18. [PMID: 22325595 DOI: 10.1016/b978-0-12-386487-1.00001-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Cell-free assays represent an important complement to studies in living cells for the elucidation of mechanisms underlying the dynamics of biological membranes, such as budding, fission, and fusion reactions. Here we describe a method for the reconstitution of endocytosis, the process through which cells internalize portions of the plasma membrane along with extracellular material, under conditions that allow the visualization of individual budding events with high spatial and temporal resolution. The method, which is based on the generation of planar plasma membrane sheets attached to a glass substrate and their subsequent incubation with a cytosolic extract, results in a very robust formation of endocytic buds, which upon appropriate conditions undergo fission. The synchronization of the endocytic events and the accessibility of the material to a variety of manipulations make this experimental system a powerful tool for the molecular dissection of endocytosis.
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Affiliation(s)
- Min Wu
- Howard Hughes Medical Institute, Department of Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
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28
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Abstract
The endo-lysosomal system is an interconnected tubulo-vesicular network that acts as a sorting station to process and distribute internalised cargo. This network accepts cargoes from both the plasma membrane and the biosynthetic pathway, and directs these cargos either towards the lysosome for degradation, the peri-nuclear recycling endosome for return to the cell surface, or to the trans-Golgi network. These intracellular membranes are variously enriched in different phosphoinositides that help to shape compartmental identity. These lipids act to localise a number of phosphoinositide-binding proteins that function as sorting machineries to regulate endosomal cargo sorting. Herein we discuss regulation of these machineries by phosphoinositides and explore how phosphoinositide-switching contributes toward sorting decisions made at this platform.
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Affiliation(s)
- Peter J Cullen
- Henry Wellcome Integrated Signaling Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, BS8 1TD, Bristol, United Kingdom,
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29
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Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP(2)) is a membrane bound lipid molecule with capabilities to affect a wide array of signaling pathways to regulate very different cellular processes. PIP(2) is used as a precursor to generate the second messengers PIP(3), DAG and IP(3), indispensable molecules for signaling events generated by membrane receptors. However, PIP(2) can also directly regulate a vast array of proteins and is emerging as a crucial messenger with the potential to distinctly modulate biological processes critical for both normal and pathogenic cell physiology. PIP(2) directly associates with effector proteins via unique phosphoinositide binding domains, altering their localization and/or enzymatic activity. The spatial and temporal generation of PIP(2) synthesized by the phosphatidylinositol phosphate kinases (PIPKs) tightly regulates the activation of receptor signaling pathways, endocytosis and vesicle trafficking, cell polarity, focal adhesion dynamics, actin assembly and 3' mRNA processing. Here we discuss our current understanding of PIPKs in the regulation of cellular processes from the plasma membrane to the nucleus.
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30
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Unoki T, Matsuda S, Kakegawa W, Van N, Kohda K, Suzuki A, Funakoshi Y, Hasegawa H, Yuzaki M, Kanaho Y. NMDA Receptor-Mediated PIP5K Activation to Produce PI(4,5)P2 Is Essential for AMPA Receptor Endocytosis during LTD. Neuron 2012; 73:135-48. [DOI: 10.1016/j.neuron.2011.09.034] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2011] [Indexed: 10/14/2022]
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Abstract
Synaptic transmission is amongst the most sophisticated and tightly controlled biological phenomena in higher eukaryotes. In the past few decades, tremendous progress has been made in our understanding of the molecular mechanisms underlying multiple facets of neurotransmission, both pre- and postsynaptically. Brought under the spotlight by pioneer studies in the areas of secretion and signal transduction, phosphoinositides and their metabolizing enzymes have been increasingly recognized as key protagonists in fundamental aspects of neurotransmission. Not surprisingly, dysregulation of phosphoinositide metabolism has also been implicated in synaptic malfunction associated with a variety of brain disorders. In the present chapter, we summarize current knowledge on the role of phosphoinositides at the neuronal synapse and highlight some of the outstanding questions in this research field.
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Affiliation(s)
- Samuel G Frere
- Department of Pathology and Cell Biology, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, 630 West 168th Street, P&S 12-420C, 10032, New York, USA
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Wieffer M, Haucke V, Krauss M. Regulation of phosphoinositide-metabolizing enzymes by clathrin coat proteins. Methods Cell Biol 2012; 108:209-25. [PMID: 22325605 DOI: 10.1016/b978-0-12-386487-1.00011-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Clathrin plays key roles in endocytic and endo-lysosomal membrane dynamics by facilitating the formation of coated vesicles at the plasma membrane and at the trans-Golgi network (TGN)/endosomal boundary. Assembly of the clathrin lattice critically depends on adaptor proteins and accessory proteins, which connect the clathrin scaffold to the membrane and to transmembrane cargo including receptors, transporters, channels, and SNARE proteins. The recruitment of adaptor proteins to membrane surfaces is triggered by coincidence-detection mechanisms involving phosphoinositides (PIs), cargo proteins, and in many cases small GTPases. To tightly regulate coat formation, there is extensive cross-talk between PI-metabolizing enzymes and adaptor proteins. One of the best studied examples is the endocytic clathrin adaptor complex AP-2, which binds plasma membrane-enriched PI(4,5)P(2). In neurons, PI(4,5)P(2) is synthesized from PI(4)P primarily by the γ-isoform of the type I phosphatidylinositol 4-phosphate 5-kinase family (PIPKIγ), whose enzymatic activity is regulated by direct binding to, amongst others, the small GTPase Arf6 and AP-2. Cargo-bound AP-2 potently stimulates PIPK1γ activity and thereby drives AP-2-membrane interactions. This feed-forward loop is thought to facilitate membrane translocation of additional AP-2 molecules and concomitantly clathrin, but also of endocytic accessory proteins, many of which directly associate with PI(4,5)P(2). It is likely that similar mechanisms support the formation of coated vesicles at the trans-Golgi network (TGN) and on endosomes, involving PI(4)P and PI(3)P respectively, but detailed knowledge is lacking to date. To explore how coat proteins regulate kinase activity, assays are needed to sensitively detect subtle changes in PI synthesis and to discriminate between the various PI species. Here we describe a sensitive and specific radioactivity-based assay to measure PI kinase activity.
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Affiliation(s)
- Marnix Wieffer
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Takustraße, Berlin, Germany
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Antonescu CN, Aguet F, Danuser G, Schmid SL. Phosphatidylinositol-(4,5)-bisphosphate regulates clathrin-coated pit initiation, stabilization, and size. Mol Biol Cell 2011; 22:2588-600. [PMID: 21613550 PMCID: PMC3135483 DOI: 10.1091/mbc.e11-04-0362] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Clathrin-mediated endocytosis (CME) is the major mechanism for internalization in mammalian cells. CME initiates by recruitment of adaptors and clathrin to form clathrin-coated pits (CCPs). Nearly half of nascent CCPs abort, whereas others are stabilized by unknown mechanisms and undergo further maturation before pinching off to form clathrin-coated vesicles (CCVs). Phosphatidylinositol-(4,5)-bisphosphate (PIP(2)), the main lipid binding partner of endocytic proteins, is required for CCP assembly, but little is currently known about its contribution(s) to later events in CCV formation. Using small interfering RNA (siRNA) knockdown and overexpression, we have analyzed the effects of manipulating PIP(2) synthesis and turnover on CME by quantitative total internal reflection fluorescence microscopy and computational analysis. Phosphatidylinositol-4-phosphate-5-kinase cannot be detected within CCPs but functions in initiation and controls the rate and extent of CCP growth. In contrast, the 5'-inositol phosphatase synaptojanin 1 localizes to CCPs and controls early stabilization and maturation efficiency. Together these results suggest that the balance of PIP(2) synthesis in the bulk plasma membrane and its local turnover within CCPs control multiple stages of CCV formation.
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Affiliation(s)
- Costin N Antonescu
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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34
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Kwiatkowska K. One lipid, multiple functions: how various pools of PI(4,5)P(2) are created in the plasma membrane. Cell Mol Life Sci 2010; 67:3927-46. [PMID: 20559679 PMCID: PMC11115911 DOI: 10.1007/s00018-010-0432-5] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 06/01/2010] [Accepted: 06/02/2010] [Indexed: 01/25/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] is a minor lipid of the inner leaflet of the plasma membrane that controls the activity of numerous proteins and serves as a source of second messengers. This multifunctionality of PI(4,5)P(2) relies on mechanisms ensuring transient appearance of PI(4,5)P(2) clusters in the plasma membrane. One such mechanism involves phosphorylation of PI(4)P to PI(4,5)P(2) by the type I phosphatidylinositol-4-phosphate 5-kinases (PIP5KI) at discrete membrane locations coupled with PI(4)P delivery/synthesis at the plasma membrane. Simultaneously, both PI(4)P and PI(4,5)P(2) participate in anchoring PIP5KI at the plasma membrane via electrostatic bonds. PIP5KI isoforms are also selectively recruited and activated at the plasma membrane by Rac1, talin, or AP-2 to generate PI(4,5)P(2) in ruffles and lamellipodia, focal contacts, and clathrin-coated pits. In addition, PI(4,5)P(2) can accumulate at sphingolipid/cholesterol-based rafts following activation of distinct membrane receptors or be sequestered in a reversible manner due to electrostatic constrains posed by proteins like MARCKS.
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Affiliation(s)
- Katarzyna Kwiatkowska
- Laboratory of Plasma Membrane Receptors, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland.
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35
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Xu W, Wang P, Petri B, Zhang Y, Tang W, Sun L, Kress H, Mann T, Shi Y, Kubes P, Wu D. Integrin-induced PIP5K1C kinase polarization regulates neutrophil polarization, directionality, and in vivo infiltration. Immunity 2010; 33:340-50. [PMID: 20850356 DOI: 10.1016/j.immuni.2010.08.015] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Revised: 07/19/2010] [Accepted: 08/11/2010] [Indexed: 11/15/2022]
Abstract
Neutrophils are important in innate immunity and acute inflammatory responses. However, the regulation of their recruitment to sites of inflammation has not been well characterized. Here, we investigated the kinase PIP5K1C and showed that PIP5K1C deficiency impaired neutrophil recruitment because of an adhesion defect. PIP5K1C regulated the adhesion through facilitating RhoA GTPase and integrin activation by chemoattractants. Integrins could induce polarization of an isoform of PIP5K1C, PIP5K1C-90, in neutrophils through intracellular vesicle transport independently of exogenous chemoattractant. PIP5K1C-90 polarization was required for polarized RhoA activation at uropods and provided an initial directional cue for neutrophil polarization on the endothelium. Importantly, the polarization was also required for circumventing the inhibition of lamellipodium formation by RhoA so that neutrophils could form leading edges required for transendothelial migration. Because integrins are not known to regulate neutrophil polarization, our study revealed a previously underappreciated role of integrin signaling in neutrophil regulation.
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Affiliation(s)
- Wenwen Xu
- Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, China
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Nakatsu F, Perera RM, Lucast L, Zoncu R, Domin J, Gertler FB, Toomre D, De Camilli P. The inositol 5-phosphatase SHIP2 regulates endocytic clathrin-coated pit dynamics. ACTA ACUST UNITED AC 2010; 190:307-15. [PMID: 20679431 PMCID: PMC2922640 DOI: 10.1083/jcb.201005018] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
SHIP2 is recruited early to clathrin-coated pits by the scaffold protein intersectin and dissociates before fission. Phosphatidylinositol (PI) 4,5-bisphosphate (PI(4,5)P2) and its phosphorylated product PI 3,4,5-triphosphate (PI(3,4,5)P3) are two major phosphoinositides concentrated at the plasma membrane. Their levels, which are tightly controlled by kinases, phospholipases, and phosphatases, regulate a variety of cellular functions, including clathrin-mediated endocytosis and receptor signaling. In this study, we show that the inositol 5-phosphatase SHIP2, a negative regulator of PI(3,4,5)P3-dependent signaling, also negatively regulates PI(4,5)P2 levels and is concentrated at endocytic clathrin-coated pits (CCPs) via interactions with the scaffold protein intersectin. SHIP2 is recruited early at the pits and dissociates before fission. Both knockdown of SHIP2 expression and acute production of PI(3,4,5)P3 shorten CCP lifetime by enhancing the rate of pit maturation, which is consistent with a positive role of both SHIP2 substrates, PI(4,5)P2 and PI(3,4,5)P3, on coat assembly. Because SHIP2 is a negative regulator of insulin signaling, our findings suggest the importance of the phosphoinositide metabolism at CCPs in the regulation of insulin signal output.
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Affiliation(s)
- Fubito Nakatsu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
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Volpicelli-Daley LA, Lucast L, Gong LW, Liu L, Sasaki J, Sasaki T, Abrams CS, Kanaho Y, De Camilli P. Phosphatidylinositol-4-phosphate 5-kinases and phosphatidylinositol 4,5-bisphosphate synthesis in the brain. J Biol Chem 2010; 285:28708-14. [PMID: 20622009 PMCID: PMC2937898 DOI: 10.1074/jbc.m110.132191] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The predominant pathway for phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P(2)) synthesis is thought to be phosphorylation of phosphatidylinositol 4-phosphate at the 5 position of the inositol ring by type I phosphatidylinositol phosphate kinases (PIPK): PIPKIalpha, PIPKIbeta, and PIPKIgamma. PIPKIgamma has been shown to play a role in PI(4,5)P(2) synthesis in brain, and the absence of PIPKIgamma is incompatible with postnatal life. Conversely, mice lacking PIPKIalpha or PIPKIbeta (isoforms are referred to according to the nomenclature of human PIPKIs) live to adulthood, although functional effects in specific cell types are observed. To determine the contribution of PIPKIalpha and PIPKIbeta to PI(4,5)P(2) synthesis in brain, we investigated the impact of disrupting multiple PIPKI genes. Our results show that a single allele of PIPKIgamma, in the absence of both PIPKIalpha and PIPKIbeta, can support life to adulthood. In addition, PIPKIalpha alone, but not PIPKIbeta alone, can support prenatal development, indicating an essential and partially overlapping function of PIPKIalpha and PIPKIgamma during embryogenesis. This is consistent with early embryonic expression of PIPKIalpha and PIPKIgamma but not of PIPKIbeta. PIPKIbeta expression in brain correlates with neuronal differentiation. The absence of PIPKIbeta does not impact embryonic development in the PIPKIgamma knock-out (KO) background but worsens the early postnatal phenotype of the PIPKIgamma KO (death occurs within minutes rather than hours). Analysis of PIP(2) in brain reveals that only the absence of PIPKIgamma significantly impacts its levels. Collectively, our results provide new evidence for the dominant importance of PIPKIgamma in mammals and imply that PIPKIalpha and PIPKIbeta function in the generation of specific PI(4,5)P(2) pools that, at least in brain, do not have a major impact on overall PI(4,5)P(2) levels.
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Affiliation(s)
- Laura A Volpicelli-Daley
- Department of Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, the Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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Gallicchio MA, Bach LA. Advanced glycation end products inhibit Na+ K+ ATPase in proximal tubule epithelial cells: role of cytosolic phospholipase A2alpha and phosphatidylinositol 4-phosphate 5-kinase gamma. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:919-30. [PMID: 20435073 DOI: 10.1016/j.bbamcr.2010.04.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 04/09/2010] [Accepted: 04/12/2010] [Indexed: 11/18/2022]
Abstract
Chronic hyperglycaemia during diabetes leads to non-enzymatic glycation of proteins to form advanced glycation end products (AGEs) that contribute to nephropathy. In diabetes, renal Na+ K+ ATPase (NKA) activity is downregulated and phosphoinositide metabolism is upregulated. We examined the effects of AGEs on NKA activity in porcine LLC-PK1 and human HK2 proximal tubule epithelial cells. AGE-BSA increased cellular phosphoinositol 4,5 bisphosphate (PIP2) production as determined by immunofluorescence microscopy and thin layer chromatography. AGE-BSA (40 microM) induced 3H-arachidonic acid release and reactive oxygen species (ROS) production via cytosolic phospholipase A2 (cPLA2) activation. Within minutes, AGE-BSA significantly inhibited NKA surface expression and activity in a dose- and time-dependent manner as determined by immunofluorescence staining and [86Rb+] uptake, respectively, suggesting AGEs inhibit NKA by stimulating its endocytosis. The AGE-BSA-induced decrease in cell surface NKA was reversed by a cPLA2alpha inhibitor, neomycin, a PIP2 inhibitor, and PP2, a Src inhibitor. AGE-BSA increased binding of NKA to the alpha-adaptin but not beta2- or mu2-adaptin subunits of the AP-2 clathrin pit adaptor complex. Transfection of HK2 cells with PIP5Kgamma siRNA prevented AGE-BSA inhibition of NKA activity. AGEs may stimulate PIP5Kgamma to increase PIP2 production, which may enhance AP-2 localisation to clathrin pits, increase clathrin pit formation, enhance NKA cargo recognition by AP-2 and/or stimulate cPLA2alpha activity. These results suggest AGEs modulate arachidonic acid and phosphoinositide metabolism to inhibit NKA via clathrin-mediated endocytosis. Elucidation of new intracellular AGE signaling pathways may lead to improved therapies for diabetic nephropathy.
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Affiliation(s)
- Marisa A Gallicchio
- Monash University, Department of Medicine, Alfred Hospital, Commercial Rd., Prahran, 3004, Australia
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Marat AL, McPherson PS. The connecdenn family, Rab35 guanine nucleotide exchange factors interfacing with the clathrin machinery. J Biol Chem 2010; 285:10627-37. [PMID: 20154091 PMCID: PMC2856271 DOI: 10.1074/jbc.m109.050930] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 12/15/2009] [Indexed: 11/06/2022] Open
Abstract
Rabs constitute the largest family of monomeric GTPases, yet for the majority of Rabs relatively little is known about their activation and recruitment to vesicle-trafficking pathways. We recently identified connecdenn (DENND1A), which contains an N-terminal DENN (differentially expressed in neoplastic versus normal cells) domain, a common and evolutionarily ancient protein module. Through its DENN domain, connecdenn functions enzymatically as a guanine-nucleotide exchange factor (GEF) for Rab35. Here we identify two additional connecdenn family members and demonstrate that all connecdenns function as Rab35 GEFs, albeit with different levels of activity. The DENN domain of connecdenn 1 and 2 binds Rab35, whereas connecdenn 3 does not, indicating that Rab35 binding and activation are separable functions. Through their highly divergent C termini, each of the connecdenns binds to clathrin and to the clathrin adaptor AP-2. Interestingly, all three connecdenns use different mechanisms to bind AP-2. Characterization of connecdenn 2 reveals binding to the beta2-ear of AP-2 on a site that overlaps with that used by the autosomal recessive hypercholesterolemia protein and betaarrestin, although the sequence used by connecdenn 2 is unique. Loss of connecdenn 2 function through small interference RNA knockdown results in an enlargement of early endosomes, similar to what is observed upon loss of Rab35 activity. Our studies reveal connecdenn DENN domains as generalized GEFs for Rab35 and identify a new AP-2-binding motif, demonstrating a complex link between the clathrin machinery and Rab35 activation.
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Affiliation(s)
- Andrea L. Marat
- From the Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Peter S. McPherson
- From the Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
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Regulation of synaptic vesicle recycling by complex formation between intersectin 1 and the clathrin adaptor complex AP2. Proc Natl Acad Sci U S A 2010; 107:4206-11. [PMID: 20160082 DOI: 10.1073/pnas.0911073107] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Clathrin-mediated synaptic vesicle (SV) recycling involves the spatiotemporally controlled assembly of clathrin coat components at phosphatidylinositiol (4, 5)-bisphosphate [PI(4,5)P(2)]-enriched membrane sites within the periactive zone. Such spatiotemporal control is needed to coordinate SV cargo sorting with clathrin/AP2 recruitment and to restrain membrane fission and synaptojanin-mediated uncoating until membrane deformation and clathrin coat assembly are completed. The molecular events underlying these control mechanisms are unknown. Here we show that the endocytic SH3 domain-containing accessory protein intersectin 1 scaffolds the endocytic process by directly associating with the clathrin adaptor AP2. Acute perturbation of the intersectin 1-AP2 interaction in lamprey synapses in situ inhibits the onset of SV recycling. Structurally, complex formation can be attributed to the direct association of hydrophobic peptides within the intersectin 1 SH3A-B linker region with the "side sites" of the AP2 alpha- and beta-appendage domains. AP2 appendage association of the SH3A-B linker region inhibits binding of the inositol phosphatase synaptojanin 1 to intersectin 1. These data identify the intersectin-AP2 complex as an important regulator of clathrin-mediated SV recycling in synapses.
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Kahlfeldt N, Vahedi-Faridi A, Koo SJ, Schäfer JG, Krainer G, Keller S, Saenger W, Krauss M, Haucke V. Molecular basis for association of PIPKI gamma-p90 with clathrin adaptor AP-2. J Biol Chem 2010; 285:2734-49. [PMID: 19903820 PMCID: PMC2807329 DOI: 10.1074/jbc.m109.074906] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2009] [Revised: 11/06/2009] [Indexed: 12/21/2022] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) is an essential determinant in clathrin-mediated endocytosis (CME). In mammals three type I phosphatidylinositol-4-phosphate 5-kinase (PIPK) enzymes are expressed, with the I gamma-p90 isoform being highly expressed in the brain where it regulates synaptic vesicle (SV) exo-/endocytosis at nerve terminals. How precisely PI(4,5)P(2) metabolism is controlled spatially and temporally is still uncertain, but recent data indicate that direct interactions between type I PIPK and components of the endocytic machinery, in particular the AP-2 adaptor complex, are involved. Here we demonstrated that PIPKI gamma-p90 associates with both the mu and beta2 subunits of AP-2 via multiple sites. Crystallographic data show that a peptide derived from the splice insert of the human PIPKI gamma-p90 tail binds to a cognate recognition site on the sandwich subdomain of the beta2 appendage. Partly overlapping aromatic and hydrophobic residues within the same peptide also can engage the C-terminal sorting signal binding domain of AP-2mu, thereby potentially competing with the sorting of conventional YXXØ motif-containing cargo. Biochemical and structure-based mutagenesis analysis revealed that association of the tail domain of PIPKI gamma-p90 with AP-2 involves both of these sites. Accordingly the ability of overexpressed PIPKI gamma tail to impair endocytosis of SVs in primary neurons largely depends on its association with AP-2 beta and AP-2mu. Our data also suggest that interactions between AP-2 and the tail domain of PIPKI gamma-p90 may serve to regulate complex formation and enzymatic activity. We postulate a model according to which multiple interactions between PIPKI gamma-p90 and AP-2 lead to spatiotemporally controlled PI(4,5)P(2) synthesis during clathrin-mediated SV endocytosis.
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Affiliation(s)
- Nina Kahlfeldt
- From the Institute of Chemistry and Biochemistry, Departments of Membrane Biochemistry and Protein Crystallography, Freie Universität Berlin, 14195 Berlin, Germany
| | - Ardeschir Vahedi-Faridi
- From the Institute of Chemistry and Biochemistry, Departments of Membrane Biochemistry and Protein Crystallography, Freie Universität Berlin, 14195 Berlin, Germany
| | - Seong Joo Koo
- From the Institute of Chemistry and Biochemistry, Departments of Membrane Biochemistry and Protein Crystallography, Freie Universität Berlin, 14195 Berlin, Germany
| | - Johannes G. Schäfer
- From the Institute of Chemistry and Biochemistry, Departments of Membrane Biochemistry and Protein Crystallography, Freie Universität Berlin, 14195 Berlin, Germany
| | - Georg Krainer
- From the Institute of Chemistry and Biochemistry, Departments of Membrane Biochemistry and Protein Crystallography, Freie Universität Berlin, 14195 Berlin, Germany
- the Leibniz Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Sandro Keller
- the Leibniz Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Wolfram Saenger
- From the Institute of Chemistry and Biochemistry, Departments of Membrane Biochemistry and Protein Crystallography, Freie Universität Berlin, 14195 Berlin, Germany
| | - Michael Krauss
- From the Institute of Chemistry and Biochemistry, Departments of Membrane Biochemistry and Protein Crystallography, Freie Universität Berlin, 14195 Berlin, Germany
| | - Volker Haucke
- From the Institute of Chemistry and Biochemistry, Departments of Membrane Biochemistry and Protein Crystallography, Freie Universität Berlin, 14195 Berlin, Germany
- the Charité Universitätsmedizin Berlin, 14195 Berlin, Germany, and
- the Leibniz Institut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
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Botelho RJ. Changing phosphoinositides "on the fly": how trafficking vesicles avoid an identity crisis. Bioessays 2009; 31:1127-36. [PMID: 19708025 DOI: 10.1002/bies.200900060] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Joining an antagonistic phosphoinositide (PtdInsP) kinase and phosphatase into a single protein complex may regulate rapid and local PtdInsP changes. This may be important for processes such as membrane fission that require a specific PtdInsP and that are innately local and rapid. Such a complex could couple vesicle formation, with erasing of the identity of the donor organelle from the vesicle prior to its fusion with target organelles, thus preventing organelle identity intermixing. Coordinating signals are postulated to switch the relative activities of the kinase and phosphatase in a spatio-temporal manner that matches membrane fission events. The discovery of two such complexes supports this hypothesis. One regulates the interconversion of phosphatidylinositol and PtdIns(3)P by joining the Vps34 PtdIns 3-kinase and the myotubularin 3-phosphatases. The other regulates the interconversion between PtdIns(3)P and PtdIns(3,5)P(2) through the Fab1/PIKfyve kinase and the Fig4/mFig4 phosphatase. These lipids are essential components of the endosomal identity code.
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Affiliation(s)
- Roberto J Botelho
- Department of Chemistry and Biology, Ryerson University, ON, Canada.
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Two novel phosphatidylinositol-4-phosphate 5-kinase type Igamma splice variants expressed in human cells display distinctive cellular targeting. Biochem J 2009; 422:473-82. [PMID: 19548880 PMCID: PMC2782315 DOI: 10.1042/bj20090638] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The generation of various phosphoinositide messenger molecules at distinct locations within the cell is mediated via the specific targeting of different isoforms and splice variants of phosphoinositide kinases. The lipid messenger PtdIns(4,5)P2 is generated by several of these enzymes when targeted to distinct cellular compartments. Several splice variants of the type Iγ isoform of PIPK (PtdIns4P 5-kinase), which generate PtdIns(4,5)P2, have been identified, and each splice variant is thought to serve a unique functional role within cells. Here, we have identified two novel C-terminal splice variants of PIPKIγ in human cells consisting of 700 and 707 amino acids. These two splice variants are expressed in multiple tissue types and display PIPK activity in vitro. Interestingly, both of these novel splice variants display distinct subcellular targeting. With the addition of these two new splice isoforms, there are minimally five PIPKIγ splice variants that have been identified in mammals. Therefore, we propose the use of the HUGO (Human Genome Organization) nomenclature in the naming of the splice isoforms. PIPKIγ_i4 (700 amino acids) is present in the nucleus, a targeting pattern that has not been previously observed in any PIPKIγ splice variant. PIPKIγ_i5 (707 amino acids) is targeted to intracellular vesicle-like structures, where it co-localizes with markers of several types of endosomal compartments. As occurs with other PIPKIγ splice variants, the distinctive C-terminal sequences of PIPKIγ_i4 and PIPKIγ_i5 may facilitate association with unique protein targeting factors, thereby localizing the kinases to their appropriate cellular subdomains for the site-specific generation of PtdIns(4,5)P2.
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