51
|
Cellular density effect on RGD ligand internalization in glioblastoma for MRI application. PLoS One 2013; 8:e82777. [PMID: 24386117 PMCID: PMC3873929 DOI: 10.1371/journal.pone.0082777] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 10/28/2013] [Indexed: 01/12/2023] Open
Abstract
Cellular density is a parameter measured for glioma grade and invasiveness diagnosis. The characterization of the cellular density can be performed, non invasively, by magnetic resonance imaging (MRI), since, this technique displays a good resolution. Nevertheless MRI sensitivity is critical. Development of smart contrast agents appears useful to increase MRI signal to noise ratio (SNR). Tumor invasiveness is correlated with high expression of integrins that can be targeted by RGD motif. In this study, MRI contrast agents or fluorescent probes linked to RGD-peptides were used, in a glioma model, to assess the relation between RGD uptake/signal improvement/cell density and consequently tumor invasiveness. Experiments were performed in vitro with U87-MG glioma cells. Flow cytometry and microscopy experiments with RGD and iRGD-alexa488 demonstrated that cell internalization was dependent on cell density. The internalization involved a clathrin-dependent endocytosis. Cytoskeleton and particularly the microtubules were concerned. Actin filaments played a minor role. The internalization was also dependent on the glycolysis and the oxidative phosphorylations. The cellular density modulated the importance of the endocytosis pathways and of the metabolism but not the cytoskeleton contribution. The internalization of the RGD-peptide associated to gadolinium chelate increased the SNR of U87 cells. Moreover, following the cell density augmentation, the SNR increased with a low amplitude but a trend was clearly determined. In conclusion, RGD-peptide internalization appeared, in vitro, as a marker of cellular density. In perspective, the combination of these peptides with contrast agents associated to more sensitive MRI techniques could improve the MRI signal allowing the characterization of cellular density for tumor diagnosis.
Collapse
|
52
|
Zhang W, Blackman LM, Hardham AR. Transient fusion and selective secretion of vesicle proteins in Phytophthora nicotianae zoospores. PeerJ 2013; 1:e221. [PMID: 24392285 PMCID: PMC3869178 DOI: 10.7717/peerj.221] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 11/13/2013] [Indexed: 12/25/2022] Open
Abstract
Secretion of pathogen proteins is crucial for the establishment of disease in animals and plants. Typically, early interactions between host and pathogen trigger regulated secretion of pathogenicity factors that function in pathogen adhesion and host penetration. During the onset of plant infection by spores of the Oomycete, Phytophthora nicotianae, proteins are secreted from three types of cortical vesicles. Following induction of spore encystment, two vesicle types undergo full fusion, releasing their entire contents onto the cell surface. However, the third vesicle type, so-called large peripheral vesicles, selectively secretes a small Sushi domain-containing protein, PnCcp, while retaining a large glycoprotein, PnLpv, before moving away from the plasma membrane. Selective secretion of PnCcp is associated with its compartmentalization within the vesicle periphery. Pharmacological inhibition of dynamin function, purportedly in vesicle fission, by dynasore treatment provides evidence that selective secretion of PnCcp requires transient fusion of the large peripheral vesicles. This is the first report of selective protein secretion via transient fusion outside mammalian cells. Selective secretion is likely to be an important aspect of plant infection by this destructive pathogen.
Collapse
Affiliation(s)
- Weiwei Zhang
- Plant Science Division, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University , Canberra, ACT , Australia
| | - Leila M Blackman
- Plant Science Division, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University , Canberra, ACT , Australia
| | - Adrienne R Hardham
- Plant Science Division, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University , Canberra, ACT , Australia
| |
Collapse
|
53
|
Castle MJ, Perlson E, Holzbaur EL, Wolfe JH. Long-distance axonal transport of AAV9 is driven by dynein and kinesin-2 and is trafficked in a highly motile Rab7-positive compartment. Mol Ther 2013; 22:554-566. [PMID: 24100640 DOI: 10.1038/mt.2013.237] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 09/30/2013] [Indexed: 12/15/2022] Open
Abstract
Adeno-associated virus (AAV) vectors can move along axonal pathways after brain injection, resulting in transduction of distal brain regions. This can enhance the spread of therapeutic gene transfer and improve treatment of neurogenetic disorders that require global correction. To better understand the underlying cellular mechanisms that drive AAV trafficking in neurons, we investigated the axonal transport of dye-conjugated AAV9, utilizing microfluidic primary neuron cultures that isolate cell bodies from axon termini and permit independent analysis of retrograde and anterograde axonal transport. After entry, AAV was trafficked into nonmotile early and recycling endosomes, exocytic vesicles, and a retrograde-directed late endosome/lysosome compartment. Rab7-positive late endosomes/lysosomes that contained AAV were highly motile, exhibiting faster retrograde velocities and less pausing than Rab7-positive endosomes without virus. Inhibitor experiments indicated that the retrograde transport of AAV within these endosomes is driven by cytoplasmic dynein and requires Rab7 function, whereas anterograde transport of AAV is driven by kinesin-2 and exhibits unusually rapid velocities. Furthermore, increasing AAV9 uptake by neuraminidase treatment significantly enhanced virus transport in both directions. These findings provide novel insights into AAV trafficking within neurons, which should enhance progress toward the utilization of AAV for improved distribution of transgene delivery within the brain.
Collapse
Affiliation(s)
- Michael J Castle
- Research Institute of the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; W.F. Goodman Center for Comparative Medical Genetics, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Eran Perlson
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel
| | - Erika Lf Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - John H Wolfe
- Research Institute of the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; W.F. Goodman Center for Comparative Medical Genetics, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
| |
Collapse
|
54
|
Mironov AA, Sesorova IV, Beznoussenko GV. Golgi's way: a long path toward the new paradigm of the intra-Golgi transport. Histochem Cell Biol 2013; 140:383-93. [PMID: 24068461 DOI: 10.1007/s00418-013-1141-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2013] [Indexed: 11/28/2022]
Abstract
The transport of proteins and lipids is one of the main cellular functions. The vesicular model, compartment (or cisterna) maturation model, and the diffusion model compete with each other for the right to be the paradigm within the field of the intra-Golgi transport. These models have significant difficulties explaining the existing experimental data. Recently, we proposed the kiss-and-run (KAR) model of intra-Golgi transport (Mironov and Beznoussenko in Int J Mol Sci 13(6):6800-6819, 2012), which can be symmetric, when fusion and fission occur in the same location, and asymmetric, when fusion and fission take place at different sites. Here, we compare the ability of main models of the intra-Golgi transport to explain the existing results examining the evidence in favor and against each model. We propose that the KAR model has the highest potential for the explanation of the majority of experimental observations existing within the field of intracellular transport.
Collapse
Affiliation(s)
- Alexander A Mironov
- Istituto di Oncologia Molecolare di Fondazione Italiana per la Ricerca sul Cancro, 20139, Milan, Italy,
| | | | | |
Collapse
|
55
|
Sánchez-Felipe L, Villar E, Muñoz-Barroso I. Entry of Newcastle Disease Virus into the host cell: role of acidic pH and endocytosis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:300-9. [PMID: 23994097 PMCID: PMC7094467 DOI: 10.1016/j.bbamem.2013.08.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 08/02/2013] [Accepted: 08/13/2013] [Indexed: 12/24/2022]
Abstract
Most paramyxoviruses enter the cell by direct fusion of the viral envelope with the plasma membrane. Our previous studies have shown the colocalization of Newcastle Disease Virus (NDV) with the early endosome marker EEA1 and the inhibition of NDV fusion by the caveolin-phosphorylating drug phorbol 12-myristate 13-acetate (PMA) prompted us to propose that NDV enters the cells via endocytosis. Here we show that the virus-cell fusion and cell-cell fusion promoted by NDV-F are increased by about 30% after brief exposure to low pH in HeLa and ELL-0 cells but not in NDV receptor- deficient cell lines such as GM95 or Lec1. After a brief low-pH exposure, the percentage of NDV fusion at 29 °C was similar to that at 37 °C without acid-pH stimulation, meaning that acid pH would decrease the energetic barrier to enhance fusion. Furthermore, preincubation of cells with the protein kinase C inhibitor bisindolylmaleimide led to the inhibition of about 30% of NDV infectivity, suggesting that a population of virus enters cells through receptor-mediated endocytosis. Moreover, the involvement of the GTPase dynamin in NDV entry is shown as its specific inhibitor, dynasore, also impaired NDV fusion and infectivity. Optimal infection of the host cells was significantly affected by drugs that inhibit endosomal acidification such as concanamycin A, monensin and chloroquine. These results support our hypothesis that entry of NDV into ELL-0 and HeLa cells occurs through the plasma membrane as well as by dynamin- low pH- and receptor- dependent endocytosis. A pulse of low-pH enhanced NDV fusion and infectivity in a cell-dependent manner. NDV infectivity was impaired by a protein kinase C inhibitor. A specific inhibitor of the GTPase dynamin impaired NDV fusion and infectivity. Inhibition of endosomal acidification inhibited NDV fusion and infectivity. NDV may enter by dynamin-acid- and receptor-dependent endocytosis.
Collapse
Affiliation(s)
- Lorena Sánchez-Felipe
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 106/108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
| | | | | |
Collapse
|
56
|
Abstract
Secreted proteins fused to the plant photoreceptor protein UVR8 are conditionally sequestered in the ER until a pulse of light triggers trafficking through the secretory pathway, allowing precise control of forward secretory trafficking. Optical control of protein interactions has emerged as a powerful experimental paradigm for manipulating and studying various cellular processes. Tools are now available for controlling a number of cellular functions, but some fundamental processes, such as protein secretion, have been difficult to engineer using current optical tools. Here we use UVR8, a plant photoreceptor protein that forms photolabile homodimers, to engineer the first light-triggered protein secretion system. UVR8 fusion proteins were conditionally sequestered in the endoplasmic reticulum, and a brief pulse of light triggered robust forward trafficking through the secretory pathway to the plasma membrane. UVR8 was not responsive to excitation light used to image cyan, green, or red fluorescent protein variants, allowing multicolor visualization of cellular markers and secreted protein cargo as it traverses the cellular secretory pathway. We implemented this novel tool in neurons to demonstrate restricted, local trafficking of secretory cargo near dendritic branch points.
Collapse
Affiliation(s)
- Daniel Chen
- Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
| | | | | |
Collapse
|
57
|
Grossman GH, Ebke LA, Beight CD, Jang GF, Crabb JW, Hagstrom SA. Protein partners of dynamin-1 in the retina. Vis Neurosci 2013; 30:129-39. [PMID: 23746204 PMCID: PMC3936680 DOI: 10.1017/s0952523813000138] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Dynamin proteins are involved in vesicle generation, providing mechanical force to excise newly formed vesicles from membranes of cellular compartments. In the brain, dynamin-1, dynamin-2, and dynamin-3 have been well studied; however, their function in the retina remains elusive. A retina-specific splice variant of dynamin-1 interacts with the photoreceptor-specific protein Tubby-like protein 1 (Tulp1), which when mutated causes an early onset form of autosomal recessive retinitis pigmentosa. Here, we investigated the role of the dynamins in the retina, using immunohistochemistry to localize dynamin-1, dynamin-2, and dynamin-3 and immunoprecipitation followed by mass spectrometry to explore dynamin-1 interacting proteins in mouse retina. Dynamin-2 is primarily confined to the inner segment compartment of photoreceptors, suggesting a role in outer segment protein transport. Dynamin-3 is present in the terminals of photoreceptors and dendrites of second-order neurons but is most pronounced in the inner plexiform layer where second-order neurons relay signals from photoreceptors. Dynamin-1 appears to be the dominant isoform in the retina and is present throughout the retina and in multiple compartments of the photoreceptor cell. This suggests that it may function in multiple cellular pathways. Surprisingly, dynamin-1 expression and localization did not appear to be disrupted in tulp1−/− mice. Immunoprecipitation experiments reveal that dynamin-1 associates primarily with proteins involved in cytoskeletal-based membrane dynamics. This finding is confirmed by western blot analysis. Results further implicate dynamin-1 in vesicular protein transport processes relevant to synaptic and post-Golgi pathways and indicate a possible role in photoreceptor stability.
Collapse
Affiliation(s)
- Gregory H Grossman
- Department of Ophthalmic Research, Cleveland Clinic Cole Eye Institute, Cleveland, Ohio
| | | | | | | | | | | |
Collapse
|
58
|
Yun HS, Kwaaitaal M, Kato N, Yi C, Park S, Sato MH, Schulze-Lefert P, Kwon C. Requirement of vesicle-associated membrane protein 721 and 722 for sustained growth during immune responses in Arabidopsis. Mol Cells 2013; 35:481-8. [PMID: 23661365 PMCID: PMC3887875 DOI: 10.1007/s10059-013-2130-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 03/21/2013] [Accepted: 03/28/2013] [Indexed: 12/22/2022] Open
Abstract
Extracellular immune responses to ascomycete and oomycete pathogens in Arabidopsis are dependent on vesicle-associated secretion mediated by the SNARE proteins PEN1 syntaxin, SNAP33 and endomembrane-resident VAMP721/722. Continuous movement of functional GFP-VAMP722 to and from the plasma membrane in non-stimulated cells reflects the second proposed function of VAMP721/722 in constitutive secretion during plant growth and development. Application of the bacterium-derived elicitor flg22 stabilizes VAMP721/722 that are otherwise constitutively degraded via the 26S proteasome pathway. Depletion of VAMP721/722 levels by reducing VAMP721/722 gene dosage enhances flg22-induced seedling growth inhibition in spite of elevated VAMP721/722 abundance. We therefore propose that plants prioritize the deployment of the corresponding secretory pathway for defense over plant growth. Interstingly, VAMP721/722 specifically interact in vitro and in vivo with the plasma membrane syntaxin SYP132 that is required for plant growth and resistance to bacteria. This suggests that the plant growth/immunity-involved VAMP721/722 form SNARE complexes with multiple plasma membrane syntaxins to discharge cue-dependent cargo molecules.
Collapse
Affiliation(s)
- Hye Sup Yun
- Max-Planck-Institut für Züchtungsforschung, Deparment of Plant Microbe Interactions, D-50829, Köln,
Germany
- Biological Sciences Major, College of Biological Science and Biotechnology, Konkuk University, Seoul 143–701,
Korea
| | - Mark Kwaaitaal
- Max-Planck-Institut für Züchtungsforschung, Deparment of Plant Microbe Interactions, D-50829, Köln,
Germany
| | - Naohiro Kato
- Department of Biological Sciences, Louisiana State University, LA 70803-1715,
USA
| | - Changhyun Yi
- Department of Molecular Biology, Dankook University, Yongin 448–701,
Korea
| | - Sohyeon Park
- Department of Molecular Biology, Dankook University, Yongin 448–701,
Korea
| | - Masa H. Sato
- Laboratory of Cellular Dynamics, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto 606-8522,
Japan
| | - Paul Schulze-Lefert
- Max-Planck-Institut für Züchtungsforschung, Deparment of Plant Microbe Interactions, D-50829, Köln,
Germany
| | - Chian Kwon
- Max-Planck-Institut für Züchtungsforschung, Deparment of Plant Microbe Interactions, D-50829, Köln,
Germany
- Department of Molecular Biology, Dankook University, Yongin 448–701,
Korea
- Department of Integrated Molecular Sciences, Dankook University, Yongin 448–701,
Korea
| |
Collapse
|
59
|
Rivera-Molina F, Toomre D. Live-cell imaging of exocyst links its spatiotemporal dynamics to various stages of vesicle fusion. ACTA ACUST UNITED AC 2013; 201:673-80. [PMID: 23690179 PMCID: PMC3664709 DOI: 10.1083/jcb.201212103] [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: 11/22/2022]
Abstract
Tethers play ubiquitous roles in membrane trafficking and influence the specificity of vesicle attachment. Unlike soluble N-ethyl-maleimide-sensitive fusion attachment protein receptors (SNAREs), the spatiotemporal dynamics of tethers relative to vesicle fusion are poorly characterized. The most extensively studied tethering complex is the exocyst, which spatially targets vesicles to sites on the plasma membrane. By using a mammalian genetic replacement strategy, we were able to assemble fluorescently tagged Sec8 into the exocyst complex, which was shown to be functional by biochemical, trafficking, and morphological criteria. Ultrasensitive live-cell imaging revealed that Sec8-TagRFP moved to the cell cortex on vesicles, which preferentially originated from the endocytic recycling compartment. Surprisingly, Sec8 remained with vesicles until full dilation of the fusion pore, supporting potential coupling with SNARE fusion machinery. Fluorescence recovery after photobleaching analysis of Sec8 at cell protrusions revealed that a significant fraction was immobile. Additionally, Sec8 dynamically repositioned to the site of membrane expansion, suggesting that it may respond to local cues during early cell polarization.
Collapse
Affiliation(s)
- Felix Rivera-Molina
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
| | | |
Collapse
|
60
|
Lourido S, Jeschke GR, Turk BE, Sibley LD. Exploiting the unique ATP-binding pocket of toxoplasma calcium-dependent protein kinase 1 to identify its substrates. ACS Chem Biol 2013; 8:1155-62. [PMID: 23530747 PMCID: PMC3691715 DOI: 10.1021/cb400115y] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
![]()
Apicomplexan parasites rely on calcium
as a second messenger to
regulate a variety of essential cellular processes. Calcium-dependent
protein kinases (CDPK), which transduce these signals, are conserved
among apicomplexans but absent from mammalian hosts, making them attractive
targets for therapeutic intervention. Despite their importance, the
signaling pathways CDPK regulate remain poorly characterized, and
their protein substrates are completely unknown. In Toxoplasma
gondii, CDPK1 is required for calcium-regulated secretion
from micronemes, thereby controlling motility, invasion, and egress
from host cells. CDPK1 is unique among parasite and mammalian kinases
in containing glycine at the key “gatekeeper” residue,
which results in an expanded ATP-binding pocket. In the present study,
we use a synthetic ATPγS analogue that displays steric complementarity
to the ATP-binding pocket and hence allows identification of protein
substrates based on selective thiophosphorylation. The specificity
of this approach was validated by the concordance between the identified
phosphorylation sites and the in vitro substrate
preference of CDPK1. We further demonstrate that the phosphorylation
of predicted substrates is dependent on CDPK1 both in vivo and in vitro. This combined strategy for identifying
the targets of specific protein kinases provides a platform for defining
the roles of CDPKs in apicomplexans.
Collapse
Affiliation(s)
- Sebastian Lourido
- Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid
Ave., St. Louis, Missouri 63110, United States
| | - Grace R. Jeschke
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar St.,
New Haven, Connecticut 06520, United States
| | - Benjamin E. Turk
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar St.,
New Haven, Connecticut 06520, United States
| | - L. David Sibley
- Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid
Ave., St. Louis, Missouri 63110, United States
| |
Collapse
|
61
|
Wnt secretion and gradient formation. Int J Mol Sci 2013; 14:5130-45. [PMID: 23455472 PMCID: PMC3634490 DOI: 10.3390/ijms14035130] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 02/20/2013] [Accepted: 02/22/2013] [Indexed: 12/14/2022] Open
Abstract
Concentration gradients formed by the lipid-modified morphogens of the Wnt family are known for their pivotal roles during embryogenesis and adult tissue homeostasis. Wnt morphogens are also implicated in a variety of human diseases, especially cancer. Therefore, the signaling cascades triggered by Wnts have received considerable attention during recent decades. However, how Wnts are secreted and how concentration gradients are formed remains poorly understood. The use of model organisms such as Drosophila melanogaster has provided important advances in this area. For instance, we have previously shown that the lipid raft-associated reggie/flotillin proteins influence Wnt secretion and spreading in Drosophila. Our work supports the notion that producing cells secrete Wnt molecules in at least two pools: a poorly diffusible one and a reggie/flotillin-dependent highly diffusible pool which allows morphogen spreading over long distances away from its source of production. Here we revise the current views of Wnt secretion and spreading, and propose two models for the role of the reggie/flotillin proteins in these processes: (i) reggies/flotillins regulate the basolateral endocytosis of the poorly diffusible, membrane-bound Wnt pool, which is then sorted and secreted to apical compartments for long-range diffusion, and (ii) lipid rafts organized by reggies/flotillins serve as “dating points” where extracellular Wnt transiently interacts with lipoprotein receptors to allow its capture and further spreading via lipoprotein particles. We further discuss these processes in the context of human breast cancer. A better understanding of these phenomena may be relevant for identification of novel drug targets and therapeutic strategies.
Collapse
|
62
|
Otterstrom J, van Oijen AM. Visualization of membrane fusion, one particle at a time. Biochemistry 2013; 52:1654-68. [PMID: 23421412 DOI: 10.1021/bi301573w] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Protein-mediated fusion between phospholipid bilayers is a fundamental and necessary mechanism for many cellular processes. The short-lived nature of the intermediate states visited during fusion makes it challenging to capture precise kinetic information using classical, ensemble-averaging biophysical techniques. Recently, a number of single-particle fluorescence microscopy-based assays that allow researchers to obtain highly quantitative data about the fusion process by observing individual fusion events in real time have been developed. These assays depend upon changes in the acquired fluorescence signal to provide a direct readout for transitions between the various fusion intermediates. The resulting data yield meaningful and detailed kinetic information about the transitory states en route to productive membrane fusion. In this review, we highlight recent in vitro and in vivo studies of membrane fusion at the single-particle level in the contexts of viral membrane fusion and SNARE-mediated synaptic vesicle fusion. These studies afford insight into mechanisms of coordination between fusion-mediating proteins as well as coordination of the overall fusion process with other cellular processes. The development of single-particle approaches to investigate membrane fusion and their successful application to a number of model systems have resulted in a new experimental paradigm and open up considerable opportunities to extend these methods to other biological processes that involve membrane fusion.
Collapse
Affiliation(s)
- Jason Otterstrom
- Harvard Biophysics Program, Harvard Medical School , 240 Longwood Avenue, Boston, Massachusetts 02115, United States
| | | |
Collapse
|
63
|
Menon M, Schafer DA. Dynamin: expanding its scope to the cytoskeleton. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 302:187-219. [PMID: 23351711 DOI: 10.1016/b978-0-12-407699-0.00003-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The large GTPase dynamin is well known for its actions on budded cellular membranes to generate vesicles, most often, clathrin-coated endocytic vesicles. The scope of cellular processes in which dynamin-mediated vesicle formation occurs, has expanded to include secretory vesicle formation at the Golgi, from other endosomes and nonclathrin structures, such as caveolae, as well as membrane remodeling during exocytosis and vesicle fusion. An intriguing new facet of dynamin's sphere of influence is the cytoskeleton. Cytoskeletal filament networks maintain cell shape, provide cell movement, execute cell division and orchestrate vesicle trafficking. Recent evidence supports the hypothesis that dynamin influences actin filaments and microtubules via mechanisms that are independent of its membrane-remodeling activities. This chapter discusses this emerging evidence and considers possible mechanisms of action.
Collapse
Affiliation(s)
- Manisha Menon
- Department of Biology, University of Virginia, Charlottesville, VA, USA
| | | |
Collapse
|
64
|
Multiple roles for the actin cytoskeleton during regulated exocytosis. Cell Mol Life Sci 2012; 70:2099-121. [PMID: 22986507 DOI: 10.1007/s00018-012-1156-5] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/28/2012] [Accepted: 08/30/2012] [Indexed: 01/01/2023]
Abstract
Regulated exocytosis is the main mechanism utilized by specialized secretory cells to deliver molecules to the cell surface by virtue of membranous containers (i.e., secretory vesicles). The process involves a series of highly coordinated and sequential steps, which include the biogenesis of the vesicles, their delivery to the cell periphery, their fusion with the plasma membrane, and the release of their content into the extracellular space. Each of these steps is regulated by the actin cytoskeleton. In this review, we summarize the current knowledge regarding the involvement of actin and its associated molecules during each of the exocytic steps in vertebrates, and suggest that the overall role of the actin cytoskeleton during regulated exocytosis is linked to the architecture and the physiology of the secretory cells under examination. Specifically, in neurons, neuroendocrine, endocrine, and hematopoietic cells, which contain small secretory vesicles that undergo rapid exocytosis (on the order of milliseconds), the actin cytoskeleton plays a role in pre-fusion events, where it acts primarily as a functional barrier and facilitates docking. In exocrine and other secretory cells, which contain large secretory vesicles that undergo slow exocytosis (seconds to minutes), the actin cytoskeleton plays a role in post-fusion events, where it regulates the dynamics of the fusion pore, facilitates the integration of the vesicles into the plasma membrane, provides structural support, and promotes the expulsion of large cargo molecules.
Collapse
|
65
|
Reid AT, Lord T, Stanger SJ, Roman SD, McCluskey A, Robinson PJ, Aitken RJ, Nixon B. Dynamin regulates specific membrane fusion events necessary for acrosomal exocytosis in mouse spermatozoa. J Biol Chem 2012; 287:37659-72. [PMID: 22977254 DOI: 10.1074/jbc.m112.392803] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Mammalian spermatozoa must complete an acrosome reaction prior to fertilizing an oocyte. The acrosome reaction is a unique exocytotic event involving a series of prolonged membrane fusions that ultimately result in the production of membrane vesicles and release of the acrosomal contents. This event requires the concerted action of a large number of fusion-competent signaling and scaffolding proteins. Here we show that two different members of the dynamin GTPase family localize to the developing acrosome of maturing mouse germ cells. Both dynamin 1 and 2 also remain within the periacrosomal region of mature mouse spermatozoa and are thus well positioned to regulate the acrosome reaction. Two pharmacological inhibitors of dynamin, dynasore and Dyngo-4a, blocked the in vitro induction of acrosomal exocytosis by progesterone, but not by the calcium ionophore A23187, and elicited a concomitant reduction of in vitro fertilization. In vivo treatment with these inhibitors also resulted in spermatozoa displaying reduced acrosome reaction potential. Dynamin 1 and 2 phosphorylation increased on progesterone treatment, and this was also selectively blocked by dynasore. On the basis of our collective data, we propose that dynamin could regulate specific membrane fusion events necessary for acrosomal exocytosis in mouse spermatozoa.
Collapse
Affiliation(s)
- Andrew T Reid
- School of Environmental and Life Sciences, Discipline of Biological Sciences, The University of Newcastle, University Drive, Callaghan, New South Wales 2308, Australia
| | | | | | | | | | | | | | | |
Collapse
|
66
|
Anantharam A, Axelrod D, Holz RW. Real-time imaging of plasma membrane deformations reveals pre-fusion membrane curvature changes and a role for dynamin in the regulation of fusion pore expansion. J Neurochem 2012; 122:661-71. [PMID: 22671293 DOI: 10.1111/j.1471-4159.2012.07816.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Assays for real-time investigation of exocytosis typically measure what is released from the granule. From this, inferences are made about the dynamics of membrane remodeling as fusion progresses from start to finish. We have recently undertaken a different approach to investigate the fusion process, by focusing not primarily on the granule, but rather its partner in exocytosis - the plasma membrane. We have been guided by the idea that biochemical interactions between the granule and plasma membranes before and during fusion, cause changes in membrane conformation. To enable study of membrane conformation, a novel imaging technique was developed combining polarized excitation of an oriented membrane probe 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (diI) with total internal reflection fluorescence microscopy (pTIRFM). Because this technique measures changes in membrane conformation (or deformations) directly, its usefulness persists even after granule cargo reporter (catecholamine, or protein), is no longer present. In this mini-review, we first summarize the workings of pTIRFM. We then discuss the application of the technique to investigate deformations in the membrane preceding fusion, and later, during fusion pore expansion. Finally, we discuss how expansion of the fusion pore may be regulated by the GTPase activity of dynamin.
Collapse
Affiliation(s)
- Arun Anantharam
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA.
| | | | | |
Collapse
|
67
|
Mironov AA, Beznoussenko GV. The kiss-and-run model of intra-Golgi transport. Int J Mol Sci 2012; 13:6800-6819. [PMID: 22837664 PMCID: PMC3397496 DOI: 10.3390/ijms13066800] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 05/09/2012] [Accepted: 05/22/2012] [Indexed: 11/16/2022] Open
Abstract
The Golgi apparatus (GA) is the main station along the secretory pathway. Mechanisms of intra-Golgi transport remain unresolved. Three models compete with each other for the right to be defined as the paradigm. The vesicular model cannot explain the following: (1) lipid droplets and aggregates of procollagen that are larger than coatomer I (COPI)-dependent vesicles are transported across the GA; and (2) most anterograde cargoes are depleted in COPI vesicles. The compartment progression/maturation model has the following problems: (1) most Golgi-resident proteins are depleted in COPI vesicles; (2) there are no COPI vesicles for the recycling of the resident proteins in the trans-most-Golgi cisterna; and (3) different proteins have different rates of intra-Golgi transport. The diffusion model based on permanent inter-cisternal connections cannot explain the existence of lipid, ionic and protein gradients across the Golgi stacks. In contrast, the kiss-and-run model has the potential to explain most of the experimental observations. The kiss-and-run model can be symmetric when fusion and then fission occurs in the same place, and asymmetric when fusion takes place in one location, whereas fission takes place in another. The asymmetric kiss-and-run model resembles the carrier maturation mechanism, and it can be used to explain the transport of large cargo aggregates.
Collapse
Affiliation(s)
- Alexander A. Mironov
- IFOM Foundation, FIRC Institute of Molecular Oncology (IFOM-IEO Campus), Via Adamello 16, 20139, Milan, Italy
| | - Galina V. Beznoussenko
- IFOM Foundation, FIRC Institute of Molecular Oncology (IFOM-IEO Campus), Via Adamello 16, 20139, Milan, Italy
| |
Collapse
|
68
|
Cai B, Caplan S, Naslavsky N. cPLA2α and EHD1 interact and regulate the vesiculation of cholesterol-rich, GPI-anchored, protein-containing endosomes. Mol Biol Cell 2012; 23:1874-88. [PMID: 22456504 PMCID: PMC3350552 DOI: 10.1091/mbc.e11-10-0881] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
cPLA2 hydrolyzes phospholipids and regulates membrane curvature and/or tubulation. Despite disparate roles for cPLA2 at the Golgi and early endosomes, its function in the regulation of membranes containing GPI-anchored proteins is not known. A role for cPLA2α and EHD1 is identified in the vesiculation of cholesterol-rich, GPI-AP–containing membranes. The lipid modifier phospholipase A2 catalyzes the hydrolysis of phospholipids to inverted-cone–shaped lysophospholipids that contribute to membrane curvature and/or tubulation. Conflicting findings exist regarding the function of cytosolic phospholipase A2 (cPLA2) and its role in membrane regulation at the Golgi and early endosomes. However, no studies addressed the role of cPLA2 in the regulation of cholesterol-rich membranes that contain glycosylphosphatidylinositol-anchored proteins (GPI-APs). Our studies support a role for cPLA2α in the vesiculation of GPI-AP–containing membranes, using endogenous CD59 as a model for GPI-APs. On cPLA2α depletion, CD59-containing endosomes became hypertubular. Moreover, accumulation of lysophospholipids induced by a lysophospholipid acyltransferase inhibitor extensively vesiculated CD59-containing endosomes. However, overexpression of cPLA2α did not increase the endosomal vesiculation, implying a requirement for additional factors. Indeed, depletion of the “pinchase” EHD1, a C-terminal Eps15 homology domain (EHD) ATPase, also induced hypertubulation of CD59-containing endosomes. Furthermore, EHD1 and cPLA2α demonstrated in situ proximity (<40 nm) and interacted in vivo. The results presented here provide evidence that the lipid modifier cPLA2α and EHD1 are involved in the vesiculation of CD59-containing endosomes. We speculate that cPLA2α induces membrane curvature and allows EHD1, possibly in the context of a complex, to sever the curved membranes into vesicles.
Collapse
Affiliation(s)
- Bishuang Cai
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | | | | |
Collapse
|
69
|
Bucci C, Bakke O, Progida C. Charcot-Marie-Tooth disease and intracellular traffic. Prog Neurobiol 2012; 99:191-225. [PMID: 22465036 PMCID: PMC3514635 DOI: 10.1016/j.pneurobio.2012.03.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2011] [Revised: 12/23/2011] [Accepted: 03/13/2012] [Indexed: 12/23/2022]
Abstract
Mutations of genes whose primary function is the regulation of membrane traffic are increasingly being identified as the underlying causes of various important human disorders. Intriguingly, mutations in ubiquitously expressed membrane traffic genes often lead to cell type- or organ-specific disorders. This is particularly true for neuronal diseases, identifying the nervous system as the most sensitive tissue to alterations of membrane traffic. Charcot-Marie-Tooth (CMT) disease is one of the most common inherited peripheral neuropathies. It is also known as hereditary motor and sensory neuropathy (HMSN), which comprises a group of disorders specifically affecting peripheral nerves. This peripheral neuropathy, highly heterogeneous both clinically and genetically, is characterized by a slowly progressive degeneration of the muscle of the foot, lower leg, hand and forearm, accompanied by sensory loss in the toes, fingers and limbs. More than 30 genes have been identified as targets of mutations that cause CMT neuropathy. A number of these genes encode proteins directly or indirectly involved in the regulation of intracellular traffic. Indeed, the list of genes linked to CMT disease includes genes important for vesicle formation, phosphoinositide metabolism, lysosomal degradation, mitochondrial fission and fusion, and also genes encoding endosomal and cytoskeletal proteins. This review focuses on the link between intracellular transport and CMT disease, highlighting the molecular mechanisms that underlie the different forms of this peripheral neuropathy and discussing the pathophysiological impact of membrane transport genetic defects as well as possible future ways to counteract these defects.
Collapse
Affiliation(s)
- Cecilia Bucci
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Via Provinciale Monteroni, 73100 Lecce, Italy.
| | | | | |
Collapse
|
70
|
Plattner H, Sehring IM, Mohamed IK, Miranda K, De Souza W, Billington R, Genazzani A, Ladenburger EM. Calcium signaling in closely related protozoan groups (Alveolata): non-parasitic ciliates (Paramecium, Tetrahymena) vs. parasitic Apicomplexa (Plasmodium, Toxoplasma). Cell Calcium 2012; 51:351-82. [PMID: 22387010 DOI: 10.1016/j.ceca.2012.01.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 01/10/2012] [Accepted: 01/12/2012] [Indexed: 12/20/2022]
Abstract
The importance of Ca2+-signaling for many subcellular processes is well established in higher eukaryotes, whereas information about protozoa is restricted. Recent genome analyses have stimulated such work also with Alveolates, such as ciliates (Paramecium, Tetrahymena) and their pathogenic close relatives, the Apicomplexa (Plasmodium, Toxoplasma). Here we compare Ca2+ signaling in the two closely related groups. Acidic Ca2+ stores have been characterized in detail in Apicomplexa, but hardly in ciliates. Two-pore channels engaged in Ca2+-release from acidic stores in higher eukaryotes have not been stingently characterized in either group. Both groups are endowed with plasma membrane- and endoplasmic reticulum-type Ca2+-ATPases (PMCA, SERCA), respectively. Only recently was it possible to identify in Paramecium a number of homologs of ryanodine and inositol 1,3,4-trisphosphate receptors (RyR, IP3R) and to localize them to widely different organelles participating in vesicle trafficking. For Apicomplexa, physiological experiments suggest the presence of related channels although their identity remains elusive. In Paramecium, IP3Rs are constitutively active in the contractile vacuole complex; RyR-related channels in alveolar sacs are activated during exocytosis stimulation, whereas in the parasites the homologous structure (inner membrane complex) may no longer function as a Ca2+ store. Scrutinized comparison of the two closely related protozoan phyla may stimulate further work and elucidate adaptation to parasitic life. See also "Conclusions" section.
Collapse
Affiliation(s)
- H Plattner
- Department of Biology, University of Konstanz, P.O. Box 5560, 78457 Konstanz, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
71
|
Smyth JW, Vogan JM, Buch PJ, Zhang SS, Fong TS, Hong TT, Shaw RM. Actin cytoskeleton rest stops regulate anterograde traffic of connexin 43 vesicles to the plasma membrane. Circ Res 2012; 110:978-89. [PMID: 22328533 DOI: 10.1161/circresaha.111.257964] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE The intracellular trafficking of connexin 43 (Cx43) hemichannels presents opportunities to regulate cardiomyocyte gap junction coupling. Although it is known that Cx43 hemichannels are transported along microtubules to the plasma membrane, the role of actin in Cx43 forward trafficking is unknown. OBJECTIVE We explored whether the actin cytoskeleton is involved in Cx43 forward trafficking. METHODS AND RESULTS High-resolution imaging reveals that Cx43 vesicles colocalize with nonsarcomeric actin in adult cardiomyocytes. Live-cell fluorescence imaging reveals Cx43 vesicles as stationary or traveling slowly (average speed 0.09 μm/s) when associated with actin. At any time, the majority (81.7%) of vesicles travel at subkinesin rates, suggesting that actin is important for Cx43 transport. Using Cx43 containing a hemagglutinin tag in the second extracellular loop, we developed an assay to detect transport of de novo Cx43 hemichannels to the plasma membrane after release from Brefeldin A-induced endoplasmic reticulum/Golgi vesicular transport block. Latrunculin A (for specific interference of actin) was used as an intervention after reinitiation of vesicular transport. Disruption of actin inhibits delivery of Cx43 to the cell surface. Moreover, using the assay in primary cardiomyocytes, actin inhibition causes an 82% decrease (P<0.01) in de novo endogenous Cx43 delivery to cell-cell borders. In Langendorff-perfused mouse heart preparations, Cx43/β-actin complexing is disrupted during acute ischemia, and inhibition of actin polymerization is sufficient to reduce levels of Cx43 gap junctions at intercalated discs. CONCLUSIONS Actin is a necessary component of the cytoskeleton-based forward trafficking apparatus for Cx43. In cardiomyocytes, Cx43 vesicles spend a majority of their time pausing at nonsarcomeric actin rest stops when not undergoing microtubule-based transport to the plasma membrane. Deleterious effects on this interaction between Cx43 and the actin cytoskeleton during acute ischemia contribute to losses in Cx43 localization at intercalated discs.
Collapse
Affiliation(s)
- James W Smyth
- University of California San Francisco, Cardiovascular Research Institute, 555 Mission Bay Boulevard South, San Francisco, CA 94158, USA
| | | | | | | | | | | | | |
Collapse
|
72
|
Abstract
Cell-to-cell fusion plays an important role in normal physiology and in different pathological conditions. Early fusion stages mediated by specialized proteins and yielding fusion pores are followed by a pore expansion stage that is dependent on cell metabolism and yet unidentified machinery. Because of a similarity of membrane bending in the fusion pore rim and in highly curved intracellular membrane compartments, in the present study we explored whether changes in the activity of the proteins that generate these compartments affect cell fusion initiated by protein fusogens of influenza virus and baculovirus. We raised the intracellular concentration of curvature-generating proteins in cells by either expressing or microinjecting the ENTH (epsin N-terminal homology) domain of epsin or by expressing the GRAF1 (GTPase regulator associated with focal adhesion kinase 1) BAR (Bin/amphiphysin/Rvs) domain or the FCHo2 (FCH domain-only protein 2) F-BAR domain. Each of these treatments promoted syncytium formation. Cell fusion extents were also influenced by treatments targeting the function of another curvature-generating protein, dynamin. Cell-membrane-permeant inhibitors of dynamin GTPase blocked expansion of fusion pores and dominant-negative mutants of dynamin influenced the syncytium formation extents. We also report that syncytium formation is inhibited by reagents lowering the content and accessibility of PtdIns(4,5)P2, an important regulator of intracellular membrane remodelling. Our findings indicate that fusion pore expansion at late stages of cell-to-cell fusion is mediated, directly or indirectly, by intracellular membrane-shaping proteins.
Collapse
|
73
|
Xu Y, Melia TJ, Toomre DK. Using light to see and control membrane traffic. Curr Opin Chem Biol 2011; 15:822-30. [PMID: 22079055 DOI: 10.1016/j.cbpa.2011.10.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 10/01/2011] [Accepted: 10/17/2011] [Indexed: 01/13/2023]
Abstract
Cellular compartmentalization into discrete organelles is maintained by membrane trafficking including vesiculation and tubulation. Recent advances in superresolution imaging have begun to bring these small and dynamic events into focus. Most nanoscopes exploit, and are limited by, switching dyes ON and OFF. Using ground state depletion to switch dyes into long-lived dark states can exploit specific photophysical properties of dyes, such as redox potential or pK(a), and expand the repertoire of nanoscopy probes for multicolor imaging. Seeing is not enough, and new technologies based on homodimerization, heterodimerization and selective release can manipulate membrane trafficking in pulse-chase and light-controlled ways. Herein we highlight the utility and promise of these strategies and discuss their current limitations.
Collapse
Affiliation(s)
- Yingke Xu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520-8002, USA
| | | | | |
Collapse
|
74
|
Entry pathways of herpes simplex virus type 1 into human keratinocytes are dynamin- and cholesterol-dependent. PLoS One 2011; 6:e25464. [PMID: 22022400 PMCID: PMC3192061 DOI: 10.1371/journal.pone.0025464] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 09/05/2011] [Indexed: 12/21/2022] Open
Abstract
Herpes simplex virus type 1 (HSV-1) can enter cells via endocytic pathways or direct fusion at the plasma membrane depending on the cell line and receptor(s). Most studies into virus entry have used cultured fibroblasts but since keratinocytes represent the primary entry site for HSV-1 infection in its human host, we initiated studies to characterize the entry pathway of HSV-1 into human keratinocytes. Electron microscopy studies visualized free capsids in the cytoplasm and enveloped virus particles in vesicles suggesting viral uptake both by direct fusion at the plasma membrane and by endocytic vesicles. The ratio of the two entry modes differed in primary human keratinocytes and in the keratinocyte cell line HaCaT. Inhibitor studies further support a role for endocytosis during HSV-1 entry. Infection was inhibited by the cholesterol-sequestering drug methyl-β-cyclodextrin, which demonstrates the requirement for host cholesterol during virus entry. Since the dynamin-specific inhibitor dynasore and overexpression of a dominant-negative dynamin mutant blocked infection, we conclude that the entry pathways into keratinocytes are dynamin-mediated. Electron microscopy studies confirmed that virus uptake is completely blocked when the GTPase activity of dynamin is inhibited. Ex vivo infection of murine epidermis that was treated with dynasore further supports the essential role of dynamin during entry into the epithelium. Thus, we conclude that HSV-1 can enter human keratinocytes by alternative entry pathways that require dynamin and host cholesterol.
Collapse
|
75
|
Sonnemann KJ, Bement WM. Wound repair: toward understanding and integration of single-cell and multicellular wound responses. Annu Rev Cell Dev Biol 2011; 27:237-63. [PMID: 21721944 DOI: 10.1146/annurev-cellbio-092910-154251] [Citation(s) in RCA: 224] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The importance of wound healing to medicine and biology has long been evident, and consequently, wound healing has been the subject of intense investigation for many years. However, several relatively recent developments have added new impetus to wound repair research: the increasing application of model systems; the growing recognition that single cells have a robust, complex, and medically relevant wound healing response; and the emerging recognition that different modes of wound repair bear an uncanny resemblance to other basic biological processes such as morphogenesis and cytokinesis. In this review, each of these developments is described, and their significance for wound healing research is considered. In addition, overlapping mechanisms of single-cell and multicellular wound healing are highlighted, and it is argued that they are more similar than is often recognized. Based on this and other information, a simple model to explain the evolutionary relationships of cytokinesis, single-cell wound repair, multicellular wound repair, and developmental morphogenesis is proposed. Finally, a series of important, but as yet unanswered, questions is posed.
Collapse
Affiliation(s)
- Kevin J Sonnemann
- Department of Zoology and Laboratory of Cell and Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706;
| | | |
Collapse
|
76
|
Liu D, Martina JA, Wu XS, Hammer JA, Long EO. Two modes of lytic granule fusion during degranulation by natural killer cells. Immunol Cell Biol 2011; 89:728-38. [PMID: 21483445 PMCID: PMC3257049 DOI: 10.1038/icb.2010.167] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Lytic granules in cytotoxic lymphocytes, which include T cells and natural killer (NK) cells, are secretory lysosomes that release their content upon fusion with the plasma membrane (PM), a process known as degranulation. Although vesicle exocytosis has been extensively studied in endocrine and neuronal cells, much less is known about the fusion of lytic granules in cytotoxic lymphocytes. Here, we used total internal reflection fluorescence microscopy to examine lytic granules labeled with fluorescently tagged Fas ligand (FasL) in the NK cell line NKL stimulated with phorbol ester and ionomycin and in primary NK cells activated by physiological receptor–ligand interactions. Two fusion modes were observed: complete fusion, characterized by loss of granule content and rapid diffusion of FasL at the PM; and incomplete fusion, characterized by transient fusion pore opening and retention of FasL at the fusion site. The pH-sensitive green fluorescence protein (pHluorin) fused to the lumenal domain of FasL was used to visualize fusion pore opening with a time resolution of 30 ms. Upon incomplete fusion, pHluorin emission lasted several seconds in the absence of noticeable diffusion. Thus, we conclude that lytic granules in NK cells undergo both complete and incomplete fusion with the PM, and propose that incomplete fusion may promote efficient recycling of lytic granule membrane after the release of cytotoxic effector molecules.
Collapse
Affiliation(s)
- Dongfang Liu
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
| | | | | | | | | |
Collapse
|
77
|
Anantharam A, Bittner MA, Aikman RL, Stuenkel EL, Schmid SL, Axelrod D, Holz RW. A new role for the dynamin GTPase in the regulation of fusion pore expansion. Mol Biol Cell 2011; 22:1907-18. [PMID: 21460182 PMCID: PMC3103406 DOI: 10.1091/mbc.e11-02-0101] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The role of dynamin GTPase activity in controlling fusion pore expansion and postfusion granule membrane topology was investigated. The experiments show that, in addition to playing a role in endocytosis, GTPase activity of dynamin regulates the rapidity of fusion pore expansion from tens of milliseconds to seconds after fusion. Dynamin is a master regulator of membrane fission in endocytosis. However, a function for dynamin immediately upon fusion has also been suspected from a variety of experiments that measured release of granule contents. The role of dynamin guanosine triphosphate hydrolase (GTPase) activity in controlling fusion pore expansion and postfusion granule membrane topology was investigated using polarization optics and total internal reflection fluorescence microscopy (pTIRFM) and amperometry. A dynamin-1 (Dyn1) mutant with increased GTPase activity resulted in transient deformations consistent with rapid fusion pore widening after exocytosis; a Dyn1 mutant with decreased activity slowed fusion pore widening by stabilizing postfusion granule membrane deformations. The experiments indicate that, in addition to its role in endocytosis, GTPase activity of dynamin regulates the rapidity of fusion pore expansion from tens of milliseconds to seconds after fusion. These findings expand the membrane-sculpting repertoire of dynamin to include the regulation of immediate postfusion events in exocytosis that control the rate of release of soluble granule contents.
Collapse
Affiliation(s)
- Arun Anantharam
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA.
| | | | | | | | | | | | | |
Collapse
|
78
|
Calabia-Linares C, Robles-Valero J, de la Fuente H, Perez-Martinez M, Martín-Cofreces N, Alfonso-Pérez M, Gutierrez-Vázquez C, Mittelbrunn M, Ibiza S, Urbano-Olmos FR, Aguado-Ballano C, Sánchez-Sorzano CO, Sanchez-Madrid F, Veiga E. Endosomal clathrin drives actin accumulation at the immunological synapse. J Cell Sci 2011; 124:820-30. [DOI: 10.1242/jcs.078832] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antigen-specific cognate interaction of T lymphocytes with antigen-presenting cells (APCs) drives major morphological and functional changes in T cells, including actin rearrangements at the immune synapse (IS) formed at the cell–cell contact area. Here we show, using cell lines as well as primary cells, that clathrin, a protein involved in endocytic processes, drives actin accumulation at the IS. Clathrin is recruited towards the IS with parallel kinetics to that of actin. Knockdown of clathrin prevents accumulation of actin and proteins involved in actin polymerization, such as dynamin-2, the Arp2/3 complex and CD2AP at the IS. The clathrin pool involved in actin accumulation at the IS is linked to multivesicular bodies that polarize to the cell–cell contact zone, but not to plasma membrane or Golgi complex. These data underscore the role of clathrin as a platform for the recruitment of proteins that promote actin polymerization at the interface of T cells and APCs.
Collapse
Affiliation(s)
- Carmen Calabia-Linares
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Hospital de la Princesa (IP), Diego de León, 62, 28006 Madrid, Spain
| | - Javier Robles-Valero
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Hospital de la Princesa (IP), Diego de León, 62, 28006 Madrid, Spain
| | - Hortensia de la Fuente
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Hospital de la Princesa (IP), Diego de León, 62, 28006 Madrid, Spain
| | - Manuel Perez-Martinez
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Hospital de la Princesa (IP), Diego de León, 62, 28006 Madrid, Spain
| | - Noa Martín-Cofreces
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Hospital de la Princesa (IP), Diego de León, 62, 28006 Madrid, Spain
- Department Biología Vascular e Inflamación, Centro Nacional de Investigaciones Cardiovasculares, Melchor Fernández Almagro s/n, 28029 Madrid, Spain
| | - Manuel Alfonso-Pérez
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Hospital de la Princesa (IP), Diego de León, 62, 28006 Madrid, Spain
| | - Cristina Gutierrez-Vázquez
- Department Biología Vascular e Inflamación, Centro Nacional de Investigaciones Cardiovasculares, Melchor Fernández Almagro s/n, 28029 Madrid, Spain
| | - María Mittelbrunn
- Department Biología Vascular e Inflamación, Centro Nacional de Investigaciones Cardiovasculares, Melchor Fernández Almagro s/n, 28029 Madrid, Spain
| | - Sales Ibiza
- Department Biología Vascular e Inflamación, Centro Nacional de Investigaciones Cardiovasculares, Melchor Fernández Almagro s/n, 28029 Madrid, Spain
| | - Francisco R. Urbano-Olmos
- Laboratorio de Microscopía Electrónica de Transmisión, Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo s/n, 28029 Madrid, Spain
| | - Covadonga Aguado-Ballano
- Laboratorio de Microscopía Electrónica de Transmisión, Facultad de Medicina, Universidad Autónoma de Madrid, Arzobispo Morcillo s/n, 28029 Madrid, Spain
| | - Carlos Oscar Sánchez-Sorzano
- Unidad de Biocomputación, Centro Nacional de Biotecnología (CSIC), Campus Universidad Autónoma s/n, 28049 Cantoblanco, Madrid
| | - Francisco Sanchez-Madrid
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Hospital de la Princesa (IP), Diego de León, 62, 28006 Madrid, Spain
- Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Esteban Veiga
- Servicio de Inmunología, Hospital Universitario de la Princesa, Instituto de Investigación Sanitaria Hospital de la Princesa (IP), Diego de León, 62, 28006 Madrid, Spain
- Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain
- Centro Nacional de Biotecnología (CSIC), Campus Universidad Autónoma s/n, 28049 Cantoblanco, Madrid
| |
Collapse
|
79
|
Bond LM, Peden AA, Kendrick-Jones J, Sellers JR, Buss F. Myosin VI and its binding partner optineurin are involved in secretory vesicle fusion at the plasma membrane. Mol Biol Cell 2011; 22:54-65. [PMID: 21148290 PMCID: PMC3016977 DOI: 10.1091/mbc.e10-06-0553] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 10/14/2010] [Accepted: 10/21/2010] [Indexed: 12/14/2022] Open
Abstract
During constitutive secretion, proteins synthesized at the endoplasmic reticulum (ER) are transported to the Golgi complex for processing and then to the plasma membrane for incorporation or extracellular release. This study uses a unique live-cell constitutive secretion assay to establish roles for the molecular motor myosin VI and its binding partner optineurin in discrete stages of secretion. Small interfering RNA-based knockdown of myosin VI causes an ER-to-Golgi transport delay, suggesting an unexpected function for myosin VI in the early secretory pathway. Depletion of myosin VI or optineurin does not affect the number of vesicles leaving the trans-Golgi network (TGN), indicating that these proteins do not function in TGN vesicle formation. However, myosin VI and optineurin colocalize with secretory vesicles at the plasma membrane. Furthermore, live-cell total internal reflection fluorescence microscopy demonstrates that myosin VI or optineurin depletion reduces the total number of vesicle fusion events at the plasma membrane and increases both the proportion of incomplete fusion events and the number of docked vesicles in this region. These results suggest a novel role for myosin VI and optineurin in regulation of fusion pores formed between secretory vesicles and the plasma membrane during the final stages of secretion.
Collapse
Affiliation(s)
- Lisa M. Bond
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Andrew A. Peden
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | | | - James R. Sellers
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| |
Collapse
|
80
|
Affiliation(s)
- Derek Toomre
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8002; ,
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8002; ,
| |
Collapse
|
81
|
Mattheyses AL, Simon SM, Rappoport JZ. Imaging with total internal reflection fluorescence microscopy for the cell biologist. J Cell Sci 2010; 123:3621-8. [PMID: 20971701 PMCID: PMC2964103 DOI: 10.1242/jcs.056218] [Citation(s) in RCA: 236] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Total internal reflection fluorescence (TIRF) microscopy can be used in a wide range of cell biological applications, and is particularly well suited to analysis of the localization and dynamics of molecules and events near the plasma membrane. The TIRF excitation field decreases exponentially with distance from the cover slip on which cells are grown. This means that fluorophores close to the cover slip (e.g. within ~100 nm) are selectively illuminated, highlighting events that occur within this region. The advantages of using TIRF include the ability to obtain high-contrast images of fluorophores near the plasma membrane, very low background from the bulk of the cell, reduced cellular photodamage and rapid exposure times. In this Commentary, we discuss the applications of TIRF to the study of cell biology, the physical basis of TIRF, experimental setup and troubleshooting.
Collapse
Affiliation(s)
- Alexa L Mattheyses
- Laboratory of Cellular Biophysics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | | | | |
Collapse
|
82
|
Rapid delivery of internalized signaling receptors to the somatodendritic surface by sequence-specific local insertion. J Neurosci 2010; 30:11703-14. [PMID: 20810891 DOI: 10.1523/jneurosci.6282-09.2010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The recycling pathway is a major route for delivering signaling receptors to the somatodendritic plasma membrane. We investigated the cell biological basis for the remarkable selectivity and speed of this process. We focused on the mu-opioid neuropeptide receptor and the beta(2)-adrenergic catecholamine receptor, two seven-transmembrane signaling receptors that traverse the recycling pathway efficiently after ligand-induced endocytosis and localize at steady state throughout the postsynaptic surface. Rapid recycling of each receptor in dissociated neuronal cultures was mediated by a receptor-specific cytoplasmic sorting sequence. Total internal reflection fluorescence microscopy imaging revealed that both sequences drive recycling via discrete vesicular fusion events in the cell body and dendritic shaft. Both sequences promoted recycling via "transient"-type events characterized by nearly immediate lateral spread of receptors after vesicular insertion resembling receptor insertion events observed previously in non-neural cells. The sequences differed in their abilities to produce distinct "persistent"-type events at which inserted receptors lingered for a variable time period before lateral spread. Both types of insertion event generated a uniform distribution of receptors in the somatodendritic plasma membrane when imaged over a 1 min interval, but persistent events uniquely generated a punctate surface distribution over a 10 s interval. These results establish sequence-directed recycling of signaling receptors in CNS neurons and show that this mechanism has the ability to generate receptor-specific patterns of local surface distribution on a timescale overlapping that of rapid physiological signaling.
Collapse
|
83
|
Low PC, Misaki R, Schroder K, Stanley AC, Sweet MJ, Teasdale RD, Vanhaesebroeck B, Meunier FA, Taguchi T, Stow JL. Phosphoinositide 3-kinase δ regulates membrane fission of Golgi carriers for selective cytokine secretion. ACTA ACUST UNITED AC 2010; 190:1053-65. [PMID: 20837769 PMCID: PMC3101599 DOI: 10.1083/jcb.201001028] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phosphoinositide 3-kinase (PI3K) p110 isoforms are membrane lipid kinases classically involved in signal transduction. Lipopolysaccharide (LPS)-activated macrophages constitutively and abundantly secrete proinflammatory cytokines including tumor necrosis factor-α (TNF). Loss of function of the p110δ isoform of PI3K using inhibitors, RNA-mediated knockdown, or genetic inactivation in mice abolishes TNF trafficking and secretion, trapping TNF in tubular carriers at the trans-Golgi network (TGN). Kinase-active p110δ localizes to the Golgi complex in LPS-activated macrophages, and TNF is loaded into p230-labeled tubules, which cannot undergo fission when p110δ is inactivated. Similar blocks in fission of these tubules and in TNF secretion result from inhibition of the guanosine triphosphatase dynamin 2. These findings demonstrate a new function for p110δ as part of the membrane fission machinery required at the TGN for the selective trafficking and secretion of cytokines in macrophages.
Collapse
Affiliation(s)
- Pei Ching Low
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
84
|
Abstract
Formation of virus-specific replicative complexes (RCs) in infected cells is one of the most intriguing and important processes that determine virus replication and ultimately their pathogenesis on the molecular and cellular levels. Alphavirus replication was known to lead to formation of so-called type 1 cytopathic vacuoles (CPV1s), whose distinguishing feature is the presence of numerous membrane invaginations (spherules) and accumulation of viral nonstructural proteins (nsPs) at the cytoplasmic necks of these spherules. These CPV1s, modified endosomes and lysosomes, were proposed as the sites of viral RNA synthesis. However, our recent studies have demonstrated that Sindbis virus (SINV)-specific, double-stranded RNA (dsRNA)- and nonstructural protein (nsP)-containing RCs are initially formed at the plasma membrane. In this new study, we present extensive evidence that (i) in cells of vertebrate origin, at early times postinfection, viral nsPs colocalize with spherules at the plasma membrane; (ii) viral dsRNA intermediates are packed into membrane spherules and are located in their cavities on the external surface of the plasma membrane; (iii) formation of the membrane spherules is induced by the partially processed nonstructural polyprotein P123 and nsP4, but synthesis of dsRNA is an essential prerequisite of their formation; (iv) plasma membrane-associated dsRNA and protein structures are the active sites of single-stranded RNA (ssRNA) synthesis; (v) at late times postinfection, only a small fraction of SINV nsP-containing complexes are relocalized into the cytoplasm on the endosome membrane. (vi) pharmacological drugs inhibiting different endocytotic pathways have either only minor or no negative effects on SINV RNA replication; and (vii) in mosquito cells, at any times postinfection, dsRNA/nsP complexes and spherules are associated with both endosomal/lysosomal and plasma membranes, suggesting that mechanisms of RC formation may differ in cells of insect and vertebrate origins.
Collapse
|
85
|
Zhang Z, Zhang Z, Jackson MB. Synaptotagmin IV modulation of vesicle size and fusion pores in PC12 cells. Biophys J 2010; 98:968-78. [PMID: 20303854 DOI: 10.1016/j.bpj.2009.11.024] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 10/30/2009] [Accepted: 11/18/2009] [Indexed: 01/27/2023] Open
Abstract
Many synaptotagmins are Ca(2+)-binding membrane proteins with functions in Ca(2+)-triggered exocytosis. Synaptotagmin IV (syt IV) has no Ca(2+) binding activity, but nevertheless modulates exocytosis. Here, cell-attached capacitance recording was used to study single vesicle fusion and fission in control and syt IV overexpressing PC12 cells. Unitary capacitance steps varied widely in size, indicating that both microvesicles (MVs) and dense-core vesicles (DCVs) undergo fusion. Syt IV overexpression reduced the size of DCVs and endocytotic vesicles but not MVs. Syt IV also reduced the basal rate of Ca(2+)-induced fusion. During kiss-and-run, syt IV increased the conductance and duration of DCV fusion pores but not MV fusion pores. During full-fusion of DCVs syt IV increased the fusion pore conductance but not the duration. Syt IV overexpression increased the duration but not the conductance of fission pores during endocytosis. The effects of syt IV on fusion pores in PC12 cells resembled the effects on fusion pores in peptidergic nerve terminals. However, differences between these and results obtained with amperometry may indicate that amperometry and capacitance detect the fusion of different populations of vesicles. The effects of syt IV on fusion pores are discussed in terms of structural models and kinetic mechanisms.
Collapse
Affiliation(s)
- Zhenjie Zhang
- Department of Physiology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | | | | |
Collapse
|
86
|
Trahey M, Hay JC. Transport vesicle uncoating: it's later than you think. F1000 BIOLOGY REPORTS 2010; 2:47. [PMID: 20706600 PMCID: PMC2919759 DOI: 10.3410/b2-47] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Transport vesicle coat proteins play active roles in vesicle cargo sorting as well as membrane deformation and fission during vesicle biogenesis. For years, it was assumed that this was the extent of the coats’ function and that the coats depolymerized immediately after vesicle budding, leaving the exposed fusion machinery free to find, dock, and fuse with the proper target membrane. Recently, however, it has become increasingly clear that the coat remains on transport vesicles during their post-budding life and in fact helps properly pair up the vesicle with its intended target membrane. These data have brought up urgent questions about exactly when vesicles do uncoat and how uncoating is regulated. Here, we summarize the latest round of evidence for post-budding roles for coats, including a few hints about how the uncoating process may be coupled to docking and fusion. We also speculate about the possibility of post-fusion functions for residual coats.
Collapse
Affiliation(s)
- Meg Trahey
- Division of Biological Sciences and Center for Structural and Functional Neuroscience, The University of Montana, 32 Campus Drive, HS104, Missoula, MT 59812-4824, USA
| | | |
Collapse
|
87
|
Khandelwal P, Ruiz WG, Apodaca G. Compensatory endocytosis in bladder umbrella cells occurs through an integrin-regulated and RhoA- and dynamin-dependent pathway. EMBO J 2010; 29:1961-75. [PMID: 20461056 PMCID: PMC2892371 DOI: 10.1038/emboj.2010.91] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Accepted: 04/20/2010] [Indexed: 11/09/2022] Open
Abstract
Compensatory endocytosis (CE) ensures recycling of membrane components and maintenance of plasma membrane size; however, the mechanisms, regulation, and physiological functions of clathrin-independent modes of CE are poorly understood. CE was studied in umbrella cells, which undergo regulated exocytosis of subapical discoidal/fusiform vesicles (DFV) during bladder filling, and may then replenish the pool of DFV by internalizing apical membrane during voiding. We found that voiding-stimulated CE, which depended on beta(1) integrin-associated signalling pathways, occurred by a dynamin-, actin-, and RhoA-regulated mechanism and was independent of caveolins, clathrin, and flotillin. Internalized apical membrane and fluid were initially found in ZO-1-positive vesicles, which were distinct from DFV, classical early endosomes, or the Golgi, and subsequently in lysosomes. We conclude that clathrin-independent CE in umbrella cells functions to recover membrane during voiding, is integrin regulated, occurs by a RhoA- and dynamin-dependent pathway, and terminates in degradation and not recapture of membrane in DFV.
Collapse
Affiliation(s)
- Puneet Khandelwal
- Department of Medicine, Laboratory of Epithelial Cell Biology and Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, USA
| | - Wily G Ruiz
- Department of Medicine, Laboratory of Epithelial Cell Biology and Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, USA
| | - Gerard Apodaca
- Department of Medicine, Laboratory of Epithelial Cell Biology and Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA, USA
| |
Collapse
|
88
|
Smyth JW, Shaw RM. Forward trafficking of ion channels: what the clinician needs to know. Heart Rhythm 2010; 7:1135-40. [PMID: 20621620 DOI: 10.1016/j.hrthm.2010.05.030] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Accepted: 05/20/2010] [Indexed: 11/25/2022]
Abstract
Each heartbeat requires precisely orchestrated action potential propagation through the myocardium, achieved by coordination of about a million ion channels on the surface of each cardiomyocyte. Specific ion channels must occur within discrete subdomains of the sarcolemma to exert their electrophysiological effects with highest efficiency (e.g., voltage-gated Ca(2+) channels at T-tubules and gap junctions at intercalated discs). Regulation of ion channel movement to their appropriate membrane subdomain is an exciting research frontier with opportunity for novel therapeutic manipulation of ion channels in the treatment of heart disease. Although much research has generally focused on internalization and subsequent degradation of ion channels, the field of forward trafficking of de novo ion channels from the cell interior to the sarcolemma has now emerged as a key regulatory step in cardiac electrophysiological function. In this brief review, we provide an overview of the current understanding of the cellular biology governing the forward trafficking of ion channels.
Collapse
Affiliation(s)
- James W Smyth
- Cardiovascular Research Institute and Department of Medicine, University of California San Francisco, San Francisco, California, USA.
| | | |
Collapse
|
89
|
Anantharam A, Onoa B, Edwards RH, Holz RW, Axelrod D. Localized topological changes of the plasma membrane upon exocytosis visualized by polarized TIRFM. ACTA ACUST UNITED AC 2010; 188:415-28. [PMID: 20142424 PMCID: PMC2819686 DOI: 10.1083/jcb.200908010] [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: 11/22/2022]
Abstract
Imaging of individual secretory granules reveals how exocytosis curves the membrane. Total internal reflection fluorescence microscopy (TIRFM) images the plasma membrane–cytosol interface and has allowed insights into the behavior of individual secretory granules before and during exocytosis. Much less is known about the dynamics of the other partner in exocytosis, the plasma membrane. In this study, we report the implementation of a TIRFM-based polarization technique to detect rapid submicrometer changes in plasma membrane topology as a result of exocytosis. A theoretical analysis of the technique is presented together with image simulations of predicted topologies of the postfusion granule membrane–plasma membrane complex. Experiments on diI-stained bovine adrenal chromaffin cells using polarized TIRFM demonstrate rapid and varied submicrometer changes in plasma membrane topology at sites of exocytosis that occur immediately upon fusion. We provide direct evidence for a persistent curvature in the exocytotic region that is altered by inhibition of dynamin guanosine triphosphatase activity and is temporally distinct from endocytosis measured by VMAT2-pHluorin.
Collapse
Affiliation(s)
- Arun Anantharam
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA.
| | | | | | | | | |
Collapse
|
90
|
Dynamin 2 and human diseases. J Mol Med (Berl) 2010; 88:339-50. [PMID: 20127478 DOI: 10.1007/s00109-009-0587-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 12/21/2009] [Accepted: 12/25/2009] [Indexed: 10/25/2022]
Abstract
Dynamin 2 (DNM2) mutations cause autosomal dominant centronuclear myopathy, a rare form of congenital myopathy, and intermediate and axonal forms of Charcot-Marie-Tooth disease, a peripheral neuropathy. DNM2 is a large GTPase mainly involved in membrane trafficking through its function in the formation and release of nascent vesicles from biological membranes. DNM2 participates in clathrin-dependent and clathrin-independent endocytosis and intracellular membrane trafficking (from endosomes and Golgi apparatus). Recent studies have also implicated DNM2 in exocytosis. DNM2 belongs to the machinery responsible for the formation of vesicles and regulates the cytoskeleton providing intracellular vesicle transport. In addition, DNM2 tightly interacts with and is involved in the regulation of actin and microtubule networks, independent from membrane trafficking processes. We summarize here the molecular, biochemical, and functional data on DNM2 and discuss the possible pathophysiological mechanisms via which DNM2 mutations can lead to two distinct neuromuscular disorders.
Collapse
|
91
|
Burchfield JG, Lopez JA, Mele K, Vallotton P, Hughes WE. Exocytotic vesicle behaviour assessed by total internal reflection fluorescence microscopy. Traffic 2010; 11:429-39. [PMID: 20070611 DOI: 10.1111/j.1600-0854.2010.01039.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The regulated trafficking or exocytosis of cargo-containing vesicles to the cell surface is fundamental to all cells. By coupling the technology of fluorescently tagged fusion proteins with total internal reflection fluorescence microscopy (TIRFM), it is possible to achieve the high spatio-temporal resolution required to study the dynamics of sub-plasma membrane vesicle trafficking and exocytosis. TIRFM has been used in a number of cell types to visualize and dissect the various steps of exocytosis revealing how molecules identified via genetic and/or biochemical approaches are involved in the regulation of this process. Here, we summarize the contribution of TIRFM to our understanding of the mechanism of exocytosis and discuss the novel methods of analysis that are required to exploit the large volumes of data that can be produced using this technique.
Collapse
Affiliation(s)
- James G Burchfield
- The Garvan Institute of Medical Research, 384 Victoria Street, Sydney, New South Wales 2010, Australia
| | | | | | | | | |
Collapse
|
92
|
Plattner H. Membrane Trafficking in Protozoa. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 280:79-184. [DOI: 10.1016/s1937-6448(10)80003-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
93
|
Simon SM. Partial internal reflections on total internal reflection fluorescent microscopy. Trends Cell Biol 2009; 19:661-8. [PMID: 19818624 DOI: 10.1016/j.tcb.2009.08.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 08/18/2009] [Accepted: 08/19/2009] [Indexed: 11/28/2022]
Abstract
Microscopy, especially fluorescence microscopy, has proven to be a powerful method for studying biological processes. Unfortunately, some of the same features that make biological membranes powerful (for example, all of the action taking place across a narrow 4nm film) also make it difficult to visualize by fluorescence. Over the past 30 years, numerous tricks have been developed to narrow the plane over which data is collected. One approach, total internal reflection (TIR) fluorescence microscopy, is particularly well suited for studying membrane events. A key issue to address when using TIR to tackle a new biological problem is: how can one judge whether the signals being observed are actually the biological phenomena that one wishes to study?
Collapse
|