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In JG, Ihrke G, Tuma PL. Analysis of polarized membrane traffic in hepatocytes and hepatic cell lines. CURRENT PROTOCOLS IN CELL BIOLOGY 2012; Chapter 15:Unit 15.17. [PMID: 22422475 PMCID: PMC4390120 DOI: 10.1002/0471143030.cb1517s54] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The protocols described in this unit were developed to monitor membrane traffic in cultured cell monolayers that display hepatic polarity. In general, the assays are designed to visualize and/or quantitate membrane trafficking by monitoring the fates of antibodies bound to specific membrane proteins. We first describe how to infect cells with recombinant adenovirus, the preferred method for introducing exogenous genes into hepatic cells. We next provide a morphological assay to monitor basolateral to apical transcytosis. In a supporting protocol, we describe how to visualize apical recycling and/or retention. In an additional supporting protocol, we provide a semi-quantitative method to measure the relative extents of apical delivery. Finally, we describe quantitative assays to measure basolateral internalization and recycling. The methods presented in this unit provide a relatively simple, yet powerful approach to examining hepatic membrane traffic.
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Affiliation(s)
- Julie G In
- Department of Biology, The Catholic University of America, Washington, DC, USA
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2
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Wüstner D, Brewer JR, Bagatolli L, Sage D. Potential of ultraviolet wide-field imaging and multiphoton microscopy for analysis of dehydroergosterol in cellular membranes. Microsc Res Tech 2011; 74:92-108. [PMID: 21181715 DOI: 10.1002/jemt.20878] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Dehydroergosterol (DHE) is an intrinsically fluorescent sterol with absorption/emission in the ultraviolet (UV) region and biophysical properties similar to those of cholesterol. We compared the potential of UV-sensitive low-light-level wide-field (UV-WF) imaging with that of multiphoton (MP) excitation microscopy to monitor DHE in living cells. Significantly reduced photobleaching in MP microscopy of DHE enabled us to acquire three-dimensional z-stacks of DHE-stained cells and to obtain high-resolution maps of DHE in surface ruffles, nanotubes, and the apical membrane of epithelial cells. We found that the lateral resolution of MP microscopy is ∼1.5-fold higher than that of UV-WF deconvolution microscopy, allowing for improved spatiotemporal analysis of plasma membrane sterol distribution. Surface intensity patterns of DHE with a diameter of 0.2 μm persisting over several minutes could be resolved by MP time-lapse microscopy. Diffusion coefficients of 0.25-μm-diameter endocytic vesicles containing DHE were determined by MP spatiotemporal image correlation spectroscopy. The requirement of extremely high laser power for visualization of DHE by MP microscopy made this method less potent for multicolor applications with organelle markers like green fluorescent protein-tagged proteins. The signal-to-noise ratio obtainable by UV-WF imaging could be significantly improved by pixelwise bleach rate fitting and calculation of an amplitude image from the decay model and by frame averaging after pixelwise bleaching correction of the image stacks. We conclude that UV-WF imaging and MP microscopy of DHE provide complementary information regarding membrane distribution and intracellular targeting of sterols.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark.
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3
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Wojtal KA, Diskar M, Herberg FW, Hoekstra D, van Ijzendoorn SCD. Regulatory subunit I-controlled protein kinase A activity is required for apical bile canalicular lumen development in hepatocytes. J Biol Chem 2009; 284:20773-80. [PMID: 19465483 DOI: 10.1074/jbc.m109.013599] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Signaling via cAMP plays an important role in apical cell surface dynamics in epithelial cells. In hepatocytes, elevated levels of cAMP as well as extracellular oncostatin M stimulate apical lumen development in a manner that depends on protein kinase A (PKA) activity. However, neither the identity of PKA isoforms involved nor the mechanisms of the cross-talk between oncostatin M and cAMP/PKA signaling pathways have been elucidated. Here we demonstrate that oncostatin M and PKA signaling converge at the level of the PKA holoenzyme downstream of oncostatin M-stimulated MAPK activation. Experiments were performed with chemically modified cAMP analogues that preferentially target regulatory subunit (R) I or RII holoenzymes, respectively, in hepatocytes. The data suggest that the dissociation of RI- but not RII-containing holoenzymes, as well as catalytic activity of PKA, is required for apical lumen development in response to elevated levels of cAMP and oncostatin M. However, oncostatin M signaling does not stimulate PKA holoenzyme dissociation in living cells. Based on pharmacological and cell biological studies, it is concluded that RI-controlled PKA activity is essential for cAMP- and oncostatin M-stimulated development of apical bile canalicular lumens.
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Affiliation(s)
- Kacper A Wojtal
- Department of Cell Biology, Section of Membrane Cell Biology, University Medical Center Groningen, University of Groningen, Groningen 9713AV, The Netherlands
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4
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Westerlund B, Slotte JP. How the molecular features of glycosphingolipids affect domain formation in fluid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:194-201. [DOI: 10.1016/j.bbamem.2008.11.010] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Revised: 10/28/2008] [Accepted: 11/12/2008] [Indexed: 12/11/2022]
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5
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Cholesterol regulation of rab-mediated sphingolipid endocytosis. Glycoconj J 2008; 26:705-10. [PMID: 18841464 DOI: 10.1007/s10719-008-9191-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 09/05/2008] [Accepted: 09/08/2008] [Indexed: 12/21/2022]
Abstract
Despite a tight regulation of its intracellular content, cholesterol is found accumulated in pathological conditions such as sphingolipidosis as well as after cell treatment with drugs like hydrophobic amines. Furthermore, cellular cholesterol increases when cultured cells approach confluence. Under these conditions, the endocytic pathways of plasma membrane sphingolipids are differently affected. In this short review, we will summarize recent results from our laboratory as well as those of other groups, indicating that the intracellular accumulation of cholesterol inhibits the dissociation of rab GTPases from the target membranes, causing the alteration of rab-mediated membrane traffic.
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Moore ER, Fischer ER, Mead DJ, Hackstadt T. The chlamydial inclusion preferentially intercepts basolaterally directed sphingomyelin-containing exocytic vacuoles. Traffic 2008; 9:2130-40. [PMID: 18778406 DOI: 10.1111/j.1600-0854.2008.00828.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Chlamydiae replicate intracellularly within a unique vacuole termed the inclusion. The inclusion circumvents classical endosomal/lysosomal pathways but actively intercepts a subset of Golgi-derived exocytic vesicles containing sphingomyelin (SM) and cholesterol. To further examine this interaction, we developed a polarized epithelial cell model to study vectoral trafficking of lipids and proteins to the inclusion. We examined seven epithelial cell lines for their ability to form single monolayers of polarized cells and support chlamydial development. Of these cell lines, polarized colonic mucosal C2BBe1 cells were readily infected with Chlamydia trachomatis and remained polarized throughout infection. Trafficking of (6-((N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl) amino)hexanoyl)sphingosine) (NBD-C(6)-ceramide) and its metabolic derivatives, NBD-glucosylceramide (GlcCer) and NBD-SM, was analyzed. SM was retained within L2-infected cells relative to mock-infected cells, correlating with a disruption of basolateral SM trafficking. There was no net retention of GlcCer within L2-infected cells and purification of C. trachomatis elementary bodies from polarized C2BBe1 cells confirmed that bacteria retained only SM. The chlamydial inclusion thus appears to preferentially intercept basolaterally-directed SM-containing exocytic vesicles, suggesting a divergence in SM and GlcCer trafficking. The observed changes in lipid trafficking were a chlamydia-specific effect because Coxiella burnetii-infected cells revealed no changes in GlcCer or SM polarized trafficking.
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Affiliation(s)
- Elizabeth R Moore
- Host-Parasite Interactions Section, Laboratory of Intracellular Parasites, National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratories, 903 South 4th Street, Hamilton, Montana 59840, USA
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7
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Abstract
Viruses exploit signaling pathways to their advantage during multiple stages of their life cycle. We demonstrate a role for protein kinase A (PKA) in the hepatitis C virus (HCV) life cycle. The inhibition of PKA with H89, cyclic AMP (cAMP) antagonists, or the protein kinase inhibitor peptide reduced HCV entry into Huh-7.5 hepatoma cells. Bioluminescence resonance energy transfer methodology allowed us to investigate the PKA isoform specificity of the cAMP antagonists in Huh-7.5 cells, suggesting a role for PKA type II in HCV internalization. Since viral entry is dependent on the host cell expression of CD81, scavenger receptor BI, and claudin-1 (CLDN1), we studied the role of PKA in regulating viral receptor localization by confocal imaging and fluorescence resonance energy transfer (FRET) analysis. Inhibiting PKA activity in Huh-7.5 cells induced a reorganization of CLDN1 from the plasma membrane to an intracellular vesicular location(s) and disrupted FRET between CLDN1 and CD81, demonstrating the importance of CLDN1 expression at the plasma membrane for viral receptor activity. Inhibiting PKA activity in Huh-7.5 cells reduced the infectivity of extracellular virus without modulating the level of cell-free HCV RNA, suggesting that particle secretion was not affected but that specific infectivity was reduced. Viral particles released from H89-treated cells displayed the same range of buoyant densities as did those from control cells, suggesting that viral protein association with lipoproteins is not regulated by PKA. HCV infection of Huh-7.5 cells increased cAMP levels and phosphorylated PKA substrates, supporting a model where infection activates PKA in a cAMP-dependent manner to promote virus release and transmission.
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Petersen NH, Faergeman NJ, Faegeman NJ, Yu L, Wüstner D. Kinetic imaging of NPC1L1 and sterol trafficking between plasma membrane and recycling endosomes in hepatoma cells. J Lipid Res 2008; 49:2023-37. [PMID: 18523240 DOI: 10.1194/jlr.m800145-jlr200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Niemann-Pick C1-like 1 (NPC1L1) is a recently identified protein that mediates intestinal cholesterol absorption and regulates biliary cholesterol excretion. The itineraries and kinetics of NPC1L1 trafficking remain uncertain. In this study, we have visualized movement of NPC1L1-enhanced green fluorescent protein (NPC1L1-EGFP) and cholesterol analogs in hepatoma cells. At steady state, about 42% of NPC1L1 resided in the transferrin (Tf)-positive, sterol-enriched endocytic recycling compartment (ERC), whereas time-lapse microscopy demonstrated NPC1L1 traffic between the plasma membrane and the ERC. Fluorescence recovery after photobleaching revealed rapid recovery (half-time approximately 2.5 min) of about 35% of NPC1L1 in the ERC, probably replenished from peripheral sorting endosomes. Acute cholesterol depletion blocked internalization of NPC1L1-EGFP and Tf and stimulated recycling of NPC1L1-EGFP from the ERC to the plasma membrane. NPC1L1-EGFP facilitated transport of fluorescent sterols from the plasma membrane to the ERC. Insulin induced translocation of vesicles containing NPC1L1 and fluorescent sterol from the ERC to the cell membrane. Upon polarization of hepatoma cells, NPC1L1 resided almost exclusively in the canalicular membrane, where the protein is highly mobile. Our study demonstrates dynamic trafficking of NPC1L1 between the cell surface and intracellular compartments and suggests that this transport is involved in NPC1L1-mediated cellular sterol uptake.
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Affiliation(s)
- Nicole Hartwig Petersen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, Odense M, Denmark
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9
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Wojtal KA, Hoekstra D, van Ijzendoorn SCD. cAMP-dependent protein kinase A and the dynamics of epithelial cell surface domains: moving membranes to keep in shape. Bioessays 2008; 30:146-55. [PMID: 18200529 DOI: 10.1002/bies.20705] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cyclic adenosine monophosphate (cAMP) and cAMP-dependent protein kinase A (PKA) are evolutionary conserved molecules with a well-established position in the complex network of signal transduction pathways. cAMP/PKA-mediated signaling pathways are implicated in many biological processes that cooperate in organ development including the motility, survival, proliferation and differentiation of epithelial cells. Cell surface polarity, here defined as the anisotropic organisation of cellular membranes, is a critical parameter for most of these processes. Changes in the activity of cAMP/PKA elicit a variety of effects on intracellular membrane dynamics, including membrane sorting and trafficking. One of the most intriguing aspects of cAMP/PKA signaling is its evolutionary conserved abundance on the one hand and its precise spatial-temporal actions on the other. Here, we review recent developments with regard to the role of cAMP/PKA in the regulation of intracellular membrane trafficking in relation to the dynamics of epithelial surface domains.
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Affiliation(s)
- Kacper A Wojtal
- Division of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland
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10
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Wojtal KA, Hoekstra D, van IJzendoorn SC. Anchoring of protein kinase A-regulatory subunit IIalpha to subapically positioned centrosomes mediates apical bile canalicular lumen development in response to oncostatin M but not cAMP. Mol Biol Cell 2007; 18:2745-54. [PMID: 17494870 PMCID: PMC1924835 DOI: 10.1091/mbc.e06-08-0732] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Oncostatin M and cAMP signaling stimulate apical surface-directed membrane trafficking and apical lumen development in hepatocytes, both in a protein kinase A (PKA)-dependent manner. Here, we show that oncostatin M, but not cAMP, promotes the A-kinase anchoring protein (AKAP)-dependent anchoring of the PKA regulatory subunit (R)IIalpha to subapical centrosomes and that this requires extracellular signal-regulated kinase 2 activation. Stable expression of the RII-displacing peptide AKAP-IS, but not a scrambled peptide, inhibits the association of RIIalpha with centrosomal AKAPs and results in the repositioning of the centrosome from a subapical to a perinuclear location. Concomitantly, common endosomes, but not apical recycling endosomes, are repositioned from a subapical to a perinuclear location, without significant effects on constitutive or oncostatin M-stimulated basolateral-to-apical transcytosis. Importantly, however, the expression of the AKAP-IS peptide completely blocks oncostatin M-, but not cAMP-stimulated apical lumen development. Together, the data suggest that centrosomal anchoring of RIIalpha and the interrelated subapical positioning of these centrosomes is required for oncostatin M-, but not cAMP-mediated, bile canalicular lumen development in a manner that is uncoupled from oncostatin M-stimulated apical lumen-directed membrane trafficking. The results also imply that multiple PKA-mediated signaling pathways control apical lumen development and that subapical centrosome positioning is important in some of these pathways.
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Affiliation(s)
- Kacper A. Wojtal
- Department of Cell Biology/Membrane Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Dick Hoekstra
- Department of Cell Biology/Membrane Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Sven C.D. van IJzendoorn
- Department of Cell Biology/Membrane Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
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11
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Wojtal KA, de Vries E, Hoekstra D, van IJzendoorn SC. Efficient trafficking of MDR1/P-glycoprotein to apical canalicular plasma membranes in HepG2 cells requires PKA-RIIalpha anchoring and glucosylceramide. Mol Biol Cell 2006; 17:3638-50. [PMID: 16723498 PMCID: PMC1525225 DOI: 10.1091/mbc.e06-03-0230] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
In hepatocytes, cAMP/PKA activity stimulates the exocytic insertion of apical proteins and lipids and the biogenesis of bile canalicular plasma membranes. Here, we show that the displacement of PKA-RIIalpha from the Golgi apparatus severely delays the trafficking of the bile canalicular protein MDR1 (P-glycoprotein), but not that of MRP2 (cMOAT), DPP IV and 5'NT, to newly formed apical surfaces. In addition, the direct trafficking of de novo synthesized glycosphingolipid analogues from the Golgi apparatus to the apical surface is inhibited. Instead, newly synthesized glucosylceramide analogues are rerouted to the basolateral surface via a vesicular pathway, from where they are subsequently endocytosed and delivered to the apical surface via transcytosis. Treatment of HepG2 cells with the glucosylceramide synthase inhibitor PDMP delays the appearance of MDR1, but not MRP2, DPP IV, and 5'NT at newly formed apical surfaces, implicating glucosylceramide synthesis as an important parameter for the efficient Golgi-to-apical surface transport of MDR1. Neither PKA-RIIalpha displacement nor PDMP inhibited (cAMP-stimulated) apical plasma membrane biogenesis per se, suggesting that other cAMP effectors may play a role in canalicular development. Taken together, our data implicate the involvement of PKA-RIIalpha anchoring in the efficient direct apical targeting of distinct proteins and glycosphingolipids to newly formed apical plasma membrane domains and suggest that rerouting of Golgi-derived glycosphingolipids may underlie the delayed Golgi-to-apical surface transport of MDR1.
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Affiliation(s)
- Kacper A. Wojtal
- Section of Membrane Cell Biology, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Erik de Vries
- Section of Membrane Cell Biology, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Dick Hoekstra
- Section of Membrane Cell Biology, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Sven C.D. van IJzendoorn
- Section of Membrane Cell Biology, Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 AV Groningen, The Netherlands
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12
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Wüstner D. Improved visualization and quantitative analysis of fluorescent membrane sterol in polarized hepatic cells. J Microsc 2005; 220:47-64. [PMID: 16269063 DOI: 10.1111/j.1365-2818.2005.01516.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Dehydroergosterol is a natural yeast sterol which has recently been employed for direct observation of intracellular sterol transport by UV microscopy. Here, methods are described for improved visualization and quantification of dehydroergosterol in the membranes of polarized HepG2 cells. Using a new online assay, it is shown that dehydroergosterol derived from a cyclodextrin complex inserted into the plasma membrane with a half time of t(1/2) approximately 34 s. Based on a detailed bleaching analysis of dehydroergosterol, slightly different bleaching rates for dehydroergosterol in the basolateral and canalicular membrane were found, indicating different fluorophore environments. Bleaching correction in concert with 3D imaging allows for detection of dehydroergosterol enrichment in microvilli of the canalicular membrane forming the biliary canaliculus. Evidence is provided that some dehydroergosterol accumulating in a subapical compartment or apical recycling compartment can rapidly (t(1/2) approximately 2 min) exchange in vesicles towards the biliary canaliculus while the majority of dehydroergosterol does not redistribute from this compartment. The rapidly exchanging pool resembles only a small portion of the total subapical compartment or apical recycling compartment-associated dehydroergosterol (about 15-30%). Kinetic modelling supports the theory that the subapical compartment or apical recycling compartment to biliary canaliculus transport pathway for sterol is unidirectional. This pathway might be important for rapid biliary transport of free sterol produced by hydrolysis of cholesteryl esters derived from high density lipoprotein.
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Affiliation(s)
- D Wüstner
- Theoretical Biophysics Group, Max-Delbrück Center for Molecular Medicine, Berlin, Germany.
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13
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Hoekstra D, Tyteca D, van IJzendoorn SCD. The subapical compartment: a traffic center in membrane polarity development. J Cell Sci 2005; 117:2183-92. [PMID: 15126620 DOI: 10.1242/jcs.01217] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Spatially separated apical and basolateral plasma membrane domains that have distinct functions and molecular compositions are a characteristic feature of epithelial cell polarity. The subapical compartment (SAC), also known as the common endosome (CE), where endocytic pathways from both surfaces merge, plays a crucial role in the maintenance and probably the biogenesis of these distinct membrane domains. Although differences in morphology are apparent, the same principal features of a SAC can be distinguished in different types of epithelial cells. As polarity develops, the compartment acquires several distinct machineries that, in conjunction with the cytoskeleton, are necessary for polarized trafficking. Disrupting trafficking via the SAC and hence bypassing its sorting machinery, as occurs upon actin depolymerization, leads to mis-sorting of apical and basolateral molecules, thereby compromising the development of polarity. The structural and functional integrity of the compartment in part depends on microtubules. Moreover, the acquisition of a particular set of Rab proteins, including Rab11 and Rab3, appears to be crucial in regulating molecular sorting and vesicular transport relevant both to recycling to either plasma membrane domain and to de novo assembly of the apical domain. Furthermore, subcompartmentalization of the SAC appears to be key to its various functions.
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Affiliation(s)
- Dick Hoekstra
- Department of Membrane Cell Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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14
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Van IJzendoorn SCD, Théard D, Van Der Wouden JM, Visser W, Wojtal KA, Hoekstra D. Oncostatin M-stimulated apical plasma membrane biogenesis requires p27(Kip1)-regulated cell cycle dynamics. Mol Biol Cell 2004; 15:4105-14. [PMID: 15240818 PMCID: PMC515344 DOI: 10.1091/mbc.e04-03-0201] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2004] [Revised: 06/17/2004] [Accepted: 06/24/2004] [Indexed: 11/11/2022] Open
Abstract
Oncostatin M regulates membrane traffic and stimulates apicalization of the cell surface in hepatoma cells in a protein kinase A-dependent manner. Here, we show that oncostatin M enhances the expression of the cyclin-dependent kinase (cdk)2 inhibitor p27(Kip1), which inhibits G(1)-S phase progression. Forced G(1)-S-phase transition effectively renders presynchronized cells insensitive to the apicalization-stimulating effect of oncostatin M. G(1)-S-phase transition prevents oncostatin M-mediated recruitment of protein kinase A to the centrosomal region and precludes the oncostatin M-mediated activation of a protein kinase A-dependent transport route to the apical surface, which exits the subapical compartment (SAC). This transport route has previously been shown to be crucial for apical plasma membrane biogenesis. Together, our data indicate that oncostatin M-stimulated apicalization of the cell surface is critically dependent on the ability of oncostatin M to control p27(Kip1)/cdk2-mediated G(1)-S-phase progression and suggest that the regulation of apical plasma membrane-directed traffic from SAC is coupled to centrosome-associated signaling pathways.
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Affiliation(s)
- Sven C D Van IJzendoorn
- Department of Membrane Cell Biology, University of Groningen, 9713 AV, Groningen, The Netherlands.
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15
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Van IJzendoorn SCD, Van Der Wouden JM, Liebisch G, Schmitz G, Hoekstra D. Polarized membrane traffic and cell polarity development is dependent on dihydroceramide synthase-regulated sphinganine turnover. Mol Biol Cell 2004; 15:4115-24. [PMID: 15229289 PMCID: PMC515345 DOI: 10.1091/mbc.e04-04-0290] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2004] [Revised: 06/09/2004] [Accepted: 06/17/2004] [Indexed: 01/22/2023] Open
Abstract
Sphingoid bases have been implicated in various cellular processes including cell growth, apoptosis and cell differentiation. Here, we show that the regulated turnover of sphingoid bases is crucial for cell polarity development, i.e., the biogenesis of apical plasma membrane domains, in well-differentiated hepatic cells. Thus, inhibition of dihydroceramide synthase or sphinganine kinase activity with fumonisin B1 or N,N-dimethylsphingosine, respectively, dramatically perturbs cell polarity development, which is due to increased levels of sphinganine. Consistently, reduction of free sphinganine levels stimulates cell polarity development. Moreover, dihydroceramide synthase, the predominant enzyme responsible for sphinganine turnover, is a target for cell polarity stimulating cAMP/protein kinase A (PKA) signaling cascades. Indeed, electrospray ionization tandem mass spectrometry analyses revealed a significant reduction in sphinganine levels in cAMP/PKA-stimulated cells. These data suggest that sphinganine turnover is critical for and is actively regulated during HepG2 cell polarity development. Previously, we have identified an apical plasma membrane-directed trafficking pathway from the subapical compartment. This transport pathway, which is part of the basolateral-to-apical transcytotic itinerary, plays a crucial role in apical plasma membrane biogenesis. Here, we show that, as a part of the underlying mechanism, the inhibition of dihydroceramide synthase activity and ensuing increased sphinganine levels specifically perturb the activation of this particular pathway in the de novo apical membrane biogenesis.
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Affiliation(s)
- Sven C D Van IJzendoorn
- Department of Cell Biology/Section Membrane Cell Biology, University of Groningen, 9713-AV Groningen, The Netherlands.
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16
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van der Wouden JM, Maier O, van IJzendoorn SCD, Hoekstra D. Membrane dynamics and the regulation of epithelial cell polarity. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 226:127-64. [PMID: 12921237 DOI: 10.1016/s0074-7696(03)01003-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Plasma membranes of epithelial cells consist of two domains, an apical and a basolateral domain, the surfaces of which differ in composition. The separation of these domains by a tight junction and the fact that specific transport pathways exist for intracellular communication between these domains and distinct intracellular compartments relevant to cell polarity development, have triggered extensive research on issues that focus on how the polarity is generated and maintained. Apart from proper assembly of tight junctions, their potential functioning as landmark for the transport machinery, cell-cell adhesion is obviously instrumental in barrier formation. In recent years, distinct endocytic compartments, defined as subapical compartment or common endosome, were shown to play a prominent role in regulating membrane trafficking to and from polarized membrane domains. Sorting devices remain to be determined but likely include distinct rab proteins, and evidence is accumulating to indicate that signaling events may direct intracellular membrane transport, intimately involved in the biogenesis and maintenance of polarized membrane domains and hence the development of cell polarity.
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Affiliation(s)
- Johanna M van der Wouden
- Department of Membrane Cell Biology, University of Groningen, Antonius Deusinglaan 1, 9713AV Groningen, The Netherlands
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17
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Wüstner D, Mondal M, Huang A, Maxfield FR. Different transport routes for high density lipoprotein and its associated free sterol in polarized hepatic cells. J Lipid Res 2003; 45:427-37. [PMID: 14679167 DOI: 10.1194/jlr.m300440-jlr200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
We analyzed the intracellular transport of HDL and its associated free sterol in polarized human hepatoma HepG2 cells. Using pulse-chase protocols, we demonstrated that HDL labeled with Alexa 488 at the apolipoprotein (Alexa 488-HDL) was internalized by a scavenger receptor class B type I (SR-BI)-dependent process at the basolateral membrane and became enriched in a subapical/apical recycling compartment. Most Alexa 488-HDL was rapidly recycled to the basolateral cell surface and released from cells. Within 30 min of chase at 37 degrees C, approximately 3% of the initial cell-associated Alexa 488-HDL accumulated in the biliary canaliculus (BC) formed at the apical pole of polarized HepG2 cells. Even less Alexa 488-HDL was transported to late endosomes or lysosomes. The fluorescent cholesterol analog dehydroergosterol (DHE) incorporated into Alexa 488-HDL was delivered to the BC within a few minutes, independent of the labeled apolipoprotein. This transport did not require metabolic energy and could be blocked by antibodies against SR-BI. The fraction of cell-associated DHE transported to the BC was comparable when cells were incubated with either Alexa 488-HDL containing DHE or with DHE bound to methyl-beta-cyclodextrin. We conclude that rapid, nonvesicular transport of sterol to the BC and efficient recycling of HDL particles underlies the selective sorting of sterol from HDLs in hepatocytes.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA
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18
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Wong W, Schlichter LC. Differential recruitment of Kv1.4 and Kv4.2 to lipid rafts by PSD-95. J Biol Chem 2003; 279:444-52. [PMID: 14559911 DOI: 10.1074/jbc.m304675200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activity of voltage-gated potassium (Kv) channels, and consequently their influence on cellular functions, can be substantially altered by phosphorylation. Several protein kinases that modulate Kv channel activity are found in membrane subdomains known as lipid rafts, which are thought to organize signaling complexes in the cell. Thus, we asked whether Kv1.4 and Kv4.2, two channels with critical roles in excitable cells, are found in lipid rafts. Acylation can target proteins to raft regions; however, Kv channels are not acylated, and therefore, a different mechanism must exist to bring them into these membrane subdomains. Because both Kv1.4 and Kv4.2 interact with postsynaptic density protein 95 (PSD-95), which is acylated (specifically, palmitoylated), we examined whether PSD-95 can recruit these channels to lipid rafts. We found that a portion of Kv1.4 and Kv4.2 protein in rat brain membranes is raft-associated. Lipid raft patching and immunostaining confirmed that some Kv4.2 is in Thy-1-containing rafts in rat hippocampal neurons. Using a heterologous expression system, we determined that palmitoylation of PSD-95 was crucial to its localization to lipid rafts. We then assessed the contribution of PSD-95 to the raft association of these channels. Co-expression of PSD-95 increased the amount of Kv1.4, but not Kv4.2, in lipid rafts. Deleting the PSD-95 binding motif of Kv1.4 eliminated this recruitment, as did substituting a palmitoylation-deficient PSD-95 mutant. This work represents the first evidence that PSD-95 binding can recruit Kv channels into lipid rafts, a process that could facilitate interactions with the protein kinases that affect channel activity.
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Affiliation(s)
- Wei Wong
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada
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19
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Abstract
Transcytosis, the vesicular transport of macromolecules from one side of a cell to the other, is a strategy used by multicellular organisms to selectively move material between two environments without altering the unique compositions of those environments. In this review, we summarize our knowledge of the different cell types using transcytosis in vivo, the variety of cargo moved, and the diverse pathways for delivering that cargo. We evaluate in vitro models that are currently being used to study transcytosis. Caveolae-mediated transcytosis by endothelial cells that line the microvasculature and carry circulating plasma proteins to the interstitium is explained in more detail, as is clathrin-mediated transcytosis of IgA by epithelial cells of the digestive tract. The molecular basis of vesicle traffic is discussed, with emphasis on the gaps and uncertainties in our understanding of the molecules and mechanisms that regulate transcytosis. In our view there is still much to be learned about this fundamental process.
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Affiliation(s)
- Pamela L Tuma
- Hunterian 119, Department of Cell Biology, 725 N Wolfe St, Baltimore, MD 21205, USA
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20
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Hoekstra D, Maier O, van der Wouden JM, Slimane TA, van IJzendoorn SCD. Membrane dynamics and cell polarity: the role of sphingolipids. J Lipid Res 2003; 44:869-77. [PMID: 12639977 DOI: 10.1194/jlr.r300003-jlr200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In recent years, glycosphingolipids (GSLs) have attracted widespread attention due to the appreciation that this class of lipids has a major impact on biological life. Inhibition of the synthesis of glucosylceramide, which serves as a precursor for the generation of complex glycosphinglipids, is embryonic lethal. GSLs play a major role in growth and development. Metabolites of sphingolipids, such as ceramide, sphinganine, and sphingosine, may function as second messengers or regulators of signal transduction that affect events ranging from apoptosis to the (co)regulation of the cell cycle. In addition, GSLs can provide a molecular platform for clustering of signal transducers. The ability of sphingolipids, with or without cholesterol, to form microdomains or rafts is critical in sorting and membrane transport that underlies the biogenesis of polarized membrane domains. Here, a brief summary is presented of some recent developments in this field, with a particular emphasis on raft assembly and membrane transport in the establishment of membrane polarity.
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Affiliation(s)
- Dick Hoekstra
- University of Groningen, Department of Membrane Cell Biology, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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21
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Slimane TA, Trugnan G, Van IJzendoorn SCD, Hoekstra D. Raft-mediated trafficking of apical resident proteins occurs in both direct and transcytotic pathways in polarized hepatic cells: role of distinct lipid microdomains. Mol Biol Cell 2003; 14:611-24. [PMID: 12589058 PMCID: PMC149996 DOI: 10.1091/mbc.e02-08-0528] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2002] [Revised: 10/04/2002] [Accepted: 10/25/2002] [Indexed: 11/11/2022] Open
Abstract
In polarized hepatic cells, pathways and molecular principles mediating the flow of resident apical bile canalicular proteins have not yet been resolved. Herein, we have investigated apical trafficking of a glycosylphosphatidylinositol-linked and two single transmembrane domain proteins on the one hand, and two polytopic proteins on the other in polarized HepG2 cells. We demonstrate that the former arrive at the bile canalicular membrane via the indirect transcytotic pathway, whereas the polytopic proteins reach the apical membrane directly, after Golgi exit. Most importantly, cholesterol-based lipid microdomains ("rafts") are operating in either pathway, and protein sorting into such domains occurs in the biosynthetic pathway, largely in the Golgi. Interestingly, rafts involved in the direct pathway are Lubrol WX insoluble but Triton X-100 soluble, whereas rafts in the indirect pathway are both Lubrol WX and Triton X-100 insoluble. Moreover, whereas cholesterol depletion alters raft-detergent insolubility in the indirect pathway without affecting apical sorting, protein missorting occurs in the direct pathway without affecting raft insolubility. The data implicate cholesterol as a traffic direction-determining parameter in the direct apical pathway. Furthermore, raft-cargo likely distinguishing single vs. multispanning membrane anchors, rather than rafts per se (co)determine the sorting pathway.
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Affiliation(s)
- Tounsia Aït Slimane
- Department of Membrane Cell Biology, University of Groningen, The Netherlands
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22
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Maier O, Hoekstra D. Trans-Golgi network and subapical compartment of HepG2 cells display different properties in sorting and exiting of sphingolipids. J Biol Chem 2003; 278:164-73. [PMID: 12407103 DOI: 10.1074/jbc.m208259200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In HepG2 cells, the subapical compartment (SAC) is involved in the biogenesis of membrane polarity. By contrast, direct apical transport originating from the trans-Golgi network (TGN), which may contribute to polarity establishment, has been poorly defined in these cells. Thus, although newly synthesized sphingolipids can be directly transported from the TGN to the apical membrane, numerous apical resident proteins are traveling via the transcytotic route. Here, we developed an in vitro transport assay and compared the molecular sorting of 6-[N-(7-nitrobenz-2-oxa-1,3 diazol-4-yl)amino] hexanoyl-sphingomyelin (C(6)NBD-SM) and C(6)NBD-glucosylceramide (C(6)NBD-GlcCer) in TGN and SAC. SM is released from both TGN and SAC in the lumenal leaflet of transport vesicles. This holds also for GlcCer released from the SAC but not for a substantial fraction that departed from the Golgi. Distinct transport vesicles, enriched in either SM or GlcCer are released from SAC, consistent with their rigid sorting in this compartment. Different vesicle populations could not be recovered from TGN, although in situ experiments reveal that GlcCer is preferentially transported to the apical membrane, reflecting different transport mechanisms. The results indicate that in HepG2 cells sphingolipids are mainly sorted in the SAC membrane and that the release of SM from SAC and TGN is differentially regulated.
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Affiliation(s)
- Olaf Maier
- Department of Membrane Cell Biology, Faculty of Medical Sciences, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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23
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van Ijzendoorn SCD, Mostov KE, Hoekstra D. Role of Rab Proteins in Epithelial Membrane Traffic. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 232:59-88. [PMID: 14711116 DOI: 10.1016/s0074-7696(03)32002-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Small GTPase rab proteins play an important role in various aspects of membrane traffic, including cargo selection, vesicle budding, vesicle motility, tethering, docking, and fusion. Recent data suggest also that rabs, and their divalent effector proteins, organize organelle subdomains and as such may define functional organelle identity. Most rabs are ubiquitously expressed. However, some rabs are preferentially expressed in epithelial cells where they appear intimately associated with the epithelial-specific transcytotic pathway and/or tight junctions. This review discusses the role of rabs in epithelial membrane transport.
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Affiliation(s)
- Sven C D van Ijzendoorn
- Department of Membrane Cell Biology, University of Groningen, Groningen 9713AV, The Netherlands
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24
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van der Wouden JM, van IJzendoorn SC, Hoekstra D. Oncostatin M regulates membrane traffic and stimulates bile canalicular membrane biogenesis in HepG2 cells. EMBO J 2002; 21:6409-18. [PMID: 12456648 PMCID: PMC136933 DOI: 10.1093/emboj/cdf629] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Hepatocytes are the major epithelial cells of the liver and they display membrane polarity: the sinusoidal membrane representing the basolateral surface, while the bile canalicular membrane is typical of the apical membrane. In polarized HepG2 cells an endosomal organelle, SAC, fulfills a prominent role in the biogenesis of the canalicular membrane, reflected by its ability to sort and redistribute apical and basolateral sphingolipids. Here we show that SAC appears to be a crucial target for a cytokine-induced signal transduction pathway, which stimulates membrane transport exiting from this compartment promoting apical membrane biogenesis. Thus, oncostatin M, an IL-6-type cytokine, stimulates membrane polarity development in HepG2 cells via the gp130 receptor unit, which activates a protein kinase A-dependent and sphingomyelin-marked membrane transport pathway from SAC to the apical membrane. To exert its signal transducing function, gp130 is recruited into detergent-resistant membrane microdomains at the basolateral membrane. These data provide a clue for a molecular mechanism that couples the biogenesis of an apical plasma membrane domain to the regulation of intracellular transport in response to an extracellular, basolaterally localized stimulus.
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Affiliation(s)
| | | | - Dick Hoekstra
- Department of Membrane Cell Biology, University of Groningen, Antonius Deusinglaan 1, 9713AV Groningen, The Netherlands
Corresponding author e-mail:
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25
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Abstract
Sphingolipids represent a minor, but highly dynamic subclass of lipids in all eukaryotic cells. They are involved in functions that range from structural protection to signal transduction and protein sorting, and participate in lipid raft assembly. In polarized epithelial cells, which display an asymmetric apical and basolateral membrane surface, rafts have been proposed as a sorting principle for apical resident proteins, following their biosynthesis. However, raft-mediated trafficking is ubiquitous in cells. Also, sphingolipids per se, which are strongly enriched in the apical domain, are subject to sorting in polarity development. Next to the trans Golgi network, a subapical compartment called SAC or common endosome appears instrumental in regulating these sorting events.
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Affiliation(s)
- Tounsia Aït Slimane
- University of Groningen, Department of Membrane Cell Biology, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands
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26
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Wüstner D, Herrmann A, Hao M, Maxfield FR. Rapid nonvesicular transport of sterol between the plasma membrane domains of polarized hepatic cells. J Biol Chem 2002; 277:30325-36. [PMID: 12050151 DOI: 10.1074/jbc.m202626200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We studied the transport of the fluorescent cholesterol analog dehydroergosterol (DHE) in polarized HepG2 human hepatoma cells. DHE delivered via methyl-beta-cyclodextrin was delivered to both the apical and basolateral membranes and became concentrated in the apical membrane within 1 min. Intracellular DHE was targeted mainly to vesicles of the subapical compartment or apical recycling compartment (SAC/ARC), where it colocalized with fluorescent transferrin and fluorescent analogs of phosphatidylcholine and sphingomyelin. In contrast, transport of DHE from the plasma membrane to the trans-Golgi network was found to be very low. Vesicles containing DHE traversed the cells in both directions, but vesicular export of DHE from the SAC/ARC to the plasma membrane domains was low. Disruption of the microtubule cytoskeleton disturbed vesicular transport of DHE but not its enrichment in the apical (canalicular) membrane. Transport of DHE to the canalicular membrane after photobleaching was very rapid (t(12) = 1.6 min) and was largely ATP-independent in contrast to enrichment of DHE in the SAC/ARC. Release of DHE from the canalicular membrane was also ATP-independent but slower than the enrichment of sterol in the biliary canaliculus (t(12) = 5.4 min). Canalicular DHE could completely redistribute to the basolateral plasma membrane but could not transfer from one cell to the other cell of an HepG2 couplet. We conclude that sterol shuttles rapidly among the plasma membrane domains and other membrane organelles and that this nonvesicular pathway includes fast transbilayer migration.
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Affiliation(s)
- Daniel Wüstner
- Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10021, USA
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27
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Wüstner D, Herrmann A, Hao M, Maxfield FR. Rapid Nonvesicular Transport of Sterol between the Plasma Membrane Domains of Polarized Hepatic Cells. J Biol Chem 2002. [DOI: 10.1016/s0021-9258(18)75705-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Affiliation(s)
- Gerrit van Meer
- Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, P. O. Box 22700, 1100 DE Amsterdam, The Netherlands.
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29
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Maier O, Oberle V, Hoekstra D. Fluorescent lipid probes: some properties and applications (a review). Chem Phys Lipids 2002; 116:3-18. [PMID: 12093532 DOI: 10.1016/s0009-3084(02)00017-8] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Odd as it may seem, experimental challenges in lipid research are often hampered by the simplicity of the lipid structure. Since, as in protein research, mutants or overexpression of lipids are not realistic, a considerable amount of lipid research relies on the use of tagged lipid analogues. However, given the size of an average lipid molecule, special care is needed for the selection of probes, since if the size and intramolecular localization of the probe is not specifically taken into account, it may dramatically affect the properties of the lipids. The latter is particularly important in cell biological studies of lipid trafficking and sorting, where the probed lipid should resemble its natural counterpart as closely as possible. On the other hand, for biophysical applications, these considerations may be less critical. Here we provide a brief overview of the application of several lipid probes in cell biological and biophysical research, and critically analyze their validity in the various fields.
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Affiliation(s)
- Olaf Maier
- Department of Membrane Cell Biology, Faculty of Medical Sciences, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
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30
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Masserini M, Ravasi D. Role of sphingolipids in the biogenesis of membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1532:149-61. [PMID: 11470236 DOI: 10.1016/s1388-1981(01)00128-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In recent years, a huge interest in sphingolipid- and cholesterol-enriched membrane domains has risen, after their involvement in fundamental membrane-associated events such as signal transmission, cell adhesion and lipid/protein sorting was postulated. Theoretical considerations and several experimental data suggest that sphingolipids play an important role in the biogenesis and function of domains. In fact, their physicochemical features, different from those of other membrane lipids, allow their interaction either with other sphingolipids or with other membrane components and external ligands. Owing to these features, sphingolipids may undergo segregation and represent a nucleation point for co-clustering with other lipids and proteins in a complex, functional domain. Moreover, sphingolipids confer dynamic properties on domains, a fundamental feature for the modulation of their postulated functions.
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Affiliation(s)
- M Masserini
- Department of Experimental, Environmental Medicine and Biotechnology, University of Milan-Bicocca, Via Cadore 48, 20052 Monza, Italy.
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31
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Wüstner D, Mukherjee S, Maxfield FR, Müller P, Herrmann A. Vesicular and nonvesicular transport of phosphatidylcholine in polarized HepG2 cells. Traffic 2001; 2:277-96. [PMID: 11285138 DOI: 10.1034/j.1600-0854.2001.9o135.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have investigated the transport and canalicular enrichment of fluorescent phosphatidylcholine (PC) in HepG2 cells using the fluorescent analogs of PC C6-NBD-PC and beta-BODIPY-PC. Fluorescent PC was efficiently transported to the biliary canaliculus (BC) and became enriched on the lumenal side of the canalicular membrane as shown for C6-NBD-PC. Some fluorescent PC was transported in vesicles to a subapical compartment (SAC) or apical recycling compartment (ARC) in polarized HepG2 cells as shown by colocalization with fluorescent sphingomyelin (C6-NBD-SM) and fluorescent transferrin, respectively. Extensive trafficking of vesicles containing fluorescent PC between the basolateral domain, the SAC/ARC and the BC as well as endocytosis of PC analogs from the canalicular membrane were found. Evidence for nonvesicular transport included enrichment of the PC-analog beta-BODIPY-PC in the BC (t1/2 = 3.54 min) prior to its accumulation in the SAC/ARC (t1/2 = 18.5 min) at 37 degrees C. Transport of fluorescent PC to the canalicular membrane also continued after disruption of the actin or microtubule cytoskeleton and at 2 degrees C. These results indicate that: (i) a nonvesicular transport pathway significantly contributes to the canalicular enrichment of PC in hepatocytic cells, and (ii) vesicular transport of fluorescent PC occurs from both membrane domains via the SAC/ARC.
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Affiliation(s)
- D Wüstner
- Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, Institut für Biologie/Biophysik, Invalidenstr. 43, D-10115 Berlin, Germany
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32
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Maier O, Aït Slimane T, Hoekstra D. Membrane domains and polarized trafficking of sphingolipids. Semin Cell Dev Biol 2001; 12:149-61. [PMID: 11292381 DOI: 10.1006/scdb.2000.0232] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The plasma membrane of polarized cells consists of distinct domains, the apical and basolateral membrane, that are characterized by a distinct lipid and protein content. Apical protein transport is largely mediated by (glyco)sphingolipid--cholesterol enriched membrane microdomains, so called rafts. In addition changes in the direction of polarized sphingolipid transport appear instrumental in cell polarity development. Knowledge is therefore required of the mechanisms that mediate sphingolipid sorting and the complexity of the trafficking pathways that are involved in polarized transport of both sphingolipids and proteins. Here we summarize specific biophysical properties that underly mechanisms relevant to sphingolipid sorting, cargo recruitment and polarized trafficking, and discuss the central role of a subapical compartment, SAC or common endosome (CE), as a major intracellular site involved in polarized sorting of sphingolipids, and in development and maintenance of membrane polarity.
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Affiliation(s)
- O Maier
- Department of Membrane Cell Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
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33
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Wang X, Kumar R, Navarre J, Casanova JE, Goldenring JR. Regulation of vesicle trafficking in madin-darby canine kidney cells by Rab11a and Rab25. J Biol Chem 2000; 275:29138-46. [PMID: 10869360 DOI: 10.1074/jbc.m004410200] [Citation(s) in RCA: 234] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polarized epithelial cells maintain the polarized distribution of basolateral and apical membrane proteins through a process of receptor-mediated endocytosis, sorting, and then recycling to the appropriate membrane domain. We have previously shown that the small GTP-binding proteins, Rab11a and Rab25, are associated with the apical recycling system of Madin-Darby canine kidney cells. Here we have utilized inducible expression of wild-type, dominant negative, and constitutively active mutants to directly compare the functions of Rab25 and Rab11a in postendocytic vesicular transport. We found that a Rab11a mutant deficient in GTP binding, Rab11aS25N, potently inhibited both transcytosis and apical recycling yet failed to inhibit transferrin recycling. Similarly, expression of either wild type Rab25 or the active mutant Rab25S21V inhibited both apical recycling and transcytosis of IgA by greater than 50% but had no effect on basolateral recycling of transferrin. Interestingly, the GTPase-deficient mutant Rab11aS20V inhibited basolateral to apical transcytosis of IgA, but had no effect on either apical or basolateral recycling. These results indicate that neither Rab11a nor Rab25 function in the basolateral recycling of transferrin in polarized Madin-Darby canine kidney cells cells, consistent with recent morphological observations by others. Thus, transferrin receptors must be recycled to the plasma membrane prior to sorting of apically directed cargoes into Rab11a/Rab25-positive apical recycling endosomes.
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Affiliation(s)
- X Wang
- Institute for Molecular Medicine and Genetics, Departments of Medicine, Surgery and Cellular Biology and Anatomy, Medical College of Georgia and the Augusta Veterans Affairs Medical Center, Augusta, Georgia 30912, USA
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34
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Wang TY, Silvius JR. Different sphingolipids show differential partitioning into sphingolipid/cholesterol-rich domains in lipid bilayers. Biophys J 2000; 79:1478-89. [PMID: 10969009 PMCID: PMC1301041 DOI: 10.1016/s0006-3495(00)76399-5] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Two fluorescence-based approaches have been applied to examine the differential partitioning of fluorescent phospho- and sphingolipid molecules into sphingolipid-enriched domains modeling membrane "lipid rafts." Fluorescence-quenching measurements reveal that N-(diphenylhexatrienyl)propionyl- (DPH3:0-)-labeled gluco- and galactocerebroside partition into sphingolipid-enriched domains in sphingolipid/phosphatidylcholine/cholesterol bilayers with substantially higher affinity than do analogous sphingomyelin, ceramide, or phosphatidylcholine molecules. By contrast, the affinity of sphingomyelin and ceramide for such domains is only marginally greater than that of a phosphatidylcholine with similar hydrocarbon chains. By using direct measurements of molecular partitioning between vesicles of different compositions, we show that the relative affinities of different C(6)-NBD- and C(5)-Bodipy-labeled sphingolipids for sphingolipid-enriched domains are quantitatively, and in most circumstances even qualitatively, quite different from those found for species whose N-acyl chains more closely resemble the long saturated chains of cellular sphingolipids. These findings lend support in principle to previous suggestions that differential partitioning of different sphingolipids into "raft" domains could contribute to the differential trafficking of these species in eukaryotic cells. However, our findings also indicate that short-chain sphingolipid probes previously used to examine this phenomenon are in general ill-suited for such applications.
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Affiliation(s)
- T Y Wang
- Department of Biochemistry, McGill University, Montréal, Québec H3G 1Y6, Canada
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35
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Hoekstra D, van IJzendoorn SC. Lipid trafficking and sorting: how cholesterol is filling gaps. Curr Opin Cell Biol 2000; 12:496-502. [PMID: 10873825 DOI: 10.1016/s0955-0674(00)00122-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Recent research has highlighted a role for cholesterol homeostasis in the regulation of trafficking and sorting of sphingolipids. This sorting may dictate the nature of the acyl chain species of phospholipids in the plasma membrane which, in turn, may govern the selective partitioning of these lipids into lateral domains. Recently, several proteins have been identified that play a role in the flow and sorting of all major lipid classes.
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Affiliation(s)
- D Hoekstra
- Department of Physiological Chemistry, University of Groningen, Groningen, 9713 AV, The Netherlands.
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36
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Van IJzendoorn SC, Maier O, Van Der Wouden JM, Hoekstra D. The subapical compartment and its role in intracellular trafficking and cell polarity. J Cell Physiol 2000; 184:151-60. [PMID: 10867639 DOI: 10.1002/1097-4652(200008)184:2<151::aid-jcp2>3.0.co;2-r] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In polarized epithelial cells and hepatocytes, apical and basolateral plasma membrane surfaces are maintained, each displaying a distinct molecular composition. In recent years, it has become apparent that a subapical compartment, referred to as SAC, plays a prominent if not crucial role in the domain-specific sorting and targeting of proteins and lipids that are in dynamic transit between these plasma membrane domains. Although the molecular identity of the traffic-regulating devices is still obscure, the organization of SAC in distinct subcompartments and/or subdomains may well be instrumental to such functions. In this review, we will focus on the potential subcompartmentalization of the SAC in terms of regulation of membrane traffic, on how SAC relates to the endosomal system, and on how this compartment may operate in the context of other intracellular sorting organelles such as the Golgi complex, in generating and maintaining cell polarity.
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Affiliation(s)
- S C Van IJzendoorn
- Department of Physiological Chemistry, University of Groningen, Groningen, The Netherlands
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37
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Abstract
Detergent insoluble sphingolipid-cholesterol enriched 'raft'-like membrane microdomains have been implicated in a variety of biological processes including sorting, trafficking, and signaling. Mutant cells and knockout animals of sphingolipid biosynthesis are clearly useful to understand the biological roles of lipid components in raft-like domains. It is suggested that raft-like domains distribute in internal vacuolar membranes as well as plasma membranes. In addition to sphingolipid-cholesterol-rich membrane domains, recent studies suggest the existence of another lipid-membrane domain in the endocytic pathway. This domain is enriched with a unique phospholipid, lysobisphosphatidic acid (LBPA) and localized in the internal membrane of multivesicular endosome. LBPA-rich membrane domains are involved in lipid and protein sorting within the endosomal system. Possible interaction between sphingolipids and LBPA in sphingolipid-storage disease is discussed.
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Affiliation(s)
- T Kobayashi
- Supra-Biomolecular System Research Group, Frontier Research System, The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama, Japan.
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38
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van IJzendoorn SC, Hoekstra D. Polarized sphingolipid transport from the subapical compartment changes during cell polarity development. Mol Biol Cell 2000; 11:1093-101. [PMID: 10712522 PMCID: PMC14833 DOI: 10.1091/mbc.11.3.1093] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The subapical compartment (SAC) plays an important role in the polarized transport of proteins and lipids. In hepatoma-derived HepG2 cells, fluorescent analogues of sphingomyelin and glucosylceramide are sorted in the SAC. Here, evidence is provided that shows that polarity development is regulated by a transient activation of endogenous protein kinase A and involves a transient activation of a specific membrane transport pathway, marked by the trafficking of the labeled sphingomyelin, from the SAC to the apical membrane. This protein kinase A-regulated pathway differs from the apical recycling pathway, which also traverses SAC. After reaching optimal polarity, the direction of the apically activated pathway switches to one in the basolateral direction, without affecting the apical recycling pathway.
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Affiliation(s)
- S C van IJzendoorn
- Department of Physiological Chemistry, University of Groningen, Groningen, the Netherlands
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