DOCSLIB.ORG

Diacylglycerol Guides the Hopping of Clathrin-Coated Pits Along Microtubules for Exo-Endocytosis Coupling

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Diacylglycerol Guides the Hopping of Clathrin-Coated Pits Along Microtubules for Exo-Endocytosis Coupling Article Diacylglycerol Guides the Hopping of Clathrin- Coated Pits along Microtubules for Exo-Endocytosis Coupling Graphical Abstract Authors Tianyi Yuan, Lin Liu, Yongdeng Zhang, ..., Jean Salamero, Yanmei Liu, Liangyi Chen Correspondence [email protected] (Y.L.), [email protected] (L.C.) In Brief Yuan et al. demonstrate that pre-formed clathrin-coated pits move to vesicle fusion sites along tracks provided by cortical microtubules, guided by local diacylglycerol concentration. This coupling mechanism mediates fast recycling of both plasma membrane and vesicular proteins, and it is required for the sustained exocytosis during repetitive stimulations. Highlights d Pre-formed CCPs hop to nascent fusion sites to couple endocytosis with exocytosis d Cortical microtubules anchored on the plasma membrane provide tracks for CCP hopping d Local, transient diacylglycerol gradients guide the direction of CCP hopping d Coupled endocytosis mediates rapid clearance of fusion sites for sustained exocytosis Yuan et al., 2015, Developmental Cell 35, 120–130 October 12, 2015 ª2015 Elsevier Inc. http://dx.doi.org/10.1016/j.devcel.2015.09.004 Developmental Cell Article Diacylglycerol Guides the Hopping of Clathrin-Coated Pits along Microtubules for Exo-Endocytosis Coupling Tianyi Yuan,1,2,7 Lin Liu,1,2,7 Yongdeng Zhang,3,7 Lisi Wei,1,2,7 Shiqun Zhao,1,2 Xiaolu Zheng,1,2 Xiaoshuai Huang,1,2 Jerome Boulanger,4 Charles Gueudry,5,6 Jingze Lu,3 Lihan Xie,1,2 Wen Du,3 Weijian Zong,1,2 Lu Yang,1,2 Jean Salamero,4,5 Yanmei Liu,1,2,* and Liangyi Chen1,2,* 1State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking University, Beijing 100871, China 2National Center for Nanoscience and Technology, Beijing 100871, China 3National Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China 4UMR144 CNRS/UPMC, Institut Curie, 75005 Paris, France 5PICT Cell and Tissue Imaging Core Facility, Institut Curie, 75005 Paris, France 6Roper Scientific SAS, 91017 Evry, France 7Co-first author *Correspondence: [email protected] (Y.L.), [email protected] (L.C.) http://dx.doi.org/10.1016/j.devcel.2015.09.004 SUMMARY and maintain the balance of cell surface membrane (Haucke et al., 2011). Many receptor-mediated endocytic processes are CME initiates with the budding of clathrin-coated pits (CCPs) mediated by constitutive budding of clathrin-coated that recruit numerous proteins, which bend surface membrane, pits (CCPs) at spatially randomized sites before interact with specific cargo proteins, facilitate clathrin coat as- slowly pinching off from the plasma membrane (60– sembly, and mediate final membrane scission (McMahon and 100 s). In contrast, clathrin-mediated endocytosis Boucrot, 2011). In non-excitable cells, CCPs constitutively bud (CME) coupled with regulated exocytosis in excitable at spatially random sites before slowly pinching off from the plasma membrane with cargo proteins to be retrieved (60– cells occurs at peri-exocytic sites shortly after vesicle 100 s) (Ehrlich et al., 2004; Loerke et al., 2009). In neuron and fusion ( 10 s). The molecular mechanism underlying endocrine cells, membrane depolarization evokes massive this spatiotemporal coupling remains elusive. We exocytosis followed by coupled fast CME (time constants, show that coupled endocytosis makes use of pre- 3–10 s) (Artalejo et al., 2002; He et al., 2008; Jockusch et al., formed CCPs, which hop to nascent fusion sites 2005; Wu et al., 2009; Zhu et al., 2009). Moreover, regulated nearby following vesicle exocytosis. A dynamic CME occurs mostly at the spatially confined peri-active zone cortical microtubular network, anchored at the cell after stimulation in neurons (Marie et al., 2004; Roos and Kelly, surface by the cytoplasmic linker-associated protein 1999; Wahl et al., 2013). How the slow, spatially randomized on microtubules and the LL5b/ELKS complex on the CME is synchronized to regulated exocytosis in time and space plasma membrane, provides the track for CCP hop- in excitable cells remains enigmatic. ping. Local diacylglycerol gradients generated upon Using dual-color total internal reflection fluorescence (TIRF) microscopy to monitor discrete exocytic and endocytic exocytosis guide the direction of hopping. Overall, events simultaneously, here we visualize elementary exocy- the CCP-cytoskeleton-lipid interaction demon- tosis-coupled CME in insulin-secreting INS-1 cells. In addition strated here mediates exocytosis-coupled fast recy- to direct hits of exocytosis onto sites close to pre-formed cling of both plasma membrane and vesicular pro- CCPs or de novo formation of CCPs at fusion sites after exocy- teins, and it is required for the sustained exocytosis tosis, we reveal an unexpected hopping of pre-formed CCPs to during repetitive stimulations. nearby nascent fusion sites. These hopping CCPs move on the plasma membrane, with cargo proteins such as Syt VII, to fusion sites before endocytosis. Cortical microtubules underneath the INTRODUCTION plasma membrane provide tracks for the hopping of CCPs, and transient diacylglycerol (DAG) gradients at fusion sites Clathrin-mediated endocytosis (CME) mediates constitutive, convey the spatial orientation of the movement. Overall, we pre- receptor-mediated endocytosis in all eukaryotic cells. In sent a concept that lateral hopping of CCPs with directionality neuron and endocrine cells, rapid release of neurotransmitters precisely couples CME with exocytosis in space and time. In and hormones is accompanied by massive addition of newly conjunction with membrane-cytoskeleton interaction and DAG fused vesicle membrane to the plasma membrane. Subse- gradient, hopping of CCPs may represent an efficient method quently, coupled endocytosis rapidly initiates to clear the to actively recycle vesicular components and clear fusion sites plasma membrane for the next round of fusion (Neher, 2010) in excitable cells. 120 Developmental Cell 35, 120–130, October 12, 2015 ª2015 Elsevier Inc. Figure 1. Pre-formed LCa Puncta Hop A 0 s 23 s 25 s 30 s 100 s 103 s 1.2 1.04 toward Nascent Fusion Sites for the Exo- F/F 0 Endocytosis Coupling 1.02 0 F/F 1.1 (A) Spatiotemporal association of clathrin with VAMP2 1.00 1.0 exocytosis in INS-1 cells co-transfected with Fusion sites VAMP2-pHluorin and LCa-DsRed. (Left) Time- 10 20 30 40 50 lapse images show the average VAMP2-pHluorin Time (s) signal (467 fusion events) at fusion sites (top) and LCa 1.0 the corresponding average LCa signal at fusion Non-fusion sites sites (middle) and at random sites (n = 467, bot- 0.5 tom). (Right) Time courses of normalized fluo- rescence signals from average images on the left LCa Norm. intensity 0.0 (top) and spatial profiles of the average VAMP2- 0 500 1000 1500 pHluorin and LCa signals at fusion sites (bottom). Inset is the overlaid image. B Length (nm) Hopping CCP (B) An example of a hopping CCP (arrowheads, see also Movie S1). (Left) Time-lapse images show t 1.6 VAMP2-pHluorin (top) and LCa signal (middle) at a fusion site, at 3-s intervals. Kymographs (bottom) VAMP2 1.4 are 150 s and 1.3 mm high. (Right) Time courses 0 LCa 1.2 show normalized VAMP2-pHluorin (green) and F/F LCa (red) signals at the fusion site. The dotted line 1.0 represents the time course of normalized LCa 0.8 signal at the original site before hopping, and departure time (t) represents the latency of a CCP Kymograph 40 50 60 departure after a fusion event. Time (s) C D (C) Normalized histogram of all exocytosis- CCP departure time Hopping CCP departure time coupled CCP departure times at fusion sites is 0.03 0.03 shown (n = 215). (D) Normalized histogram of departure times of 0.02 0.02 hopping CCPs at fusion sites (n = 74) is shown. Scale bars, 500 nm. See also Figure S1 for other 0.01 Frequency Frequency 0.01 types of CCP recruitments at fusion sites and hopping CCP dynamics analysis and Figure S2 for 0.00 0.00 coupled recruitment of Dyn1 at fusion sites. 0 20 40 60 80 100 0 20 40 60 80 t (s) t (s) RESULTS (n = 467) evoked a focal LCa accumulation that overlapped with the VAMP2-pHluorin peak in space (Figure 1A). The departure The Elementary Coupling between CME and Exocytosis time of an LCa punctum from the fusion site (t) was calculated We labeled VAMP2 with the fluorophore pHluorin, which remains as the interval between the moments that the VAMP2-pHluorin quenched by acidic luminal pH until a vesicle fuses. At a cell foot- signal reached a peak and the sudden disappearance of the print, a sudden focal brightening indicates a fusion pore opening; LCa punctum (Figure 1B). We found that the histogram of depar- and the ensuing circular spread of the pHluorin signal signifies ture time followed a two-Gaussian distribution, with the centers VAMP2 proteins diffusing away from the fusion site (Figure S1A; at 6.9 and 28.9 s (Figure 1C). Thus, direct visualization reveals Allersma et al., 2004). To simultaneously detect endocytosis, we fast and slow exocytosis-coupled clathrin recruitments. tagged the light chain of clathrin (LCa) with DsRed (Ehrlich et al., In addition to the endocytosis of CCPs, some of the LCa 2004; Merrifield et al., 2002), so that the budding off of a CCP puncta disappearance events might have been due to the non- could be recorded as the sudden disappearance of an LCa productive disassembly of clathrin clusters (Aguet et al., 2013; punctum (Figures S1A and S1B; Ehrlich et al., 2004; Loerke Ehrlich et al., 2004; Loerke et al., 2009). To exclude that possibil- et al., 2009; Merrifield et al., 2005). Stimulation with high glucose ity, we investigated the spatiotemporal correlation of exocytosis and high potassium evoked massive exocytosis and the disap- with labeled dynamin-1 (Dyn1) (Figure S2A), a mechanochemical pearance of LCa puncta over the entire cell footprint.
Load more

Recommended publications
  • Identification of Caveolin and Caveolin-Related Proteins in the Brain
    The Journal of Neuroscience, December 15, 1997, 17(24):9520–9535 Identification of Caveolin and Caveolin-Related Proteins in the Brain Patricia L. Cameron, Johnna W. Ruffin, Roni Bollag, Howard Rasmussen, and Richard S. Cameron Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912-3175 Caveolae are 50–100 nm, nonclathrin-coated, flask-shaped brane. Immunoblot analyses demonstrate that detergent- plasma membrane microdomains that have been identified in insoluble complexes isolated from astrocytes are composed of most mammalian cell types, except lymphocytes and neurons. caveolin-1a, an identification verified by Northern blot analyses To date, multiple functions have been ascribed to caveolae, and by the cloning of a cDNA using reverse transcriptase-PCR including the compartmentalization of lipid and protein compo- amplification from total astrocyte RNA. Using a full-length nents that function in transmembrane signaling events, biosyn- caveolin-1 probe, Northern blot analyses suggest that the ex- thetic transport functions, endocytosis, potocytosis, and trans- pression of caveolin-1 may be regulated during brain develop- cytosis. Caveolin, a 21–24 kDa integral membrane protein, is ment. Immunoblot analyses of detergent-insoluble complexes the principal structural component of caveolae. We have initi- isolated from cerebral cortex and cerebellum identify two im- ated studies to examine the relationship of detergent-insoluble munoreactive polypeptides with apparent molecular weight and complexes identified
    [Show full text]
  • Internalization of Lectins in Neuronal Gerl
    INTERNALIZATION OF LECTINS IN NEURONAL GERL NICHOLAS K. GONATAS, SEUNG U. KIM, ANNA STIEBER, and STRATIS AVRAMEAS From the Division of Neuropathology, Department of Pathology, University of PennsylvaniaSchool of Medicine, Philadelphia, Pennsylvania 19174, and the Laboratory of Immunocytochemistry,Pasteur Institute, Paris, France ABSTRACT Conjugates of ricin agglutinin and phytohemagglutinin with horseradish peroxi- dase (HRP) were used for a cytochemical study of internalization of their plasma membrane "receptors" in cultured isolated mouse dorsal root ganglion neurons. Labeling of cells with lectin-HRP was done at 4~ and internalization was performed at 37~ in a culture medium free of lectin-HRP. 15-30 rain after incubation at 37~ lectin-HRP-receptor complexes were seen in vesicles or tubules located near the plasma membrane. After 1-3 h at 37~ lectin-HRP- receptor complexes accumulated in vesicles and tubules corresponding to acid phosphatase-rich vesicles and tubules (GERL) at the trans aspect of the Golgi apparatus. A few coated vesicles and probably some dense bodies contained HRP after 3-6 h of incubation at 37~ Soluble HRP was not endocytosed under the conditions of this experiment or when it was present in the incubation medium at 37~ Internalization of lectin-HRP-receptor conjugates was decreased or in- hibited by mitochondrial respiration inhibitors but not by cytochalasin B or colchicine. These studies indicate that lectin-labeled plasma membrane moieties of neurons are endocytosed primarily in elements of GERL. Considerable information concerning the mobility tors" for ricin (Ric) and phytohemagglutinin and distribution of plasma membrane proteins has (PHA) labeled with horseradish peroxidase been gained with the use of various ligands.
    [Show full text]
  • Endocytosis of Viruses and Bacteria
    Downloaded from http://cshperspectives.cshlp.org/ on September 29, 2021 - Published by Cold Spring Harbor Laboratory Press Endocytosis of Viruses and Bacteria Pascale Cossart1 and Ari Helenius2 1Institut Pasteur, Unite´ des Interactions Bacte´ries-Cellules, Paris F-75015, France; INSERM U604, Paris F-75015, France; and INRA, USC2020, Paris F-75015, France 2Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland Correspondence: [email protected]; [email protected] Of the many pathogens that infect humans and animals, a large number use cells of the host organism as protected sites for replication. To reach the relevant intracellular compartments, they take advantage of the endocytosis machinery and exploit the network of endocytic organelles for penetration into the cytosol or as sites of replication. In this review, we discuss the endocytic entry processes used by viruses and bacteria and compare the strategies used by these dissimilar classes of pathogens. any of the most widespread and devastat- valuable insights into fundamental aspects of Ming diseases in humans and livestock are cell biology. caused by viruses and bacteria that enter cells for Here, we focus on the mechanisms by which replication. Being obligate intracellular para- viral and bacterial pathogens exploit the endo- sites, viruses have no choice. They must trans- cytosis machinery for host cell entry and rep- port their genome to the cytosol or nucleus of lication. Among recent reviews on this topic, infected cells to multiply and generate progeny. dedicated uniquely to either mammalian vi- Bacteria and eukaryotic parasites do have other ruses or bacterial pathogens, we recommend options; most of them can replicate on their the following: Cossart and Sansonetti (2004); own.
    [Show full text]
  • Review Caveolae: Where Incoming and Outgoing Messengers Meet Richard G
    Proc. Natl. Acad. Sci. USA Vol. 90, pp. 10909-10913, December 1993 Review Caveolae: Where incoming and outgoing messengers meet Richard G. W. Anderson Department of Cell Biology and Neuroscience, University of Texas Southwestem Medical Center, Dallas, TX 75235 ABSTIRACT Plasmalemmal caveolae ing. At the same time, this information is This portable, membrane-bound com- were flrst identified as an endocytic com- used to construct several models that partment has been found to contain a partment In endothelial cells, where they illustrate the different ways that caveolae number of molecules that are known to appear to move molecules across the cell might function in both intracellular and participate in cell signaling. There are by transcytosis. More recently, they have intercellular communication. three classes of molecules: enzymes that been found to be sites where small mole- generate messengers from substrates in cules are concentrated and internalized by Caveolae the environment, high-affinity binding a process called potocytosis. A growing sites that concentrate chemical signals, body of biochemical and morphological Each caveola is a dynamic piece ofmem- and substrates that are enzymatically evidence indicates that a variety of mole- brane that is either open for receiving and converted into messengers. cules known to function directly or indi- releasing material or closed for process- GPI. Insulin was the first hormone rectly in signal transduction are enriched ing, storage, and delivery to the cell (11). suspected of using inositol phosphogly- in caveolae. This raises the possibility that The exact nature of the closed compart- can (IPG) or a molecule derived from IPG a third function for caveolae is to process ment is still unclear.
    [Show full text]
  • Membrane Capacitance Recordings Resolve Dynamics and Complexity Of
    www.nature.com/scientificreports OPEN Membrane capacitance recordings resolve dynamics and complexity of receptor-mediated endocytosis in Received: 22 October 2018 Accepted: 20 August 2019 Wnt signalling Published: xx xx xxxx Vera Bandmann1, Ann Schirin Mirsanaye1, Johanna Schäfer1, Gerhard Thiel1, Thomas Holstein2 & Melanie Mikosch-Wersching1,2 Receptor-mediated endocytosis is an essential process in signalling pathways for activation of intracellular signalling cascades. One example is the Wnt signalling pathway that seems to depend on endocytosis of the ligand-receptor complex for initiation of Wnt signal transduction. To date, the roles of diferent endocytic pathways in Wnt signalling, molecular players and the kinetics of the process remain unclear. Here, we monitored endocytosis in Wnt3a and Wnt5a-mediated signalling with membrane capacitance recordings of HEK293 cells. Our measurements revealed a swift and substantial increase in the number of endocytic vesicles. Extracellular Wnt ligands specifcally triggered endocytotic activity, which started immediately upon ligand binding and ceased within a period of ten minutes. By using specifc inhibitors, we were able to separate Wnt-induced endocytosis into two independent pathways. We demonstrate that canonical Wnt3a is taken up mainly by clathrin-independent endocytosis whereas noncanonical Wnt5a is exclusively regulated via clathrin-mediated endocytosis. Our fndings show that membrane capacitance recordings allow the resolution of complex cellular processes in plasma membrane signalling pathways in great detail. Wnt signalling is a highly-conserved signalling pathway with important functions in development, tissue-homeostasis, stem cell biology and many diseases, including cancer. Afer three decades of dedicated research we have come to understand many of the fundamental components of Wnt signalling pathways.
    [Show full text]
  • EFFECT of PHAGOCYTOSIS on MEMBRANE TRANSPORT of NONELECTROLYTES* by MIN-FU TSAN, M.D., and RICHARD D. BERLIN, M.D.:~ (From the D
    EFFECT OF PHAGOCYTOSIS ON MEMBRANE TRANSPORT OF NONELECTROLYTES* BY MIN-FU TSAN, M.D., AND RICHARD D. BERLIN, M.D.:~ (From the Department of Physiology, Harvard Medical School, Boston, Massachusetts 02115) (Received for publication 3 June 1971) Phagocytosis and carrier-mediated membrane transport are two distinct membrane functions by which substances are translocated across the plasma membrane. Yet, little is known about the distribution of these functions over the cell surface. During phagocytosis, a part of the plasma membrane is internalized (1, 2). This internalized membrane may include transport sites (carriers). On the other hand, transport sites may be distributed in such a way that different parts of the plasma membrane are involved in transport and phagocytosis. In this study, the activities of specific transport systems were determined before and after large portions of the surface membrane had been interiorized by phagocytosis of inert particles. Five separate transport systems characterized in this laboratory, whose activity can be measured with great sensitivity, have been examined: adenosine 1 and two adenine (3) transport systems in rabbit po]ymorphonuclear leukocytes; adenosine 2 and lysine (4) transport systems in alveolar macrophages. The results show that the rates of transport were un- affected in all systems, even after an estimated 35-50% of the membrane had been internalized. It was also shown that the constancy of transport did not depend on the introduction into the surface of new transport sites during phago- cytosis. The results indicate that the membrane is mosaic in character with geographically separate transport and phagocytic sites. Materials and Methods Animals.--New Zealand white rabbits of either sex, weighing between 2 and 4 kg each, were used.
    [Show full text]
  • Exo-Endocytosis at Mossy Fiber Terminals: Toward Capacitance Measurements in Cells with Arbitrary Geometry
    Exo-endocytosis at mossy fiber terminals: Toward capacitance measurements in cells with arbitrary geometry Christopher Kushmerick and Henrique von Gersdorff* The Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239 xocytosis and endocytosis are real time as a decrease in membrane ments have been made on secretory ubiquitous cellular phenomena capacitance back to baseline resting lev- cells for which the compact isopotential necessary for diverse functions els (6–9). approximation seems, prima facie,tobe such as secretion, internal sig- Most measurements obtained to date justified, including adrenal chromaffin Enaling, protein traffic, and motility. have relied on one of two general tech- cells (10), mast cells (11), and neuroen- Many different techniques have been niques to relate membrane current to docrine cells (12), which secrete via developed to assay exocytosis and endo- capacitance (6, 9). Time-domain meth- large dense-core vesicles. In addition, cytosis, but to date only electrical mea- ods use the amplitude and time course small clear-core synaptic vesicle fusion surements of plasma membrane capaci- of membrane current relaxations after and membrane retrieval have been mea- tance have had the time resolution step changes in electrical potential to sured from retinal bipolar cell terminals necessary to capture both the fusion and determine cell membrane parameters. (2, 3, 13), hair cells (4, 5), and photore- reuptake of small clear-core vesicle ceptors (14). However, these sensory membrane during fast neurotransmis- neurons contain nonconventional rib- sion. In this issue of PNAS, Hallermann bon-type active zones (3, 13, 15). et al. (1) present capacitance measure- These are the first Recently, attempts have been made to ments from hippocampal mossy fiber measure exocytosis in cells with complex nerve terminals during stimulated exocy- membrane capacitance geometry and multiple electrical com- tosis.
    [Show full text]
  • Sodium-Coupled Glucose Transport, the SLC5 Family, and Therapeutically Relevant Inhibitors: from Molecular Discovery to Clinical Application
    Pflügers Archiv - European Journal of Physiology (2020) 472:1177–1206 https://doi.org/10.1007/s00424-020-02433-x INVITED REVIEW Sodium-coupled glucose transport, the SLC5 family, and therapeutically relevant inhibitors: from molecular discovery to clinical application Gergely Gyimesi1 & Jonai Pujol-Giménez1 & Yoshikatsu Kanai2 & Matthias A. Hediger1 Received: 4 March 2020 /Revised: 24 June 2020 /Accepted: 2 July 2020 / Published online: 7 August 2020 # The Author(s) 2020 Abstract Sodium glucose transporters (SGLTs) belong to the mammalian solute carrier family SLC5. This family includes 12 different members in human that mediate the transport of sugars, vitamins, amino acids, or smaller organic ions such as choline. The SLC5 family belongs to the sodium symporter family (SSS), which encompasses transporters from all kingdoms of life. It furthermore shares similarity to the structural fold of the APC (amino acid-polyamine-organocation) transporter family. Three decades after the first molecular identification of the intestinal Na+-glucose cotransporter SGLT1 by expression cloning, many new discoveries have evolved, from mechanistic analysis to molecular genetics, structural biology, drug discovery, and clinical applications. All of these advances have greatly influenced physiology and medicine. While SGLT1 is essential for fast absorption of glucose and galactose in the intestine, the expression of SGLT2 is largely confined to the early part of the kidney proximal tubules, where it reabsorbs the bulk part of filtered glucose. SGLT2 has been successfully exploited by the pharmaceutical industry to develop effective new drugs for the treatment of diabetic patients. These SGLT2 inhibitors, termed gliflozins, also exhibit favorable nephroprotective effects and likely also cardioprotective effects.
    [Show full text]
  • Chapter 4 Movement of Molecules Across Cell Membranes = Trans-Membrane Traffic
    Chapter 4 Movement of Molecules Across Cell Membranes = Trans-Membrane Traffic Diffusion: solute moves down its concentration gradient: • simple diffusion: small (e.g., oxygen, carbon dioxide) lipid soluble (e.g., steroids) • facilitated diffusion: requires transporter (e.g., glucose) Chapter 4 Movement of Molecules Across Cell Membranes = Trans-Membrane Traffic (cont.) Active transport: solute moves against its concentration gradient: • primary active transport: ATP directly consumed (e.g., Na+ K+ATPase) • secondary active transport: energy of ion gradient (usually Na+) used to move second solute (e.g., nutrient absorption in gut) Exo- and endo- cytosis: large scale movements of molecules Figure 4-1 START: Initially higher concentration of molecules randomly move toward lower concentration. Over time, solute molecules placed in a solvent will evenly distribute themselves. Diffusional equilibrium is the result (Part b). At time B, some glucose has crossed into side Figure 4-2 2 as some cross into side 1. Note: the partition between the two compartments is a membrane that allows this solute to move through it. Net flux accounts for solute Figure 4-3 movements in both directions. 3 cartoon models of integral membrane proteins that function as ion channels; the regulated opening and closing of these channels is the basis of how neurons function. Figure 4-5 A thin shell of positive (outside) and negative (inside) charge provides the electrical gradient that drives ion movement across the membranes of excitable cells. Figure 4-6 Figure 4-7 The opening and closing of ion channels results from conformational changes in integral proteins. Discovering the factors that cause these changes is key to understanding excitable cells.
    [Show full text]
  • Mediate Endocytosis and Phagocytosis
    Proc. Nati. Acad. Sci. USA Vol. 89, pp. 5030-5034, June 1992 Immunology Two forms of the low-affinity Fc receptor for IgE differentially mediate endocytosis and phagocytosis: Identification of the critical cytoplasmic domains (CD23/endocytosis/phagocytosis) AKIRA YOKOTA*, KAzUNORI YUKAWA*, AKITSUGU YAMAMOTOt, KENJI SUGIYAMA*, MASAKI SUEMURAt, YUTAKA TASHIROt, TADAMITSU KISHIMOTO*t, AND HITOSHI KIKUTANI* *Institute for Molecular and Cellular Biology, Osaka University, 1-3, Yamada-oka, Suita, Osaka 565, Japan; *Department of Medicine III, Osaka University Medical School, 1-1-50, Fukushima, Fukushima-ku, Osaka 553, Japan; and tDepartment of Physiology, Kansai Medical University, Moriguchi-shi, Osaka 570, Japan Contributed by Tadamitsu Kishimoto, February 21, 1992 ABSTRACT We have previously identified two species of FceRIIb may be involved in B-cell function and IgE-mediated the low-affinity human Fc receptor for IgE, FceRIIa and immunity, respectively. FceRIIb, which differ only in a short stretch of amino acids at In this paper, we have attempted to elucidate the molecular the N-terminal cytoplasmic end. Their differential expressions basis ofthe functional difference between these two forms of on B cells and monocytes suggest that FceRlla and FceRIIb are receptor molecules by using stable transfectants expressing involved in B-cell function and IgE-mediated immunity, re- either human wild-type or mutated FceRII and have demon- spectively. Here we show that FceRII-mediated endocytosis is strated that endocytosis is mediated only through FceRIIa observed only in FceRlia-expressing cells, whereas IgE- and that phagocytosis is mediated only through FceRIIb. dependent phagocytosis isobserved only in FceRIEb-expressing Furthermore, the minimum amino acid residues necessary cells, demonstrating the functional difference between FceRIIa for endocytosis and phagocytosis have been determined.
    [Show full text]
  • Localized Pinocytosis in Human Neutrophils R-Mediated Phagocytosis Stimulates Γ Fc
    FcγR-Mediated Phagocytosis Stimulates Localized Pinocytosis in Human Neutrophils Roberto J. Botelho, Hans Tapper, Wendy Furuya, Donna Mojdami and Sergio Grinstein This information is current as of October 1, 2021. J Immunol 2002; 169:4423-4429; ; doi: 10.4049/jimmunol.169.8.4423 http://www.jimmunol.org/content/169/8/4423 Downloaded from References This article cites 61 articles, 30 of which you can access for free at: http://www.jimmunol.org/content/169/8/4423.full#ref-list-1 Why The JI? Submit online. http://www.jimmunol.org/ • Rapid Reviews! 30 days* from submission to initial decision • No Triage! Every submission reviewed by practicing scientists • Fast Publication! 4 weeks from acceptance to publication *average by guest on October 1, 2021 Subscription Information about subscribing to The Journal of Immunology is online at: http://jimmunol.org/subscription Permissions Submit copyright permission requests at: http://www.aai.org/About/Publications/JI/copyright.html Email Alerts Receive free email-alerts when new articles cite this article. Sign up at: http://jimmunol.org/alerts The Journal of Immunology is published twice each month by The American Association of Immunologists, Inc., 1451 Rockville Pike, Suite 650, Rockville, MD 20852 Copyright © 2002 by The American Association of Immunologists All rights reserved. Print ISSN: 0022-1767 Online ISSN: 1550-6606. The Journal of Immunology Fc␥R-Mediated Phagocytosis Stimulates Localized Pinocytosis in Human Neutrophils1 Roberto J. Botelho,2* Hans Tapper,2† Wendy Furuya,* Donna Mojdami,* and Sergio Grinstein3,4* Engulfment of IgG-coated particles by neutrophils and macrophages is an essential component of the innate immune response.
    [Show full text]
  • Reduction of Caveolin and Caveolae in Oncogenically Transformed Cells (Cancer/Growth Regulation/Oncogene/Potocytosis)
    Proc. Natl. Acad. Sci. USA Vol. 92, pp. 1381-1385, February 1995 Cell Biology Reduction of caveolin and caveolae in oncogenically transformed cells (cancer/growth regulation/oncogene/potocytosis) ANThoNY J. KOLESKE*, DAVID BALTIMORE*, AND MICHAEL P. LISANTIt *Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139; and tWhitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142 Contributed by David Baltimore, November 28, 1994 ABSTRACT Caveolae are flask-shaped non-clathrin- Caveolae may regulate the proliferation of normal cells in coated invaginations of the plasma membrane. In addition to vitro. We have recently observed that NIH 3T3 cell lines the demonstrated roles for caveolae in potocytosis and trans- transformed by several different oncogenes express greatly cytosis, caveolae may regulate the transduction of signals reduced levels of caveolin. Furthermore, the reduction of from the plasma membrane. Transformation of NIH 3T3 cells caveolin in these cell lines correlates with the size of colonies by various oncogenes- leads to reductions in cellular levels of they form upon growth in soft agar. Electron microscopy caveolin, a principal component of the protein coat of caveo- reveals that caveolae are missing from the transformed cells lae. The reduction in caveolin correlates very well with the size that express reduced levels ofcaveolin. The reduction in caveo- of colonies formed by these transformed cells when grown in lin does not correlate with serum requirements for growth of soft agar. Electron microscopy reveals that caveolae are mor- these cell lines in culture. The loss of caveolin could contribute phologically absent from these transformed cell lines.
    [Show full text]