DOCSLIB.ORG

Exo-Endocytosis at Mossy Fiber Terminals: Toward Capacitance Measurements in Cells with Arbitrary Geometry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read 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. These are the first time-resolved partments by using capacitance mea- membrane capacitance measurements measurements from surements. Hsu and Jackson (16) first from bona fide (albeit relatively large) bona fide bouton-type showed that capacitance measurements bouton-type synaptic terminals, with di- are possible in pituitary slices from ameters of Ϸ3 ␮m and a resting capaci- synaptic terminals. nerve varicosities (with attached axons) tance of Ϸ1 pF. The results obtained that secrete both via dense- and clear- not only provide important data on ba- core vesicles (17). Mennerick et al. (18) sic synaptic properties of this nerve ter- used the time-domain method to analyze Frequency-domain methods use the minal, in particular on the vesicle pool the electrotonic structure of the intact phase shift between an applied sinusoi- size and the question of multivesicular goldfish retinal bipolar cell, consisting of dal membrane potential and the induced release, but also provide an example of a soma and terminal connected by a current to calculate the complex imped- how to extend capacitance measure- short axon. They showed that a two- ance of the circuit. In both techniques ments from cells with simple and com- compartment model adequately de- voltage-dependent conductances are pact geometry to more general classes scribed their recordings and, under the avoided (pharmacologically and by care- of neurons and nerve terminals. assumption of high membrane resis- ful choice of membrane potential) such The accessibility of exocytosis and tance, allowed for unique determination that only passive (capacitive and leak) endocytosis to voltage-clamp measure- of the resistance of the axon and the currents remain. ments stems from the fact that these capacitance of the soma and terminal. A Regardless of the choice of technique, processes, by their nature, change the third example, the calyx of Held, is a interpretation of the data depends on surface area of the plasma membrane. giant nerve terminal in the brainstem the use of an a priori electrical model of Because the plasma membrane acts as ascending auditory pathway. This syn- the preparation. The simplest model, an electrical capacitor, changes in sur- apse, unlike the bipolar cell synapse, appropriate for a compact isopotential face area can be detected as changes in contains conventional active zones. De- cell, consists of the membrane capaci- its total capacitance. Thus by electrical pending on the length of the attached tance in parallel with its conductance measurements, net changes in plasma axon, the calyx appears as one or more membrane (i.e., exocytosis minus endo- (6). The rest of the circuit (recording electrotonic compartments (19). Sun cytosis) can be measured. Coupled with patch pipette, cytoplasm, and extracellu- and Wu (20) used frequency-domain voltage protocols that open voltage- lar path) is combined into the series re- capacitance measurements and the com- gated calcium channels, this technique sistance term for a total of three passive pact isopotential cell approximation to can be used to follow membrane parameters (Cm, Gm, and Rs; see Fig. 1). measure exocytosis in calyces that be- 2ϩ changes during Ca -dependent secre- In this case, theoretical time-domain haved as a single electrical compartment tion of neurotransmitters. If exocytosis responses consist of single exponential (i.e., calyces that appeared to have a and endocytosis are temporally distinct relaxations from which the three cell single exponential current relaxation in phenomena, the rate of exocytosis can parameters can be uniquely determined. response to a step hyperpolarization). be determined by measuring capacitance Likewise, for a sinusoidal excitation, the Using the same measurement technique, jumps triggered by step depolarizations components of current in phase and 90° of different durations (see refs. 2–5). In out of phase with the voltage stimulus addition, synaptic vesicle membrane re- can be analyzed by using standard cir- See companion article on page 8975. trieval (or reinternalization via endocy- cuit theory to determine Cm, Gm, and *To whom correspondence should be addressed. E-mail: tosis) after fusion can be monitored in Rs. To date, most capacitance measure- [email protected]. 8618–8620 ͉ PNAS ͉ July 22, 2003 ͉ vol. 100 ͉ no. 15 www.pnas.org͞cgi͞doi͞10.1073͞pnas.1633427100 Downloaded by guest on October 2, 2021 COMMENTARY the mossy fiber terminal, during which Ca2ϩ influx occurred. They found two components of capacitance increase in response to varying length depolariza- tions: a fast component with a time con- stant near 1 ms and a second, slower component with a time constant near 20 ms. They interpreted these components as distinct pools of synaptic vesicles with differential release kinetics. Recovery of membrane capacitance (i.e., putative endocytosis) after a maximally effective stimulation that depleted the releasable pool of vesicles occurred on a time scale of several seconds. Perhaps the most provocative aspect of the article concerns the quantitative estimate of the rate of vesicle release per active zone and implications for multivesicular release (i.e., release of more than one vesicle per active zone per action potential) (22). The argu- ments stem from the observation that during a prolonged depolarizing voltage step, the calculated release corre- Fig. 1. Model circuits for different cell geometries. (A) Spherical isopotential cells. These cells can be sponded, on average, to more than one described by three passive circuit parameters: membrane capacitance (Cm), membrane conductance (Gm), vesicle per active zone per millisecond. and series resistance (Rs, a composite parameter usually dominated by the resistance of the attached If release were uniform in time during whole-cell mode recording patch pipette but also including the resistance of the cytoplasmic and the depolarization, this would imply that extracellular paths). (B) Two-compartment model proposed by Mennerick et al. (18) to describe goldfish lateral inhibition of release of vesicles retinal bipolar neurons. This four-component model assumes negligibly low membrane conductance and from the same active zone, if present, axon capacitance. R2 is the axon resistance, C1 and C2 are the synaptic terminal and cell soma capacitance, Ͻ and R1 is series resistance of a patch pipette recording from the synaptic terminal. (C) General n- was very short-lived ( 1 ms, compare compartment model described by 3n parameters. with action potential duration half-width of Ϸ0.6 ms). In fact, during the fast component of release, the rate per ac- Taschenberger et al. (21) demonstrated The authors then used their model tive zone may have been much higher. empirically that capacitance jumps fol- cell to test several time- and frequency- Assuming that all the increase in capaci- lowing exocytosis were similar across domain capacitance measurements tech- tance signal is due to exocytosis of syn- calyces, independent of whether the niques to determine which most faith- aptic vesicles that are docked at active structure consisted of one or two elec- fully reported simulated changes in the zones, this measurement implies that trical compartments. Thus it seems that electrical parameters of the bouton. multivesicular release occurs at this syn- capacitance measurements in the calyx Notwithstanding the complex structure, apse. The list of synapses that experi- of Held are not greatly affected by the they found that time- or frequency-do- ence multivesicular release has been attached
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 Transport Quiz
    Membrane Transport Quiz 1. Which of the following is an example of extracellular fluid? a. Cytosol b. Plasma c. Interstitial Fluid d. Both b and c 2. Which of the following correctly describes passive transport? a. the cell uses ATP in passive transport b. most pumps are examples of passive transport c. diffusion is an example of passive transport d. exocytosis is an example of passive transport 3. Simple diffusion occurs ______________. a. with transporters in the cell membrane b. directly across the cell membrane c. through exocytosis d. through endocytosis 4. Which of the following is an example of active transport? a. Filtration b. Osmosis c. Endocytosis d. Exocytosis e. Both c and d 5. Which type of active transport uses ATP directly? a. Primary Active Transport b. Secondary Active Transport c. Both a and b 6. Which of the following is an example of receptor mediated endocytosis? a. Phagocytosis b. Primary Active Transport c. Exocytosis d. ALL are For use with TCC iTunes University Membrane Transport Lecture. 1 Developed by: Martha Kutter 2009 for the Learning Commons at Tallahassee Community College. 7. A transporter that moves one type of particle in one direction is _______________. a. Uniporter b. Symporter c. Antiporter 8. A transporter the moves two different particles in two different directions is ________. a. Endocytosis b. Exocytosis c. Uniporter d. Symporter e. Antiporter 9. Which of the following is an example of a primary active transporter? a. Na+/Ca2+ transporter on cardiac contractile cells b. Na+ channels on neurons c. Na+/K+ ATPase on all cells d.
    [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]
  • Exocytosis by Networks of Rab Gtpases Decoding the Regulation
    The Journal of Immunology Decoding the Regulation of Mast Cell Exocytosis by Networks of Rab GTPases Nurit P. Azouz,* Takahide Matsui,† Mitsunori Fukuda,† and Ronit Sagi-Eisenberg* Exocytosis is a key event in mast cell functions. By this process, mast cells release inflammatory mediators, contained in secretory granules (SGs), which play important roles in immunity and wound healing but also provoke allergic and inflammatory responses. The mechanisms underlying mast cell exocytosis remained poorly understood. An essential step toward deciphering the mechanisms behind exocytosis is the identification of the cellular components that regulate this process. Because Rab GTPases regulate specific trafficking pathways, we screened 44 Rabs for their functional impacts on exocytosis triggered by the Fc«RI or combination of Ca2+ ionophore and phorbol ester. Because exocytosis involves the continuous reorganization of the actin cytoskeleton, we also repeated our screen in the presence of cytochalasin D that inhibits actin polymerization. In this paper, we report on the identification of 30 Rabs as regulators of mast cell exocytosis, the involvement of 26 of which has heretofore not been recognized. Unexpectedly, these Rabs regulated exocytosis in a stimulus-dependent fashion, unless the actin skeleton was disrupted. Functional clustering of the identified Rabs suggested their classification as Rabs involved in SGs biogenesis or Rabs that control late steps of exocytosis. The latter could be further divided into Rabs that localize to the SGs and Rabs that regulate transport from the endocytic recycling compartment. Taken together, these findings unveil the Rab networks that control mast cell exocytosis and provide novel insights into their mechanisms of action.
    [Show full text]
  • Exocytosis and Endocytosis
    Exocytosis and Endocytosis Exocytosis and Endocytosis A Closer Look at Cell Membranes . Aim: How do large particles enter and exit cells? . Do Now: Name some molecules/materials that enter and exit the cell. How would you describe the cell membrane that allows passage of these materials? Exocytosis and Endocytosis Exocytosis and Endocytosis . Exocytosis (out of the cell) • The fusion of a vesicle with the cell membrane, releasing its contents to the surroundings . Endocytosis (into the cell) • The formation of a vesicle from cell membrane, enclosing materials near the cell surface and bringing them into the cell Exocytosis and Endocytosis Endocytosis . Phagocytosis – solid . Pinocytosis – liquid (general) Endocytosis: . Uptake of substances . Transport of protein or lipid components of compartments . Metabolic or division signaling . Defense to microorganisms Endocytosis . Clathrin-coated vesicles . Non-clathrin coated vesicles . Macropinocytosis . Potocytosis Exocytosis and Endocytosis Endocytosis Required: . signal . membrane receptor (Fc receptor for Ab) . formation of pseudopodium . cortical actin network The formed vesicle: phagosome (hetero-; auto-) Endocytosis . Clathrin-coated vesicles . Non-clathrin coated vesicles . Macropinocytosis . Potocytosis Endocytosis and Exocytosis Examples Three Pathways of Endocytosis . Bulk-phase endocytosis • Extracellular fluid is captured in a vesicle and brought into the cell; the reverse of exocytosis . Receptor-mediated endocytosis • Specific molecules bind to surface receptors, which are then enclosed in an endocytic vesicle . Phagocytosis • Pseudopods engulf target particle and merge as a vesicle, which fuses with a lysosome in the cell Phagocytosis (“engulfment”) Exocytosis and Endocytosis Membrane Cycling . Exocytosis and endocytosis continually replace and withdraw patches of the plasma membrane . New membrane proteins and lipids are made in the ER, modified in Golgi bodies, and form vesicles that fuse with plasma membrane Exocytic Vesicle 5.5 Key Concepts: Membrane Trafficking .
    [Show full text]
  • Lysosomal Biology and Function: Modern View of Cellular Debris Bin
    cells Review Lysosomal Biology and Function: Modern View of Cellular Debris Bin Purvi C. Trivedi 1,2, Jordan J. Bartlett 1,2 and Thomas Pulinilkunnil 1,2,* 1 Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4H7, Canada; [email protected] (P.C.T.); jjeff[email protected] (J.J.B.) 2 Dalhousie Medicine New Brunswick, Saint John, NB E2L 4L5, Canada * Correspondence: [email protected]; Tel.: +1-(506)-636-6973 Received: 21 January 2020; Accepted: 29 April 2020; Published: 4 May 2020 Abstract: Lysosomes are the main proteolytic compartments of mammalian cells comprising of a battery of hydrolases. Lysosomes dispose and recycle extracellular or intracellular macromolecules by fusing with endosomes or autophagosomes through specific waste clearance processes such as chaperone-mediated autophagy or microautophagy. The proteolytic end product is transported out of lysosomes via transporters or vesicular membrane trafficking. Recent studies have demonstrated lysosomes as a signaling node which sense, adapt and respond to changes in substrate metabolism to maintain cellular function. Lysosomal dysfunction not only influence pathways mediating membrane trafficking that culminate in the lysosome but also govern metabolic and signaling processes regulating protein sorting and targeting. In this review, we describe the current knowledge of lysosome in influencing sorting and nutrient signaling. We further present a mechanistic overview of intra-lysosomal processes, along with extra-lysosomal processes, governing lysosomal fusion and fission, exocytosis, positioning and membrane contact site formation. This review compiles existing knowledge in the field of lysosomal biology by describing various lysosomal events necessary to maintain cellular homeostasis facilitating development of therapies maintaining lysosomal function.
    [Show full text]
  • Synaptic Vesicle Dynamics in Living Cultured Hippocampal Neurons Visualized with CY3-Conjugated Antibodies Directed Against the Lumenal Domain of Synaptotagmin
    The Journal of Neuroscience, June 1995, 1~76): 4328-4342 Synaptic Vesicle Dynamics in Living Cultured Hippocampal Neurons Visualized with CY3-Conjugated Antibodies Directed against the Lumenal Domain of Synaptotagmin Kajetan Kraszewski,’ Olaf Mundigl,’ Laurie DanielI,’ Claudia Verclerio,* Michela Matteoli,2 and Pietro De Camilli’ ‘Department of Cell Biology and Howard Hughes Medical Institute, Yale University School Medicine, New Haven, Connecticut 06510 and XNR Center of Cytopharmacology and Department of Medical Pharmacology, University of Milano, Milano, Italy Antibodies directed against the lumenal domain of synap- which representthe presynaptic elementsof synapses.They un- totagmin I conjugated to CY3 (CYB-Syt,-Abs) and video mi- dergo exocytosis selectively at specialized regions of the pre- croscopy were used to study the dynamics of synaptic ves- synaptic plasmalemmacalled active zones and their rate of exo- icles in cultured hippocampal neurons. When applied to cytosis is dramatically stimulated by depolarization-induced cultures after synapse formation, CY3-Syt,-Abs produced a Ca2+ influx (De Camilli and Jahn, 1990; Jesse1and Kandel, strong labeling of presynaptic vesicle clusters which was 1992; Stidhof et al., 1993; Bennett and Scheller, 1994). markedly increased by membrane depolarization. The in- Until recently, the properties of SVs in situ could only be crease of the rate of CYSSyt,-Ab uptake in a high K+ me- studied by conventional morphological approacheswhich in- dium was maximal during the first few minutes but per- volve cell fixation, or by using electrophysiological techniques sisted for as long as 60 min. In axons developing in iso- which detect effects produced by neurotransmitterrelease. New lation, CYSSyt,-Abs, in combination with electron micros- probes have now been developed which make possibleto mon- copy immunocytochemistry, revealed the presence of itor morphologically, at the light microscopic level, SV dynam- synaptic vesicle clusters which move in bulk in antero- ics in the living cell.
    [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]