Plasma Membrane Chapter 2 PDF

Chapitre 2 : PLASMA MEMBRANE Pr Aboussaouira Module : Cell Biology & Genetic ½ Module : Cell Biology Semester 1 www.um6ss.ma...

Chapitre 2 : PLASMA MEMBRANE Pr Aboussaouira Module : Cell Biology & Genetic ½ Module : Cell Biology Semester 1 www.um6ss.ma Academic year : 2023/2024 1  Chapter Content Components Exchanges Membrane Cell Signaling Cell Adhesion Plasma membrane (PM) Components Red Cell MP components : - 40% of lipids - 50% of proteins - 10% of carbohydrates  1. Lipids : phospholipids & cholesterol Phospholipid (75%) Lipid with 1 glycérol, 2 fatty acid chains (hydrophobic), 1 phosphate, 1 of 4 little molécules (hydrophilic) : Choline => phosphatidyl-choline (most abundant) Inositol => la phosphatidyl-inositol (cell signaling) Serine => la phosphotidyl-serine Ethanol => la phosphotidyl-ethanolamine Phospholipids constitute a double layer Medical Application : Found nutrients with cholin, serin, inositol ?  Cholesterol (25%) Formed by : - 1 molecule of alcohool (hydrophilic) - 4 cycles - 1 hydrocarbonated chain (hydrophobic). Inserted between phospholipids Play an important role in PM waterproofing Medical Application : Found nutrients with cholesterol, saturated & in saturated fatty acids ?  2. Proteins 2 types : Peripheral & Integral, between lipids Peripheral Proteins : hydrophilic, - In cytosolic and extracellular sides, in blue ex : clathrin, G protein (cf. next paragraphs) Integral Protines : Amphothere, with : - hydrophobic part buried into lipidic bilayer -hydrophilic part : emerge into cytoplasm or extracellular sides Could : - Be integrated into a half layer ex : spectrin - Cross all the lipid bilayer = Transmembrane protein ; ex : pumps, permease, ion channels.  3. Carbohydrates - 2 types : Oligosaccharids or polysaccharids - Atached to lipids (glycolipids) or to proteins (glycoproteins) - Only on the extracell side : PM non symetric - Form a carbohydrate protective envelope : Cell coat or glycocalyx Cell coat roles : Antigenic role : more importante in some tissues (epidermis, gums) PM : All the molecules move in all directions : Fluid Membrane Various molecules (Lipids, Proteins, Carbohydrates) : Mosaic Fluid Mosaic Membrane 8 Physiological roles of Cell Membrane Nutrient exchanges Cell Signaling Cell Adhesion  Nutrient Exchanges CM is semi permeable : it choose the molecules that cross Nutrients Small Interstitial Intracellular Intestine Blood fluid environment Nutrients Waste  2 types of Cell exchange According to the nutrients size Permeability, diffusion, transport (Low molecular weight) - Small molecules : amino acid, fatty acid, ions, glucose - without PM deformation Vesicular Exchange - Large molecules : proteins, lipides, carbohydrats (High molecular weight) - With PM deformation, - use vesicules  Permeability / Diffusion / Transport Passive transport, without ATP Active transport, with ATP  Passive Transport Without consuming ATP Follow the concentration gradient Without membrane transportor (simple diffusion) With membrane transportor (facilitated diffusion)  Simple Diffusion Concern : gas (O2, CO2 et NO) Water Ions (Na+, Cl-, Mg++, Ca++, …..) small molecules not electrically charged ; ex : urea, amino acids, fatty acids, glycerol, glucose, …precursors Facilitated Diffusion by Aquaporine, Permease (Glut4), ionic chanels 15  Water Exchange : osmosis and filtration Water cross hydrophobic tails membrane using molecular adhesion phenomenon : water molecules are linked to each others, neutralizing by this manner their opposite electrostatic charges and forming a rosary that easily crosses the membrane At many levels of the human body (blood capillaries, urinary tubes), blood water with molecules cross through aquaporin => Filtration phenomenon  Facilitated Diffusion by carrier proteins Concerns privileged molecules as glucose Use carrier proteins that accelerated the diffusio speed Carrier protein : specific transmembrane protein with specific binding site to the ligand (glucose) Mecanism : - Ligand (Glucose) binding to its specific site on the carrier protein - Carrier protein conformation change using the energy of the concentration gradient - Ligand Internalization into the cell - Back to the carrier protein initial conformation  Carrier proteins Aquaporin Ionic Chanel Aquaporin Glucose carrier protein  Active Transport Transport coupled to ATP hydrolysis : used ATP Concerns essentially ions (Na+, K+, H+ ,Cl-, Ca2+) Against concentration gradient Use pump : ATPase, specific ATPase Na+/K+ : -Transmembrane protein formed by 2 sub-unites : one with Na+ specific site, the other with K+ with specific site -Na+ & K+ Transport coupled to ATP hydrolysis and allows K+ entrance in the cell and Na+ exit out of the cell ATPase Na+/K+  Na+/K+Na+/K+ Mechanism Mécanisme ATPaseATPase -Fixation of intracell Na+ ions on its specific site -Hydrolysis of ATP to ADP + Pi + E -Phosphorylation and conformation change of the pump using ATP -Release of Na+ out of the cell -Fixation of extracell K+ on their specific site -Dephosphorylation of the pump -Back the pump to initial conformation using ATP energy rest -Release K+ in the cytosol Rq : 1 ATP is suficient by cycle  Multi-Drug-Resistants (MDR, ABC) Membrane Proteins Ensure the transport of numerous drugs out of cell not specific, ATP-dependant Developed in normal and cancerous cell Explain drug resistance of some tumerous cells to chimiotherapy and of some cells infected by plasmodium to anti malaria drugs. Medicale Application : Antibiotic Resistance  2 Vesicular Exchange Concerns macromolecules, bacteries, viruses Deforms plasma membrane and forms vesicules Consumes ATP 2 processus : Endocytosis : substances internalisation into the cell and forms vesicules Exocytosis : expels substances out of cell and vesicules disappearence  Endocytosis Located Phenomenon (clathrines) that internalise substances into the cell : Phagocytosis : Macrophage, Küpffer cell in liver, osteoclast Phagocytosis for solid substances Pinocytosis for liquid substances Mechanism - Adsorption of substance on membrane over the clathrins of the membrane - Invagination of membrane via clathrins - Formation of endocytosis vesicule - Retraction of membrane and detachement of endocytosis vesicule (EV) - Migration of EV into cytoplasm -Fusion of EV with lysosome and formation of digestive vacuole Clathrin : Peripheral cytosolic membrane protein de la MP qui est sous forme de triskerion (3 bras).  Exocytosis The opposite of the endocytosis Cell export substances (secrets, excretions) contained into exocytosis vesicules Mechanism : -Migration of exocytosis vesicule toword membrane -Fusion of the 2 membranes (vesicule & membrane) -Formation of diaphragme, more fragile -Breakup of diaphragme -Discharge of vesicule content out of cell. Ex of substances éeiminated by exocytosis : Saliva, the most hormones, residues of digestive vacuoles, zymogens (precursors of digestives enzymes secreted by the pancreas and spilled into duodenum) Fusion of 2 membranes via SNARE proteins  Medicales Applications : Personnel Work (Corrected in PW) Effets pharmacologiques sur perméabilité membranaire 1) Type of hemodialysis membrane 2) Type of Exchanges during hemodialysis 2) Effects of some pharmacological substances on membrane exchanges : -Antibiotics : -Local Anesthetics : -Snake Venom :  Membrane Exchanges Summury 2 modalities according to the substance sizes : Permeability : Passive (Simple/Facilitated) + Active (ATPase / MDR) Vesicular Exchange : Endocytosis (Clathrins)+ Exocytosis (SNARE)  Membrane Exchanges Diagram 2 modaliities Of PM exchange according to substance sizes Permability Vesicular Exchange Passive Active Transport Endocytosis Exocytosis Transport (0 ATP) (with ATP) (Clathrin) (SNARE) Phagocytosis Pinocytosis Facilitated Simple Diffusion (solid (liquid Diffusion Substances) substances)  Cell Signaling (Cell Communication) To ensure a function the cell receive an apropriate signal : Mitosis Metabolism Secretion Differentiation Contraction Neurotransmission Migration …….. If the cell does receive no signal => it goes to apoptosis (death)  Cell signal types - Growth factors (Polypeptides) : mitosis - Hormons (Protéines) : metabolism, secretion, contraction, …; - Lipids : imunological reaction - Photons : vision - …. - Signal lifespan : very brief ; prevents the signal modification to another one Cell signaling general diagram 1. Signal 2. Membrane Receptor 3. Signaling Cascade (Kinases) 4. Cell Answer 32 A cell receives many signals and has many receptors  Cell Signaling studied types 3 types of signal - Hormons (H) - Growth Factors : EGF, NGF, FGF, PDGF ; for mitosis -Death Factors during cell death or apoptosis: Xenobiotics, UV, H2O2, ROS 3 types of Membrane Receptors - G Protein Coupled to Receptor (GPCR) : for hormons -Thyrosine Kinase coupled to Receptor (TKR) : for Growth factors - Death Receptor : for apoptosis 4 Signaling pathways : PKA, PKC, MAPKinase, Apoptosis external pathway  Others receptors : non étudiés Ionic Chanel Coupled to Receptor (ICCR) : cf Physiology Serin Threonin kinase Receptor, Tall Like Receptor: cf Immunology Cytosolic Receptor cytosolique et nucléaire : cf. Physiology 35  1. Hormone Signaling Pathway Signal : Hormone (ex : insuline) Secreted by endocrine cell (pancreas) Bind to specific receptor PGCR on the target cell (liver, muscle) PGCR Receptor G protein : cytosolic protein ; trimric & GTP-dependant  Hormonal signal Transduction by PKA pathway Mechanism - Binding of hormon to specific GPCR - Hydrolysis of GTP - Phosphorylation and activation G protein - Displacement of G protein and activation of adenylyl cyclase (AC) -Formation of AMPc by ATP degradation by AC - Activation of protein kinase A (PKA) - Phosphorylation of target protein (ionic chanel, Enzyme or Transcription factor depends of hormon - Cell answer ; ex : gene transcription 38 Transduction of hormonal signal by PKC pathway Mecahnism - Binding of the hormone to specific GPCR - - Hydrolysis of GTP - Phosphorylation and activation of G protein - Displacement of G protein and activation of phospholipase C (PLC) - Degradation of phospholipide inositol to Diacyl glycerol (DAG) and Inositol phosphate (IP3) - IP3 bind to calcic chanel of REL and open it => calcium mobilization or exit - Activationof proteinekinase C (PKC) by DAG + Ca++ - Phosphorylation of target protein (ionic chanel, or enzyme depends tohormone - Cell answer , ex : muscle contraction, controlled secretion.  PKA versus PKC AC Signaling pathway of l’ACTH 41 Inositol Triphosphate (IP3) Pathway 42  Seconds messengers (intracellulars) a)Ca2+ : PKC b)AMPc : PKA  2. MAPKinase signaling pathway Signal : Growth Factor for mitosis or proliferation Receptor : RTK, receptor coupled to thyrosine kinase enzyme Cascade of cytosol : small G protein, several kinases, Transcription factor, cell proliferation  MAPkinase signaling pathway ▪ Growth Factor (EGF, PDGF, NGF,…) on RTK Receptor Dimerisation of RTK receptor ▪ Autophosphorylation of receptor ▪ Recrutement and activation of the small G protein Ras (and/or Rac, Rho or Cdc45) ▪ Activation of cascade of kinases  PDGF and RTK PDGF PDGF PDGF P P P Receptor Kinase Receptor Dimerisation Activation Phosphorylation Signalisation après dimérisation et phosphorylation du RTK PDGF P Voie des MAP kinases P (Mitogen-Activated Protein Kinase) P Voie PI3kinase/Akt ou PKB Activation facteurs transcription Prolifération MAPKinase pathway and cascade of activation Facteur de croissance Ras Rac Raf MEKK1 MKK1 MKK4 Erk1/2 Jnk Elk1 c-jun Phosphorylation /Déphosphorylation 49 Facteurs de croissance et RTK spécifiques  Medical Application : MAPK and Cancer In several cancers, Ras shows a punctual mutation => Ras activated permanently MAPK Continous Mutated Ras Always active proliferation Ras is the ONCOGENE Others mutations of MAPK pathwayand cancers 52 Apoptosis External Pathway or cell death Death Receptor FADD Procaspase 8 Caspase 8 Effectrices Caspases 3,6,7  Death factors inducing Apoptoise Xenobiotics, UV, H2O2, ROS, TNF, FasL Cytosolic lymphocytes T cytotoxiques ou NK activés (FasL) Apoptosis : In vivo : 20 à 30 min ; In vitro : 2 à 6 h  Apoptosis external pathway steps apoptosis Death Signal bind to death Receptor which trimerise ; ex : TNFR, FasR Recruitment of adaptator proteins (intracytoplasmic death domaine) (DD, FADD et TRADD) Recruitment of inactive procaspase 8 and its transformation to active caspase 8 Activation of effectrices caspases3, 6, 7 by caspase 8 cutoff cell proteins with cystein amino acid  Cell damaged proteins by caspases effectrices Cytoskeleton proteins : actin, βcatenin, adhesion proteins Nuclear proteins : lamins, cyclins Decrease of Telomerase activity : fixed telomeres or chromosom ends Activation of CAD (Caspase Activated DNAse) : cutoff DNA  Physiological Inhibitors of apoptosis 1) IAPs : IAP, Survivine, XIAP (increase in cancerous cells) 2) Negative regulators of IAPs : Smac/DIABLO, XAF1 (used against cancerous cell) Ex : read this signaling pathway  Fit the following table PKA PKC MAPK Apoptose Signal Receptor Cytosolic Cascade Example of Cell answer 59  Cell Adhesion The cells adhere : - To each others by membrane glycoprotiens named CAM (Cell adhesion molecules) - To extracell matrix (ECM by SAM (Substrat adhesion molecules) Deux sortes de molécules d’adhésion : CAM et SAM CAM + SAM  Selectin Family : 3 members L slectins (leucocytes) P selectins (platelettes) E selectins (endothelial cells)  ICAM Family : 100 members Interactions between immun & nervous cell systems ex : Vascular cell adhesion molecules (VCAM) Neural cell adhesion molecules (NCAM) Intercellular adhesion molecules (ICAM) 63  Cadherins : 20 types - Glycoproteins, calcium +/- calcium - 20 types : E-cadherin (epithelial cells) P-cadherin (placenta) N-cadherin (neurones) VE-cadherin (vascular endothelial cells) 64  Integrins Family (Cell/ECM, SAM) : 20 types Heterodimeres with 2 sub units : alpha & beta Interact with the ECM extracell componants (fibronectin, laminin, collagen,…) 65  Medical Applications -Integrins & metastasis -Platelettes, integrins deficit & continous bleeding -Pemphigus or bullous disease  To keep in mind PM components and rules (Table) Membrane Exchanges (Table) Cell Signaling pathways (Table) Cell Adhesion (Classification) Medical Applications 67  Bibliography: 1- Anatomie et physiologie du corps humaines. Elaien Marieb et Katja Hoehn. ISBN-13: 9780321695987. Pearson 15 novembre 2019. Paper, 656 pp 2- Biologie cellulaire. Yann BASSAGLIA, éditeur MALOINE, collection Sciences fondamentales, 2013, ISBN 9782224032555. 1. 3- Cours de Biologie cellulaire (Les cours du PCEM). Pierre Cau et Raymond Seite - 5e édition. Collection Ellipses. Paris. 2012 4- L’essentiel de la biologie cellulaire Alberts Bray - Johnson Lewis Raff - Roberts Walter. Ed. Médecine - Sciences- Flammarion, Paris, 1999. 5. Lexique de Biologie (Biologie cellulaire- Cytogénétique- Embryologie-Histologie) T. Aboussaouira. ed. Dar Nachr Al Mâarifa, Rabat, 1998 6- QCM de Biologie avec réponses commentées. Chraibi-Hajji F. et Aboussaouira T. ed. Gaëtan -Morin Maghreb, Casablanca, 1996 7- Vocabulaire d’Histologie M. Guerbaoui et Aboussaouira - Yahyaoui - Jarmouni - Benaddi. Casablanca, 1999. 8- Questions Corrigées et Commentées d’Histologie - Embryologie. nRadallah D, Amrani Najat, Yahyaoui O, Benmessaoud Jarmouni L, Benaddi A, Aboussaouira T 9- L’Elévation du Plancher sinusien en Implantologie Orale. ElHamid A - Lazaroo B - Tilotta F - Aboussaouira T - Baite M - Benjelluon A Eddaif M. 2016. 10- Webographie : Youtube : Harvard cell animation - Laurent Martorell : animation cellule, transduction du signal 68  Bibliography: 1- Anatomie et physiologie du corps humaines. Elaien Marieb et Katja Hoehn. ISBN-13: 9780321695987. Pearson 15 novembre 2019. Paper, 656 pp 2- Biologie cellulaire. Yann BASSAGLIA, éditeur MALOINE, collection Sciences fondamentales, 2013, ISBN 9782224032555. 1. 3- Cours de Biologie cellulaire (Les cours du PCEM). Pierre Cau et Raymond Seite - 5e édition. Collection Ellipses. Paris. 2012 4- L’essentiel de la biologie cellulaire Alberts Bray - Johnson Lewis Raff - Roberts Walter. Ed. Médecine - Sciences- Flammarion, Paris, 1999. 5. Lexique de Biologie (Biologie cellulaire- Cytogénétique- Embryologie-Histologie) T. Aboussaouira. ed. Dar Nachr Al Mâarifa, Rabat, 1998 6- QCM de Biologie avec réponses commentées. Chraibi-Hajji F. et Aboussaouira T. ed. Gaëtan -Morin Maghreb, Casablanca, 1996 7- Vocabulaire d’Histologie M. Guerbaoui et Aboussaouira - Yahyaoui - Jarmouni - Benaddi. Casablanca, 1999. 8- Questions Corrigées et Commentées d’Histologie - Embryologie. nRadallah D, Amrani Najat, Yahyaoui O, Benmessaoud Jarmouni L, Benaddi A, Aboussaouira T 9- L’Elévation du Plancher sinusien en Implantologie Orale. ElHamid A - Lazaroo B - Tilotta F - Aboussaouira T - Baite M - Benjelluon A Eddaif M. 2016. 10- Webographie : Youtube : Harvard cell animation - Laurent Martorell : animation cellule, transduction du signal 69