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Chapter 11 Cell Communication PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cell communication processes share common features that reflect a shared evolutionary history. • The basics of cell communication are found in all living things. • Signals from other cells or the environment can be stimulatory (turn on a gene or protein) or inhibitory (turn off a gene or protein) • Natural selection favors correct and appropriate signal transduction processes. • In single-celled organisms, signal transduction pathways influence how the cell responds to its environment. Cell-to-cell communication is essential for ALL organisms to detect changes in the environment and respond appropriately. 1. 1. Signal (usually a molecule) 2. 2. Signal Receptor (protein) Protein activated or inactivated 3. 4. Gene expression turned on or off Group behaviors that promotes individuals’ survival are an adaptation favored by natural selection 3. Signal Transduction (other proteins/ molecules that convert the signal into a response ) 4. Cell Response (change in gene expression and or protein activity) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Quorum Sensing in Bacteria reveals the evolutionary origins of cell communication • Signaling molecule concentration allows bacteria to detect population density • Bacteria evolved the beginnings of multicellularity: – self vs. other Group behavior gene expression turned on Capsule protein to form colony Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Bacterial Biofilm Formation involves cell signaling 1. Attachment: Motile bacteria swim towards surface rich with nutrients. Turn on genes associated with forming a biofilm. 2. Growth: Bacteria in biofilm grow and divide. 3. Dispersal. Bacteria in center do not receive as much nutrition, this turns on motility associated genes. Bactera disperse to find a new nutrient source. Essential knowledge: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. • Cell To Cell Contact: Using membrane bound receptors • Short (local signaling): Secreted molecules that diffuse over short distances • Long Distances: Secreted molecules that travel throughout the body Cell communication is essential for individual cells support the function of the organism as a whole. In other words.. “All for one and one for all” Stress Epinephrine Glycogen Glucose Cell to Cell Contact: used to distinguish “self” from “other” • Animal cells have MHC proteins on the surface of the cell to distinguish “self” from “other” • Antigen Presenting Cells present antigen to T cells by cell-cell contact. • Recognition of foreign antigen causes T cell to signal to other immune cells to mature. B Cells are antigen presenting cells to T helper cells • B cells present antigen to TH cell. • If the T cell receptor recognizes the antigen it will release lymphokines • The B cell matures into a plasma cell and releases antibodies into the blood plasma. Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell. Local signaling • Neurotransmitters released in the synapse Electrical signal Target cell along nerve cell triggers release of neurotransmitter Secreting cell Local regulator diffuses through extracellular fluid (a) Paracrine signaling Neurotransmitter diffuses across synapse Secretory vesicle Target cell is stimulated (b) Synaptic signaling Long-distance signaling Signals released by one cell type can travel long distances to target cells of another cell type. Endocrine cell Blood vessel Hormone travels in bloodstream to target cells Target cell (c) Hormonal signaling 1. The endocrine hormones FSH and LH are made by the pituitary gland in the brain. 2. These hormones coordinate the maturation of ovules and and Endometrium The Three Stages of Cell Signaling – Reception – Transduction – Response Animation: Overview of Cell Signaling Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 11-6-1 EXTRACELLULAR FLUID 1 Reception Receptor Signaling molecule CYTOPLASM Plasma membrane Fig. 11-6-2 CYTOPLASM EXTRACELLULAR FLUID Plasma membrane 1 Reception 2 Transduction Receptor Relay molecules in a signal transduction pathway Signaling molecule Fig. 11-6-3 CYTOPLASM EXTRACELLULAR FLUID Plasma membrane 1 Reception 2 Transduction 3 Response Receptor Activation of cellular response Relay molecules in a signal transduction pathway Signaling molecule Receptors can exist on the surface of the cell or in the cytoplasm Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein EXTRACELLULAR FLUID Plasma membrane CYTOPLASM 1 Reception Receptor CYTOPLASM DNA Signaling molecule NUCLEUS Signal transduction pathways link signal reception with cellular response. 1. Signaling recognition: chemical messenger (ligand) binds to receptor protein. – Chemical messenger can be a peptide, small inorganic molecule, or lipid hormone – Receptor and ligand have complementary structures and fit together like a lock and key. (Concepts from enzymes such as affinity apply) 2. Binding causes change in receptor protein shape 3. Shape change initiates transduction of the signal. Receptors in the Plasma Membrane • Most water-soluble signal molecules bind to receptor proteins in the plasma membrane • There are three main types of membrane receptors: – G protein-coupled receptors – Receptor tyrosine kinases – Ion channel receptors Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 11-7b G Protein Coupled Receptors Plasma membrane G protein-coupled receptor Activated receptor Signaling molecule GDP CYTOPLASM GDP Enzyme G protein (inactive) 1 Activated Adenylyl Cyclase GTP 2 GTP GDP Pi ATP Signal is terminated Cellular response 4 3 cAMP Other Enzymes Activated Inactive Adenylyl Cyclase Fig. 11-7c Receptor Tyrosine Kinase Ligand-binding site Signaling molecule (ligand) Signaling molecule Tyrosines Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Tyr Receptor tyrosine kinase proteins CYTOPLASM Dimer 1 2 Activated relay proteins Tyr Tyr Tyr Tyr P Tyr P Tyr Tyr Tyr P 6 ATP Activated tyrosine kinase regions 6 ADP Tyr Tyr P Tyr Tyr P Tyr P Tyr P Tyr Tyr P P P P Tyr P Tyr Fully activated receptor tyrosine kinase Inactive relay proteins 3 4 Cellular response 1 Cellular response 2 Fig. 11-7d Ligand-gated ion channel receptors Lingand binding causes channel to change shape 1 Signaling molecule (ligand) Gate closed Ligand-gated ion channel receptor 2 Channel opening can allow specific ions, such as Na+ or Ca2+, through a channel in the receptor. Ions Plasma membrane Gate open Cellular response 3 Gate closed Fig. 11-8-5 Intracellular Receptors •Hydrophobic molecules can diffuse directly through the membrane and bind to receptors in the cytoplasm Hormone (testosterone) EXTRACELLULAR FLUID Plasma membrane Receptor protein Hormonereceptor complex DNA •Activated hormonereceptor complex goes to the nucleus and can turn on specific genes mRNA NUCLEUS CYTOPLASM New protein Signal transduction coverts the signal to a cellular response 1. Signaling transduction cascades involve: • Modifying Protein structure • Generate second messenger • Phosphorylation cascade • Amplification of signal Fig. 11-14 Signaling cascades involve: •Generation of a Second Messenger •Phosphorylation cascade •Protein Modification •Amplification Growth factor Reception Receptor Phosphorylation cascade Transduction CYTOPLASM Inactive transcription factor Active transcription factor P Response DNA Gene NUCLEUS mRNA Common Second Messengers • Second Messenger: a small non protein molecule that diffuses rapidly through the cell during signal transduction. – Cyclic AMP (cAMP) – Inositol triphosphate (IP3) – Calcium ion (Ca2+) Fig. 11-11 First messenger Adenylyl cyclase G protein G protein-coupled receptor GTP •Protein Modification •Second Messenger •Phosphorylation cascade •Amplification ATP cAMP Second messenger Protein kinase A Cellular responses G protein-coupled receptor: found in the cell membrane • Ligand binding activates the G protein • Signal Transduction occurs inside the cell – The G protein activates Adenylyl Cyclase – Adenylyl Cyclase makes a second messenger Cyclic AMP – Cyclic AMP activates Protein Kinase A – Protien Kinase A activates a phosphorylation cascade Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings •Protein Modification •Second Messenger •Phosphorylation cascade •Amplification Fig. 11-13-3 EXTRACELLULAR FLUID Signaling molecule (first messenger) G protein DAG GTP G protein-coupled receptor Phospholipase C PIP2 IP3 (second messenger) IP3-gated calcium channel Endoplasmic reticulum (ER) CYTOSOL Ca2+ Various proteins activated Ca2+ (second messenger) Cellular responses Fig. 11-9 Signaling molecule Receptor •Protein Modification •Second Messenger •Phosphorylation cascade •Amplification Activated relay molecule Inactive Kinase 1 Active Kinase 1 Inactive Kinase 2 ATP ADP Pi P Active Kinase 2 PP Inactive Kinase 3 ATP ADP Pi P Active Kinase 3 PP Inactive protein ATP P ADP Pi PP Active protein Cellular response Definitions • Ligand: the chemical signal that binds to a receptor. • Receptor: a protein that can bind to the signal (in the case of a molecule) or detect a signal in the case of light or other non-molecule signals. • Kinase: an enzyme that attaches a phosphate to another protein (usually activating it) • Phosphatase: an enzyme that removes phosphate from a protein (usually inactivating it) • Second Messenger: a small non protein molecule that diffuses rapidly through the cell during signal transduction. Examples include cAMP, IP3, DAG, Ca2+ • Reception: when the receptor binds to the signal, causing the receptor to change shape. • Signal Transduction: converting a signal into a cellular response. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 11-10 In case you were curious… modification of ATP to form cyclic AMP Adenylyl cyclase Phosphodiesterase Pyrophosphate P ATP Pi cAMP AMP Cell Communication Review: 1. What are the 4 basic parts/ requirements of cell signaling? 2. Give/ describe an example of how bacteria detect and respond to their environment using cell signaling. 3. Why is cell signaling a universal characteristic of life (why is it necessary, what advantages does it give)? 4. What are the two basic cellular responses to a signal? 5. What are the three types of cell to cell communication in multicellular organisms. Give an example of each type. 6. Describe the nature of a ligand-receptor interaction and state how such interactions initiate a signal-transduction system. 7. Explain how an original signal molecule can produce a cellular response when it may not even enter the target cell. 8. What are the four features of signal transduction cascade. Give an example of each type from one of the types of signaling pathways discussed? 9. Define the term second messenger; briefly describe the role of these molecules in signaling pathways 10. Explain why different types of cells may respond differently to the same signal molecule. For example, Epinephrine causes relaxation of smooth muscle and contraction of skeletal muscle.