Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Chapter 11 Cell Communication

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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 1. Signal (usually a molecule) 2. Signal Receptor (protein) 3. Signal Transduction (other proteins/ molecules that convert the signal into a response ) 4. Cell Response (change in gene expression and or protein activity) Gene expression turned on or off Protein activated or inactivated Group behaviors that promotes individuals’ survival are an adaptation favored by natural selection

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Group behavior gene expression turned on Capsule protein to form colony

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.

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 Essential knowledge: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.

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” Epinephrine GlucoseGlycogen Stress

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. Cell to Cell Contact: used to distinguish “self” from “other”

B Cells are antigen presenting cells to T helper cells B cells present antigen to T H 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. Neurotransmitters released in the synapse Local signaling Target cell Secretory vesicle Secreting cell Local regulator diffuses through extracellular fluid (a) Paracrine signaling (b) Synaptic signaling Target cell is stimulated Neurotransmitter diffuses across synapse Electrical signal along nerve cell triggers release of neurotransmitter

Signals released by one cell type can travel long distances to target cells of another cell type. Long-distance signaling 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 Animation: Overview of Cell Signaling Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig Reception 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM 1 Receptor

Fig EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM Transduction 2 Relay molecules in a signal transduction pathway Reception 1 Receptor

Fig EXTRACELLULAR FLUID Plasma membrane CYTOPLASM Receptor Signaling molecule Relay molecules in a signal transduction pathway Activation of cellular response TransductionResponse 2 3 Reception 1

Receptors can exist on the surface of the cell or in the cytoplasm Reception 1 EXTRACELLULAR FLUID Signaling molecule Plasma membrane CYTOPLASM 1 Receptor Hormone (testosterone) Receptor protein Plasma membrane EXTRACELLULAR FLUID DNA NUCLEUS CYTOPLASM

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 receptor Plasma membrane Enzyme G protein (inactive) GDP CYTOPLASM Activated Adenylyl Cyclase GTP Cellular response GDP P i Activated receptor GDP GTP Signaling molecule Inactive Adenylyl Cyclase ATP G Protein Coupled Receptors cAMP Other Enzymes Activated Signal is terminated

Fig. 11-7c Signaling molecule (ligand) Ligand-binding site Tyrosines Tyr Receptor tyrosine kinase proteins CYTOPLASM Signaling molecule Tyr Dimer Activated relay proteins Tyr P P P P P P Cellular response 1 Cellular response 2 Inactive relay proteins Activated tyrosine kinase regions Fully activated receptor tyrosine kinase 6 6 ADP ATP Tyr P P P P P P Receptor Tyrosine Kinase

Fig. 11-7d Signaling molecule (ligand) Gate closed Ions Ligand-gated ion channel receptor Plasma membrane Gate open Cellular response Gate closed Ligand-gated ion channel receptors Lingand binding causes channel to change shape Channel opening can allow specific ions, such as Na + or Ca 2+, through a channel in the receptor.

Fig Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA mRNA NUCLEUS New protein CYTOPLASM Intracellular Receptors Hydrophobic molecules can diffuse directly through the membrane and bind to receptors in the cytoplasm Activated hormone- receptor complex goes to the nucleus and can turn on specific genes

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 Growth factor Receptor Phosphorylation cascade Reception Transduction Active transcription factor Response P Inactive transcription factor CYTOPLASM DNA NUCLEUS mRNA Gene Signaling cascades involve: Generation of a Second Messenger Phosphorylation cascade Protein Modification Amplification

Common Second Messengers Second Messenger: a small non protein molecule that diffuses rapidly through the cell during signal transduction. – Cyclic AMP (cAMP) – Inositol triphosphate (IP 3 ) – Calcium ion (Ca 2+)

First messenger Fig G protein Adenylyl cyclase GTP ATP cAMP Second messenger Protein kinase A G protein-coupled receptor Cellular responses Protein Modification Second Messenger Phosphorylation cascade Amplification

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

Fig G protein EXTRA- CELLULAR FLUID Signaling molecule (first messenger) G protein-coupled receptor Phospholipase C PIP 2 DAG IP 3 (second messenger) IP 3 -gated calcium channel Endoplasmic reticulum (ER) Ca 2+ CYTOSOL Various proteins activated Cellular responses Ca 2+ (second messenger) GTP Protein Modification Second Messenger Phosphorylation cascade Amplification

Fig Signaling molecule Receptor Activated relay molecule Inactive Kinase 1 Active Kinase 1 Inactive Kinase 2 ATP ADP Active Kinase 2 P P PP Inactive Kinase 3 ATP ADP Active Kinase 3 P P PP i ATP ADP P Active protein PP P i Inactive protein Cellular response Phosphorylation cascade i Protein Modification Second Messenger Phosphorylation cascade Amplification

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 Definitions

Adenylyl cyclase Fig Pyrophosphate P P i ATP cAMP Phosphodiesterase AMP In case you were curious… modification of ATP to form cyclic 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.