Cell Communication Warm-Up 1. Why do you communicate? 2. How do you communicate? 3. How do you think cells communicate? 4. Do you think bacteria can communicate? Explain. Warm-Up 1. Compare the structure & function of these receptor proteins: GPCR, tyrosine kinase and ligand-gated ion channels. 2. What is a second messenger? What are some examples of these molecules? 3. What are the possible responses to signal transduction in a cell? Cell Communication CHAPTER 11 What you should know: The 3 stages of cell communication: reception, transduction, and response. How G-protein-coupled receptors receive signals and start transduction. How receptor tyrosine kinase receive cell signals and start transduction. How a cell signal is amplified by a phosphorylation cascade. How a cell response in the nucleus turns on genes while in the cytoplasm it activates enzymes. What apoptosis means and why it is important to normal functioning of multicellular organisms. Do bacteria communicate? Bonnie Bassler on How Bacteria Talk Video Questions: 1. Why are scientists studying how bacteria (and not just human cells) communicate? 2. What is quorum sensing? 3. Describe how Vibrio fischeri use quorum sensing in squid. 4. According to Bonnie Bassler (Princeton University), what are scientists hoping to use as the next class of antibiotics? Cell Signaling Animal cells communicate by: Direct contact (gap junctions) Secreting local regulators (growth factors, neurotransmitters) Long distance (hormones) Cell Signaling Examples 3 Stages of Cell Signaling: 1. Reception: Detection of a signal molecule (ligand) coming from outside the cell 2. Transduction: Convert signal to a form that can bring about a cellular response 3. Response: Cellular response to the signal molecule Video: Cell Signaling Basics (Chapman) https://www.youtube.com/watch?v=8FJkjiNRLh8 https://www.youtube.com/watch?v=8FJkjiNRLh8 **Note- Signal Transduction is defined as a process that converts a signal on cells surface to a specific cellular response in a series of steps Reception Transduction Response 1. Reception Binding between signal molecule (ligand) + receptor is highly specific. Types of Receptors: a) Plasma membrane receptor water-soluble ligands b) Intracellular receptors (cytoplasm, nucleus) hydrophobic or small ligands Eg. testosterone or nitric oxide (NO) Ligand binds to receptor protein protein changes SHAPE initiates transduction signal Plasma Membrane Receptors G-Protein Coupled Receptor (GPCR) Tyrosine Kinase Ligand-Gated Ion Channels G-Protein-Coupled Receptor Short video https://www.youtube.com/watch?v=xT0mAQ4726s (G Protein Receptor Activation Video by Z Abrahim) **Others on youtube: (Chapman) https://www.youtube.com/watch?v=On8CGKDfXd8 https://www.youtube.com/watch?v=On8CGKDfXd8 Others on Cell Communication: Garland Science Videos; Kahn Academy G-Protein-Coupled Receptor Plasma Membrane Receptors G-Protein Coupled Receptor (GPCR) Tyrosine Kinase Ligand-Gated Ion Channels 7 transmembrane segments in membrane G protein + GTP activates enzyme one cellular response Receptor Tyrosine Kinase https://www.youtube.com/watch?v=ObrsQl-vPA4 (Receptor Tyrosine Kinase by HeyNow 1003) **Others recommended: (Chapman) https://www.youtube.com/watch?v=J_vdVcuzi1U https://www.youtube.com/watch?v=J_vdVcuzi1U Receptor Tyrosine Kinase Plasma Membrane Receptors G-Protein Coupled Receptor (GPCR) Tyrosine Kinase Ligand-Gated Ion Channels Attaches (P) to tyrosine Activate multiple cellular responses at once Ligand Gated Ion Channels Short video: Ion Channel Receptors (HeyNow1103): Recommended: (Chapman) https://www.youtube.com/watch?v=USKkLQYhuyY&ind ex=4&list=PLyV_IM5FlqWpW17e8xRPaWUQip2o-- uPC https://www.youtube.com/watch?v=USKkLQYhuyY&ind ex=4&list=PLyV_IM5FlqWpW17e8xRPaWUQip2o-- uPC Ligand-Gated Ion Channel Plasma Membrane Receptors G-Protein Coupled Receptor (GPCR) Tyrosine Kinase Ligand-Gated Ion Channels Signal on receptor changes shape Regulate flow of specific ions (Ca 2+, Na + ) Plasma Membrane Receptors G-Protein Coupled Receptor (GPCR) Tyrosine Kinase Ligand-Gated Ion Channels 7 transmembrane segments in membrane Attaches (P) to tyrosine Signal on receptor changes shape G protein + GTP activates enzyme cell response Activate multiple cellular responses at once Regulate flow of specific ions (Ca 2+, Na + ) Intracellular Receptors Molecules that are small enough or hydrophobic and pass through the membrane - directly activate intracellular receptors in the cytoplasm or nucleus of target cell Intracellular Receptors Quick and easy: https://www.youtube.com/watch?v=upEV52vdhuk https://www.youtube.com/watch?v=upEV52vdhuk A little more detailed: https://www.youtube.com/watch?v=Nm9u4lNCPyM https://www.youtube.com/watch?v=Nm9u4lNCPyM Both are by Biology/ Medicine *Chapman has videos on youtube for this entire unit. Search John Chapman Biology. Very good at explaining the info in your book. 2. Transduction- Overview (primarily next test) Cascades of molecular interactions relay signals from receptors target molecules Protein kinase: enzyme that phosphorylates and activates proteins at next level Phosphorylation cascade: enhance and amplify signal *See next slide for overview, which you should be able to generally recognize on this test. CW- Videos Bozeman AP Biology Video #36 (Evolution of Cell Communication): Answer these questions in your journal: 1- What is quorum sensing?; 2- Explain how this process works Bozeman AP Video #38. Watch and complete the review sheet Transduction Specific mechanisms will be on Test #4, along with the remainder of Ch 11, including apoptosis Second Messengers- (next test) small, nonprotein molecules/ions that can relay signal inside cell Eg. cyclic AMP (cAMP), calcium ions (Ca 2+ ), inositol triphosphate (IP 3 ) cAMP cAMP = cyclic adenosine monophosphate GPCR adenylyl cyclase (convert ATP cAMP) activate protein kinase A 3. Response Regulate protein synthesis by turning on/off genes in nucleus (gene expression) Regulate activity of proteins in cytoplasm An Example of Cell Communication Signal Transduction Pathway Problems/Defects: Examples: Diabetes Cholera Autoimmune disease Cancer Neurotoxins, poisons, pesticides Drugs (anesthetics, antihistamines, blood pressure meds) Cholera Disease acquired by drinking contaminated water (w/human feces) Bacteria (Vibrio cholerae) colonizes lining of small intestine and produces toxin Toxin modifies G-protein involved in regulating salt & water secretion G protein stuck in active form intestinal cells secrete salts, water Infected person develops profuse diarrhea and could die from loss of water and salts Viagra Used as treatment for erectile dysfunction Inhibits hydrolysis of cGMP GMP Prolongs signal to relax smooth muscle in artery walls; increase blood flow to penis Viagra inhibits cGMP breakdown Apoptosis = cell suicide Cell is dismantled and digested Triggered by signals that activate cascade of suicide proteins (caspase) Why? Protect neighboring cells from damage Animal development & maintenance May be involved in some diseases (Parkinsons, Alzheimers) Apoptosis of a human white blood cell Left: Normal WBC Right: WBC undergoing apoptosis shrinking and forming lobes (blebs) Effect of apoptosis during paw development in the mouse