Cell Communication Chapter 9 PDF

Cell Communication Chapter 9  Core concepts 9.1 Sending and receiving signals 9.2 Signal classification 9.3 Cell-surface and intracellular receptors 9.4 G Protein-coupled receptors 9.5 Receptor kinases 9.1 Principles of Cell Communication Essential Elements for Communicatio...

Cell Communication Chapter 9  Core concepts 9.1 Sending and receiving signals 9.2 Signal classification 9.3 Cell-surface and intracellular receptors 9.4 G Protein-coupled receptors 9.5 Receptor kinases 9.1 Principles of Cell Communication Essential Elements for Communication Signaling cell Signaling molecule Receptor molecule Receptor cell Steps in Cell Signaling  Communication in Bacterial Cells: Uptake of DNA from the Environment 9.2 Cell Signaling Over Long and Short Distances Signaling Over Long and Short Distances 1. Endrocrine – large distances 2. Paracrine – up to ~20 cells away 3. Autocrine – cell is the signaling and responding cell (self) 4. Juxtacrine – Direct physical contact 1. Endocrine signaling 1. Endocrine signaling 2. Paracrine signaling Growth Factors 3. Autocrine signaling 4. Juxtacrine signaling  Contact-Dependent Signaling: Vertebrate CNS Development Some undifferentiated cells will begin to express the protein Delta. Delta is the signal, and Notch is the receptor. Cells expressing Delta will become neurons, and cells expressing Notch bound to a cell expressing Delta will become the glial cells that support neurons. 9.3 Cell-Surface and Intracellular Receptors Signaling Molecule and Receptors Ligand: signaling molecule Ligand-binding site: location on the receptor to which the ligand binds The ligand binding to ligand-binding site causes a conformational change in the receptor  Intracellular Receptors Nonpolar signaling molecules (e.g., steroid hormones) are able to cross the cell membrane and bind an intracellular receptor in the cytoplasm or nucleus.  Cell-Surface Receptors Polar signaling molecules cannot cross the cell membrane and instead bind to transmembrane proteins that are cell-surface receptors. Once bound to its ligand, the cell-surface receptor/ligand complex undergoes a conformation change and the receptor is activated. Receptor Behavior  Three Types of Cell-Surface Receptors There can be thousands of different proteins on the surface of any given cell. The proteins involved in cell signaling can be classified into three main groups: 1. G protein-coupled receptors 2. receptor kinases 3. ion channels Two Types of Intracellular Receptors 1. In the cytosol → nucleus 2. In nucleus  Cell-Surface Receptors 1. G protein-coupled receptor 2. Receptor kinase 3. Ligand-gated ion channel  Intracellular receptors 1. Cytosol → nucleus 2. Nucleus Activated Activated receptor receptor 9.4 G Protein-coupled Receptors and Short-term Response 1. G Protein Activation Example of G Protein Activation Adrenaline signaling in heart and muscle Amplification of Adrenaline Signal  All Signaling Must End: G Protein Signal Termination When the concentration of adrenaline eventually wanes, adrenaline will diffuse off of the receptor and the receptor will then revert to its inactive form. The receptor no longer activates the G protein, GTP is converted to GDP, and adenylyl cyclase no longer produces the second messenger cAMP.  G Protein Signal Termination: The Role of Phosphatases Enzymes in the cytosol degrade cAMP, which stops the activation of more protein kinase A molecules. Phosphatases remove phosphate groups from activated proteins, making them inactive. Signaling: Fight-or-Flight Response 9.5 Receptor Kinases and Long-term Responses 2. Receptor Kinases Receptor Kinase Activation and Signaling  The MAP Kinase Pathway E.g. Platelet derived growth factor (PDGF) The MAP Kinase Pathway 3. Ligand-Gated Ion Channel  Cell Signaling and Cancer Increased or altered receptors Overproduced or altered signaling molecule Ras mutations  Integration of Signaling Pathways Effects can be: – Simple or complex – Different depending on cell type – Integrated