Cell Communication Topics 4.1 through 4.2
Topic 4.1 Cell Communication
Importance of Cell Communication • Cell signaling allows cells to communicate with one another and coordinate the functions/activities of the organism • Communication pathways usually involve the plasma membrane
Cell Communication • Cells communicate with one another through cell-to-cell contact or from a distance via chemical signaling • Correct and appropriate signal transduction pathways are generally under strong selective pressure
Single-Celled Organisms (How Bacteria “Talk”, 18:14) • In single-celled organisms, cell communication pathways influence how the cell responds to its environment • Example: quorum sensing in bacteria
Multicellular Organisms • In multicellular organisms, cell communication pathways coordinate the activities within individual cells that support the function of the organism as a whole • Example: Epinephrine stimulation of glycogen breakdown in mammals
Cell Communication Cell-to-Cell Chemical Contact Signaling Local Plasmodesmata Regulators Immune Hormones System Cells
Examples of Cell-to-Cell Contact
Plasmodesmata • Microscopic channels which traverse the cell walls of plant cells and some algal cells, enabling transport and communication between them • Allow material to be transported from cell to cell (proteins, ions, etc.)
Immune System Cells • Some immune cells interact by cell-to-cell contact • Examples include antigen-presenting cells (APCs), helper T-cells , and killer T-cells
What are antigens and antibodies? • Antigen: any substance that causes the immune system to produce antibodies (“antibody - generating”) • Antibodies: Y-shaped proteins that are produced by B cells , identify and neutralize pathogens (antigens)
How Antibodies Work
Immune Cell: Antigen-Presenting Cell (Antigen Processing and Presentation Animation 2:30) • Antigen-presenting cells process and present antigens for recognition by certain lymphocytes such as T cells • Examples of antigen-presenting cells include macrophages , dendritic cells , and B cells
MHC Molecules
Immune Cell: Helper T • Helper T cells are the most important cells in adaptive immunity • Three ways in which helper T cells “help” the immune response: – stimulate B cells to produce more antibodies to the specific antigen – activate and increase the number of macrophages – activate cytotoxic (killer) T cells to kill infected cells
Helper T Cells
Immune Cell: Cytotoxic (Killer) T • Cytotoxic T cells target and destroy cells that are infected with pathogens
Examples of Chemical Signaling
Local Regulators • Local regulators are signaling molecules that only target cells in the vicinity of the signal emitting cell (short distance) • Examples of local regulators include neurotransmitters , morphogens , and quorum sensing
Local Regulator: Neurotransmitters
Local Regulator: Morphogens • Morphogens are a group of chemicals that are involved in the patterning of cells during embryonic development
Local Regulator: Quorum Sensing • Bacteria produce and release chemical signal molecules called autoinducers that increase in concentration as a function of cell density
Hormones • Hormones produced by endocrine cells travel long distances, through the blood, to reach their target cells • Examples of hormones include insulin and human growth hormone
Insulin Signaling Pathway (Insulin Signaling Animation 4:42) • Insulin is produced by the pancreas and targets cells of the liver, skeletal muscle and fat
Plant Hormones • Ethylene – gaseous hormone that ripens fruit • Auxin – chemical messenger that influences fruit development and cell growth
Topic 4.2 Introduction to Signal Transduction
Signal Transduction Pathway • The general pathway of signal transduction for cell-to-cell contact or chemical signaling is the same
Signal Transduction Pathway Professor Dave Explains Signal Transduction (6:32)
Signal Transduction • Signal transduction pathways link signal reception with a cellular response • Many signal transduction pathways include protein modification (shape change) and phosphorylation cascades
Stage 1: Signal Reception • Signaling begins with the recognition of a chemical messenger – a ligand - by a receptor protein in a target cell • The ligand has a complementary shape to the receptor
Ligand Types • The chemical messengers, or ligands, can be a peptide, a small chemical, or protein, in a specific one-to-one relationship with the receptor
Types of Receptor Proteins • Receptor proteins may be embedded within the plasma membrane or located within the cytoplasm or nucleus
Transmembrane Receptors • Embedded within the membrane, also known as extracellular receptors • Examples include GPCRs and ligand-gated ion channels
G protein-coupled receptors (GPCRs) • An example of a receptor protein found in eukaryotes, thousands of different types • The epinephrine signaling pathway involves a GPCR
Epinephrine Signaling Pathway Epinephrine Signaling Animation 3:10
Ligand-Gated Ion Channels
Intracellular Receptors • Located within the cytoplasm or nucleus • Targeted by lipid soluble ligands that are able to pass through the plasma membrane
Stage 2: Signal Transduction • Signal transduction is the process by which a signal is converted to a cellular response • After the ligand binds, the intracellular domain of a receptor protein changes shape, initiating transduction of the signal • Occurs in one step or a series of many steps
Signal Transduction • Signaling cascades relay signals from receptors to cell targets, often amplifying the incoming signals • Some signaling cascades utilize second messengers (such as cyclic AMP, or cAMP) during the signal transduction pathway to relay and amplify the intracellular signal
Enzymes Involved in Signal Transduction • Protein kinases – turn “on” or activate proteins by adding phosphates to the proteins ( phosphorylation cascade ) • Protein phosphatases – turn “off” or deactivate proteins and kinases by removing phosphates from the proteins ( dephosphorylation )
Second Messengers
Stage 3: Cellular Response • The signal transduction pathway initiates a change in cellular activity • Response occurs in the cytoplasm or nucleus
Cellular Response • Cellular responses include cell growth, secretion of molecules, or gene expression, among others • Most signaling pathways activate transcription factors that control the cellular response – Examples: Epidermal growth factor and testosterone
Epidermal Growth Factor • Signaling pathway that promotes cell growth and division
Testosterone Cellular response increases gene activity for proteins involved in: • Muscle mass • Bone growth • Body hair • Reproductive tissue
Transcription Factors • Transcription factors regulate cellular responses by: - Turning “on” genes Protein OR - Turning “off” genes No protein OR - Regulating the activity of a particular protein
Signal Transduction Review
Cell Communication 4.1 and 4.3 Direct Contact What type of cell is this?
Cell Communication and Cell Signaling Why is cell signaling important? Why
Cell Communication Cell Communication Communication between cells requires:
Communication Analysis of the Communication Analysis of the Communication
Cell to Cell signalling and communication during the establishment of the
INVESTIGATING THE EFFECTS OF NOISE ON A CELL-TO-CELL COMMUNICATION MECHANISM
The TUDelft iGEM team presents: Bacterial Relay Race 09 An illustration of a
INTRODUCING SIMULATED STEM CELLS INTO A BIO-INSPIRED CELL- CELL COMMUNICATION
U U U U U U U- U - - communication - - - - - communication
Cells to Tissues What well talk about Types and properties of tissues Cell
PARTICLE-CELL INTERACTIONS AND THEIR IMPLICATIONS IN LUNG DEFENSE MECHANISMS
The Major Histocompatibility Complex Peter Burrows 2008 4-6529
Forget Moonshots Biomedicine Needs an Air Traffic Control System Jeff
5529 ADXS11-001 IMMUNOTHERAPY: 12 MONTH SURVIVAL AND SAFETY DATA FROM A
Designing cancer vaccines with deep learning Mikhail Ignatov, Applied
Molecular determinants of factor VIII immunogenicity Moderator Prof. dr.
Immuno-Oncology Applications Lee S. Schwartzberg, MD, FACP West Clinic, P.C.;
University of Cologne Institute of Virology HLA alleles in the context of
plc Developing Innovative Peptides August 2019 Compa pany ny overv rview
Sergio E. Baranzini, Ph.D. Professor Department of Neurology, UCSF
BriaCell Therapeutics Corp. OTCQB: BCTXF JULY 2016 TSX-V: BCT Forward-Looking
Presentation by Dr Lindsay Nicholson LDA Conference 2011 Overview Immune