Cell communication

Cell communication

1. Signal Transduction

   • The process by which extracellular signalling molecules cause changes in target cells.
   • The ability of organisms, or individual cells within an organism, to sense and respond to the signals in their environment is crucial to their development and survival.
     • - even single celled organisms eg. yeast Dictyostelium

2. Types of signals

   • Proteins
     • Insulin
     • Hedgehog
     • Wnt
   • Small peptides
     • Endorphins
     • ACTH
   • Amino acids
     • Glutamate
   • Nucleotides
     • ATP
   • Steroids
     • Oestrogen
     • Testosterone
   • Fatty acid derivatives
     • Prostaglandins
   • Dissolved gases
     • Nitric oxide

3. Classes of receptors

   • Cell surface receptors
   • Intracellular receptors
     • Intracellular signalling
       • See along bottom of page
   • Ion-channel-coupled receptors
   • G-protein coupled receptors
   • Enzyme-coupled receptors

4. Short range signalling

   • Signalling via Gap Junctions ‘sharing signals’
     • Cells are coupled metabolically and electrically

5. Long range signalling

   • Endrocrine vs. Synaptic Signalling

6. Mechanisms of response

   • Altered protein function
   • Cells respond to many signals
     • cells exist in a complex environment exposed to many signals
     • Different types of cells often respond differently to the same signal
   • Signal integration

7. Studying signalling

   • General methods
     • in vivo whole organism studies
       • in vitro biochemical experiments
         • in vitro experiments in cultured cells
     • Visualisation or detection of interactions/ signalling
       • imaging or measuring interaction
       • Biochemical methods
       • protein-protein interactions, kinetics
     • Inhibitors
       • to disrupt signalling by manipulating a particular component, inhibitors or mutations
     • Misexpression/overexpression
       • wild-type, constitutively active or dominant negative molecules
     • Genetic methods
       • classical and molecular, transgenics, mutation analysis
   • Endogenous vs. Exogenous
     • Endogenous refers to the naturally occurring genes, RNA and proteins in cells or organisms.
     • Exogenous refers to experimental manipulation of genes, RNA or proteins added to cells or organisms.
       • usually involves transfection of cells or generation of transgenic animals or the injection of RNA/DNA/protein.
   • Live vs Fixed
     • Some systems allow the measurement of effects on live cells/tissues/organisms in real time
       • - electrophysiology, GFP-tags, bio-sensors
     • Other methods require the cells/tissues/organisms to be fixed or processed in some way
       • - immunohistochemistry and biochemistry
   • Labelling techniques
     • Direct
       • Radioactive
       • Photoreactive or chemically reactive
       • Green fluorescent protein (GFP; other colours available)
     • Indirect
       • Immunological
         • antibodies labeled with fluorescent tags, or enzymes with easily detected products
   • Fusion Proteins
     • Diagram
   • Protein-protein interactions
     • Why?
       • Many signalling molecules bind to each other in order to function
       • Methods
         • Co-immunoprecipitation
         • GST “pull-downs”
         • Yeast two-hybrid
         • Fluorescence resonance energy transfer (FRET)
   • Methods for studying transcriptional regulation by signaling pathways
     • in vivo
       • in situ hybridization
       • reporter constructs (lacZ; GFP)
     • in cultured cells
       • reporter constructs (lacZ; CAT; luciferase)
       • RNAse protection
     • Whole genome approaches
       • microarrays

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