Cell communication

Signal Transduction
1. The process by which extracellular signalling molecules cause changes in target cells.
2. 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.
  1. - even single celled organisms eg. yeast Dictyostelium
Types of signals
1. Proteins
  1. Insulin
  2. Hedgehog
  3. Wnt
2. Small peptides
  1. Endorphins
  2. ACTH
3. Amino acids
  1. Glutamate
4. Nucleotides
  1. ATP
5. Steroids
  1. Oestrogen
  2. Testosterone
6. Fatty acid derivatives
  1. Prostaglandins
7. Dissolved gases
  1. Nitric oxide
Classes of receptors
1. Cell surface receptors
2. Intracellular receptors
  1. Intracellular signalling
    1. See along bottom of page
3. Ion-channel-coupled receptors
4. G-protein coupled receptors
5. Enzyme-coupled receptors
Short range signalling
1. Signalling via Gap Junctions ‘sharing signals’
  1. Cells are coupled metabolically and electrically
Long range signalling
1. Endrocrine vs. Synaptic Signalling
Mechanisms of response
1. Altered protein function
2. Cells respond to many signals
  1. cells exist in a complex environment exposed to many signals
  2. Different types of cells often respond differently to the same signal
3. Signal integration
Studying signalling
1. General methods
  1. in vivo whole organism studies
    1. in vitro biochemical experiments
      1. in vitro experiments in cultured cells
  2. Visualisation or detection of interactions/ signalling
    1. imaging or measuring interaction
    2. Biochemical methods
    3. protein-protein interactions, kinetics
  3. Inhibitors
    1. to disrupt signalling by manipulating a particular component, inhibitors or mutations
  4. Misexpression/overexpression
    1. wild-type, constitutively active or dominant negative molecules
  5. Genetic methods
    1. classical and molecular, transgenics, mutation analysis
2. Endogenous vs. Exogenous
  1. Endogenous refers to the naturally occurring genes, RNA and proteins in cells or organisms.
  2. Exogenous refers to experimental manipulation of genes, RNA or proteins added to cells or organisms.
    1. usually involves transfection of cells or generation of transgenic animals or the injection of RNA/DNA/protein.
3. Live vs Fixed
  1. Some systems allow the measurement of effects on live cells/tissues/organisms in real time
    1. - electrophysiology, GFP-tags, bio-sensors
  2. Other methods require the cells/tissues/organisms to be fixed or processed in some way
    1. - immunohistochemistry and biochemistry
4. Labelling techniques
  1. Direct
    1. Radioactive
    2. Photoreactive or chemically reactive
    3. Green fluorescent protein (GFP; other colours available)
  2. Indirect
    1. Immunological
      1. antibodies labeled with fluorescent tags, or enzymes with easily detected products
5. Fusion Proteins
  1. Diagram
6. Protein-protein interactions
  1. Why?
    1. Many signalling molecules bind to each other in order to function
    2. Methods
      1. Co-immunoprecipitation
      2. GST “pull-downs”
      3. Yeast two-hybrid
      4. Fluorescence resonance energy transfer (FRET)
7. Methods for studying transcriptional regulation by signaling pathways
  1. in vivo
    1. in situ hybridization
    2. reporter constructs (lacZ; GFP)
  2. in cultured cells
    1. reporter constructs (lacZ; CAT; luciferase)
    2. RNAse protection
  3. Whole genome approaches
    1. microarrays

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Cell communication

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