Lecture 8 CSF Cell Communication

Cell Communication L&F

Enables cells to communicate and respond to their environment and other cells, signals can be hormonal or sensory input

Paracrine Signalling L&F

Acts locally too effect nearby target cells (eg fibroblast growth factor FGF)

Synpatic Signalling L&F

Acts locally from cell to cell going through synaptic space (eg Acetycholine - ACH)

Endocrine (Hormone) Signalling L&F

Acts long distance from endocrine cell into the bloodstream

3 Main steps of cell signalling

1. Reception - Signalling molecules bind to receptor proteins, causing shape/chemical changes

2. Transduction - Altered receptor activates a protein causing a relay ion changes, relay molecules such as “second messengers” may be activated (eg IP3, cAMP)

   - Each activated protein causes a series of changes via phosphorylation, known as the phosphorylation cascade

3. Response - Final output is cellular response

GPCRS F and 4 steps

• Transmembrane protein, GPCRs couple with G proteins and they act as molecular switches - on or off depending if GDP or GTP is bound, functions are development, sensory reception

  1. At rest receptor is unbound, G protein is bound to GDP, enzyme inactive

  2. Ligand binds to receptor, and binds G protein, GTP replaces GDP, enzyme still inactive

  3. G protein is active and releases, enzyme is active for cellular response

  4. G protein has GTPase meaning GDP is back on receptor and resting state, enzyme inactive

Receptor L&F

Molecule/protein which responds to specific ligand/signal

Ligand L&F

Signalling molecule that binds specifically to another protein

Ion Channel L&F

Membrane protein through which specific ions can travel through

Ion channel receptor L&F

Membrane protein where specific ions can travel in resoponse to ligand binding

Ligand-Gated Ion channels 3 steps

1. At rest ligand is unbound, gate is closed

2. Ligand binds, gate opens, specific ions can flow into cell

3. Ligand leaves, gate closes, resting state

Signal Transduction (Phosphorylation Cascade) L&F

Protein kinases are enzymes that transfer a phosphate to the next kinase - phosphates are enzymes that dephosphorylate making the protein inactive but recyclable

cAMP L&F

Acts as a second messenger =, activates protein kinase, involved in GPCR signalling pathways

CA2+ L&F

Used in signalling due to concentration gradients, high to low concentration, activates proteins for cellular response

Calcium concentrations high in ER< mitochondrial matrix, outside of cell

Ca2+ and IP3 in GPCR signalling L&F

The activated protein which is Phospholipase which cleaves PIP2 into DAG and IP3, IP3 diffuses through the cytosol and binds to gated channel in ER, calcium ions flow out ER down the concentration gradient and actoivates proteins for cellular response

List of Cellular responses

• Gene expression alteration

• Protein activity changes

• Ion channel regulation

• Organelle regulation

• Metabolism adjustments

• Cytoskeletal adjustments

Adrenaline application

One adrenaline molecule can generate millions of glucose molecules through signalling pathways

Receptors specificity and importance of response turning off

• Receptors are specific, only certain target receptors will interact with the signal/ligan

• Response must be turned off to ensure homeostatic equilibrium