Receptor Signalling Flashcards
What is cell signalling?
Release by one cell of substances that transmit information to other cells
Define a ligand
Molecule that binds specifically/reversibly to another molecule to form a complex
Define a receptor
Molecular structure within a cell/on the surface characterised by selective binding of a specific molecule and a specific physiologic effect that accompanies the binding
What do receptors respond to?
Specific ligands, different cells respond differently to same ligand
What is extracellular signalling?
These molecules are cues eg growth factors, hormones, cytokines, NT > Transmit specific info to target cells
How are extracellular signalling molecules recognised?
By cognate receptors on surface of target cells to initiate intracellular signalling cascades elicit specific cellular responses
Where are receptor found and their function?
Not all receptors exist on exterior of cell (some deep inside or in nucleus)
These receptors bind to molecules that pass through plasma membrane eg gases like nitrous oxide and steroid hormones eg oestrogen
Describes ligand signalling
Binds specifically to receptor molecule
Changes properties of receptor
Ligand modified/degraded by cell to change/end response
Range of molecules act as ligands, various size, solubility, receptor location
What are the different types of signalling?
Endocrine, autocrine, paracrine, signalling by plasma membrane-attached proteins
What are the different types of cell-surface receptors?
G-protein coupled, tyrosine kinase, enzyme linked receptors, ion channels, toll-like receptors
Describe adrenaline action
Fight/flight response
Orchestrated action eg - Inc heart rate, Inc glucose avaliability for muscle, Dec digestion
9 different receptors
Describe the adrenergic receptor pathway
Adrenaline binds to adrenergic receptor activates G-protein complex
Alpha subunit dissociates with beta+gamma, associates with adenylyl cyclase activating it
Adenylyl cyclase converts ATP to cyclic AMP
cAMP stimulates further signalling cascade moves to nucleus with results in transcription of target gene
Endogenous GTPase hydrolyses GTP returning G-protein to pre-stimulated level of activity
Describe enzyme linked receptors
Binding of ligand to external surface activates enzymatic activity inside cell
Only has one transmembrane domain
What is the most comon enzyme linked receptor?
Tyrosine kinases
Describe tyrosine kinases
Transfers phosphorus from ATP to protein molecules activating them
Occurs in pairs/dimerise on activation phosphorylating each other
Respond to growth factors, cytokines and hormones
Control many parts of cell/ organism growth, differentiation and function
Describe epidermal growth factor receptors (EGFRs)
Regulates many transcription factors involved in cell proliferation
Hyper activation occurs if - Overexpression of receptor, Overproduction of ligand, Receptor mutation which causes signalling pathway to be continually active
Dysregulation lead to tumorigenesis
Overexpressed in cancers
Describe Acetylcholine
Chemical released by nerve cells, send signals to other cells
Describe Ach receptors
Membrane protein with aqueous pore running through it
Describe ion channel activation
Soluble material eg ions can’t travel across membrane by passive diffusion
When Ach molecules bind to receptor, gated channel is open so ions flood into cell
Where are toll-like receptors expressed?
On membrane of immune cells/non-immune cells eg epithelial, endothelial and fibroblasts
Receptor spans membrane with single pass
Describe the activation of toll-like receptors
Activation leads to antigen induces signal pathway in cell dependant on type: Cytokine production, Proliferation, Extravasation pass through capillary via the vein eg exocytosis, Antigen presentation
Describe the movement and activation of neutrophils through blood vessels
Rolling, Capture, Adhesion/Activation, Spreading, Extravasation (exo) > Phagocytosis
How are signals initiated in cell signalling pathways?
By chemical interaction via many signalling molecules with a receptor on CS
Describe the cell signalling pathways
Binding triggers chain of events that carries signal to cell interior/amplify it
Cells send signalling molecules to other cells - Chemical signals from NT travelling short distance, Hormones released from glands to blood for systematic response
Eg Receptor activated, Signal transduction, Regulates gene transcription, Commands cell activity
