Introduction to Cell Signalling (Week 1) Flashcards
What is autocrine signalling?
Signalling molecules bind to receptors on the same cell that secreted them
Example autocrine hormone name, cell that secretes it and pathway
Somatostatin
Secreted by D cells in gastric glands
Binds SST2 receptor which inhibits adenylyl cyclase decreasing cAMP and then HCl secretion
Paracrine signalling
Signalling molecules excreted to extracellular space and bind adjacent cell without passing through the circulatory system
Example paracrine molecule name, secretory cell and pathway
Histamine
Secreted by enterochromaffin-like cell in response to acetylcholine
Bind H2 receptors on parietal cells activating adenylyl cyclase which increases the number of proton pumps
Endocrine signalling
signalling molecules are secreted from secretory glands into the bloodstream and activate a distant receptor
Endocrine example molecule name, secreted from, and target
ACTH
Released from pituatary gland hypophyseal portal system
Kidneys
Synaptic transmission
electrical signals being transmitted between electrically excitable cells (neurons/muscle cells)
Why are neurons and muscle cells electrically excitable
They have many ion channels
What do action potentials cause at the bouton
Opening of voltage gated ion channels and depolarisation of the membrane
What does neuron membrane depolarisation cause
Opening of calcium channels
What happens when calcium enters the synaptic bouton
It binds microtubules causing vesicles to be pushed to the synaptic cleft and exocytosis - release of neurotransmitters
What do neurotransmitters bind on the post synaptic neuron
GPCRs leading to a ion channels opening and a new action poteintial
Ligand-gated ion channel structure and function
Multiple protein subunits around a central channel. Change the polarisation of a cell
G-protein coupled receptors structure and function
7-transmembrane polypeptide chain with extracellular N terminus and intracellular C terminus associated with a G protein system. Act through second-messenger activity
Ligand-gated ion channel response time
Milliseconds
Nicotinic acetylcholine receptor structure and function
5 subunit non-specific cation (positive) ion channel. Cholinergic neurotransmission
GPCR response time
Seconds and effects last longer than ion channels
Adrenaline binding beta2-adrenoreceptors
Conformational change
GDP attached to alpha G-protein replaced with GTP
GTP-G alpha cyclase moves to activate adenylyl cyclase
cAMP activates PKA leading to the inhibition of MLCK
Bronchodilation
Adrenaline binding alpha2- adrenoreceptors
Conformational change
GDP attached to alpha G-protein replaced with GTP
GTP-G alpha cyclase moves to inhibit adenylyl cyclase
Less cAMP leads to relaxation of GI tract
Adrenaline binding alpha1-adreoreceptors
Conformational change
GDP attached to alpha G-protein replaced with GTP
GTP-G alpha cyclase moves to activate phospholipase C which converts PIP2 to DAG and IP3
Less Ca2+ leads to vasoconstriction
Kinase-linked receptor response time
Hours
Nuclear receptor response time
Hours
Nuclear receptor structure and function
Protein monomers that contain a DNA-binding domain. Control gene transcription
What type of receptors are nicotinic
Cholinergic ligand-gated ion channels
What type of receptors are muscarinic
Cholinergic GPCRs
What physiological processes are enzyme-coupled receptors key in and why
Metabolism and growth
They are multi-faceted
What type of receptors do steroids generally bind
Nuclear
Steroids: lipophilic or hydrophilic
lipophilic/hydrophobic
What type of receptors are linked with signal amplification by second messengers
GPCRs
What protein transports steroids through the blood
Albumin
Explain signal amplification
Adenylyl cyclase: ATP -> cAMP
Each cAMP activates a kinase
Each kinase phosphorylates many enzymes
Each enzyme produces many products
How many transmembrane domains do GPCRs have
7
Define a second messenger
A signal molecule which acts as a result of another pathway but does not change another molecule
Define affinity
The tendency of a (signalling) molecule to bind its receptor
