Hormonal signalling Flashcards
Describe some general themes for signal transduction
- specificity
- coordination of multiple events
- amplification
- integration with other pathways
- processing
- sub-cellular localisation
- speed
- duration
- tissue localisation
- cost of machinery and metabolism
Describe an all-or-none curve
looks like tan
Describe a hyperbolic curve
the first half of a parabola
Describe contact-dependent pathways
- developmental
- signalling cell delivers membrane-bound signal molecule to target cell
Describe paracrine pathways
- spatially localised
- diffusible signal
- local mediators
Describe endocrine pathways
- steroid hormones
- peptide hormones
- travel in bloodstream to receptors on target cells
Describe synaptic pathways
- neuronal: long distance, fast
- from cell body along axons
- neurotransmitters diffuse across synapses to target cells
Describe signalling via lipid soluble steroid hormones - the basics
- diffuse across PM and activate members of the intracellular receptor superfamily
- persist for hours/days
- mediate long-term responses
Describe steroid hormones
- small, hydrophobic molecules
- transported in the blood
- often associated with carrier proteins
List some steroid hormones
- cortisol
- estradiol
- testosteron
- retinoic acid
- thyroxine
- vitamin D3
Describe signalling via lipid soluble steroid hormones - the specifics
- attached to carrier protein in blood
- diffuse into cells
- bind to steroid receptor binding element
- releases inhibitory protein from intracellular receptor
- moves into nucleus
- activate gene regulatory proteins
Give the structure of a steroid hormone
- COOH
- ligand binding domain
- inhibitory proteins
- DNA-binding domain
- transcription-activating domain
- co-activator binding proteins
- H2N
List the three classes of cell surface receptor
- enzyme-linked receptors
- G-protein coupled receptors
- ion channel receptors
Describe enzyme-linked receptors
- inactive catalytic domain binds to dimeric signal molecule to form active catalytic domain
- OR signal molecule binds to receptor to form an activated, associated enzyme
Describe G-protein coupled receptors
- inactive receptor followed by an inactive protein, followed by an inactive enzyme
- signal molecule binds to create an activated receptor and G protein
- creates activated enzyme
Describe ion channel receptors
ions bind to signal molecule to travel through the PM
Describe signalling via enzyme-linked cell-surface receptors
- enzyme-linked receptors are catalytically active or associate with catalytic subunits
- most are single-pass membrane proteins
- often involved in development, activating cell division and growth
Describe RTKs functionally
- Receptor tyrosine kinases
- assemble as dimers on binding the target ligand and autophosphorylate their cytoplasmic tails
Describe TGF-Beta
- growth factor
- activates serine/threonine receptor kinases
Describe RTKs morphologically
- cystine-rich domains
- tyrosine kinase domains
- EGF receptors
- insulin, IGF1 receptors
- NGF receptors
- PDGF, MCSF receptors
- FGF receptors
- immunoglobin-like domains
- VEGF receptor with kinase insert region
- Eph receptor with fibronectin-type-III-like domain
Describe the binding of a ligand to the RTK
- leads to receptor dimerisation
- initiates tyrosine auto-phosphorylation
- adapter proteins bind to phospho-tyrosine through SH2 domains
- guanine exchange factors bind to SH3 domains on the adapter protein
- GEF proteins activate small GTPases by catalysing exchange of GDP for GTP
Give an example of an adapter protein in RTK-ligand binding
GRB2
Give an example of a guanine-exchange factor
SOS
Give an example of a small GTPase
Ras
What does activated Ras do?
- released
- binds to Raf
Raf
- a serine/threonine kinase
- can initiate a MAPK cascade
MAP
mitogen-activated protein
MAPK
- mitogen-activated protein kinase
- the terminal enzyme in a three-kinase cascade
- phosphorylates and activates transcription factors
- is phosphorylated by MAPKK on two sites
MAPKK
- MAPK kinase
- is phosphorylated by MAPKKK on two sites
MAPKKK
MAPKK Kinase
List some signals acting via RTKs
- EGF
- insulin
- IGF1
- NGF
- PDGF
- MCSF
- FGF
- VEGF
- ephrin
EGF
- epidermal growth factor
- EGF receptors
- stimulates cell survival, growth, proliferation, or differentiation of various cell types
- acts as inductive signal in development
Insulin
- insulin receptor
- stimulates carbohydrate utilisation and protein synthesis
IGF1
- IGF receptor-1
- stimulates cell growth and survival in many cell types
NGF
- nerve growth factor
- Trk receptors
- stimulates survival and growth of some neurones
PDGF
- PDGF receptors
- stimulates survival, growth, proliferation and migration of various cell types
MCSF
- macrophage-colony-stimulating factor
- MCSF receptor
- stimulates monocyte/macrophage proliferation and differentiation
FGF
- fibroblast growth factor
- FGF receptors
- stimulates proliferation of various cell types
- inhibits differentiation of some precursor cells
- acts as inductive signal in development
VEGF
- vascular endothelial growth factor
- VEGF receptors
- stimulates angiogenesis
Ephrin
- Eph receptors
- stimulates angiogenesis
- guides cell and axon migration
Describe G-protein coupled receptors with respect to the cell membrane
- extracellular signal acts as first messenger
- receptor
- transducer with G-protein attached to GTP
- amplifier region
- intracellular signal acts as second messenger
Describe the fundamentals of the G-protein coupled receptors
- > 800
- 4% of the total human genome
- major drug targets
Describe the 7-Membrane Spanning Domain G-protein receptors
- G protein-linked receptors have 7 membrane spanning alpha-helices
- N-terminus and extracellular cytoplasmic loops bind the ligand
- large cytoplasmic loop interacts with G-proteins
Describe coupling via trimeric G-proteins
- ligand binds to receptor
- The β-gamma subunits can also initiate signal transduction
- receptor undergoes conformational change
- G-protein binds to receptor and exchanges GDP for GTP
- GTP-alpha-subunit dissociates and binds to target enzyme
- target enzyme activated
- bound GTP hydrolysed and -subunit dissociates
Describe the GDP protein before coupling
- inactive
- trimeric
- with alpha, beta and gamma subunits
Describe adrenaline (epinephrine) action
- triggers tissue-specific responses via cAMP
- beta-adrenergic receptors are coupled to adenylate cyclase by G-proteins
Describe adrenaline
- epinephrine
- synthesised in adrenal medulla and released into bloodstream in response to stress
- binds to beta-adrenergic receptors on the surface of muscle, liver and adipose cells
cAMP
triggers glycogen breakdown via a kinase cascade
Describe the glycogen breakdown kinase cascade
- PKA dissociates from cAMP
- phosphorylated by phosphorylase kinase (ATP -> ADP and Pi)
- phosphorylated by glycogen kinase
- glycogen converted to glucose 1-phosphate
Describe feedback loops that desensitise beta-adrenergic receptors
- GTP transferred from beta-adrenergic receptors to adenylate cyclase
- reacts with ATP and cAMP to produce PKA
- inactivated by phosphorylation
List some hormone-induced cell responses mediated by cAMP
- thyroid
- adrenal cortex
- ovary
- muscle
- bone
- heart
- liver
- kidney
- fat
Describe the thyroid gland
- TSH
- thyroid hormone synthesis and secretion
TSH
thyroid-stimulating hormone
Adrenal cortex
- ACTH
- cortisol secretion
ACTH
adrenocorticotrophic hormone
Describe the ovary
- LH
- progesterone secretion
LH
luteinising hormone
Describe the muscle
- adrenaline
- glycogen breakdown
Describe the bone
- parathormone
- bone resorption
Heart
- adrenaline
- increase in heart rate and force of contraction
Liver
- glucagon
- glycogen breakdown
Kidney
- vasopressin
- water reabsorption
Fat
- adrenaline, ACTH, glucagon, TSH
- triglyceride breakdown
Describe the inositol signalling pathway
- PI is phosphorylated to PIP, which is phosphorylated to PIP2
- passes through G-coupled PLC using GTP, across DAG to PKC
- GTP produces InsP3 which binds to ER to secrete calcium, which migrates to PKC on PM
- sets up positive feedback loop of calcium
- SOCE achieved by calcium influx through ORA1 (attached to STIM1) delivered to SERCA in ER membrane, that transports back to calcium pump
List some of the roles of the IP3/Ca2+ signalling pathway
- metabolism
- contraction
- fluid secretion
- neuronal synaptic plasticity
- aggregation
- ion channel opening
- aldosterone secretion
- differentiation
- proliferation
- exocytosis
Describe the IP3/Ca2+ signalling pathway in metabolism
liver cells
Describe the IP3/Ca2+ signalling pathway in contraction
- ventricular cells
- atrial cells
- smooth muscle
- mesangial cells
Describe the IP3/Ca2+ signalling pathway in fluid secretion
- intestinal cells
- parietal cells
- pancreas
- salivary glands
- sweat glands
Describe the IP3/Ca2+ signalling pathway in neuronal synaptic plasticity
- purkinje neurones
- hippocampal neurones
Describe the IP3/Ca2+ signalling pathway in aggregation
blood platelets
Describe the IP3/Ca2+ signalling pathway in ion channel opening
- astrocytes
- T cells
Describe the IP3/Ca2+ signalling pathway in aldosterone secretion
glomerulosa cell
Describe the IP3/Ca2+ signalling pathway in differentiation
- osteoblasts
- brown fat cells
Describe the IP3/Ca2+ signalling pathway in proliferation
- T cells
- mesangial cells
- smooth muscles
- brown fat cells
Describe the IP3/Ca2+ signalling pathway in exocytosis
- b-Cells
- L Cells
- mast cells
- macrophages
- parathyroid glands
- astrocytes
- renin-producing granular cells
Describe the imaging of Ca2+-dynamics
- in C. elegans pharyngeal muscle
- using cameleon 2.1 (transgenic probes for Ca2+)
Describe the role of phosphatidyl inositols as membrane scaffolds
- PIP
- PI(4)P
- PI(4,5)P2
- PI(3,4,5)P3
- phosphorylation by PI 3-kinase
- can interact with cytoskeleton
What links PKA, CaM-kinase, PKC and MAPK
they are transcription regulators
Summarise GCPR pathway 1
- G protein
- adenylyl cyclase
- cyclic AMP
- PKA
- protein targeting/transcriptional regulation
Summarise GCPR pathway 2
- G protein
- phospholipase C
- IP3
- Ca2+
- calmodulin
- CaM-kinase
- protein targeting/transcriptional regulation
Summarise GCPR pathway 3
- G protein
- phospholipase C
- diacylglycerol
- PKC
- protein targeting/transcriptional regulation
Summarise RTK pathway 1
- phospholipase C
- diacylglycerol
- PKC
- protein targeting/transcriptional regulation
Summarise RTK pathway 2
- Grb2
- Ras-GEF (Sos)
- Ras
- MAPKKK
- MAPKK
- MAPK
- protein targeting/transcriptional regulation
Summarise RTK pathway 3
- PI 3-kinase
- PI(3,4,5)P3
- (PDKT)
- Akt kinase
- protein targeting/transcriptional regulation
Summarise RTK pathway 4
- Grb2
- Ras-GEF (Sos)
- Ras
- PI 3-kinase
- PI(3,4,5)P3
- (PDKT)
- Akt kinase
- protein targeting/transcriptional regulation
Describe the analysis of downstream signalling in multiple MAPK pathways
- DNA microarray with >97% of known or predicted genes from Saccharomyces cerevisiae
- make green fluorescently labelled probes from cDNA library of normal cells
- make red fluorescently labelled probes from cDNA library of cells treated with mating pheromome
- apply probes to array and measure the red/green ratio
- red = upregulated after pheromone, green=down regulated
Describe the cluster analysis of gene behaviour in yeast
- > 200 gene transcripts found to increase in abundance
- > 200 decrease in abundance
- 383 genes changed by >3 fold
Describe the testing of the pheromone hypothesis using mutants
- genome-wide transcript profiling repeated in different mutant backgrounds
- deletion in ste2 abolishes the entire pheromone response
- deletion in far1 does not affect induction of pheromone genes, but abolishes repression of cell cycle genes
ste2
pheromone receptor
far1
cdk inhibitor
Describe the acetylcholine receptor
- nAChR
- archetypal pentameric ligand gated channel (alpha, alpha, beta, gamma, delta)
- charges above and below the pore confer specificity for cations
- alpha-subunits have binding sites for ACh and show cooperativity
- Na+ is the main ion transported as it is far from equilibrium
Describe GABA and glycine receptors
- pentameric channels permeable to chloride ions
- inhibit generation of an action potential by maintaining membrane hyperpolarisation
- activated by benzodiazepines and barbiturates
- inhibited by strychnine.
GABA
gamma-amino butyric acid
benzodiazepines
valium
Describe ionotropic glutamate receptors
- NMDA receptors
- AMPA receptors
Describe NMDA receptors
- permeable to Ca2+
- promote depolarisation
- blocked by Mg2+ until ejected by depolarisation
NMDA
N-methyl-D-aspartate
Describe AMPA receptors
- permeable to Na+
- promote depolarisation
AMPA
α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid
Describe metabotropic glutamate receptors
- glutamate receptors initiate a
G-protein cascade that activates adenylate cyclase and PKA - Na+ channels activated by phosphorylation (by PKA)
Summarise the G protein cascade
- GDP to GTP
- GTP binds adenylate cyclase
- ATP to produce cAMP
- releases pKA
- goes to membrane receptor
Describe 5-HT receptors activate channels directly, or via the IP3 and cAMP pathways
5-HT
- 5-hydroxytryptamine
- serotonin
