Cell Signalling Flashcards
Why do cells need to communicate?
- Process information - sensory
- Self-preservation - reflexes
- Voluntary movement
- Homeostasis
Which cells secrete glucagon?
α cells of Islet of Langerhans in pancreas
In response to what is glucagon secreted and what does it do?
In response to hypoglycaemic features, stimulates glycogenolysis and gluconeogenesis
What is endocrine signalling?
Hormone travels within blood vessels to acts on a distant target cell
What is paracrine signalling?
Signalling molecules act on an adjacent cell
Insulin inhibiting glucagon secretion is an example of what type of signalling?
Paracrine signalling
Adrenalin acting on the trachea is an example of what type of signalling?
Endocrine signalling
Glucagon and insulin acting on the liver is an example of what type of signalling?
Endocrine signalling
Nitric oxide produced by endothelial cells causing vasodilation is an example of what type of signalling?
Paracrine signalling as they act on the nearby smooth muscle cells
What is signalling between membrane attached proteins?
Plasma membrane proteins on adjacent cells interacting
Hepatitis C detected are recognised by which cells in the bloodstream?
Antigen presenting cells (APC)
Osteoclast activating factors produced by adjacent osteoblasts is an example of what type of signalling?
Paracrine signalling
What happens after APC recognised the pathogen?
APC expressing major histo-compatibility (MHC) class II molecules on surface after digesting the pathogen
MHC II interacts with what to alert the lymphocytes?
T-cell receptor (TCR)
What type of signalling occurs between APC and T-lymphocyte?
Signalling between membrane attached proteins - Class II MHC and TCR
Interaction of HIV GP120 with CD4 receptors of T cells is an example of what type of signalling?
Signalling between membrane attached proteins
Bacterial cell wall components interact with toll-like receptors on haematopoietic cells in what type of signalling?
Signalling between membrane attached proteins
What is autocrine signalling?
Signalling molecule acts on same cell
What cascade of reactions occur after TCR activation?
Expression of IL-2 receptors → Secretion of IL-2
What types of signalling are involved in IL-2 secretion by T cells?
Autocrine and paracrine signalling - IL-2 binds to IL-2 receptors on same cell and adjacent cells
What type of signalling is involved in positive and negative self-feedback on neurones?
Autocrine signalling
ACh providing positive feedback for the presynaptic neurone is an example of what type of signalling?
Autocrine signalling - ACh binds to presynaptic M2-muscarinic receptors to promote NT secretion
Which type of signalling is used by the growth factor TGFβ?
Autocrine signalling as it promotes mitogenesis of the same cell
What are the 4 main steps of neurotransmission?
- Propagation of AP
- NT release from vesicles
- Activation of postsynaptic receptors
- Disposal or recollection of NT
What are the 4 main types of receptors?
- Ionotropic
- G-protein coupled
- Enzyme-linked
- Intracellular
Identify the activation and function mechanisms of G-protein coupled receptors?
Ligand binding → activates intracellular G-protein
Identify the activation and function mechanisms of ionotropic receptors?
Ligand binding → opens ion permeable pore traversing the membrane
Identify the activation and function mechanisms of enzyme-linked receptors?
Ligand binding → receptor clustering → activates internal enzymes
Identify the activation mechanism of intracellular receptors?
A membrane permeable ligand binds to receptor inside cell
What type of receptor is Nicotinic ACh receptor?
Ionotropic
What is the activator ligand, location and physiological effect of Nicotinic ACh receptor?
Ligand: ACh
Location: Skeletal muscle
Physiological effect: Muscle contraction
What is the action mechanism of GPCR?
GPCR activated by ligand binding → changes conformation of receptor binding to G protein → GTP replaces GDP binding to G protein → G protein dissociates into α and βγ subunits → Gα:GTP complex acts on the target protein → GTP dephosphorylated forcing Gα to couple back with Gβγ
What are the components of heterotrimeric G protein?
α, β and γ subunits
Why is the protein Gs named that way?
(s)timulates adenylyl cyclase
Why is the protein Gi named that way?
(i)nhibits adenylyl cyclase
What happens when adenylyl cyclase is stimulated?
converts ATP to cAMP → cAMP activates protein kinase A (PKA)
What happens when adenylyl cyclase is inhibited?
PKA level reduced
What is an example of GPCR activating Gs?
β1-adrenergic receptor
What is an example of GPCR activating Gi?
M2-muscarinic receptor
Which protein does Gq act on?
stimulates phospholipase C (PLC)
What happens when PLC is stimulated?
Converts PIP2 to IP3 and DAG → IP3 stimulates Ca2+ release and DAG activates PKC
Which type of G protein couples with AT-1 (angiotensin) receptor?
Gq protein
Which ligand binds and activates the CD220 receptor?
Insulin - resulting in glucose uptake by the cell
What type of receptor is CD220?
Enzyme-linked receptor
Which ligands bind to the ErbB receptor?
Epidermal growth factor and Transforming growth factor β
What is the physiological effect of ErbB when ligand is present?
Cell growth, proliferation
What are the 2 types of intracellular receptors?
Type 1 - Cytoplasmic
Type 2 - Nuclear
Which type of intracellular receptors is associated with heat shock proteins (chaperone molecules, hsp)?
Type 1 - Cytoplasmic
What is the action mechanism of cytoplasmic intracellular receptors?
hormone binds to receptor → hsp dissociates → 2 hormone bound receptors form a homodimer → The homodimer translocates to the nucleus binding to DNA
What is the action mechanism of nuclear intracellular receptors?
hormone binds to receptor → transcriptional regulation
What type of receptor is glucocorticoid receptor?
Type 1 intracellular receptor
Which ligands bind to glucocorticoid receptor?
Cortisol and Corticosterone
What are the physiological effects of active glucocorticoid receptors?
Reduced immune response and increased gluconeogenesis
What type of receptor is thyroid hormone receptor?
Type 2 intracellular receptor
Which ligands bind to thyroid hormone receptor?
T3 (thyroxine) and T4 (triiodothyronine)
What are the physiological effects of active thyroid hormone receptors?
Growth and development
