Receptors In Cell Signalling, Receptor Structure And Common Structural Motifs (6) Flashcards
What is paracrine signalling?
- Signalling cell secretes local mediators to multiple target cells
What are the two main ways of intracellular signalling?
- Via secreted molecules
- Via plasma membrane-bound molecules
What is endocrine signalling?
- Signalling cell secretes hormone into blood stream to target cells
What is synaptic signalling?
- Neurotransmitters across synaptic clefts.
What are the two main types of molecules that are involved in intracellular signalling and how do they reach the target cell?
- Steroid
- Thyroid
- Via carrier proteins in the blood diffusing across membrane
What is the definition of a receptor?
- A molecule that recognises specifically a second molecule/family of molecules
- In response to ligand binding, regulation of cellular processes occur.
What role does a receptor have when unbound?
- Nothing
What is a ligand?
- Any molecule that binds specifically to a receptor site.
What do ligands do?
- May produce activation of a receptor - agonist
- May combine with a receptor site without causing activation - antagonist
Give comparisons of receptor affinity to enzyme affinity to ligand binding.
- Receptor: 10^-9M - 10^-6M
- Enzyme: 10^-6M - 10^-3M
How are receptors classified?
- Via specific physiological signalling molecule (agonist) recognised
How are receptors subclassified?
- Affinity (tightness of binding) of a series of antagonists
What are the agonists of the following:
- Nicotinic
- Muscarinic
- Nicotine
- Muscarine
What do the following muscarinic receptor subtypes bind to?
- M1
- M2
- M3
- M1: Pirenzipine
- M2: Gallanine
- M3: Hexahydrosiladiphenol
What is the difference between a receptor and an acceptor?
- Receptor: Silent at rest & antagonist binding stimulates a biological response
- Acceptor: Operates in absence of ligand & ligand binding alone produces no response
How are extracellular signals transduced into intracellular signals?
- Membrane bound receptors with integral ion channels
- Membrane bound receptors with integral enzyme activity
- Membrane bound receptors which couple to effectors via transducing proteins
- Intracellular receptors
Give examples of membrane bound receptors with integral ion channels.
- nAChR: gated Na/K/Ca channels
- GABA: gated Cl channels
- Glycine: gates Cl channels
- Glutamate (NMDA/AMPA): gated Ca
Describe the look and function of membrane bound receptors with integral enzyme activity.
- N end outside cell - binding domain
- C end inside cell - catalytic domain
Give examples of membrane bound receptors with integral enzyme activity.
- Platelet derived growth factor receptor (PDGF)
Describe how signalling via tyrosine kinase linked receptors works.
- Receptor + agonist -> agonist bound receptor with auto phosphorylation -> a) Direct to enzymes OR b) Uses transducer to reach enzyme.
How do insulin receptors work?
- alpha molecules bind to beta transmembrane receptors via the insulin binding domain
- This activates the tyrosine kinase domain to cause an effect
What is the role of G-protein coupled receptors?
- They produce both Gs (stimulatory) and Gi (inhibitory)
- These allow for regulation of target cell activity
What does G proteins stand for?
- GTP binding regulatory proteins
What is the role of G proteins in 7TMD receptors
- Adrenaline binding to beta-adrenoreceptors activates ATP cAMP via Gs
- ACh binding to M2 muscarinic ACh receptors simulate K channel opening via Gi
How can amplification in cellular signalling occur?
- Receptors stimulated and release GDP to attach to another protein and form a protein-GTP complex which produces cAMP
- cAMP stimulates protein kinase release to stimulate enzyme production
- Product of this is huge amplification
