P2: Receptors and Cell Signalling Flashcards
What are the 4 types of receptor?
List them in decreasing signalling speed
- Ion channels (fastest)
- G protein-coupled receptors (GCPRs)
- Tyrosine kinase linked receptors
- Nuclear receptors (slowest)
What occurs during signal amplification?
Binding of a ligand to a receptor induces activation of intracellular second messenger signalling cascades
Give some examples of second messengers
- cAMP
- cGMP
- Ca2+
- Diacylglycerol (DAG)
- Inositol triphosphate (IP3)
- Prostaglandins
A nicotinic Acetylcholine receptor is an example of which receptor?
Ion channel
How many molecules of Ach bind to stimulates excitation?
2 molecules of Ach bind to stimulates excitation
Give an example of an inhibitory ion channel
GABAa chloride channel
What are the 3 major families of G proteins?
- Gs
- Gi/o
- Gq
How does GPCR signalling occur?
- Ligand binds and activates a receptor
- Conformational change occurs
- The α subunit releases its bound GDP, allowing GTP to bind in its place.
- This exchange causes the trimer to dissociate into two activated components an α subunit and a βγ complex
- Activation is terminated through the action of Regulators of G protein signalling that catalyse the hydrolysis of bound GTP to GDP
What are the 3 subunits for a G protein?
α, β and γ
Outline the Adenylate cyclase/cAMP pathway
Gi/o and Gs
- Ligand binds to receptor activating it
- Causes GDP to be released and GTP to bind to α-subunit of G-protein
- Binding of GTP causes increase/decreased levels of adenyl cyclase
- ATP to cAMP reaction is initiated
- cAMP activates protein kinase A which phosphorylates many other proteins
- cAMP is broken down by phosphodiesterase to AMP
Outline the Phosphatidylinositol signal pathway (Gq)
- Ligand binds to receptor and GTP binds to G protein
- This activates phospholipase C (PLC)
- Which hydrolyses PIP2 -> DAG + IP3 (via PLC)
- IP3 release Ca2+ stores from ER (Ca2+ activates multiple kinases including PKC)
- DAG activates other protein kinases
Receptor tyrosine kinases are high affinity receptors for which molecules?
- Peptide growth factors
- Cytokines
- Hormones
Explain Tyrosine Kinase signalling
- Ligand binds
- Causing conformational change results in the formation of a dimer.
- This causes ATP to ADP reaction resulting in phosphorylation of receptors.
What is Tyrosine Kinase signalling predominately involved in?
Cell growth and differentiation
What type of drugs and hormones can cross cell membranes?
Lipophilic or Lipophobic?
Lipophilic
What are nuclear receptors?
What do they use as 2nd messengers?
- Ligand activated transcription factors
- Calcium ions
List some examples of intracellular roles calcium signalling can mediate.
- Muscle contraction
- Neuronal transmission
- Apoptosis
- Saliva secretion
What determines whether or not a protein is active or not
Gain or loss of phosphate groups
What are ionotropic receptors also known as
ligand gated ion channels
used for very rapid signalling
What do phosphorylated tyrosine kinase receptors do
Act as docking stations for many other signalling molecules, triggering a wide range of pathways
What are Ryanodine receptors and how are they activated
- Dihydropyridine receptors (DHPR) is a voltage gated Ca2+ channel.
- incoming action potential triggers opening of DHPR channels and influx of Ca2+
- increased cytosolic Ca2+ triggers opening of ryanodine receptor and release from sarcoplasmic reticulum7
