Lecture 11 part 3 Flashcards
G protein-coupled receptors include (ligands, receptors and signal transduction)?
Ligands:
epinephrine, glucagon, serotonin etc.
Receptors:
seven transmembrane alpha helices; cytosolic domain associated with a membrane-coupled trimeric G protein.
Signal transduction:
(1) Second-messenger pathways involving cAMP or others; (2) linked ion channels; (3)
MAP kinase pathway.
Receptor tyrosine kinases (RTKs) includes (ligands, receptors and signal transduction)?
Ligands:
insulin, epidermal growth factor (EGF), fibroblast growth factor (FGF) etc.
Receptors:
single transmembrane alpha helix; protein
tyrosine kinase activity in cytosolic domain.
Signal transduction:
(1) Ras–MAP kinase pathway; (2) IP3/DAG pathway; (3) PIP3 kinase pathway.
Ligand-gated ion channels includes (ligands, receptors and signal transduction?
Ligands:
neurotransmitters (e.g., acetylcholine, glutamate), cGMP, physical factors (e.g., touch, stretching), IP3 (receptor in ER membrane).
Receptors:
four or five subunits with a homologous segment in each subunit lining the ion channel.
Signal transduction:
(1) localized change in membrane potential due to ion influx, (2) elevation of cytosolic Ca2+.
Intracellular receptors are for?
Receptors for steroid hormones, thyroid hormones, retinoids and vitamin D.
What domain intracellular receptors include?
A transcription-activating domain, a DNA-binding domain and a ligand-binding domain;
What does hormone response element means?
The receptor–ligand complex binds a promoter region of the target genes; in the case of hormones
GPCR’s can regulate what functions?
Immune system, growth, sensen like smell or taste, visual, behaviour etc.
What GPCR’s are able to bind?
GTP and CDP. Guanosine triphospohate and guanosine diphosphate.
What are G-protein subunits?
Alpha- bete and gamma subunits. Alpha- and gamme subunits are attached to the cell membrane via lipid anchors.
What does G-protein bind when inactive?
GDP, to the alpha subunit.
What happens when a ligand binds to, for example, to a GPCR?
A conformational change. In a case of GPCR the G-protein will look different. Alpha unit separates it self from others (dissociates).
AND it exchanges GDP to GTP!
What happens after a GPCR has gone over a conformational change and the subunits are separated+
They will find a protein in the membrane. The subunit is going to alter and regulate the function of that protein found.
What can the target proteins be?
Enzymes that produce a second messengers or ion channels that also lets ions be second messengers
How can we make GPCR go back to normal?
GTP can be hydrolized to GDP. Loses a phosphate.
What is special about enzyme linked receptors?
In addition to just receiving signals; they also function as enzymes.
What is the most common enzyme linked receptor?
Receptor tyrosine kinases
What does receptor tyrosine kinases regulate?
Cell growth, growth factors
What does kinase mean?
Ability to transfer phosphorus molecules. Usually from a high energy substance like ATP
Receptor tyrosine kinases have the ability to?
To transfer phosphorus from ATP to intracellular proteins which activates them.
What is a gross-linked dimer?
When a signalling molecule binds to RTK, it causes the other RTK to associate with each other.
Why does RTK’s need to act in pairs?
Cross-linking activates the tyrosine kinase activity in RTK’s thorugh phosphorylation. So they phosphorylates the tyrosines with crossing each others.
Ones we have phosphorus’s on the tyrosines what can be done?
Different proteins can come by and attach themselves to them. The proteins need to have a SH2 domain.
What are ligand-gated ion channels?
Transmembrane ion channels that are open or closed in response to binding of a ligand.
When a ligand binds to a receptor for a ligand-gated ion channel?
The channel opens. Allosteric binding -> away from the ion channel.
