Lecture 8 - Cell Communication II, Intracellular signalling Flashcards
what is an intracellular receptor?
a lipophilic receptor that is for steroid and thyroid (tyrosine derivatives and lipophilic) hormones
what is the function of carrier proteins of intracellular receptors?
can carry the signal molecules inside the cell to either the nucleus or cytoplasm receptor that are both within the nucleus
what are the classical intracellular signalling method?
steroid hormones
where is the steroid hormone receptor commonly located?
commonly located in the cytoplasm
how does a steroid hormone initiate an early primary response?
by entering the plasma membrane and binding with a receptor. Binding creates a steroid hormone-receptor complex
where does the steroid hormone-receptor complex translocate too?
translocates to the nucleus and activates gene transcription
what receptor does thyroid hormone signalling act on?
acts on a nuclear receptor
what occurs when thyroid hormones enter the cell?
they enter via diffusion and once inside, T4 is converted to T3 and the addition of a cofactor causing binding to the receptor
what does binding to the receptor of thyroid hormones activate and increase?
activates gene transcription and increases metabolism
what are cell surface receptors?
lipophilic plasma membrane receptors that activate intracellular machinery to act as a second messenger by binding the signal to the plasma membrane receptor
what triggers the opening of ligand-gated ion channels?
upon an influx of ions or signal molecule binding channels are opened
what binds to DNA in terms of receptors?
steroid hormone-receptor complex binds to DNA
what is Gs?
the G-protein that stimulates the second messenger system
what is Gi?
the G-protein that inhibits the second messenger system (not the cell itself)
what is the function of GTP?
activates the alpha-subunit and the beta-gamma-subunit to activate downstream functions of the cell
what activates adenylylcyclase?
activates by Galpha
what does an activated adenylylcyclase activate?
activates protein kinase A (PKA)
what does an activated protein kinase A (PKA) activate?
CREB binding to DNA inducing gene transcription
what is CREB?
a common substrate of PKA
what is Gq?
the G-protein that doesn’t act through cAMP (cyclic AMP)
what are the second messengers of GPCR’s?
IP3 (inositol triphosphate)
DAG (diaglycerol)
what is the function of inositol triphosphate (IP3)?
through receptors on the ER and ligand-gated ion channels Ca2+ is released to activate Ca2+ dependant pathways
what is the function of diaglycerol (DAG)?
helps to activate protein kinase C and this produces the cells response to the protein P04
what are receptor protein kinases?
receptors that have a tyrosine kinase within their structure
what is the function of tyrosine kinases?
part of the receptor that phosphorylates tyrosine’s on proteins leading to protein activation
what are enzyme-linked receptors?
when a signal molecule acts as a dimer to activate the inactive catalytic domain or the signal molecule activates an enzyme, stabilising a complex to allow reactions with the intracellular portion of a cell
what is a type of enzyme-linked receptor?
tyrosine-kinase associated receptor (not the same as receptor tyrosine kinases)
what binds to a tyrosine-kinase associated receptor?
a neurotransmitter/hormone binds to a receptor associated with JAK (janus kinase) that is bound to a different molecule
what is regulated intramembrane proteolysis?
proteolysis by a metalloproteinase then release by the beta-gamma-secretase/presenilin complex
what are eicosanoid receptors?
receptors that activate phospholipase A and this breaks down phospholipids (only the lipids are broken down not proteins)
what is the pathway of the breakdown of phospholipids?
phospholipase A2 –> arachidonic acid –> cyclcoxygenase pathway –> prostaglandins –> vascular actions + inflammation + uterine contractions for birth
what is the result of the breakdown of phospholipids?
vascular actions
inflammation
uterine contractions for birth
