Module 7: V1-V3 Flashcards
Why do cells communicate?
survive
grow + divide
differentiate
die
What is signal transduction?
movement of signal from the outside of a cell to the inside of a cell
What are the different ways in which a signal is transmitted?
contact-dependent
paracrine
synaptic
endocrine
What is specificity?
signal molecule fits binding site on its complementary receptor; other signals do not fit
What is amplification?
when enzymes activate enzymes, the number of affected molecules increases geometrically in an enzyme cascade
What is modularity?
proteins with multivalent affinities form diverse signaling complexes from interchangeable parts
phosphorylation provides reversible points of interaction
Signalling molecules are usually expressed and degraded __________. (very fast / very slow)
very fast
How are molecular switches turned on / off?
either signaling by phosphorylation or GTP-binding
What are GPCRs associated with?
a guanine nucleotide-binding protein (G protein)
What type of activity does the ɑ subunit of a G protein have?
GTPase activity as the ɑ subunit has a GDP-binding site
What do the ɑ and ɣ subunits of a G protein have?
lipid molecules that insert into the membrane
What does the activation of an enzyme by a G protein result in?
results in increased enzymatic activity and therefore an increased signal output
How is a β-adrenergic receptor activated by adrenaline?
adrenaline binds -> G protein GDP is replaced by GTP = activation -> G protein activates adenylyl cyclase (AC) -> AC catalyses formation of cAMP -> cAMP activates PKA -> PKA phosphorylates cellular proteins = cellular response (>100,000 molecules liberated)
What are receptor tyrosine kinases stimulated by?
growth factor
What is the structure of a receptor tyrosine kinase?
a receptor coupled to an enzyme
What does downstream signalling of receptor tyrosine kinase stimulate?
survival, growth and proliferation
issues with these receptors are linked to cancer
What is cross-phosphorylation by activated kinase domains?
when one receptor by itself cannot become activated but once it is paired up with a partner it can
What is dominant-negative inhibition by receptor tyrosine kinase?
if one receptor is mutated and has no activity then downstream signalling is not able to occur because it cannot pair up with a partner
How to RTK signalling pathways progress?
activated receptor -> phosphorylates downstream target (e.g. transcription factor) which becomes a docking site for other signalling molecules -> amplification through multiple rounds of enzyme activation
Cell signalling is often described like electric circuitry. What key features do you think they share that make this analogy a good one?
both allow for the movement of a signal from one place to another
as well as this circuits and cell signalling can both be switched on or off
Does protein phosphorylation always activate a protein. Why, why not?
no, because sometimes phosphorylation results in inactivation of a protein
Does ligand binding always need to cause receptor tyrosine kinases to dimerise? What does it need to cause?
no, the ligand must bind to the extracellular domain
