Signaling Flashcards
common features of signaling pathways (6)
reception, discrimination, info transfer, amplification, adaptation and integration
what receives signalling ligand in pathways?
usually receptor protein, either on cell-surface or intracellular
what does signaling discrimination mean?
only certain signals are capable of activating a given pathway
T/F. The form of signaling information can change throughout a pathway.
True. Chemical energy can be transduced into electrical energy, for example.
What is the process of signalling adaptation?
when you are continually exposed to a signal, the activity through that pathway decreases
why is amplification important?
sensitivity to signals, which may be present in vanishingly small concentrations - but which are still very important
how are signal transduction processes classified?
1) type of signal - chemical (small molecules, carbs, peptides) vs physical (electromagnetic, thermal, mechanical)
2) type of signal transduction molecules involved
3) Site of detection (plasma membrane or intracellular)
4) Origin and route of signal - diffusible vs anchored signals
cGAS
live with it
how are diffusible signals broken down?
by distance they have to travel from production to target - endocrine are distant, paracrine are nearby (ie neuronal synapse), autocrine are detected by same cells that produce them
what can receptors do (6)
1) bind ligand - saturable and specific
2) transduce signal across either plasma membrane or within cell
3) catalytic activity
4) complex with other subunits
5) experience occupancy-induced changes in activity
6) internalize ligand
What are some ways receptors can complex with other subunits?
They can be constutively complexed, or inducibly.
They can be composed of the same types of proteins or different types.
ligand binding assay - how do you overcome a small number of receptors per cell?
you can either use radioactive or fluorescent ligant, or overexpress recombinant receptor or purify native receptor
ligand binding assay - how to overcome rapid dissociation of bound ligand from receptor?
could do rapid filtration and wash, or centrifuge through mineral oil - or rapid size exclusion chromatography
ligand binding assay - what to do to make sure your ligand isn’t binding to non-receptor sites (nonsaturable)
competition with excess unlabeled ligand
ligand binding assay - what to do to make sure your ligand isn’t binding to other receptors (nonspecific)
competition with excess site-specific ligand
what are some ways to deduce receptor structure?
biochemical purification/characterization, cDNA cloning, primary sequence analysis of cDNA, topology mapping (protease accessibility), heterologous expression studies, structural analysis of purified receptor protein
how can you tell what side of the plasma membrane the N/C termini of a receptor are on?
protease accessibility or epitope tagging
what are some roles of adaptor molecules in signaling?
scaffolding, activation of effectors (enzymes or ion channels)
effectors to know: adenylyl cyclase
ATP —> cAMP + PPi
effectors to know: protein kinase
phosphorylates proteins on Seer/Thr or Tyr residues
effectors to know: phospholipase C
PIP2 —-> Diacylglycerol + IP3
effectors to know: nitric oxide synthase
arginine —-> citrulline + NO
effectors to know: guanine nucleotide exchange factor
exchange of GTP for GDP on guanine nucleotide regulatory proteins
effectors to know: ion channel
mediates ion flux across membranes
