lecture 12 - broad principles of cell signaling Flashcards
why is cell signalling important
transfer information
- from environment to cell
- from cell to cell
cell signaling effects
metabolism
nervous system
cell cycle
development
immunology
physiology
pharmacology
cells respond to
physical and chemical signals
methods of cell to cell communication
gap junctions
autocrine and paracrine signals (cells release a signal and can feedback onto that cell or other cells that are local)
hormone
neurotransmitter
neurotransmitter
neurochrome
signaling pathways we will learn
- steroid hormones
- ligand gated ion channels
- cyclic AMP pathway
- phosphoinositide pathway
- tyrosine kinase pathway
chemical signal
e.g. pheromones, hormones, neurotransmitters, cell surface molecules
receptor
e.g. ion channel linked, G protein linked, tyrosine kinase linked
transducer
e.g. G proteins, non receptor tyrosine kinases
amplifier
e.g. adenylyl cyclase, phospholipase C
2nd messenger
e.g. cyclic AMP, IP3, Ca2+, DAG, proteins
effectors
e.g. protein kinases, Ca2+ binding proteins
response element
e.g. enzymes, ion channels, transcription factors
response
e.g. metabolism, secretion, contraction, excitability, gene transcription, cell growth
amplification
a single hormone receptor interaction can be amplified by up to 10^6
heterogeneity - concept of diversity
each pathway component often has multiple forms and cells can mix and match components
dynamics
responses are dependent on both temporal and spatial aspects of signaling components
amplification example
cAMP signaling pathway:
signal molecule binds to G protein linked receptor which activated the G protein
G protein turns on adenylyl cyclase an amplifier enzyme
adenylyl cyclase converts ATP to cAMP
cAMP activates protein kinase A
protein kinase A phosphorylates other proteins leading to a cellular response
information transfer
can be through conformational change
e.g.
chemical signal to receptor, receptor to G protein, G protein to amplifier, 2nd messenger to protein kinase
can be through covalent modification
e.g. phosphorylation
add phosphate from ADP something
alpha subunit of G protein is activated when ___ is bound
GTP
activated alpha subunit binds to target protein and
activates it
hydrolysis of GTP by alpha subunit inactivates the subunit causing it to
dissociate from the target protein
inactive alpha subunit re assembles with the beta gamma complex to reform
the G protein ( this is an example of a conformational change having an affect)
covalent modification - phosphorylation
addition of phosphate group of ATP to hydroxyl group of amino acid which changes the activity of function of the protein
this is reversed by
protein phosphatases
