Cell Signalling Flashcards
what are the 2 types of signals?
+ what they consist of (6)
- chemical → hormones, metabolites, gases, PAMPs
- physical → light, pressure/touch
PAMPs → pathogen-associated molecular patterns
the pathway of signalling
signals are perceived by receptor trigerring an intracellular signaling cascade which leads to a response
3 types of hormones
- steroid hormones
- amino acid derivatives
- peptide hormones
hormones bind w high affinity to receptors
steroid hormones (5)
- derived from cholesterol,
- regulate metabolism,
- salt & water balance,
- inflammatory responses,
- sexual function
amino acids derivatives (4)
- regulates smooth muscle function
- blood pressure,
- cardiac rate
- thyroid hormones → stimulate metabolism
e.g. epinephrine
peptide hormones (2)
- regulate processes in all tissues
- incl relase of yet other hormones
endocrine signalling (3)
- TSH produced in pituitary gland
- moves through blood to thyroid gland (release thyroxine in response)
- acts over large distance
TSH → thyroid stimulating hormone
GR
glucocorticoid receptor
response elements (cis-elements)
palindromic DNA sites that bind several major nuclear receptors as dimers
reporter assays to investigate transcriptional regulation by steroid receptors in vitro
steps (6)
- prepare reporter gene plasmid/construct containing steroid response element linked upstream of a reporter gene
- obtain expression vector/plasmid for steroid receptor
- transfect both plasmids into mammal cell line cultured w mutli-well plates in an incubator in the lab, that doesn’t express that receptor
- have controls (some incubations = leave out reporter gene construct & others = leave out receptor expression vector
- incubate these cells with & without (another control) steroid ligand for that receptor
- lyze cells → add luciferase substrate & measure relative light units in lyzates
3 types of cell surface receptor superfamilies
- GPCRs
- tyrosine kinase (guanylyl cyclase activity)
- oligomeric ion channels
GPCRs
g protein coupled receptors
- integral membrane proteins
- intracellular site for a GTP binding protein
tyrosine kinase or guanylyl cyclase
single-transmembrane-segment catalytic receptors-intracellular domain
oligomeric ion channels
- multisubunit structures
- function as ligand-gated ion channels
- ligands - NTs
GPCRs effectors
2
- adenylyl cyclase
- phospholipase C
GPCRs second messengers (4)
- cAMP
- IP3
- DAG
- calcium
GPCRs are…
7-transmembrane segement (TMS) integral membrane proteins
how do GPCRs work (6)
+ cellular effects
hormone binds GPCR → conformation change → activates G protein (trimeric GTP-binding protein) → triggers cellular effects → activating kinases → activate TFs
cellular effects triggered incl: activ of adenylyl and guanlyl cyclases, activ of phospholipases, activ of ion channels
how do GPCRs lead to changes in cAMP & kinase activation (7)
GPCR → g protein → adenylyl cyclase (effector enzyme) → cAMP (2nd messenger) → PKA (protein kinase A) → CREB phosphorylates (cAMP-response element binding protein) → TFs
rhodopsin
receptor for vision, signal = light quanta, coupled to G protein
2 types of G proteins
heterotrimeric G proteins
small G proteins
α-subunit of heterotrimeric g protien function (2)
binds GDP/GTP
has intrinsic GTPase activity
what happens to heterotrimeric g proteins when hormone binds to receptor
stimulates GTP-GDP exchange
causes Gα to dissociate from other subunits and associate w effector protein (e.g. adenylyl cyclase)
how do some GPCRs activate the effector phospholipase C?
+ second messengers
via a Gq G protein to produce second messengers IP3 & DAG
explain the IP3/DAG mediated signal transduction pathways (6)
GCPR → G protein (Gq) → phospholipase C (effector enzyme) → IP3 & DAG & Ca2+ (2nd messengers) → PKC & CaM kinase (kinase) → various targets
