week 6 reading Flashcards
intracellular signaling molecules: function
act as “molecular switches”
intracellular signaling molecules: examples
kinase, phosphatase
GTP, GDP
kinases: function and target
adds phosphate
targets serine/threonine, sometimes tyrosine
phosphatase: function
removes phosphate
GTP and GDP molecular switches
GTP = on
GDP = off
GCPRs: 3 examples
Gαq
Gαi
GαS
Gαq pathway (with PLC and PKC)
- ligand binds
- recruits GTP, which binds α subunit, α subunit consequently loses affinity for βγ subunit
- βγ released
- PLC is activated, cleaves PI4,5P2 into DAG and IP3
- IP3 binds IP3R in ER, Ca2+ released
- Ca2+ recruits PKC to DAG
cAMP/PKA pathway
- Gαs-GTP binds, stimulates AC to convert ATP to cAMP
- cAMP binds inactive PKA, PKA loses affinity for R and dissociates
- PKA is active
GαS and Gαi functions
GαS: inhibits AC, cAMP decreases
Gαi: stimulates AC, cAMP increases
GCPR attenuation steps
- GCPR is phosphorylated by kinase or GRKs
- arrestin binds and promotes endocytosis
- RGS binds GTP-α, hydrolyzes to GDP
- α rebinds βγ
scaffold proteins: function
bind together like legos
signaling complexes
allows similar signaling pathways to be activated by different receptors
SH2 function
binds phosphorylated tyrosines
mediates tyrosine phosphorylation downstream
SH3
binds proline-rich regions
PH
binds charged head groups of PIPs
paracrine signaling
local mediators act on neighboring cells when released in extracellular space
endocrine signaling
hormone goes thru the bloodstream to reach target cell
second messengers: general
rapidly diffusing, non-protein, move quickly
second messenger examples
Ca2+
DAG
IP3
