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
