Cell Biology Lecture 19: Cell Signaling

Why two cells respond or don’t to signal

Receptor determine ability to respond

Why two cells respond differently to same signal

Same receptor but different downstream signaling proteins leads to unique outcomes

Fast Responses

post translational modifications, protein-protein interactions, protein localization, more reversible

Why fast responses are fast

because there is no need to create new protein just modify 

Slow responses

changes in gene expression, less reversible

Cortisol

In the absence of cortisol, receptor localizes to cytoplasm, cortisol binding exposes NLS, recepor relocalized to nucleus, induces gene expression. 

Simple relay

1 thing to 1 thing

Amplification

1 thing to many things

Integration

many things to one thing

Distribution

multiple response effectors activated by one thing

ICCR

signal binding opens/closes an ion channel 

GPCR

receptor associated with heterotrimeric G protein 

ECR

receptor is enzyme or coupled with enzyme.

What are ligand-gated activated by

signal/ligand molecule

What are voltage gated activated by

changes in membrane potential

In absnece of signal, GPCR

GCR does not interact with G proteins, G alpha: GDP

In absence of signal, GPCR

promotes conf. change in GPCR, bind G alpha and act as a GEF, G alpha GTP dissociates from G beta. G alpha GTP activate downstream effector, GAP promotes GTP hydrolsis GDP rebind with G beta

Adrenaline

adrenaline activates, GPCR activates G alpha, G alpha activates AC, AC produces cAMP, cAMP activates PKA, PKA activates GP, GP promotes release of glucose from glycogen leading to fight/flight