BIOLOGY 2B03 Lecture Notes - Lecture 14: Adenylyl Cyclase, Alpha Helix, Second Messenger System
GPCRs&
All&GPCRs&share&the&same&structure:&a&7&membrane&spanning&
domain&which&consists&of&7&transmembrane&alpha&helices&that&loop&
through&the&membrane&of&the&cell&
•
Examples&of&GPCRs&can&be&found&throughout&the&body&and&in&
systems&that&initiate&stress&
•
In&terms&of&the&adrenergic&stress&response:
the&signal&is&catecholamine,&which&include&epinephrine,&
norepinephrine&and&dopamine&
-
The&receptor&is&GPCR&
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The&effector&enzyme&is&Adenylyl&cyclase&
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The&secondary&messenger&is&cAMP&
-
The&cellular& response&is&the&release& of&stored&energy&via&the&
fast&(enzyme&activation)&and&slow&(the&activation&of&
transcription)&
-
•
The&adrenergic&receptors&fall&into&two&subclasses:&
•
The&stress&response&increases&the&supply&of&ATP&to&cells&through&
the&breakdown&of&energy&stores&(glycogen&and&triacylglycerol&in&the&
liver&and&lipolysis&leads&to&breakdown&of&fatty&acids)&
•
The&G&protein&once&activated&interacts&with&the&effector&enzyme&
(the&fast&mechanism)&and&uses>Pase&to&turn&off/&become&inactive&
•
In&beta&adrenergic&receptors,&the&effector&enzyme&(adenylyl&
cyclase)&increases&the&intracellular& concentration&of&the&secondary&
messenger&(cAMP)
•
In&alpha2&adrenergic&receptors,&adenylyl&cyclase&is&inhibited,&when&
this&occurs&there&is&a&drop&in&cAMP&concentration&as&
phosphodiesterase&constantly&breaks&down&cAMP&into&5'AMP&
•
Adenylyl&cyclase&converts&ATP&into&cAMP,&which&is&responsible&for&
modulating&the&activity&of&target&proteins&such&as&protein&kinase&
A/PKA
•
PKA&targets&the&release&of&glucose&from&glycogen&by&inhibiting&
glycogen&synthase&and&promoting&glycogen&phosphorylase,&
resulting&in&ATP&for&the&muscles&and&brain&
•
PKA&results&in&the&phosphorylation&and&activation&of&the&
transcription&factor,&CREB,&which&binds&to&the&cAMP&response&
element&
•
Amplification&is&an&important&part&of&all&signaling&pathways,&there&
10^8&fold&lification&in&response&
•
Module'6:'Lecture'3
Sunday,&March&25,&2018
12:37&PM
Document Summary
All gpcrs share the same structure: a 7 membrane spanning domain which consists of 7 transmembrane alpha helices that loop through the membrane of the cell. Examples of gpcrs can be found throughout the body and in systems that initiate stress. In terms of the adrenergic stress response: the signal is catecholamine, which include epinephrine, norepinephrine and dopamine. The cellular response is the release of stored energy via the fast (enzyme activation) and slow (the activation of transcription) The stress response increases the supply of atp to cells through the breakdown of energy stores (glycogen and triacylglycerol in the liver and lipolysis leads to breakdown of fatty acids) The g protein once activated interacts with the effector enzyme (the fast mechanism) and uses gtpase to turn off/ become inactive. In beta adrenergic receptors, the effector enzyme (adenylyl. In beta adrenergic receptors, the effector enzyme (adenylyl cyclase) increases the intracellular concentration of the secondary messenger (camp)