BIOLOGY 2B03 Chapter Notes - Chapter 6: Adenylyl Cyclase, Saccharomyces Cerevisiae, Smooth Muscle Tissue
17 Jun 2018
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BIOLOGY 2B03 - Module 6 Lecture III
G-protein Coupled Receptors
GPCRs’ common structure: a seven-membrane spanning domain which consists of seven
transmembrane alpha helices that loop through the membrane of the cell
● This creates four extracellular segments (E1-4)
○ Fold in the extracellular space to form the signal-binding domain
● Also creates for cytoplasmic segments (C1-4)
○ Fold to form an internal domain that interacts with a trimeric G protein
● 800 genome sequence analysis
○ Abrogation of GPCR → many disease
Well studies examples of GPCRs:
● Receptors that initiate stress responses
● Light-activated rhodopsins in the eye
● Odorant receptors in the mammalian nose
● Hormone & neurotransmitter receptors
● Plant growth hormone receptors
● GPCR system in the Saccharomyces cerevisiae
Adrenergic Stress Receptors: a2 and B
Example: GPCR-mediated pathway used in the stress response in mammalian cells
● Catecholamine: water soluble signals; circulate in the bloodstream
○ Abundant catecholamine → epinephrine (adrenaline), norepinephrine
(noradrenaline), and dopamine
● Release of norepinephrine from the adrenal medulla of adrenal glands: part of the fight-or-
flight response
● GPCR is catecholamine receptor
● Intracellular signaling pathway involves activation of the receptor associated trimeric G-
protein an effector protein (adenylyl cyclase)
○ Adenylyl cyclase: modulates the cytosolic concentration of secondary messenger
(cAMP)
Many cellular effect of increase cAMP concentration
● Fight-or-flight response required to impact the release of stored energy
● Fast response requires the activation of an enzyme
● Slow response requires to active transcription
Two subclasses of adrenergic receptors:
● Alpha-2 and beta adrenergic receptors
● Epinephrine can bind to each of these two receptors
○ Induces different response though (response is cell type specific)
○ Coordinated responses
● Beta: stimulatory; in the liver and adipose cells stimulate glycolysis and lipolysis
○ On heart → increases muscle contraction → increased blood supplies to tissues
○ On smooth muscle cell in the intestine → relaxation; no expansion for
unnecessary energy
● Alpha-2: inhibitory; found in cell of the blood vessels in the skin, the kidney and in the
smooth muscle cells of the intestine
○ Arteries constriction and reduction of blood supplies to the periphery
Catecholamines: Epinephrine or Adrenaline
Catecholamines are the product of the adrenal glands
find more resources at oneclass.com
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Document Summary
Gpcrs" common structure: a seven-membrane spanning domain which consists of seven transmembrane alpha helices that loop through the membrane of the cell. Fold in the extracellular space to form the signal-binding domain. Fold to form an internal domain that interacts with a trimeric g protein. Example: gpcr-mediated pathway used in the stress response in mammalian cells. Catecholamine: water soluble signals; circulate in the bloodstream. Abundant catecholamine epinephrine (adrenaline), norepinephrine (noradrenaline), and dopamine. Release of norepinephrine from the adrenal medulla of adrenal glands: part of the fight-or- flight response. Intracellular signaling pathway involves activation of the receptor associated trimeric g- protein an effector protein (adenylyl cyclase) Adenylyl cyclase: modulates the cytosolic concentration of secondary messenger (camp) Fight-or-flight response required to impact the release of stored energy. Fast response requires the activation of an enzyme. Epinephrine can bind to each of these two receptors. Induces different response though (response is cell type specific)
