Signal Transduction

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Starring


1. GPCR = G-protein-coupled receptor (a.k.a. 7-helix GPCR)

2. G-protein = GTP-binding protein

3. AC = adenylyl cyclase

4. cAMP = cyclic adenosine monophosphate "second messenger"

5. PKA = protein kinase A (cAMP-dependent protein kinase)

*G-protein is heterotrimeric and is composed of three subunits:
G alpha (G_α), G beta (G_β), and G gamma (G_γ).

Also:
GTP/GDP = guanosine tri/diposphate
ATP = adenosine triphosphate

"How does the hormone adrenaline - "fight or flight hormone" - increase blood glucose?"


Hormone
{adrenaline}

1↓binds to and alters the conformation of

Receptor
{7hGPCR}

2↓activates [GTP displaces GDP, and binds to G_α]

G_αs.GTP
"G-alpha-s, GTP"

3↓detaches from G-protein, and activates

AC

4↓catalyzes conversion of ATP to

cAMP

5↓binds to and activates

PKA


Now PKA has more than just one intracellular target protein.
Examples:

---(i)---
PKA

6↓enters nucleus, and activates

KERB

7↓↓↓many steps

alters gene expression


---(ii)---
PKA

6↓activates

Phosphorylase kinase

7↓activates glycogen phosphorylase b to form

Glycogen phosphorylase a

8↓catalyzes conversion of glycogen to form

Glucose 1-phosphate

9↓↓↓many steps

Glucose


So, there you have it (at first-semester level).

The steps via which adrenaline increases blood glucose. □

NobelPrize.org

Credits:
A/Prof M. A. Bogoyevitch (Week 10 lecturer)
Nelson & Cox, Lehninger Principles of Biochemistry (4th ed.)
Signal Transduction in Cells - NobelPrize.org