Wednesday, 21 May 2008

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 (Gα), G beta (Gβ), and G gamma (Gγ).

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

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


Hormone
{adrenaline}

1binds to and alters the conformation of

Receptor
{7hGPCR}

2activates [GTP displaces GDP, and binds to Gα]

Gαs.GTP
"G-alpha-s, GTP"


3detaches from G-protein, and activates

AC

4catalyzes conversion of ATP to

cAMP

5binds to and activates

PKA


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

---(i)---
PKA

6enters nucleus, and activates

KERB

7↓↓↓many steps

alters gene expression


---(ii)---
PKA

6activates

Phosphorylase kinase

7activates glycogen phosphorylase b to form

Glycogen phosphorylase a

8catalyzes 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


3 comments:

ArMs said...

Crez... give us some pics of you with ladies man...

haaha! but seriously.

LimZhi said...

Wow? U all gotta study till so in detail?

Patrick Leong said...

Hahaha.....

Let me help you...

G1P undergoes an isomerase reaction to G6P, and G6P is dephosphorylated by Glucose-6-phosphatase, G6Pase to form glucose, which is then secreted into blood.

Oh...and actually PKA first activates phosphorylase kinase before glycogen phosphorylase is activated.

At the same time, PKA (and phosphorylase kinase) phosphorylates Glycogen synthase, thus inhibiting its function.

Btw btw.......do you have any notes on cellular signalling? Aka....transport proteins like dyeneins and kinesins + all the G protein shit + serine/threonine/tyrosine kinases? Exam lol.....