Question

Briefly, describe the general idea behind the concept of amplification of the signal delivered by the hormone when it stimulates a 2nd messenger cascade.

Answer 1

Hormones got receptors in cell membrane
1 GPCR ( G- Protein coupled receptor )
They have seven membrane spanning domains - alpha,Beta and Gamma complex bound to GDP in resting state .When hormone comes and binds there will be a change in configuration from GDP( guanosine diphosphate ) it get converted into GTP (guanosine triphosphate ).Now alpha GTP dissociates and bind to effector which are second messenger ( CAMP ,IP3/DAG,CGMP) .

a)Hormone acting Via CAMP -
CAMP ( cyclic adenosine monophosphate ) converts Inactive protein kinase A into Active Protein kinase A which ultimately cause protein phosphorylation so the system is called CAMP/PKA system .
Eg .CRH ( corticotrophic releasing hormone ) TSH ( Thyroid stimulating hormone )

b)Hormones acting via CGMP
They are mostly vasodilators
Eg.Nitic oxide

c)Hormones acting Via IP3 /DAG

Phosphoinositol pyrophosphate (PIP2) get converted into Diacyl glycerol ( DAG) and Inositol triphosphate (IP3 ) by Phospholipase C

DAG activates protein Kinase C
IP3 activate Calcium calmodulin pathway

Most vasoconstrictors act via IP3 pathway .
Eg .V1 receptor Of ADH ( Antidiuretic hormone ),Oxytocin