5 Most common steps and comparison of cAMP & PIP2 through Pathway Systems

Free Online lectures on Medical Biochemistry for Medical students by the Biochemistry Club

cAMP System

The cAMP and the PIP₂ pathways are compared together for better understanding of the sequences involving the 5 main steps regarding the signal transduction through cell surface receptors in water soluble hormones.

The cAMP Pathway

The hormones that work through the cAMP pathway are:

1. Epinephrine β (G_s)
2. Epinephrine α₂ (G_i)
3. Acetylcholine M₂ (G_i)
4. Dopamine & Serotonin both (G_s & G_i)
5. TSH (G_s)
6. Vasopressin in kidneys (G_s)

Remember the 5 steps told in the previous lesson.

In the first step the hormone binds to the receptor. This receptor is a single protein having 7 transmembrane domains.

The receptor that has 7 transmembrane domains is a G Protein receptor.

This binding of the hormone activates the G Protein inside the membrane (hormone binding is outside the membrane).

Now if the signal is stimulatory (Gs) then it will activate the enzyme Adenyl cyclase, but if it Gi then it will inhibit the enzyme.

Adenyl cyclase will then increase the production of cAMP through the production of ATP.

cAMP then in turn will activate the Protein kinase A.

Protein kinase A will in turn will work on two different pathways:

On one side it will activate the Protein kinases in the cell. These Protein kinases will phosphorylate the enzymes.

One the other side Protein kinase A will phosphorylate CREB.

The phosphorylated CREB will enter the nucleus and will activate the CRE.

CRE in turn will activate gene and thus inducing transcription.

FOR COMPLETE LESSON PLEASE CLICK HORMONES AND SIGNAL TRANSDUCTION IN BIOCHEMISTRY II AND THIS WILL SHOW THE COMPLETE LIST OF LESSONS IN THE SUBJECT