Which of the following could be used to demonstrate the prin

Which of the following could be used to demonstrate the principle of co-incidence detection in a signaling pathway ?

A Activity of the androgen receptor at both the cytoplasmic leaflet of the plasma membrane and within the nucleus.

B Activation of PKC at the plasma membrane by Ca2+ and DAG.

C Binding of GDP or GTP to a heterotrimeric GTPase.

D Reassociation of subunits of PKA.

E Binding of Ca2+ to the ER lumenal domain of STIM1.

Solution

Co-incidence detection in signalling pathway can be explained following mechanism.

The phosphatidyl inositol cycle mediates the actions of hormones like vasopressin and epinephrine. Diacyl glycerol is a second messenger molecule formed during phosphatidylinositol – 4, 5 – bisphosphate (PIP₂) cleavage by phospholipase C enzyme. The DAG activates the protein kinase C (PKC). The reaction of phosphatidylinositol – 4, 5 – bisphosphate (PIP₂) cleavage by phospholipase C enzyme results in formation of inositol – 1,4,5 – triphosphate and diacylglycerol (DAG). After formation the IP₃ diffuses into calcisome of smooth endoplasmic reticulum and binds to its receptor (a calcium channel).

Calcium ions mediate the large number of cellular processes including the activation of plasma membrane – associated protein kinase C (PKC). Calcium binding sites of calcium regulated proteins exhibit the high affinity for calcium ions. Calmodulin a type of calcium binding protein involved in the mediation of many calcium regulated reactions. Option B is correct.