Question

Keeping GPCR signaling and its relationship to Glycogen metabolism pathway in mind (as per problem set for signaling mechanisms), will glucose level decrease or increase in blood in the following scenarios? Provide reasoning for your answer. a. Gα subunit loses its ability to bind to GTP. b. Regulatory subunits of PKA can not be separated from its catalytic subunits.

Answer 1

Gα subunit helps in the increase in the cAMP level inside the cell by activating adenylyl cyclase. Then cAMP binds to the regulatory subunits of PKA releasing its catalytic units which further activates the downstream signaling molecules that stimulate the activation of glycogen phosphorylase and inactivation of glycogen synthase, as result glucose concentration increases inside the cell from which it is transported into the blood.

a. If the Gα subunit becomes inactivated, the cAMP concentration will be decreasing leading to the decrease in the glucose concentration in the blood.

b. In this case, also the glucose concentration will decrease in the blood because the catalytic units are not free to phosphorylate the downstream signaling molecules.