Which of the following receptor proteins can initiate cascad

Which of the following receptor proteins can initiate cascades of membrane proteins that eventually activate a second messenger within the cell? (choose all that apply) Select one or more: a. intracellular receptors b. G protein-coupled receptor c. Ligand-gated channel d. Enzyme/enzyme-linked receptor e. cGMP

Solution

Choices a, b, d and e are correct.

Explanation: Intracellular signalling cascades are dependent upon sequential activation of biomolecules in a cell after a signalling moleucle binds to a cellular receptor such as G-protein coupled receptors or GPCR. The binding of the ligand to the receptor induces conformational changes in the outer surface of the receptor and the intracellular domain of the receptor called the cytoplasmic side. As the cytoplasmic side of receptor tail changes conformationally, ATP dependent release of a subunit of this cascade. This process is often accompanied with phosphorylation and activation of intracellular side of the receptor which is often enzyme linked in nature. As the phosphorylation takes place, the enzyme gets activated and released into the cytoplasm with subsequent activation of a secondary signalling molecule such as free radical, cGMP etc. The phosphorylated secondary signal then transits to its target location and subseqeuntly activates the downstream signallng cascades.

These types of signalling are often seen in GPCR, PI3K, IGF and TNFalpha mediated receptor bound signalling cascades.