Question

Describe the mechanisms of receptor down-regulation and their implications

Answer 1

when the concentration and affinity of receptors decreases on the cell to a molecule such are hormone, neurotrasmitter etc , this mechanism is referred as receptor downregulation. downregulation of the receptors is also known as desensitization of the receptor and the cell is then termed as desensitized cell.

it is done in order to permanently terminate the response .cell terminate the response even in the presence of ligand is referred as desensitization where the cell downregulates the receptor.

it is done in GPCR signalling , suppose if it is needed to downregulate the adrenergic receptors( these are the receptors for epinephrin) and GPCR itself has no enzymatic action that is why during the desensitization the cytosolic protein beeta adrenergic kinase( BARK) is recruited by G_?? subunit of trimeric G protein which phosphorylates the serine residues present at carboxy terminal of the receptor, after phosphorylation another protein ? arrestin binds to serine residue which is already phosphorylated. when ?arrestin interacts with the receptor , conformational changes occur in the receptor and endocytosis of the receptor is occured.