Question

LULJLIUILL1 PUNILI OD Activation of metabotropic receptors by a neurotransmitter can have a lasting effect (hours to days) by what mechanism? Phosphorylation of ion channels enhancing their stability in the membrane. O Phosphorylation of SNARE proteins leading to an enhancement of neurotransmitter release. Phosphorylation of CREB through PKA which allows it to bind to CRE and enhance gene transcription. O Phosphorylation of CRE through PKA which allows CREB to bind to it and enhance gene transcription.

Answer 1

Metabotropic receptors are G protein coupled receptors that bind to neurotransmitters such as epinephrine, dopamine, and serotonin. Binding of ligand /neurotransmitter to the receptor causes receptor dimerization. This will cause dissociation of G alpha subunit from the G protein trimer and binding of GTP to G alpha subunit. The activated G alpha subunit then activates adenylyl cyclase. Adenylyl cyclase will breakdown ATP to cAMP. The cAMP produced will activate protein kinase alpha, which phosphorylates downstream targets. PKA will phosphorylate CREB protein at serine 133. Phosphorylated CREB (cAMP response element binding protein) translocate to the nucleus where it binds to target genes that have CRE sites. CREB then associates with CRE (cAMP response element), which then binds to the basal transcription machinery to increase transcription of target genes.

Ionotropic receptors cause phosphorylation of ion channels. SNARE phosphorylation is required for release of neurotransmitter at the axons. These neurotransmitters then bind to metabotropic receptors. PKA does not phosphorylate CRE, which are DNA sequences.

Right choice: Phosphorylation of CREB through PKA, which allows it to bind to CRE and enhance gene transcription.