Agonist-triggered downregulation of b-adrenergic receptors (ARs) constitutes vital negative feedback to prevent cellular overexcitation. Here, we report a novel downregulation of b 2 AR signaling highly specific for Ca v 1.2. We find that b 2 -AR binding to Ca v 1.2 residues 1923-1942 is required for b-adrenergic regulation of Ca v 1.2. Despite the prominence of PKA-mediated phosphorylation of Ca v 1.2 S1928 within the newly identified b 2 AR binding site, its physiological function has so far escaped identification. We show that phosphorylation of S1928 displaces the b 2 AR from Ca v 1.2 upon b-adrenergic stimulation rendering Ca v 1.2 refractory for several minutes from further b-adrenergic stimulation. This effect is lost in S1928A knock-in mice. Although AMPARs are clustered at postsynaptic sites like Ca v 1.2, b 2 AR association with and regulation of AMPARs do not show such dissociation. Accordingly, displacement of the b 2 AR from Ca v 1.2 is a uniquely specific desensitization mechanism of Ca v 1.2 regulation by highly localized b 2 AR/cAMP/PKA/ S1928 signaling. The physiological implications of this mechanism are underscored by our finding that LTP induced by prolonged theta tetanus (PTT-LTP) depends on Ca v 1.2 and its regulation by channel-associated b 2 AR.

l-Glutamate is the main excitatory neurotransmitter in the brain, with postsynaptic responses to its release predominantly mediated by AMPA-type glutamate receptors (AMPARs). A critical component of synaptic plasticity involves changes in the number of responding postsynaptic receptors, which are dynamically recruited to and anchored at postsynaptic sites. Emerging findings continue to shed new light on molecular mechanisms that mediate AMPAR postsynaptic trafficking and localization. Accordingly, unconventional secretory trafficking of AMPARs occurs in dendrites, from the endoplasmic reticulum (ER) through the ER-Golgi intermediary compartment directly to recycling endosomes, independent of the Golgi apparatus. Upon exocytosis, AMPARs diffuse in the plasma membrane to reach the postsynaptic site, where they are trapped to contribute to transmission. This trapping occurs through a combination of both intracellular interactions, such as TARP (transmembrane AMPAR regulatory protein) binding to -actinin-stabilized PSD-95, and extracellular interactions through the receptor amino-terminal domain. These anchoring mechanisms may facilitate precise receptor positioning with respect to glutamate release sites to enable efficient synaptic transmission.

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