Effect of ORL-1 on Cav1.2 calcium channels

Cav1.2 is an L-type voltage-gated Ca²⁺ channel (VGCC) that supports Ca²⁺ influx in response to membrane depolarization. Ca²⁺ entering via Cav1.2 alters gene expression, activates Ca²⁺-dependent enzymes and has been implicated in synaptic plasticity. ORL-1 is a Gi/o-coupled G protein-coupled receptor (GPCR) that is expressed in the peripheral and central nervous systems. Both Cav1.2 and ORL-1 are expressed in the hippocampus, where they have been implicated in learning and memory. It is well-documented that ORL-1 interacts with another VGCC, Cav2.2. However, less is known about potential interactions between Cav1.2 and ORL-1. Here, we examine the interplay between Cav1.2 (Cavα1c, Cavα2δ-1, Cavβ1b) and ORL-1 co-expressed in tsA-201 cells by using biochemical, electrophysiological and confocal imaging analyses. Co-immunoprecipitations revealed that ORL-1 independently interacts with Cavα1c and Cavα2δ-1 subunits of the Cav1.2 channel complex. Electrophysiological recordings revealed that co-expression with ORL-1 reduced Cav1.2 peak current density without altering its gating characteristics. Acute perfusion with the ORL-1 receptor agonist nociceptin (1 µM) did not alter Cav1.2 current density. Confocal imaging experiments revealed that ORL-1 significantly decreases Cav1.2 plasma membrane expression by disrupting forward trafficking. Interestingly, ORL-1 did not affect Cav1.2 endocytosis. Overall, our results demonstrate a previously unrecognized interaction between ORL-1 and Cav1.2 that alters Cav1.2 membrane expression without altering channel gating.