β-adrenergic control of sarcolemmal CaV1.2 abundance by small GTPase Rab proteins

摘要: The number and activity of Cav1.2 channels in the cardiomyocyte sarcolemma tunes magnitude Ca2+-induced Ca2+ release myocardial contraction. {beta}-adrenergic receptor ({beta}AR) activation stimulates sarcolemmal insertion CaV1.2 channels. This supplements pre-existing population, forming large super-clusters wherein neighboring undergo enhanced cooperative-gating behavior, amplifying influx contractility. Here, we determine this stimulated is fueled by an internal reserve early- recycling endosome-localized, pre-synthesized {beta}AR-activation decreased CaV1.2/endosome colocalization ventricular myocytes, as it triggered emptying endosomal cargo into sarcolemma. We examined rapid dynamics process with live-myocyte imaging channel trafficking, discovered that are often inserted pre-formed, multi-channel clusters. Likewise, entire clusters were removed from during endocytosis, while other cases, a more incremental suggested removal individual amplitude response was doubled co-expression constitutively-active Rab4a, halved dominant-negative Rab11a, abolished mutant Rab4a. In {beta}AR-stimulated diminished both nocodazole latrunculin-A, suggesting essential role cytoskeleton process. Functionally, cytoskeletal disruptors prevented {beta}AR-activated current augmentation. Moreover, {beta}AR-regulation when halted co-application latrunculin-A. These findings reveal {beta}AR-stimulation triggers on-demand boost abundance via targeted, Rab4a Rab11a-dependent for cardiac CaV1.2. Significance StatementThe L-type voltage-gated excitation-contraction coupling heart. During fight-or-flight response, augmented result PKA-mediated phosphorylation, downstream activation. channels, driven insertion/recycling specific containing endosomes, {beta}AR-mediated regulation these data new conceptual framework critical robust pathway tuning EC-coupling fight-or-flight.