?₂-Adrenergic receptor activation mobilizes intracellular calcium via a non-canonical cAMP-independent signaling pathway.

ABSTRACT: Beta adrenergic receptors (?ARs) are G-protein-coupled receptors essential for physiological responses to the hormones/neurotransmitters epinephrine and norepinephrine which are found in the nervous system and throughout the body. They are the targets of numerous widely used drugs, especially in the case of the most extensively studied ?AR, ?₂AR, whose ligands are used for asthma and cardiovascular disease. ?ARs signal through G?_s G-proteins and via activation of adenylyl cyclase and cAMP-dependent protein kinase, but some alternative downstream pathways have also been proposed that could be important for understanding normal physiological functioning of ?AR signaling and its disruption in disease. Using fluorescence-based Ca²⁺ flux assays combined with pharmacology and gene knock-out methods, we discovered a previously unrecognized endogenous pathway in HEK-293 cells whereby ?₂AR activation leads to robust Ca²⁺ mobilization from intracellular stores via activation of phospholipase C and opening of inositol trisphosphate (InsP₃) receptors. This pathway did not involve cAMP, G?_s, or G?_i or the participation of the other members of the canonical ?₂AR signaling cascade and, therefore, constitutes a novel signaling mechanism for this receptor. This newly uncovered mechanism for Ca²⁺ mobilization by ?₂AR has broad implications for adrenergic signaling, cross-talk with other signaling pathways, and the effects of ?AR-directed drugs.

SUBMITTER: Galaz-Montoya M 

PROVIDER: S-EPMC5473248 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature