G-protein-coupled receptor signaling components localize in both sarcolemmal and intracellular caveolin-3-associated microdomains in adult cardiac myocytes.
Head, BP Patel, HH Roth, DM Lai, NC Niesman, IR Farquhar, MG Insel, PA
||Head BP, etal., J Biol Chem. 2005 Sep 2;280(35):31036-44. Epub 2005 Jun 16.
||(View Article at PubMed) PMID:15961389
This study tests the hypothesis that G-protein-coupled receptor (GPCR) signaling components involved in the regulation of adenylyl cyclase (AC) localize with caveolin (Cav), a protein marker for caveolae, in both cell-surface and intracellular membrane regions. Using sucrose density fractionation of adult cardiac myocytes, we detected Cav-3 in both buoyant membrane fractions (BF) and heavy/non-buoyant fractions (HF); beta2-adrenergic receptors (AR) in BF; and AC5/6, beta1-AR, M4-muscarinic acetylcholine receptors (mAChR), mu-opioid receptors, and Galpha(s) in both BF and HF. In contrast, M2-mAChR, Galpha(i3), and Galpha(i2) were found only in HF. Immunofluorescence microscopy showed co-localization of Cav-3 with AC5/6, Galpha(s), beta2-AR, and mu-opioid receptors in both sarcolemmal and intracellular membranes, whereas M2-mAChR were detected only intracellularly. Immunofluorescence of adult heart revealed a distribution of Cav-3 identical to that in isolated adult cardiac myocytes. Upon immunoelectron microscopy, Cav-3 co-localized with AC5/6 and Galpha(s) in sarcolemmal and intracellular vesicles, the latter closely allied with T-tubules. Cav-3 immunoprecipitates possessed components that were necessary and sufficient for GPCR agonist-promoted stimulation and inhibition of cAMP formation. The distribution of GPCR, G-proteins, and AC with Cav-3 in both sarcolemmal and intracellular T-tubule-associated regions indicates the existence of multiple Cav-3-localized cellular microdomains for signaling by hormones and drugs in the heart.
Gene Ontology Annotations
|Genes (Rattus norvegicus)
|Adcy5 (adenylate cyclase 5)|
|Adcy6 (adenylate cyclase 6)|
|Adrb2 (adrenoceptor beta 2)|
|Cav3 (caveolin 3)|
|Chrm2 (cholinergic receptor, muscarinic 2)|
|Chrm4 (cholinergic receptor, muscarinic 4)|
|Gnai2 (G protein subunit alpha i2)|
|Gnai3 (G protein subunit alpha i3)|
|Gnas (GNAS complex locus)|
|Oprm1 (opioid receptor, mu 1)|
Objects referenced in this article
||adrenoceptor beta 1