Compartmentalized cAMP Response to EP2 Receptor Activation in Human Airway Smooth Muscle Cells
Background and Purpose
Previous studies indicate that prostaglandin EP2 receptors (EP2Rs) selectively couple to adenylyl cyclase type 2 (AC2) in non-lipid raft domains of airway smooth muscle (ASM) cells, where they regulate specific cAMP-dependent responses. The goal of the present study was to identify the cellular microdomains where EP2Rs stimulate cAMP production.
FRET-based cAMP biosensors were targeted to different subcellular locations of primary human ASM cells. The Epac2-camps biosensor, which expresses throughout the cell, was used to measure bulk cytoplasmic responses. Epac2-MyrPalm and Epac2-CAAX were used to measure responses associated with lipid raft and non-raft regions of the plasma membrane, respectively. Epac2-NLS was used to monitor responses at the nucleus.
Activation of AC with forskolin or β2-adrenergic receptors (β2ARs) with isoproterenol increased cAMP in all subcellular locations. Activation of EP2Rs with butaprost produced cAMP responses that were most readily detected by the non-raft and nuclear sensors, but only weakly detected by the cytosolic sensor and not detected at all by the lipid raft sensor. Exposure to rolipram, a phosphodiesterase type 4 (PDE4) inhibitor, unmasked the ability of EP2Rs to increase cAMP levels associated with lipid raft domains. Overexpression of AC2 selectively increased EP2R-stimulated production of cAMP in non-raft membrane domains.
Conclusions and Implications
EP2R activation of AC2 leads to cAMP production in non-raft and nuclear compartments of human ASMs, while β2AR signaling is broadly detected across microdomains. Activity of PDE4 appears to play a role in maintaining the integrity of compartmentalized EP2R responses in these cells.
K Miyashiro, SR Agarwal, H Latt, RS Ostrom and RD Harvey. Compartmentalized cAMP response to EP2 receptor activation in human airway smooth muscle cells. FASEB J, 30(1):710.13, 2016.
Federation of American Society of Experimental Biology (FASEB)