TY - JOUR T1 - Phorbol 12-myristate 13-acetate Triggers the Protein Kinase A-Mediated Phosphorylation and Activation of the PDE4D5 cAMP Phosphodiesterase in Human Aortic Smooth Muscle Cells through a Route Involving Extracellular Signal Regulated Kinase (ERK) JF - Molecular Pharmacology JO - Mol Pharmacol SP - 1100 LP - 1111 DO - 10.1124/mol.60.5.1100 VL - 60 IS - 5 AU - George Baillie AU - Simon J. MacKenzie AU - Miles D. Houslay Y1 - 2001/11/01 UR - http://molpharm.aspetjournals.org/content/60/5/1100.abstract N2 - Phosphodiesterase 4D5 is the sole PDE4D cAMP phosphodiesterase isoform expressed in human aortic smooth muscle cells (HASMC). Phorbol 12-myristate 13-acetate (PMA) challenge of HASMC rapidly activated PDE4D5 through a process ablated by the mitogen-activated protein kinase kinase inhibitor PD98059. PMA elicited an inhibitory effect on PDE4D5 activity in HASMC treated with the cyclooxygenase (COX) inhibitor indomethacin, the COX-2 selective inhibitor NS-398, the phospholipase A2 inhibitor quinacrine, and the cAMP-dependent protein kinase A (PKA) inhibitor H89. PMA challenge of COS-1 cells elicited the rapid inhibition and phosphorylation of both recombinant and endogenous PDE4D5 in a manner ablated by PD98059 and not seen in S651A mutant PDE4D5. PMA promoted the generation of PGE2 in the medium of HASMC and caused activation of both extracellular signal-regulated kinase (ERK) and PKA through a process ablated by indomethacin, NS-398, quinacrine, and PD98059. Exogenous prostaglandin (PG) E2 increased cAMP levels and activated PKA in HASMC. COX-2 was expressed in HASMC but not in COS-1 cells. Forskolin challenge of COS-1 cells activated PDE4D5 by causing the PKA-mediated phosphorylation of Ser126 as detected using a novel phosphospecific antiserum. PMA challenge of HASMC elicited phosphorylation of the stimulatory PKA-specific phosphorylation site, Ser126 in PDE4D5 in a manner ablated by PD98059, indomethacin, and H89. We propose that, in HASMC, PMA activates PDE4D5 through an ERK-controlled autocrine mechanism. This involves PGE2generation, which causes activation of adenylyl cyclase, allowing PKA to elicit net activation of PDE4D5 by phosphorylation at Ser126. ER -