Distinct signaling pathways mediate cardiomyocyte phospholipase D stimulation by endothelin-1 and thrombin

M. FAHIMI-VAHID, N. GOSAU, C. MICHALEK, L. HAN, K. H. JAKOBS, M. SCHMIDT. N. ROBERTS,, M. AVKIRAN AND T WIELAND. Distinct Signaling Pathways Mediate Cardiomyocyte Phospholipase 1) Stimulation by Endothelin-1 and Thrombin. Journal of Molecular and Cellular Cardiology (2002) 34. 441-453. Several G protein-coupled receptors which stimulate phospholipase C (PLC) also activate phospholipase 1) (111,D) in cardiomyocytes. Here. we characterized PLD activation in neonatal rat cardiomyocytes by the PLC-stimulatory thrombin receptor PAR I, in comparison to the endothelin-1 receptor ETAR, which induces PLD stimulation by activation of protein kinase C (PKC) delta and epsilon. Similar to ELR, activation of PARI induced PLD stimulation, which. however, wits insensitive to PKC inhibition. Furthermore. in contrast to EtAR, PLD stimulation by PAR1 was Suppressed by overexpression of regulators of G protein signaling specific for G(12)-type G proteins and treatment with brefeldin A, an inhibitor of guanine nucleotide exchange factors for ADP-ribosylation factor (ARF) GTPases. On the other hand, inactivation of Rho GTPases by Clostridium difficile toxin B and treatment with general tyrosine kinase inhibitors suppressed PAR1- and ETAR- as well as phorbol ester-induced PLD stimulation and was associated with a tall in the Cellular level of phosphatidylinositol 4,5-bisphosphatc (PIP2). We conclude that, in contrast to ETAK-PLD coupling, PAR1 induced cardiomyocyte PLD stimulation is PKC-independent and mediated by G(12)-type G proteins and ARF GTPases, while Rho and tyrosine kinases regulate PLD stimulation by either receptor, apparently by controlling the cellular level of PIP,, a common regulator of PLD activity. (C) 2002 Elsevier Science Ltd. All rights reserved.