title: Isoprenylcysteine carboxyl methyltransferase activity modulates endothelial cell apoptosis.
abstract: Extracellular ATP, adenosine (Ado), and adenosine plus homocysteine (Ado/HC) cause apoptosis of cultured pulmonary artery endothelial cells through the enhanced formation of intracellular S-adenosylhomocysteine and disruption of focal adhesion complexes. Because an increased intracellular ratio of S-adenosylhomocysteine/S-adenosylmethionine favors inhibition of methylation, we hypothesized that Ado/HC might act by inhibition of isoprenylcysteine-O-carboxyl methyltransferase (ICMT). We found that N-acetyl-S-geranylgeranyl-L-cysteine (AGGC) and N-acetyl-S-farnesyl-L-cysteine (AFC), which inhibit ICMT by competing with endogenous substrates for methylation, caused apoptosis. Transient overexpression of ICMT inhibited apoptosis caused by Ado/HC, UV light exposure, or tumor necrosis factor-alpha. Because the small GTPase, Ras, is a substrate for ICMT and may modulate apoptosis, we also hypothesized that inhibition of ICMT with Ado/HC or AGGC might cause endothelial apoptosis by altering Ras activation. We found that ICMT inhibition decreased Ras methylation and activity and the activation of the downstream signaling molecules Akt, ERK-1, and ERK-2. Furthermore, overexpression of wild-type or dominant active H-Ras blocked Ado/HC-induced apoptosis. These findings suggest that inhibition of ICMT causes endothelial cell apoptosis by attenuation of Ras GTPase methylation and activation and its downstream antiapoptotic signaling pathway.
authors.affiliation: Pulmonary Vascular Biology Laboratory, Providence Veterans Affairs Medical Center, Brown Medical School, Rhode Island 02908, USA.
authors.forename: Kristina
authors.initials: K
authors.lastname: Kramer
authors.forename: Elizabeth O
authors.initials: EO
authors.lastname: Harrington
authors.forename: Qing
authors.initials: Q
authors.lastname: Lu
authors.forename: Robert
authors.initials: R
authors.lastname: Bellas
authors.forename: Julie
authors.initials: J
authors.lastname: Newton
authors.forename: Kerri L
authors.initials: KL
authors.lastname: Sheahan
authors.forename: Sharon
authors.initials: S
authors.lastname: Rounds
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000378:metabolism; D000241:Adenosine / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism; D004224:Diterpenes / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011496:Protein Methyltransferases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011651:Pulmonary Artery / Q000033:anatomy & histology / Q000378:metabolism; D012435:S-Adenosylhomocysteine / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014466:Ultraviolet Rays; D018631:ras Proteins / Q000378:metabolism
chemical_list: D004224:Diterpenes; D004791:Enzyme Inhibitors; C095716:N-acetyl-S-geranylgeranyl-cysteine; D011518:Proto-Oncogene Proteins; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; D011496:Protein Methyltransferases; C056501:protein-S-isoprenylcysteine O-methyltransferase; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins; D000241:Adenosine; D003545:Cysteine; C068268:N-acetyl-S-farnesylcysteine; D000111:Acetylcysteine