title: RhoA and p38 MAPK mediate apoptosis induced by cellular cholesterol depletion.
abstract: Cholesterol is essential for cell viability, and homeostasis of cellular cholesterol is crucial to various cell functions. Here we examined the effect of cholesterol depletion on apoptosis and the mechanisms underlying this effect in NIH3T3 cells. We show that chronic cholesterol depletion achieved with lipoprotein-deficient serum (LPDS) and 25-hydroxycholesterol (25-HC) treatment resulted in a significant increase in cellular apoptosis and caspase-3 activation. This effect is not due to a deficiency of nonsterol isoprenoids, intermediate metabolites of the cholesterol biosynthetic pathway, but rather to low cholesterol levels, since addition of cholesterol together with LPDS and 25-HC nearly abolished apoptosis, whereas addition of farnesyl pyrophosphate or geranylgeranyl-pyrophosphate did not reverse the cell viability loss induced by LPDS plus 25-HC treatment. These effects were accompanied by an increase in ERK, JNK and p38 MAPK activity. However, only the inhibition of p38 MAPK with the specific inhibitor SB203580 or the overexpression of a kinase defective MKK6 resulted in a significant decrease in apoptosis and caspase-3 cleavage induced by cholesterol depletion. Furthermore, LPDS plus 25-HC increased RhoA activity, and this effect was reversed by addition of exogenous cholesterol. Finally, overexpression of the dominant negative N19RhoA inhibited p38 MAPK phosphorylation and apoptosis induced by low cholesterol levels. Together, our results demonstrate that cholesterol depletion induces apoptosis through a RhoA- and p38 MAPK-dependent mechanism.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Alcalá, Ctra. Madrid-Barcelona Km. 33, 6, E-28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Calleros
authors.forename: Marina
authors.initials: M
authors.lastname: Lasa
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Rodríguez-Alvarez
authors.forename: María J
authors.initials: MJ
authors.lastname: Toro
authors.forename: Antonio
authors.initials: A
authors.lastname: Chiloeches
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002784:Cholesterol / Q000172:deficiency* / Q000378:metabolism / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006888:Hydroxycholesterols / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D050356:Lipid Metabolism / Q000187:drug effects; D008074:Lipoproteins / Q000172:deficiency; D051379:Mice; D041681:NIH 3T3 Cells; D010766:Phosphorylation / Q000187:drug effects; D011106:Polyisoprenyl Phosphates / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012717:Sesquiterpenes; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D006888:Hydroxycholesterols; D008074:Lipoproteins; D011106:Polyisoprenyl Phosphates; D047428:Protein Kinase Inhibitors; D012717:Sesquiterpenes; C015234:geranyl pyrophosphate; C007997:25-hydroxycholesterol; C004808:farnesyl pyrophosphate; D002784:Cholesterol; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D020742:rhoA GTP-Binding Protein