title: c-Abl is an upstream regulator of acid sphingomyelinase in apoptosis induced by inhibition of integrins αvβ3 and αvβ5.
abstract: Inhibition of integrins αvβ3/αvβ5 by the cyclic function-blocking peptide, RGDfV (Arg-Gly-Asp-Phe-Val) can induce apoptosis in both normal cells and tumor cells. We show that RGDfV induced apoptosis in ECV-304 carcinoma cells, increased activity and mRNA expression of acid sphingomyelinase (ASM), and increased ceramides C(16), C(18:0), C(24:0) and C(24:1) while decreasing the corresponding sphingomyelins. siRNA to ASM decreased RGDfV-induced apoptosis as measured by TUNEL, PARP cleavage, mitochondrial depolarization, and caspase-3 and caspase-8 activities, as well as by annexinV in a 3D collagen model. These findings indicate a causal role for ASM in RGDfV-induced apoptosis in ECV-304. We have shown that c-Abl, a non-receptor tyrosine kinase, also mediates RGDfV-induced apoptosis. However, c-Abl, has not been previously linked to ASM in any system. Here we show that STI-571 (imatinib, inhibitor of c-Abl) inhibited RGDfV-induced ASM activity. Furthermore, STI-571 and c-Abl-siRNA both inhibited RGDfV-induced increase in ASM mRNA, but ASM-siRNA did not affect c-Abl phosphorylation or expression, supporting that c-Abl regulates the RGDfV-induced increase in ASM expression. These studies implicate ASM as a mediator of apoptosis induced by inhibition of integrins αvβ3/αvβ5, and for the first time place c-Abl as an upstream regulator of ASM expression and activity.
authors.affiliation: Division of Hematology-Oncology, Department of Pediatrics, Keck School of Medicine, University of Southern California and the Saban Research Institute of Children's Hospital Los Angeles, Los Angeles, California, United States of America.
authors.forename: Xiuhai
authors.initials: X
authors.lastname: Ren
authors.forename: Jingying
authors.initials: J
authors.lastname: Xu
authors.forename: Jason P
authors.initials: JP
authors.lastname: Cooper
authors.forename: Min H
authors.initials: MH
authors.lastname: Kang
authors.forename: Anat
authors.initials: A
authors.lastname: Erdreich-Epstein
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D002518:Ceramides / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008954:Models, Biological; D010456:Peptides, Cyclic / Q000494:pharmacology; D016315:Proto-Oncogene Proteins c-abl / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D019030:Receptors, Vitronectin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism*; D013109:Sphingomyelins / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D002518:Ceramides; D039302:Integrin alphaVbeta3; D010456:Peptides, Cyclic; D012333:RNA, Messenger; D019030:Receptors, Vitronectin; D013109:Sphingomyelins; C092113:cyclo(arginyl-glycyl-aspartyl-phenylalanyl-valyl); C064660:integrin alphaVbeta5; D016315:Proto-Oncogene Proteins c-abl; C543066:SMPD1 protein, human; D013108:Sphingomyelin Phosphodiesterase; D053148:Caspase 3; D053181:Caspase 8