title: Induction of group VIA phospholipase A2 activity during in vitro ischemia in C2C12 myotubes is associated with changes in the level of its splice variants.
abstract: The involvement of group VI Ca(2+)-independent PLA(2)s (iPLA(2)-VI) in in vitro ischemia [oxygen and glucose deprivation (OGD)] in mouse C2C12 myotubes was investigated. OGD induced a time-dependent (0-6 h) increase in bromoenol lactone (BEL)-sensitive iPLA(2) activity, which was suppressed by specific short interfering (si)RNA knockdown of iPLA(2)-VIA. OGD was associated with an increase in iPLA(2)-VIA protein levels, whereas mRNA levels were unchanged. The levels of iPLA(2)-VIB mRNA and protein were not increased by OGD. RT-PCR and Western blot analysis identified a mouse iPLA(2)-VIA homolog to catalytically inactive 50-kDa iPLA(2)-VIA-ankyrin variants previously identified in humans. Both the mRNA and protein levels of this approximately 50-kDa variant were reduced significantly within 1 h following OGD. In C2C12 myoblasts, iPLA(2)-VIA seemed to predominantly reside at the endoplasmatic reticulum, where it accumulated further during OGD. A time-dependent reduction in cell viability during the early OGD period (3 h) was partially prevented by iPLA(2)-VIA knockdown or pharmacological inhibition (10 microM BEL), whereas iPLA(2)-VIA overexpression had no effect on cell viability. Taken together, these data demonstrate that OGD in C2C12 myotubes is associated with an increase in iPLA(2)-VIA activity that decreases cell viability. iPLA(2)-VIA activation may be modulated by changes in the levels of active and inactive iPLA(2)-VIA isoforms.
authors.affiliation: Dept. of Molecular Biology, Univ. of Copenhagen, Universitetsparken 13, Copenhagen Ø DK-2100, Denmark. kapoulsen@aki.ku.dk
authors.forename: K A
authors.initials: KA
authors.lastname: Poulsen
authors.forename: S F
authors.initials: SF
authors.lastname: Pedersen
authors.forename: M
authors.initials: M
authors.lastname: Kolko
authors.forename: I H
authors.initials: IH
authors.lastname: Lambert
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D015687:Cell Hypoxia; D002460:Cell Line; D002470:Cell Survival; D004721:Endoplasmic Reticulum / Q000201:enzymology; D004790:Enzyme Induction; D005947:Glucose / Q000172:deficiency / Q000378:metabolism; D054513:Group IV Phospholipases A2 / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D007511:Ischemia / Q000201:enzymology* / Q000235:genetics; D051379:Mice; D008970:Molecular Weight; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000098:blood supply*; D009281:Naphthalenes / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D020033:Protein Isoforms; D011753:Pyrones / Q000494:pharmacology; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors