title: A role for PtdIns(4,5)P2 and PIP5Kalpha in regulating stress-induced apoptosis.
abstract: The phosphoinositide phosphatidylinositol 4, 5-bisphosphate (PtdIns(4,5)P(2)) is essential for many cellular processes and is linked to the etiology of numerous human diseases . PtdIns(4,5)P(2) has been indirectly implicated as a negative regulator of apoptosis ; however, it is unclear if apoptotic stimuli negatively regulate PtdIns(4,5)P(2) levels in vivo. Here, we show that two apoptotic-stress stimuli, hydrogen peroxide (H(2)O(2)) and UV irradiation, cause PtdIns(4,5)P(2) depletion during programmed cell death independently of and prior to caspase activation. Depletion of PtdIns(4,5)P(2) is essential for apoptosis because maintenance of PtdIns(4,5)P(2) levels by overexpression of PIP5Kalpha rescues cells from H(2)O(2)-induced apoptosis. PIP5Kalpha expression promotes both basal and sustained ERK1/2 activation after H(2)O(2) treatment, and importantly, pharmacological inhibition of ERK1/2 signaling blocks PIP5Kalpha-mediated cell survival. H(2)O(2) induces tyrosine phosphorylation and translocation of PIP5Kalpha away from its substrate at the plasma membrane, and both are dependent upon the activity of c-src family kinases. Furthermore, constitutively active c-src enhances tyrosine phosphorylation of PIP5Kalpha in vivo and is sufficient for the translocation of PIP5Kalpha away from the plasma membrane. These observations demonstrate that certain apoptotic stimuli initiate an essential signaling pathway during cell death, and this pathway leads to caspase-independent downregulation of PIP5Kalpha and its product PtdIns(4,5)P(2).
authors.affiliation: Division of Cellular Biochemistry and The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. jonathanhalstead@yahoo.co.uk
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Halstead
authors.forename: Jacco
authors.initials: J
authors.lastname: van Rheenen
authors.forename: Mireille H J
authors.initials: MH
authors.lastname: Snel
authors.forename: Sarah
authors.initials: S
authors.lastname: Meeuws
authors.forename: Shabaz
authors.initials: S
authors.lastname: Mohammed
authors.forename: Clive S
authors.initials: CS
authors.lastname: D'Santos
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Heck
authors.forename: Kees
authors.initials: K
authors.lastname: Jalink
authors.forename: Nullin
authors.initials: N
authors.lastname: Divecha
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D020169:Caspases / Q000378:metabolism; D015536:Down-Regulation; D004789:Enzyme Activation; D049452:Green Fluorescent Proteins / Q000032:analysis; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000032:analysis; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism; D014466:Ultraviolet Rays; D019061:src-Family Kinases / Q000502:physiology
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D014443:Tyrosine; D006861:Hydrogen Peroxide; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020169:Caspases