title: Cellular calcium deficiency plays a role in neuronal death caused by proteasome inhibitors.
abstract: Cytosolic Ca(2+) concentration ([Ca(2+)](i)) is reduced in cultured neurons undergoing neuronal death caused by inhibitors of the ubiquitin proteasome system. Activation of calcium entry via voltage-gated Ca(2+) channels restores cytosolic Ca(2+) levels and reduces this neuronal death (Snider et al. 2002). We now show that this reduction in [Ca(2+)](i) is transient and occurs early in the cell death process, before activation of caspase 3. Agents that increase Ca(2+) influx such as activation of voltage-gated Ca(2+) channels or stimulation of Ca(2+) entry via the plasma membrane Na-Ca exchanger attenuate neuronal death only if applied early in the cell death process. Cultures treated with proteasome inhibitors had reduced current density for voltage-gated Ca(2+) channels and a less robust increase in [Ca(2+)](i) after depolarization. Levels of endoplasmic reticulum Ca(2+) were reduced and capacitative Ca(2+) entry was impaired early in the cell death process. Mitochondrial Ca(2+) was slightly increased. Preventing the transfer of Ca(2+) from mitochondria to cytosol increased neuronal vulnerability to this death while blockade of mitochondrial Ca(2+) uptake via the uniporter had no effect. Programmed cell death induced by proteasome inhibition may be caused in part by an early reduction in cytosolic and endoplasmic reticulum Ca(2+,) possibly mediated by dysfunction of voltage-gated Ca(2+) channels. These findings may have implications for the treatment of disorders associated with protein misfolding in which proteasome impairment and programmed cell death may occur.
authors.affiliation: Laboratory of B. Joy Snider, Hope Center for Neurological Disorders, Saint Louis, Missouri 63110, USA.
authors.forename: Shengzhou
authors.initials: S
authors.lastname: Wu
authors.forename: Krzysztof L
authors.initials: KL
authors.lastname: Hyrc
authors.forename: Krista L
authors.initials: KL
authors.lastname: Moulder
authors.forename: Ying
authors.initials: Y
authors.lastname: Lin
authors.forename: Timothy
authors.initials: T
authors.lastname: Warmke
authors.forename: B Joy
authors.initials: BJ
authors.lastname: Snider
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects; D001703:Biophysics; D002118:Calcium / Q000172:deficiency*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D004622:Embryo, Mammalian; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology; D007976:Leupeptins / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D019579:Neocortex / Q000166:cytology; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D018408:Patch-Clamp Techniques / Q000379:methods; D061988:Proteasome Inhibitors; D012717:Sesquiterpenes / Q000494:pharmacology; D013997:Time Factors
chemical_list: D002121:Calcium Channel Blockers; D015853:Cysteine Proteinase Inhibitors; D018690:Excitatory Amino Acid Agonists; D007783:Lactones; D007976:Leupeptins; D061988:Proteasome Inhibitors; D012717:Sesquiterpenes; C013407:benzamil; C046319:thapsigargicin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000584:Amiloride; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D002118:Calcium