TY - JOUR
T1 - Glutamate-induced protease-mediated loss of plasma membrane Ca2+ pump activity in rat hippocampal neurons
AU - Pottorf, William J.
AU - Johanns, Tanner M.
AU - Derrington, Stephen M.
AU - Strehler, Emanuel E.
AU - Enyedi, Agnes
AU - Thayer, Stanley A.
PY - 2006/9
Y1 - 2006/9
N2 - Ca2+ dysregulation is a hallmark of excitotoxicity, a process that underlies multiple neurodegenerative disorders. The plasma membrane Ca 2+ ATPase (PMCA) plays a major role in clearing Ca2+ from the neuronal cytoplasm. Here, we show that the rate of PMCA-mediated Ca 2+ efflux from rat hippocampal neurons decreased following treatment with an excitotoxic concentration of glutamate. PMCA-mediated Ca2+ extrusion following a brief train of action potentials exhibited an exponential decay with a mean time constant (τ) of 8.8 ± 0.2 s. Four hours following the start of a 30 min treatment with 200 μm glutamate, a second population of cells emerged with slowed recovery kinetics (τ = 16.5 ± 0.3 s). Confocal imaging of cells expressing an enhanced green fluorescent protein (EGFP)-PMCA4b fusion protein revealed that glutamate treatment internalized EGFP and that cells with reduced plasma membrane fluorescence had impaired Ca2+ clearance. Treatment with inhibitors of the Ca 2+-activated protease calpain protected PMCA function and prevented EGFP-PMCA internalization. PMCA internalization was triggered by activation of NMDA receptors and was less pronounced for a non-toxic concentration of glutamate relative to one that produces excitotoxicity. PMCA isoform 2 also internalized following exposure to glutamate, although the Na+/K + ATPase did not. These data suggest that glutamate exposure initiated protease-mediated internalization of PMCAs with a corresponding loss of function that may contribute to the Ca2+ dysregulation that accompanies excitotoxicity.
AB - Ca2+ dysregulation is a hallmark of excitotoxicity, a process that underlies multiple neurodegenerative disorders. The plasma membrane Ca 2+ ATPase (PMCA) plays a major role in clearing Ca2+ from the neuronal cytoplasm. Here, we show that the rate of PMCA-mediated Ca 2+ efflux from rat hippocampal neurons decreased following treatment with an excitotoxic concentration of glutamate. PMCA-mediated Ca2+ extrusion following a brief train of action potentials exhibited an exponential decay with a mean time constant (τ) of 8.8 ± 0.2 s. Four hours following the start of a 30 min treatment with 200 μm glutamate, a second population of cells emerged with slowed recovery kinetics (τ = 16.5 ± 0.3 s). Confocal imaging of cells expressing an enhanced green fluorescent protein (EGFP)-PMCA4b fusion protein revealed that glutamate treatment internalized EGFP and that cells with reduced plasma membrane fluorescence had impaired Ca2+ clearance. Treatment with inhibitors of the Ca 2+-activated protease calpain protected PMCA function and prevented EGFP-PMCA internalization. PMCA internalization was triggered by activation of NMDA receptors and was less pronounced for a non-toxic concentration of glutamate relative to one that produces excitotoxicity. PMCA isoform 2 also internalized following exposure to glutamate, although the Na+/K + ATPase did not. These data suggest that glutamate exposure initiated protease-mediated internalization of PMCAs with a corresponding loss of function that may contribute to the Ca2+ dysregulation that accompanies excitotoxicity.
KW - Calpain
KW - Caspase
KW - Excitotoxicity
KW - Glutamate
KW - Plasma membrane calcium ATPase
KW - Plasma membrane calcium pump
UR - http://www.scopus.com/inward/record.url?scp=33746882821&partnerID=8YFLogxK
U2 - 10.1111/j.1471-4159.2006.04063.x
DO - 10.1111/j.1471-4159.2006.04063.x
M3 - Article
C2 - 16923173
AN - SCOPUS:33746882821
SN - 0022-3042
VL - 98
SP - 1646
EP - 1656
JO - Journal of Neurochemistry
JF - Journal of Neurochemistry
IS - 5
ER -