Expression of the endoplasmic reticulum molecular chaperone (ORP150) rescues hippocampal neurons from glutamate toxicity
Yasuko Kitao, … , Osamu Hori, Satoshi Ogawa
Yasuko Kitao, … , Osamu Hori, Satoshi Ogawa
Published November 15, 2001
Citation Information: J Clin Invest. 2001;108(10):1439-1450. https://doi.org/10.1172/JCI12978.
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Article

Expression of the endoplasmic reticulum molecular chaperone (ORP150) rescues hippocampal neurons from glutamate toxicity

Abstract

A series of events initiated by glutamate-receptor interaction perturbs cellular homeostasis resulting in elevation of intracellular free calcium and cell death. Cells subject to such environmental change express stress proteins, which contribute importantly to maintenance of metabolic homeostasis and viability. We show that an inducible chaperone present in endoplasmic reticulum (ER), the 150-kDa oxygen-regulated protein (ORP150), is expressed both in the human brain after seizure attack and in mouse hippocampus after kainate administration. Using mice heterozygous for ORP150 deficiency, exposure to excitatory stimuli caused hippocampal neurons to display exaggerated elevation of cytosolic calcium accompanied by activation of μ-calpain and cathepsin B, as well as increased vulnerability to glutamate-induced cell death in vitro and decreased survival to kainate in vivo. In contrast, targeted neuronal overexpression of ORP150 suppressed each of these events and enhanced neuronal and animal survival in parallel with diminished seizure intensity. Studies using cultured hippocampal neurons showed that ORP150 regulates cytosolic free calcium and activation of proteolytic pathways causing cell death in neurons subject to excitatory stress. Our data underscore a possible role for ER stress in glutamate toxicity and pinpoint a key ER chaperone, ORP150, which contributes to the stress response critical for neuronal survival.

Authors

Yasuko Kitao, Kentaro Ozawa, Mayuki Miyazaki, Michio Tamatani, Tomohiro Kobayashi, Hideki Yanagi, Masaru Okabe, Masahito Ikawa, Tetsumori Yamashima, David M. Stern, Osamu Hori, Satoshi Ogawa

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Figure 6

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Role of ORP150 in stress response to glutamate in vitro. (a–d) Cultured ...
Role of ORP150 in stress response to glutamate in vitro. (a–d) Cultured hippocampal neurons from ORP150–/+, nontransgenic littermates (ORP150+/+), or Tg PD-ORP150 mice (Transgenic) were exposed to the indicated concentration of either glutamate (a) or NMDA (c) for 24 hours or exposed to (b) glutamate (20 μM) or (d) NMDA (50 μM) for the indicated time. Percentage of viable neurons was determined as described in text. The mean ± SD is shown (n = 8). Asterisks indicate P < 0.01 compared with ORP150+/+ mice by multiple contrast analysis. (e–h) Hippocampal neurons were prepared from genetically manipulated mice, as above, and exposed to either (e)glutamate (10 μM) or (f–h) NMDA (50 μM). Cytosolic-free Ca++ was measured by fluorescent technique in ten representative neuron bodies, which were morphologically identified as described in the text. (e and f) Time course, mean of ten replicate experiments. (g) Peak and plateau (mean ± SD and n = 6) are shown. Ca++ was measured at the peak of NMDA-induced Ca++ (peak) and 5 minutes after the peak (plateau). *P < 0.05 and **P < 0.01 compared with ORP150–/+ neurons by multiple comparison analysis followed by one-way ANOVA. (h) Typical Ca++ image obtained at the peak by each culture is shown (Ca++ image, left panels; phase image, right panels; ×200 in each case).