Protein aggregation in neurons following OGD: a role for Na+ and Ca2+ ionic dysregulation.
In this study, we investigated whether disruption of Na(+) and Ca(2+) homeostasis via activation of Na(+)-K(+)-Cl(-) cotransporter isoform 1 (NKCC1) and reversal of Na(+)/Ca(2+) exchange (NCX(rev)) affects protein aggregation and degradation following oxygen-glucose deprivation (OGD). Cultured cortical neurons were subjected to 2 h OGD and 1-24 h reoxygenation (REOX). Redistribution of ubiquitin and formation of ubiquitin-conjugated protein aggregates occurred in neurons as early as 2 h REOX. The protein aggregation progressed further by 8 h REOX. There was no significant recovery at 24 h REOX. Moreover, the proteasome activity in neurons was inhibited by 80-90% during 2-8 h REOX and recovered partially at 24 h REOX. Interestingly, pharmacological inhibition or genetic ablation of NKCC1 activity significantly decreased accumulation of ubiquitin-conjugated protein aggregates and improved proteasome activity. A similar protective effect was obtained by blocking NCX(rev) activity. Inhibition of NKCC1 activity also preserved intracellular ATP and Na(+) homeostasis during 0-24 h REOX. In a positive control study, disruption of endoplasmic reticulum Ca(2+) with thapsigargin triggered redistribution of free ubiquitin and protein aggregation. We conclude that overstimulation of NKCC1 and NCX(rev) following OGD/REOX partially contributes to protein aggregation and proteasome dysfunction as a result of ionic dysregulation.
Neuroscience Training Program, University of Wisconsin School of Medicine and Public Health, Waisman Center, Madison, Wisconsin, USA.
Xinzhi
X
Chen
Douglas B
DB
Kintner
Akemichi
A
Baba
Toshio
T
Matsuda
Gary E
GE
Shull
Dandan
D
Sun
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002413:Cations, Divalent / Q000037:antagonists & inhibitors / Q000378:metabolism; D002414:Cations, Monovalent / Q000037:antagonists & inhibitors / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D005947:Glucose / Q000172:deficiency; D006706:Homeostasis / Q000235:genetics / Q000502:physiology; D000860:Hypoxia / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D009474:Neurons / Q000378:metabolism* / Q000502:physiology; D011247:Pregnancy; D046988:Proteasome Endopeptidase Complex / Q000502:physiology; D061988:Proteasome Inhibitors; D017510:Protein Folding; D055503:Protein Multimerization; D012964:Sodium / Q000502:physiology*; D028021:Sodium-Potassium-Chloride Symporters / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D064506:Solute Carrier Family 12, Member 2
D002413:Cations, Divalent; D002414:Cations, Monovalent; D026901:Membrane Transport Proteins; D061988:Proteasome Inhibitors; C578878:Slc12a2 protein, mouse; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D012964:Sodium; D046988:Proteasome Endopeptidase Complex; D005947:Glucose; D002118:Calcium