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The Journal of Neuroscience, March 4, 2009, 29(9):2997-3008; doi:10.1523/JNEUROSCI.0354-09.2009

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Neurobiology of Disease
Regulation of Glucose Transporter 3 Surface Expression by the AMP-Activated Protein Kinase Mediates Tolerance to Glutamate Excitation in Neurons

Petronela Weisová,¹ Caoimhín G. Concannon,¹ Marc Devocelle,² Jochen H. M. Prehn,¹ and Manus W. Ward¹

¹Department of Physiology and Medical Physics and Royal College of Surgeons in Ireland (RCSI) Neuroscience Research Centre, and ²Centre for Synthesis and Chemical Biology, Department of Pharmaceutical and Medicinal Chemistry, RCSI, Dublin 2, Ireland

Correspondence should be addressed to Dr. Manus W. Ward, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland. Email: mward2{at}rcsi.ie

Ischemic and excitotoxic events within the brain result in rapid and often unfavorable depletions in neuronal energy levels. Here, we investigated the signaling pathways activated in response to the energetic stress created by transient glutamate excitation in cerebellar granule neurons. We characterized a glucose dependent hyperpolarization of the mitochondrial membrane potential (_m) in the majority of neurons after transient glutamate excitation. Expression levels of the primary neuronal glucose transporters (GLUTs) isoforms 1, 3, 4, and 8 were found to be unaltered within a 24 h period after excitation. However, a significant increase only in GLUT3 surface expression was identified 30 min after excitation, with this high surface expression remaining significantly above control levels in many neurons for up to 4 h. Glutamate excitation induced a rapid alteration in the AMP:ATP ratio that was associated with the activation of the AMP-activated protein kinase (AMPK). Interestingly, pharmacological activation of AMPK with AICAR (5-aminoimidazole-4-carboxamide riboside) alone also increased GLUT3 surface expression, with a hyperpolarization of _m evident in many neurons. Notably, inhibition of the CaMKK (calmodulin-dependent protein kinase kinase) had little affect on GLUT translocation, whereas the inhibition or knockdown of AMPK (compound C, siRNA) activity prevented GLUT3 translocation to the cell surface after glutamate excitation. Furthermore, gene silencing of GLUT3 eradicated the increase in _m associated with transient glutamate excitation and potently sensitized neurons to excitotoxicity. In summary, our data suggest that the activation of AMPK and its regulation of cell surface GLUT3 expression is critical in mediating neuronal tolerance to excitotoxicity.

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Received Jan. 22, 2009; accepted Jan. 31, 2009.

Correspondence should be addressed to Dr. Manus W. Ward, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland. Email: mward2{at}rcsi.ie

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