TY - JOUR
T1 - Astrocyte GRK2 as a novel regulator of glutamate transport and brain damage
AU - Nijboer, Cora H.
AU - Heijnen, Cobi J.
AU - Degos, Vincent
AU - Willemen, Hanneke L.M.
AU - Gressens, Pierre
AU - Kavelaars, Annemieke
N1 - Funding Information:
The study was supported by the European Commission: Sixth Framework Program , contract no. LSHM-CT-2006-036534 : NEOBRAIN & Seventh Framework Program , contract no. HEALTH-F2-2009-241778 : NEUROBID, by Fondation Leducq and by NIH grants RO1 NS073939 and RO1 NS074999 .
PY - 2013/6
Y1 - 2013/6
N2 - G protein-coupled receptor (GPCR) kinase 2 (GRK2) regulates cellular signaling via desensitization of GPCRs and by direct interaction with intracellular signaling molecules. We recently described that ischemic brain injury decreases cerebral GRK2 levels. Here we studied the effect of astrocyte GRK2-deficiency on neonatal brain damage in vivo. As astrocytes protect neurons by taking up glutamate via plasma-membrane transporters, we also studied the effect of GRK2 on the localization of the GLutamate ASpartate Transporter (GLAST). Brain damage induced by hypoxia-ischemia was significantly reduced in GFAP-GRK2+/- mice, which have a 60% reduction in astrocyte GRK2 compared to GFAP-WT littermates. In addition, GRK2-deficient astrocytes have higher plasma-membrane levels of GLAST and an increased capacity to take up glutamate in vitro. In search for the mechanism by which GRK2 regulates GLAST expression, we observed increased GFAP levels in GRK2-deficient astrocytes. GFAP and the cytoskeletal protein ezrin are known regulators of GLAST localization. In line with this evidence, GRK2-deficiency reduced phosphorylation of the GRK2 substrate ezrin and enforced plasma-membrane GLAST association after stimulation with the group I mGluR-agonist DHPG. When ezrin was silenced, the enhanced plasma-membrane GLAST association in DHPG-exposed GRK2-deficient astrocytes was prevented. In conclusion, we identified a novel role of astrocyte GRK2 in regulating plasma-membrane GLAST localization via an ezrin-dependent route. We demonstrate that the 60% reduction in astrocyte GRK2 protein level that is observed in GFAP-GRK2+/- mice is sufficient to significantly reduce neonatal ischemic brain damage. These findings underline the critical role of GRK2 regulation in astrocytes for dampening the extent of brain damage after ischemia.
AB - G protein-coupled receptor (GPCR) kinase 2 (GRK2) regulates cellular signaling via desensitization of GPCRs and by direct interaction with intracellular signaling molecules. We recently described that ischemic brain injury decreases cerebral GRK2 levels. Here we studied the effect of astrocyte GRK2-deficiency on neonatal brain damage in vivo. As astrocytes protect neurons by taking up glutamate via plasma-membrane transporters, we also studied the effect of GRK2 on the localization of the GLutamate ASpartate Transporter (GLAST). Brain damage induced by hypoxia-ischemia was significantly reduced in GFAP-GRK2+/- mice, which have a 60% reduction in astrocyte GRK2 compared to GFAP-WT littermates. In addition, GRK2-deficient astrocytes have higher plasma-membrane levels of GLAST and an increased capacity to take up glutamate in vitro. In search for the mechanism by which GRK2 regulates GLAST expression, we observed increased GFAP levels in GRK2-deficient astrocytes. GFAP and the cytoskeletal protein ezrin are known regulators of GLAST localization. In line with this evidence, GRK2-deficiency reduced phosphorylation of the GRK2 substrate ezrin and enforced plasma-membrane GLAST association after stimulation with the group I mGluR-agonist DHPG. When ezrin was silenced, the enhanced plasma-membrane GLAST association in DHPG-exposed GRK2-deficient astrocytes was prevented. In conclusion, we identified a novel role of astrocyte GRK2 in regulating plasma-membrane GLAST localization via an ezrin-dependent route. We demonstrate that the 60% reduction in astrocyte GRK2 protein level that is observed in GFAP-GRK2+/- mice is sufficient to significantly reduce neonatal ischemic brain damage. These findings underline the critical role of GRK2 regulation in astrocytes for dampening the extent of brain damage after ischemia.
KW - Astrocytes
KW - Cytoskeleton
KW - Excitotoxicity
KW - Ezrin
KW - G protein-coupled receptor kinase 2 (GRK2)
KW - GFAP
KW - Glutamate transporter GLAST
KW - Ischemic brain injury
KW - Neuroprotection
UR - http://www.scopus.com/inward/record.url?scp=84876318167&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84876318167&partnerID=8YFLogxK
U2 - 10.1016/j.nbd.2012.12.013
DO - 10.1016/j.nbd.2012.12.013
M3 - Article
C2 - 23313319
AN - SCOPUS:84876318167
SN - 0969-9961
VL - 54
SP - 206
EP - 215
JO - Neurobiology of Disease
JF - Neurobiology of Disease
ER -