alpha-actinin-2 in rat striatum: localization and interaction with NMDA glutamate receptor subunits.
Alpha-actinin (alpha-actinin-2) is a protein which links the NR1 and NR2B subunits of N-methyl-D-aspartate (NMDA) glutamate receptors to the actin cytoskeleton. Because of the importance of NMDA receptors in modulating the function of the striatum, we have examined the localization of alpha-actinin-2 protein and mRNA in striatal neurons, and its biochemical interaction with NMDA receptor subunits present in the rat striatum. Using an alpha-actinin-2-specific antibody, we found intense immunoreactivity in the striatal neuropil and within striatal neurons that also expressed parvalbumin, calretinin and calbindin. Conversely, alpha-actinin-2 immunoreactivity was not detected in neurons expressing choline acetyltransferase and neuronal nitric oxide synthase. Dual-label in situ hybridization revealed that the highest expression of alpha-actinin-2 mRNA is in substance P-containing striatal projection neurons. The alpha-actinin-2 mRNA is also present in enkephalinergic projection neurons and interneurons expressing parvalbumin, choline acetyl transferase and the 67-kDa isoform of glutamic acid decarboxylase, but was not detected in somatostatin-expressing interneurons. Immunoprecipitation of membrane protein extracts showed that alpha-actinin-2 is present in heteromeric complexes of NMDA subunits, but is not associated with AMPA receptors in the striatum. A subunit-specific anti-NR1 antibody co-precipitated major fractions of NR2A and NR2B subunits, but only a minor fraction of striatal alpha-actinin-2. Conversely, alpha-actinin-2 antibody immunoprecipitated only modest fractions of striatal NR1, NR2A and NR2B subunits. These data demonstrate that alpha-actinin-2 is a very abundant striatal protein, but exhibits cellular specificity in its expression, with very high levels in substance-P-containing projection neurons, and very low levels in somatostatin and neuronal nitric oxide synthase interneurons. Despite the high expression of this protein in the striatum, only a minority of NMDA receptors are linked to alpha-actinin-2. This interaction may identify a subset of receptors with distinct anatomical and functional properties.
Department of Neurology, Massachusetts General Hospital and Harvard Medical School Warren 408, Boston, MA 02114, USA.
A W
AW
Dunah
M
M
Wyszynski
D M
DM
Martin
M
M
Sheng
D G
DG
Standaert
D000185:Actinin / Q000032:analysis / Q000235:genetics*; D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D064026:Calbindins; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D002795:Choline O-Acetyltransferase / Q000032:analysis; D003342:Corpus Striatum / Q000166:cytology / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009928:Organ Specificity; D010320:Parvalbumins / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000032:analysis / Q000235:genetics*; D064030:S100 Calcium Binding Protein G / Q000032:analysis; D014158:Transcription, Genetic
C498530:Actn2 protein, rat; D064026:Calbindins; D010320:Parvalbumins; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D064030:S100 Calcium Binding Protein G; D000185:Actinin; D002795:Choline O-Acetyltransferase