alpha-actinin-2 in rat striatum: localization and interaction with NMDA glutamate receptor subunits.

Academic Article

Abstract

  • 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.
  • Published In

  • Brain Research  Journal
  • Keywords

  • Actinin, Animals, Brain, Calbindins, Cerebral Cortex, Choline O-Acetyltransferase, Corpus Striatum, Immunohistochemistry, In Situ Hybridization, Male, Neurons, Organ Specificity, Parvalbumins, RNA, Messenger, Rats, Rats, Sprague-Dawley, Receptors, N-Methyl-D-Aspartate, S100 Calcium Binding Protein G, Transcription, Genetic
  • Author List

  • Dunah AW; Wyszynski M; Martin DM; Sheng M; Standaert DG
  • Start Page

  • 77
  • End Page

  • 87
  • Volume

  • 79
  • Issue

  • 1-2