title: Nanoscopic spine localization of Norbin, an mGluR5 accessory protein.
abstract: BACKGROUND
  Norbin is a neuron-specific, cytosolic protein that interacts with the metabotropic glutamate receptor 5 (mGluR5) and has a profound impact on mGluR5 signaling. Yet, little is known about its synaptic distribution.
  
  
  RESULTS
  Here we have analyzed the spatial relationship between Norbin, postsynaptic density protein 95 (PSD-95), actin and mGluR5 in spines using super-resolution microscopy. Norbin was found to have a high degree of colocalization with actin and a lower degree of colocalization with PSD-95. Co-immunoprecipitation studies confirmed that interaction occurs between Norbin and actin, but not between Norbin and PSD-95. Norbin was also found to have a high degree of colocalization with the perisynaptically located mGluR5. Findings based on structured illumination microscopy (3D-SIM) of exogenous expressed Norbin-GFP were confirmed by stimulated emission depletion microscopy (STED) of immunolabeled endogenous Norbin.
  
  
  CONCLUSIONS
  Norbin associates with actin rather than with PSD-95 in dendritic spines. Results regarding protein localization and colocalization performed with conventional confocal microscopy must be interpreted with great caution. The now available super-resolution microscopy techniques provide more accurate information about sub-cellular protein localization than previously was possible.
authors.forename: Linda
authors.initials: L
authors.lastname: Westin
authors.forename: Matthias
authors.initials: M
authors.lastname: Reuss
authors.forename: Maria
authors.initials: M
authors.lastname: Lindskog
authors.forename: Anita
authors.initials: A
authors.lastname: Aperia
authors.affiliation: Department of Women's and Children's Health, Science for Life Laboratory, Karolinska Institutet, 17165 Solna, Sweden. brismar@kth.se.
authors.forename: Hjalmar
authors.initials: H
authors.lastname: Brismar
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D049229:Dendritic Spines / Q000378:metabolism* / Q000648:ultrastructure*; D005260:Female; D008297:Male; D009479:Neuropeptides / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5 / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D000199:Actins; C578937:Grm5 protein, rat; D009479:Neuropeptides; D064529:Receptor, Metabotropic Glutamate 5; C109587:norbin