title: Association of synapse-associated protein 90/ postsynaptic density-95-associated protein (SAPAP) with neurofilaments.
abstract: BACKGROUND
  Synapse-associated protein (SAP) 90/Postsynaptic density (PSD)-95-associated protein (SAPAP) (also called Guanylate kinase-associated protein/hDLG-associated protein) interacts with the guanylate kinase domains of PSD-95 and synaptic scaffolding molecule (S-SCAM) via the middle region containing 5 repeats of 14 amino acids. SAPAP also binds the recently identified proteins, nArgBP2 and synamon (also called Shank 1a), via the proline-rich region and the C-terminus, respectively. SAPAP is highly enriched in the Triton X-100-insoluble PSD fraction, and recruits PSD-95 into the Triton X-100-insoluble fraction in transfected cells. We have further characterized here the Triton X-100-insolubility of SAPAP and tried to identify the Triton X-100-insoluble structures which SAPAP interacts with.
  
  
  RESULTS
  N-Methyl-D-aspartate receptors were recruited into the Triton X-100-insoluble fraction with PSD-95 by SAPAP. The N-terminal region of SAPAP was Triton X-100-insoluble, whereas the middle and C-terminal regions were Triton X-100-soluble. We identified proteins interacting with 35S-methionine-labelled SAPAP in the overlay assay, determined their amino acid sequences, and found them to be neurofilaments. SAPAP interacted with neurofilaments via the N-terminal region, was co-immunoprecipitated with neurofilaments from the rat brain, and co-localized with neurofilaments in transfected cells.
  
  
  CONCLUSIONS
  SAPAP associates with neurofilaments via the N-terminal region and may link various components of the PSD to neurofilaments.
authors.affiliation: Takai Biotimer Project, ERATO, Japan Science and Technology Corporation, c/o JCR Pharmaceuticals Co. Ltd, 2-2-10 Murotani, Nishi-ku, Kobe 651-2241, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hirao
authors.forename: Y
authors.initials: Y
authors.lastname: Hata
authors.forename: M
authors.initials: M
authors.lastname: Deguchi
authors.forename: I
authors.initials: I
authors.lastname: Yao
authors.forename: M
authors.initials: M
authors.lastname: Ogura
authors.forename: C
authors.initials: C
authors.lastname: Rokukawa
authors.forename: H
authors.initials: H
authors.lastname: Kawabe
authors.forename: A
authors.initials: A
authors.lastname: Mizoguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D009419:Nerve Tissue Proteins / Q000378:metabolism; D016900:Neurofilament Proteins / Q000378:metabolism; D051381:Rats; D000074407:SAP90-PSD95 Associated Proteins; D013569:Synapses; D014162:Transfection
chemical_list: D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D000074407:SAP90-PSD95 Associated Proteins