Association of synapse-associated protein 90/ postsynaptic density-95-associated protein (SAPAP) with neurofilaments.
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.
Hirao
K
K
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.
Hata
Y
Y
Deguchi
M
M
Yao
I
I
Ogura
M
M
Rokukawa
C
C
Kawabe
H
H
Mizoguchi
A
A
Takai
Y
Y
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
D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D000074407:SAP90-PSD95 Associated Proteins