title: The association of GPR85 with PSD-95-neuroligin complex and autism spectrum disorder: a molecular analysis.
abstract: BACKGROUND
  Autism spectrum disorder (ASD) has a complex genetic etiology. Some symptoms and mutated genes, including neuroligin (NLGN), neurexin (NRXN), and SH3 and multiple ankyrin repeat domains protein (SHANK), are shared by schizophrenia and ASD. Little is known about the molecular pathogenesis of ASD. One of the possible molecular pathogenesis is an imbalance of excitatory and inhibitory receptors linked with the NLGN-PSD-95-SHANK complex via postsynaptic density protein/Drosophila disc large tumor suppressor/zonula occludens-1 protein (PDZ) binding. In the present study, we focused on GPR85 as a candidate gene for ASD because the C-terminal amino acid sequence of GPR85 [Thr-Cys-Val-Ile (YCVI)] is classified as a type II PDZ-binding motif, and GPR85 is a risk factor for schizophrenia. GPR85 is an orphan receptor that regulates neural and synaptic plasticity and modulates diverse behaviors, including learning and memory. While searching for molecules that associate with GPR85, we found that GPR85 was associated with postsynaptic density protein (PSD)-95 linked with NLGN in the brain.
  
  
  METHODS
  We examined the proteins that associate with the C-terminal sequence of GPR85 by pull-down assay and immunoblot analysis and searched for a mutation of the GPR85 gene in patients with ASD. We used immunostaining to examine the intracellular localization of mutated GPR85 and its influence on the morphology of cells and neurons.
  
  
  RESULTS
  The C-terminal sequence of GPR85 interacted with PSD-95 at PDZ1, while NLGN interacted with PSD-95 at PDZ3. Two male patients with ASD from independent Japanese families possessed inherited missense mutations at conserved sites in GPR85: one had T1033C (M152T) and the other had G1239T (V221L). These mutations were located in a domain related to G protein interaction and signal transduction. In contrast to wild-type GPR85, mutated GPR85 was more preferentially accumulated, causing endoplasmic reticulum stress, and disturbed the dendrite formation of hippocampal neurons.
  
  
  CONCLUSIONS
  GPR85 associated with the PSD-95 linked with NLGN, which is related to ASD. GPR85 carrying the mutations detected in ASD patients disturbed dendrite formation that could be the candidate for molecular pathogenesis of ASD through the associated NLGN-PSD-95 receptor complex.
authors.affiliation: Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 3290498 Japan.|Medical Research Center, International University of Welfare and Health, 2600-1 Kitakanemaru, Ohtawara, 3248501 Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Fujita-Jimbo
authors.affiliation: Medical Research Center, International University of Welfare and Health, 2600-1 Kitakanemaru, Ohtawara, 3248501 Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tanabe
authors.affiliation: Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 3290498 Japan.|Department of Pediatrics, Shengjing Hospital of China Medical University, 36 Sanhao Street, Heping District, Shenyang, 100004 Liaoning China.
authors.forename: Zhiling
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 3290498 Japan.
authors.forename: Karin
authors.initials: K
authors.lastname: Kojima
authors.affiliation: Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 3290498 Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Mori
authors.affiliation: Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 3290498 Japan.|Medical Biochemical Genetics, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115 USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.affiliation: Division of Human Genetics, Center for Molecular Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 3290498 Japan.
authors.forename: Sadahiko
authors.initials: S
authors.lastname: Iwamoto
authors.affiliation: Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 3290498 Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Yamagata
authors.affiliation: Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 3290498 Japan.|Medical Research Center, International University of Welfare and Health, 2600-1 Kitakanemaru, Ohtawara, 3248501 Japan.
authors.forename: Mariko Y
authors.initials: MY
authors.lastname: Momoi
authors.affiliation: Medical Research Center, International University of Welfare and Health, 2600-1 Kitakanemaru, Ohtawara, 3248501 Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Momoi
keywords: ASD; Autism spectrum disorder; ER stress; GPCR; GPR85; Synaptic receptors