title: Increased expression of the PI3K catalytic subunit p110δ underlies elevated S6 phosphorylation and protein synthesis in an individual with autism from a multiplex family.
abstract: BACKGROUND
  Dysfunctions in the PI3K/mTOR pathway have gained a lot of attention in autism research. This was initially based on the discovery of several monogenic autism spectrum disorders with mutations or defects in PI3K/mTOR signaling components. Recent genetic studies corroborate that defective PI3K/mTOR signaling might be a shared pathomechanism in autism disorders of so far unknown etiology, but functional molecular analyses in human cells are rare. The goals of this study were to perform a functional screen of cell lines from patients with idiopathic autism for defects in PI3K/mTOR signaling, to test if further functional analyses are suitable to detect underlying molecular mechanisms, and to evaluate this approach as a biomarker tool to identify therapeutic targets.
  
  
  METHODS
  We performed phospho-S6- and S6-specific ELISA experiments on 21 lymphoblastoid cell lines from the AGRE collection and on 37 lymphoblastoid cell lines from the Simons Simplex Collection and their healthy siblings. Cell lines from one individual with increased S6 phosphorylation and his multiplex family were analyzed in further detail to identify upstream defects in PI3K signaling associated with autism diagnosis.
  
  
  RESULTS
  We detected significantly increased S6 phosphorylation in 3 of the 21 lymphoblastoid cell lines from AGRE compared to a healthy control and in 1 of the 37 lymphoblastoid cell lines from the Simons Simplex Collection compared to the healthy sibling. Further analysis of cells from one individual with elevated S6 phosphorylation showed increased expression of the PI3K catalytic subunit p110δ, which was also observed in lymphoblastoid cells from other autistic siblings but not unaffected members in his multiplex family. The p110δ-selective inhibitor IC87114 reduced elevated S6 phosphorylation and protein synthesis in this cell line.
  
  
  CONCLUSIONS
  Our results suggest that functional analysis of PI3K/mTOR signaling is a biomarker tool to identify disease-associated molecular defects that could serve as therapeutic targets in autism. Using this approach, we discovered impaired signaling and protein synthesis through the PI3K catalytic subunit p110δ as an underlying molecular defect and potential treatment target in select autism spectrum disorders. Increased p110δ activity was recently associated with schizophrenia, and our results suggest that p110δ may also be implicated in autism.
authors.affiliation: Department of Cell Biology, Emory University Medical School, 615 Michael Street, Atlanta, GA 30322 USA.
authors.forename: Ashwini C
authors.initials: AC
authors.lastname: Poopal
authors.affiliation: Division of Neurology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229 USA.
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Schroeder
authors.affiliation: Division of Neurology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229 USA ; Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229 USA.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Horn
authors.affiliation: Department of Cell Biology, Emory University Medical School, 615 Michael Street, Atlanta, GA 30322 USA.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Bassell
authors.affiliation: Department of Cell Biology, Emory University Medical School, 615 Michael Street, Atlanta, GA 30322 USA ; Division of Neurology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229 USA.
authors.forename: Christina
authors.identifier: 0000-0001-6057-2527
authors.initials: C
authors.lastname: Gross
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D001321:Autistic Disorder / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D015415:Biomarkers; D002460:Cell Line; D058534:Class I Phosphatidylinositol 3-Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D004200:Diseases in Twins; D004797:Enzyme-Linked Immunosorbent Assay; D005192:Family Health; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000201:enzymology; D008297:Male; D058990:Molecular Targeted Therapy; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011799:Quinazolines / Q000494:pharmacology; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000502:physiology
chemical_list: D015415:Biomarkers; C477872:IC 87114; D009419:Nerve Tissue Proteins; D011799:Quinazolines; C546842:MTOR protein, human; D058534:Class I Phosphatidylinositol 3-Kinases; C486018:PIK3CD protein, human; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases; D000225:Adenine
keywords: Autism; Biomarker; IC87114; PI3K/mTOR signaling; S6 phosphorylation; p110δ