Molecular Medicine

, Volume 18, Issue 3, pp 336–345 | Cite as

Excess Protein Synthesis in FXS Patient Lymphoblastoid Cells Can Be Rescued with a p110β-Selective Inhibitor

  • Christina Gross
  • Gary J. Bassell
Research Article


The fragile X mental retardation protein (FMRP) plays a key role for neurotransmitter-mediated signaling upstream of neuronal protein synthesis. Functional loss of FMRP causes the inherited intellectual disability fragile X syndrome (FXS), and leads to increased and stimulus-insensitive neuronal protein synthesis in FXS animal models. Previous studies suggested that excess protein synthesis mediated by dysregulated signal transduction contributes to the majority of neurological defects in FXS, and might be a promising target for therapeutic strategies in patients. However, possible impairments in receptor-dependent protein synthesis have not been evaluated in patient cells so far. Using quantitative fluorescent metabolic labeling, we demonstrate that protein synthesis is exaggerated and cannot be further increased by cytokine stimulation in human fragile X lymphoblastoid cells. Our previous work suggested that loss of FMRP-mediated regulation of protein expression and enzymatic function of the PI3K catalytic subunit p110β contributes to dysregulated protein synthesis in a mouse model of FXS. Here, we demonstrate that these molecular mechanisms are recapitulated in FXS patient cells. Furthermore, we show that treatment with a p110β-selective antagonist rescues excess protein synthesis in synaptoneurosomes from an FXS mouse model and in patient cells. Our work suggests that dysregulated protein synthesis and PI3K activity in patient cells might be suitable biomarkers to quantify the efficacy of drugs to ameliorate molecular mechanisms underlying FXS, and could be used for drug screens to refine treatment strategies for individual patients. Moreover, we provide rationale to pursue p110β-targeting treatments as potential therapy in FXS, and possibly other autism spectrum disorders.



The authors would like to thank M Kim and A Poopal for excellent technical assistance, and J Mowrey for valuable advice on LCL culturing. Lymphoblastoid cell lines from FXS patients and healthy controls were a kind gift from S Warren (Emory University). The authors thank S Warren for helpful discussions. The authors thank S Swanger for critically reading the manuscript, and all members of the Bassell lab for helpful discussions. This work was supported by a postdoctoral fellowship from FRAXA (to C Gross), the NIH Grant MH085617 (to GJ Bassell), the Emory/Baylor Fragile X Center Grant 3P30HD024064 (to GJ Bassell), and a Suzanne and Bob Wright Trailblazer Award form Autism Speaks (to GJ Bassell).

Supplementary material

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Excess Protein Synthesis in FXS Patient Lymphoblastoid Cells Can Be Rescued with a p110β-Selective Inhibitor


  1. 1.
    Osterweil EK, Krueger DD, Reinhold K, Bear MF. (2010) Hypersensitivity to mGluR5 and ERK1/2 leads to excessive protein synthesis in the hippocampus of a mouse model of fragile X syndrome. J. Neurosci. 30:15616–27.CrossRefGoogle Scholar
  2. 2.
    Qin M, Kang J, Burlin TV, Jiang C, Smith CB. (2005) Postadolescent changes in regional cerebral protein synthesis: an in vivo study in the Fmr1 null mouse. J. Neurosci. 25:5087–95.CrossRefGoogle Scholar
  3. 3.
    Gross C, et al. (2010) Excess phosphoinositide 3-kinase subunit synthesis and activity as a novel therapeutic target in fragile X syndrome. J. Neurosci. 30:10624–38.CrossRefGoogle Scholar
  4. 4.
    Muddashetty RS, Kelic S, Gross C, Xu M, Bassell GJ. (2007) Dysregulated metabotropic glutamate receptor-dependent translation of AMPA receptor and postsynaptic density-95 mRNAs at synapses in a mouse model of fragile X syndrome. J. Neurosci. 27:5338–48.CrossRefGoogle Scholar
  5. 5.
    Bear MF, Dolen G, Osterweil E, Nagarajan N. (2008) Fragile X: translation in action. Neuropsychopharmacology. 33:84–7.CrossRefGoogle Scholar
  6. 6.
    Bassell GJ, Warren ST. (2008) Fragile X syndrome: loss of local mRNA regulation alters synaptic development and function. Neuron. 60:201–14.CrossRefGoogle Scholar
  7. 7.
    Nosyreva ED, Huber KM. (2006) Metabotropic receptor-dependent long-term depression persists in the absence of protein synthesis in the mouse model of fragile X syndrome. J. Neurophysiol. 95:3291–5.CrossRefGoogle Scholar
  8. 8.
    Volk LJ, Pfeiffer BE, Gibson JR, Huber KM. (2007) Multiple Gq-coupled receptors converge on a common protein synthesis-dependent long-term depression that is affected in fragile X syndrome mental retardation. J. Neurosci. 27:11624–34.CrossRefGoogle Scholar
  9. 9.
    Weiler IJ, et al. (2004) Fragile X mental retardation protein is necessary for neurotransmitter-activated protein translation at synapses. Proc. Natl. Acad. Sci. U.S.A. 101:17504–9.CrossRefGoogle Scholar
  10. 10.
    Gross C, Berry-Kravis EM, Bassell GJ. (2012) Therapeutic strategies in fragile X syndrome: dysregulated mGluR signaling and beyond. Neuropsychopharmacology. 37(1):178–95.CrossRefGoogle Scholar
  11. 11.
    Krueger DD, Bear MF. (2011) Toward fulfilling the promise of molecular medicine in fragile X syndrome. Ann. Rev. Med. 62:411–29.CrossRefGoogle Scholar
  12. 12.
    Bolduc FV, Bell K, Cox H, Broadie KS, Tully T. (2008) Excess protein synthesis in Drosophila fragile X mutants impairs long-term memory. Nat. Neurosci. 11:1143–5.CrossRefGoogle Scholar
  13. 13.
    Jacquemont S, et al. (2011) Epigenetic modification of the FMR1 gene in fragile X syndrome is associated with differential response to the mGluR5 antagonist AFQ056. Sci. Translat. Med. 3:64ra61.Google Scholar
  14. 14.
    Berry-Kravis E, et al. (2008) Open-label treatment trial of lithium to target the underlying defect in fragile X syndrome. J. Dev. Behav. Pediatr. 29:293–302.CrossRefGoogle Scholar
  15. 15.
    Weng N, Weiler IJ, Sumis A, Berry-Kravis E, Greenough WT. (2008) Early-phase ERK activation as a biomarker for metabolic status in fragile X syndrome. Am. J. Med. Genet. B. Neuropsychiatr. Genet. 147B:1253–7.CrossRefGoogle Scholar
  16. 16.
    Erickson CA, et al. (2011) Open-label riluzole in fragile X syndrome. Brain Res 1380:264–270.CrossRefGoogle Scholar
  17. 17.
    Committee for the Update of the Guide for the Care and Use of Laboratory Animals, Institute for Laboratory Animal Research, Division on Earth and Life Studies. (2011) Guide for the Care and Use of Laboratory Animals. 8th edition. Washington (DC): National Academies Press. [cited 2012 Apr 17]. Available from:
  18. 18.
    Brown V, et al. (2001) Microarray identification of FMRP-associated brain mRNAs and altered mRNA translational profiles in fragile X syndrome. Cell 107:477–87.CrossRefGoogle Scholar
  19. 19.
    Feng Y, et al. (1997) FMRP associates with polyribosomes as an mRNP, and the I304N mutation of severe fragile X syndrome abolishes this association. Mol. Cell 1:109–18.CrossRefGoogle Scholar
  20. 20.
    Lugenbeel KA, Peier AM, Carson NL, Chudley AE, Nelson DL. (1995) Intragenic loss of function mutations demonstrate the primary role of FMR1 in fragile X syndrome. Nat. Genet. 10:483–5.CrossRefGoogle Scholar
  21. 21.
    Ye K, et al. (2000) PIKE: A nuclear GTPase that enhances PI3Kinase activity and is regulated by protein 4.1N. 103:919–930.Google Scholar
  22. 22.
    Altman A, Mustelin T, Coggeshall KM. (1990) T lymphocyte activation: a biological model of signal transduction. Crit. Rev. Immunol. 10:347–91.PubMedGoogle Scholar
  23. 23.
    Dieterich DC, Link AJ, Graumann J, Tirrell DA, Schuman EM. (2006) Selective identification of newly synthesized proteins in mammalian cells using bioorthogonal noncanonical amino acid tagging (BONCAT). Proc. Natl. Acad. Sci. U.S.A. 103:9482–7.CrossRefGoogle Scholar
  24. 24.
    Jackson SP, et al. (2005) PI 3-kinase p110beta: a new target for antithrombotic therapy. Nat. Med. 11:507–14.CrossRefGoogle Scholar
  25. 25.
    Dolen G, et al. (2007) Correction of fragile X syndrome in mice. Neuron. 56:955–62.CrossRefGoogle Scholar
  26. 26.
    Sharma A, et al. (2010) Dysregulation of mTOR signaling in fragile X syndrome. J. Neurosci. 30:694–702.CrossRefGoogle Scholar
  27. 27.
    Schultz-Pedersen S, Hasle H, Olsen JH, Friedrich U. (2001) Evidence of decreased risk of cancer in individuals with fragile X. Am. J. Med. Gen. 103:226–30.CrossRefGoogle Scholar
  28. 28.
    Cornish GH, Sinclair LV, Cantrell DA. (2006) Differential regulation of T-cell growth by IL-2 and IL-15. Blood. 108:600–8.CrossRefGoogle Scholar
  29. 29.
    Foukas LC, Berenjeno IM, Gray A, Khwaja A, Vanhaesebroeck B. (2010) Activity of any class IA PI3K isoform can sustain cell proliferation and survival. Proc. Natl. Acad. Sci. U.S.A. 107:11381–6.CrossRefGoogle Scholar
  30. 30.
    Markman B, Atzori F, Perez-Garcia J, Tabernero J, Baselga J. (2010) Status of PI3K inhibition and biomarker development in cancer therapeutics. Ann. Oncol. 21:683–91.CrossRefGoogle Scholar
  31. 31.
    Kotulska K, Józwiak S. (2011) Autism in monogenic disorders. Eur. J. Paediatr. Neurol. 15:177–80.CrossRefGoogle Scholar
  32. 32.
    Smalley SL. (1998) Autism and tuberous sclerosis. J. Autism Dev. Disord. 28:407–14.CrossRefGoogle Scholar
  33. 33.
    Wiznitzer M. (2004) Autism and tuberous sclerosis. J. Child Neurol. 19:675–9.CrossRefGoogle Scholar
  34. 34.
    McBride KL, et al. (2010) Confirmation study of PTEN mutations among individuals with autism or developmental delays/mental retardation and macrocephaly. Autism Res. 3:137–41.CrossRefGoogle Scholar
  35. 35.
    Cusco I, et al. (2009) Autism-specific copy number variants further implicate the phosphatidylinositol signaling pathway and the glutamatergic synapse in the etiology of the disorder. Hum. Mol. Genet. 18:1795–804.CrossRefGoogle Scholar
  36. 36.
    Ricciardi S, et al. (2011) Reduced AKT/mTOR signaling and protein synthesis dysregulation in a Rett syndrome animal model. Hum. Mol. Genet. 20:1182–96.CrossRefGoogle Scholar
  37. 37.
    Kelleher RJ, 3rd, Bear MF. (2008) The autistic neuron: troubled translation? Cell 135:401–6.CrossRefGoogle Scholar

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Authors and Affiliations

  1. 1.Emory University School of MedicineAtlantaUSA
  2. 2.Emory University School of MedicineAtlantaUSA
  3. 3.Emory University School of MedicineAtlantaUSA

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