The Cerebellum

, Volume 17, Issue 1, pp 72–77 | Cite as

Targeting the CACNA1A IRES as a Treatment for Spinocerebellar Ataxia Type 6

  • Parviz Daniel Hejazi Pastor
  • Xiaofei Du
  • Sarah Fazal
  • Andre N. Davies
  • Christopher M. GomezEmail author
Short Reports


We have discovered that the P/Q-type voltage-gated Ca2+ channel (VGCC) gene, CACNA1A, encodes both the α1A (Cav2.1) subunit and a newly recognized transcription factor, α1ACT, by means of a novel internal ribosomal entry site (IRES) within the α1A C-terminal coding region. α1ACT, when mutated with an expansion of the polyglutamine tract in the C-terminus, gives rise to spinocerebellar ataxia type 6 (SCA6). Because silencing of the entire CACNA1A gene would result in the loss of the essential Cav2.1 channel, the IRES controlling α1ACT expression is an excellent target for selective silencing of α1ACT as a therapeutic intervention for SCA6. We performed a high-throughput screen of FDA-approved small molecules using a dual luciferase reporter system and identified ten hits able to selectively inhibit the IRES. We identified four main candidates that showed selective suppression of α1ACT relative to α1A in HEK cells expressing a native CACNA1A vector. We previously pursued another avenue of molecular intervention through miRNA silencing. We studied three human miRNAs (miRNA-711, -3191-5p, -4786) that would potentially bind to sequences within the CACNA1A IRES region, based on an miRNA prediction program. Only miRNA-3191-5p was found to selectively inhibit the translation of α1ACT in cells. We developed a hyperacute model of SCA6 in mice by injecting a pathogenic form of the IRES-mediated α1ACT (AAV9-α1ACTQ33). Finally, we tested the effectiveness of the miRNA therapy by co-expressing either control miRNA or miRNA-3191-5p and found that miRNA-3191-5p decreased the levels of α1ACTQ33 and prevented the hyperacute disease in mice. These studies provide the proof of principle that a therapy directed at selectively preventing α1ACT expression could be used to treat SCA6.


IRES SCA6 Cap Independent Spinocerebellar Therapeutics miRNA Small molecules 


  1. 1.
    Solodkin A, Gomez CM. Spinocerebellar ataxia type 6. Handb Clin Neurol. 2012;103:461–73. Scholar
  2. 2.
    Zhuchenko O, Bailey J, Bonnen P, Ashizawa T, Stockton DW, Amos C, et al. Autosomal dominant cerebellar ataxia (SCA6) associated with small polyglutamine expansions in the alpha1A-voltage-dependent calcium channel. Nat Genet. 1997;15(1):62–9. Scholar
  3. 3.
    Jun K, Piedras-Renteria ES, Smith SM, et al. Ablation of P/Q-type Ca(2+) channel currents, altered synaptic transmission, and progressive ataxia in mice lacking the alpha(1A)-subunit. Proc Natl Acad Sci U S A. 1999;21:15245–50.CrossRefGoogle Scholar
  4. 4.
    Du X, Wang J, Zhu H, Rinaldo L, Lamar KM, Palmenberg AC, et al. A second cistron in the CACNA1A gene encodes a transcription factor that mediates cerebellar development and SCA6. Cell. 2013;154(1):118–33. Scholar
  5. 5.
    Watase K, Barrett CF, Miyazaki T, Ishiguro T, Ishikawa K, Hu Y, et al. Spinocerebellar ataxia type 6 knockin mice develop a progressive neuronal dysfunction with age-dependent accumulation of mutant CaV2.1 channels. Proc Natl Acad Sci U S A. 2008;105(33):11987–92. Scholar
  6. 6.
    Saegusa H, Wakamori M, Matsuda Y, Wang J, Mori Y, Zong S, et al. Properties of human Cav2.1 channel with a spinocerebellar ataxia type 6 mutation expressed in Purkinje cells. Mol Cell Neurosci. 2007;34(2):261–70. Scholar
  7. 7.
    Kordasiewicz HB, Thompson RM, Clark HB, Gomez CM. C-termini of P/Q-type Ca2+ channel alpha1A subunits translocate to nuclei and promote polyglutamine-mediated toxicity. Hum Mol Genet. 2006;15(10):1587–99. Scholar
  8. 8.
    Martinez-Salas E, Pineiro D, Fernandez N. Alternative mechanisms to initiate translation in eukaryotic mRNAs. Comp Funct Genomics. 2012;2012:1–12. Scholar
  9. 9.
    Karginov TA, Pastor Hejazi DP, Semler BL, et al. Mammalian polycistronic mRNAs and disease. Trends Genet. 2017;33(2):129–42. Scholar
  10. 10.
    MacFarlane LA, Murphy PR. MicroRNA: biogenesis, function and role in cancer. Curr Genomics. 2010;11(7):537–61. Scholar
  11. 11.
    Miyazaki Y, Du X, Muramatsu S, et al. An miRNA-mediated therapy for SCA6 blocks IRES-driven translation of the CACNA1A second cistron. Sci Transl Med. 2016;8:347–94.CrossRefGoogle Scholar
  12. 12.
    Rolf S, Bruns HJ, Wichter T, et al. The ajmaline challenge in Brugada syndrome: diagnostic impact, safety, and recommended protocol. Eur Heart J. 2003;24:1085–6.CrossRefGoogle Scholar
  13. 13.
    Vasquez RJ, Howell B, Yvon AM, Wadsworth P, Cassimeris L. Nanomolar concentrations of nocodazole alter microtubule dynamic instability in vivo and in vitro. Mol Biol Cell. 1997;8(6):973–85. Scholar
  14. 14.
    Begleiter A, Mowat M, Israels LG, et al. Chlorambucil in chronic lymphocytic leukemia: mechanism of action. Leuk Lymphoma. 1996;3:187–201.CrossRefGoogle Scholar
  15. 15.
    Porter JB, Rafique R, Srichairatanakool S, et al. Recent insights into interactions of deferoxamine with cellular and plasma iron pools: implications for clinical use. Ann N Y Acad Sci. 2005;1054(1):155–68. Scholar
  16. 16.
    Lim KRQ, Maruyama R, Tokota T. Eteplirsen in the treatment of Duchenne muscular dystrophy. Drug Des Devel Ther. 2017;11:533–45. Scholar
  17. 17.
    Chiriboga CA, Swoboda KJ, Darras BT, et al. Results from a phase 1 study of nusinersen (ISIS-SMN(Rx)) in children with spinal muscular atrophy. Neurology. 2016;8:890–7.CrossRefGoogle Scholar
  18. 18.
    Finkel RS, Chiriboga CA, Vajsar J, Day JW, Montes J, de Vivo DC, et al. Treatment of infantile-onset spinal muscular atrophy with nusinersen: a phase 2, open-label, dose-escalation study. Lancet. 2016;388(10063):3017–26. Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Parviz Daniel Hejazi Pastor
    • 1
  • Xiaofei Du
    • 1
  • Sarah Fazal
    • 2
  • Andre N. Davies
    • 3
  • Christopher M. Gomez
    • 1
    Email author
  1. 1.Department of NeurologyUniversity of ChicagoChicagoUSA
  2. 2.Cellular Screening Center CoreUniversity of ChicagoChicagoUSA
  3. 3.Department of MedicineUniversity of ChicagoChicagoUSA

Personalised recommendations