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. Gomez
Short Reports

Abstract

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.

Keywords

IRES SCA6 Cap Independent Spinocerebellar Therapeutics miRNA Small molecules 

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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
  1. 1.Department of NeurologyUniversity of ChicagoChicagoUSA
  2. 2.Cellular Screening Center CoreUniversity of ChicagoChicagoUSA
  3. 3.Department of MedicineUniversity of ChicagoChicagoUSA

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