Canal de BKCa contendo íntrons de mRNAS contribui para a excitabilidade dos neurônios do hipocampo

Cytoplasmic BK_Ca channel intron-containing mRNAs contribute to the intrinsic excitability of hippocampal neurons

1. Thomas J. Bell*, 
2. Kevin Y. Miyashiro*, 
3. Jai-Yoon Sul*,^†,
4. Ronald McCullough^‡, 
5. Peter T. Buckley*,^§, 
6. Jeanine Jochems*,
7. David F. Meaney^¶, 
8. Phil Haydon^†, 
9. Charles Cantor^‖,**,
10. Thomas D. Parsons^††,^‡‡, and 
11. James Eberwine*,^§,**

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Author Affiliations

1. 
   
   ^§Penn Genome Frontiers Institute, and
2. 
   
   Departments of *Pharmacology,
3. 
   
   ^†Neuroscience,
4. 
   
   ^¶Bioengineering, and
5. 
   
   ^††Otorhinolaryngology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104;
6. 
   
   ^‡Program of Molecular and Cellular Biology and Biochemistry, Boston University, Boston, MA 02215;
7. 
   
   ^‖Sequenom, Inc., 3595 John Hopkins Court, San Diego, CA 92121; and
8. 
   
   ^‡‡Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348

1. 
   
   Contributed by Charles Cantor, December 17, 2007 (received for review December 5, 2007)

Abstract

High single-channel conductance K⁺ channels, which respond jointly to membrane depolarization and micromolar concentrations of intracellular Ca²⁺ions, arise from extensive cell-specific alternative splicing of pore-forming α-subunit mRNAs. Here, we report the discovery of an endogenous BK_Ca channel α-subunit intron-containing mRNA in the cytoplasm of hippocampal neurons. This partially processed mRNA, which comprises ≈10% of the total BK_Ca channel α-subunit mRNAs, is distributed in a gradient throughout the somatodendritic space. We selectively reduced endogenous cytoplasmic levels of this intron-containing transcript by RNA interference without altering levels of the mature splice forms of the BK_Ca channel mRNAs. In doing so, we could demonstrate that changes in a unique BK_Ca channel α-subunit intron-containing splice variant mRNA can greatly impact the distribution of the BK_Ca channel protein to dendritic spines and intrinsic firing properties of hippocampal neurons. These data suggest a new regulatory mechanism for modulating the membrane properties and ion channel gradients of hippocampal neurons.

• dendrite
 
• epilepsy
 
• intron-retention
 
• KCNMA1
 
• local splicing

Footnotes

• **To whom correspondence may be addressed. E-mail:ccantor@sequenom.com or eberwine@pharm.med.upenn.edu
• 
  
  Author contributions: T.J.B. and K.Y.M. contributed equally to this work;  T.J.B., K.Y.M., J.-Y.S., R.M., P.T.B., C.C., T.D.P., and J.E. designed research; T.J.B., K.Y.M., J.-Y.S., R.M., P.T.B., and J.J. performed research; T.J.B., K.Y.M., J.-Y.S., R.M., P.T.B., D.F.M., P.H., C.C., and J.E. contributed new reagents/analytic tools; T.J.B., K.Y.M., J.-Y.S., R.M., P.T.B., C.C., T.D.P., and J.E. analyzed data; and T.J.B., K.Y.M., J.-Y.S., R.M., P.T.B., J.J., D.F.M., P.H., C.C., T.D.P., and J.E. wrote the paper.
• 
  
  The authors declare no conflict of interest.
• 
  
  This article contains supporting information online at www.pnas.org/cgi/content/full/0711796105/DC1.
• © 2008 by The National Academy of Sciences of the USA
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