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Author Notes:

Corresponding author: H. Criss Hartzell, 615 Michael St., 535 Whitehead Building, Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322 USA.email: criss.hartzell@emory.edu; office: 404−727−0444; mobile: 404−242−5719; fax: 404−727−6256

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Research Funding:

This work was supported by National Institutes of Health Grants GM60448 (H.C.H.), EY014852 (H.C.H.), and NS044922 (A.L.). We thank Dr. Dorothy Hanck (University of Chicago) for providing the data on the effect of hBest1 on CaV3.1; Jeremy Nathans, Dianne Lipscombe, and Eduardo Perez-Reyes for cDNA constructs; and Roger Colbran for donating the FLAG- and GST-β2a constructs.

Keywords:

  • macular degeneration
  • retinal pigment epithelium
  • ion channel
  • calcium
  • src-homology
  • chloride

The Best Disease-Linked Cl Channel hBest1 Regulates Cav1 (L-type) Ca2+ Channels Via SH3-binding Domains

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Journal Title:

Journal of Neuroscience Nursing

Volume:

Volume 28, Number 22

Publisher:

, Pages 5660-5670

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Mutations in the bestrophin-1 (Best1) gene are linked to several kinds of macular degeneration in both humans and dogs. Although bestrophins have been shown clearly to be Cl− ion channels, it is controversial whether Cl− channel dysfunction can explain the diseases. It has been suggested that bestrophins are multi-functional proteins: they may regulate voltage-gated Ca2+ channels in addition to functioning as Cl− channels. Here we show that hBest1 differentially modulates Cav1.3 (L-type) voltage-gated Ca2+ channels through association with the Cavβ subunit. In transfected HEK-293 cells, hBest1 inhibited Cav1.3. Inhibition of Cav1.3 was not observed in the absence of the β subunit. Also, the hBest1 C-terminus binds to Cavβ subunits, suggesting that the effect of hBest1 was mediated by the Cavβ subunit. The region of hBest1 responsible for the effect was localized to a region (amino acids 330 − 370) in the cytoplasmic C-terminus that contains a predicted SH3-binding domain that is not present in other bestrophin subtypes. Mutation of Pro330 and Pro334 abolished the effects of hBest1 on Cav1.3. The effect was specific to hBest1: it was not observed with mBest1, -2, or -3. Wild type hBest1 and the disease-causing mutants R92S, G299R, and D312N inhibited Cav currents the same amount, whereas the A146K and G222E mutants were less effective. We propose that hBest1 regulates Cav channels by interacting with the Cavβ subunit and altering channel availability. Our findings reveal a novel function of bestrophin in regulation of Cav channels and suggest a possible mechanism for the role of hBest1 in macular degeneration.

Copyright information:

© 2008 Society for Neuroscience

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