Functionally important calmodulin-binding sites in both NH2- and COOH-terminal regions of the cone photoreceptor cyclic nucleotide-gated channel CNGB3 subunit

Changhong Peng; Elizabeth D Rich; Christopher A Thor; Michael D Varnum

doi:10.1074/jbc.M301699200

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Functionally important calmodulin-binding sites in both NH2- and COOH-terminal regions of the cone photoreceptor cyclic nucleotide-gated channel CNGB3 subunit

Journal article

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Functionally important calmodulin-binding sites in both NH2- and COOH-terminal regions of the cone photoreceptor cyclic nucleotide-gated channel CNGB3 subunit

Changhong Peng, Elizabeth D Rich, Christopher A Thor and Michael D Varnum

The Journal of biological chemistry, Vol.278(27), pp.24617-24623

07/04/2003

DOI: https://doi.org/10.1074/jbc.M301699200

Handle:

https://hdl.handle.net/2376/109141

PMID: 12730238

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Abstract

Recombinant Proteins - metabolism

Xenopus

Calmodulin - metabolism

Calcium - metabolism

Humans

Electrophysiology

Recombinant Proteins - chemistry

Photoreceptor Cells - chemistry

Ion Channels - physiology

Animals

Protein Binding

Calmodulin - chemistry

Binding Sites

Cyclic Nucleotide-Gated Cation Channels

Dimerization

Ion Channel Gating

Ion Channels - chemistry

Photoreceptor Cells - physiology

Whereas an important aspect of sensory adaptation in rod photoreceptors and olfactory receptor neurons is thought to be the regulation of cyclic nucleotide-gated (CNG) channel activity by calcium-calmodulin (Ca2+-CaM), it is not clear that cone photoreceptor CNG channels are similarly modulated. Cone CNG channels are composed of at least two different subunit types, CNGA3 and CNGB3. We have investigated whether calmodulin modulates the activity of these channels by direct binding to the CNGB3 subunit. Heteromeric channels were formed by co-expression of human CNGB3 with human CNGA3 subunits in Xenopus oocytes; CNGB3 subunits conferred sensitivity to regulation by Ca2+-CaM, whereas CaM regulation of homomeric CNGA3 channels was not detected. To explore the mechanism underlying this regulation, we localized potential CaM-binding sites in both NH2- and COOH-terminal cytoplasmic domains of CNGB3 using gel-overlay and glutathione S-transferase pull-down assays. For both sites, binding of CaM depended on the presence of Ca2+. Individual deletions of either CaM-binding site in CNGB3 generated channels that remained sensitive to regulation by Ca2+-CaM, but deletion of both together resulted in heteromeric channels that were not modulated. Thus, both NH2- and COOH-terminal CaM-binding sites in CNGB3 are functionally important for regulation of recombinant cone CNG channels. These studies suggest a potential role for direct binding and unbinding of Ca2+-CaM to human CNGB3 during cone photoreceptor adaptation and recovery.

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Title: Functionally important calmodulin-binding sites in both NH2- and COOH-terminal regions of the cone photoreceptor cyclic nucleotide-gated channel CNGB3 subunit
Creators: Changhong Peng - Department of Veterinary and Comparative Anatomy, Washington State University, Pullman 99164-6520, USA
Elizabeth D Rich
Christopher A Thor
Michael D Varnum
Publication Details: The Journal of biological chemistry, Vol.278(27), pp.24617-24623
Academic Unit: Integrative Physiology and Neuroscience, Department of
Publisher: United States
Grant note: EY12836 / NEI NIH HHS
Identifiers: 99900547294201842
Language: English
Resource Type: Journal article