Two structural components in CNGA3 support regulation of cone CNG channels by phosphoinositides

Gucan Dai; Changhong Peng; Chunming Liu; Michael D Varnum

doi:10.1085/jgp.201210944

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Two structural components in CNGA3 support regulation of cone CNG channels by phosphoinositides

Journal article

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Peer reviewed

Two structural components in CNGA3 support regulation of cone CNG channels by phosphoinositides

Gucan Dai, Changhong Peng, Chunming Liu and Michael D Varnum

The Journal of general physiology, Vol.141(4), pp.413-430

04/2013

DOI: https://doi.org/10.1085/jgp.201210944

Handle:

https://hdl.handle.net/2376/106991

PMCID: PMC3607822

PMID: 23530136

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Abstract

Protein Structure, Tertiary

Amino Acid Sequence

Phosphatidylinositol Phosphates - metabolism

Allosteric Regulation

Humans

Protein Multimerization

Xenopus laevis

Cyclic Nucleotide-Gated Cation Channels - genetics

Molecular Sequence Data

Mutation, Missense

Protein Subunits - metabolism

Phosphatidylinositol 4,5-Diphosphate - metabolism

Cyclic Nucleotide-Gated Cation Channels - chemistry

Animals

Cyclic GMP - metabolism

Binding Sites

Cyclic AMP - metabolism

Ion Channel Gating

Cyclic Nucleotide-Gated Cation Channels - metabolism

Cyclic nucleotide-gated (CNG) channels in retinal photoreceptors play a crucial role in vertebrate phototransduction. The ligand sensitivity of photoreceptor CNG channels is adjusted during adaptation and in response to paracrine signals, but the mechanisms involved in channel regulation are only partly understood. Heteromeric cone CNGA3 (A3) + CNGB3 (B3) channels are inhibited by membrane phosphoinositides (PIP(n)), including phosphatidylinositol 3,4,5-triphosphate (PIP(3)) and phosphatidylinositol 4,5-bisphosphate (PIP(2)), demonstrating a decrease in apparent affinity for cyclic guanosine monophosphate (cGMP). Unlike homomeric A1 or A2 channels, A3-only channels paradoxically did not show a decrease in apparent affinity for cGMP after PIP(n) application. However, PIP(n) induced an ∼2.5-fold increase in cAMP efficacy for A3 channels. The PIP(n)-dependent change in cAMP efficacy was abolished by mutations in the C-terminal region (R643Q/R646Q) or by truncation distal to the cyclic nucleotide-binding domain (613X). In addition, A3-613X unmasked a threefold decrease in apparent cGMP affinity with PIP(n) application to homomeric channels, and this effect was dependent on conserved arginines within the N-terminal region of A3. Together, these results indicate that regulation of A3 subunits by phosphoinositides exhibits two separable components, which depend on structural elements within the N- and C-terminal regions, respectively. Furthermore, both N and C regulatory modules in A3 supported PIP(n) regulation of heteromeric A3+B3 channels. B3 subunits were not sufficient to confer PIP(n) sensitivity to heteromeric channels formed with PIP(n)-insensitive A subunits. Finally, channels formed by mixtures of PIP(n)-insensitive A3 subunits, having complementary mutations in N- and/or C-terminal regions, restored PIP(n) regulation, implying that intersubunit N-C interactions help control the phosphoinositide sensitivity of cone CNG channels.

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Title: Two structural components in CNGA3 support regulation of cone CNG channels by phosphoinositides
Creators: Gucan Dai - Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USA
Changhong Peng
Chunming Liu
Michael D Varnum
Publication Details: The Journal of general physiology, Vol.141(4), pp.413-430
Academic Unit: Integrative Physiology and Neuroscience, Department of
Publisher: United States
Grant note: R01 EY012836 / NEI NIH HHS EY12836 / NEI NIH HHS
Identifiers: 99900546992201842
Language: English
Resource Type: Journal article