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Figure 7. Intersubunit N–C coupling controls phosphoinositide sensitivity of CNGA3 channels. (A) Coexpression of PA-LA subunits with RR-QQ subunits, both of which individually form channels insensitive to 1 µM PIP3 regarding cAMP efficacy, generated channels that were sensitive to PIP3. The Imax cAMP/cGMP (PIP3/control) for coexpression of A3 PA-LA with A3 RR-QQ was 1.67 ± 0.06 (n = 6, P < 0.001). (B) Coexpression of A3 wild type (WT) and A3 N7R-A,613X subunits generated channels that exhibited an increased K1/2 cGMP after 1 µM PIP3 application. Channels formed by A3 WT//A3 N7R-A,613X tandem dimers exhibited enhanced sensitivity to PIP3-induced inhibition of apparent cGMP affinity. Ratio K1/2 cGMP (PIP3/control) was significantly greater for A3//A3 N7R-A,613X dimers (n = 4) compared with channels formed by coexpression of A3 with A3-N7R-A,613X (n = 8; P < 0.05). The broken horizontal lines refer to a ratio of one, equivalent to no change in the parameter after PIPn application. Error bars indicate mean ± SEM. Image published in: Dai G et al. (2013) © 2013 Dai et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View

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