Xenbase Image ID: 128510

Figure 5. Heteromeric CNGA3+CNGB3 channels are inhibited by PIP3 or PIP2. (A) Representative current traces for heteromeric CNGA3+CNGB3 channels, elicited by subsaturating concentrations of cGMP (5 µM), before (black) and after (red) 1 µM PIP3 or 10 µM PIP2 application for ∼5 min. (B) Representative dose–response relationships for the activation of heteromeric CNGA3+CNGB3 channels by cGMP before and after PIP3 or PIP2 application. The shadings indicate the approximate physiological range of intracellular cGMP levels within vertebrate photoreceptors in the dark. The Hill parameters for each representative patch were: K1/2 cGMP = 16.1 µM, h = 2.05 before PIP3; K1/2 cGMP = 26.5 µM, h = 2.0 after PIP3; K1/2 cGMP = 12.8 µM, h = 1.8 before PIP2; and K1/2 cGMP = 24.5 µM, h = 1.6 after PIP2. (C) Plot of percentage increase in K1/2 cGMP for heteromeric A3+B3 channels at different concentrations of PIP3 (closed squares), PIP2 (closed circles), and natural PIP2 (open circles; n = 4–5 for each PIPn concentration). The PIPn concentration–response relationships were fitted with the Hill equation, and the Hill parameters (K1/2 and h) for each phosphoinositide species were as follows: 0.58 µM and 1.4 for PIP3 (diC8-PIP3), 3.44 µM and 1.5 for PIP2 (diC8-PIP2), and 2.84 µM and 1.4 for natural PIP2. 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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