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Fig 8. Expression of Kv4.2 and KChIP2 in Xenopus oocytes.Two-electrode voltage-clamp experiments were performed on individual oocytes following cRNA injection. A. Currents obtained with depolarizing voltage jumps from -80 to +40 mV (voltage protocols below traces) 48 h after cRNA injection. Different amounts of KChIP2 cRNA (ng per oocyte indicated above traces) were coinjected with a fixed amount of Kv4.2 cRNA (1 ng per oocyte). Note the tight correlation between KChIP2 cRNA amount and peak current amplitude. B. Idealized current traces based on the mean fit results obtained with a double-exponential function (Kv4.2/KChIP2-mediated currents with 0–12.8 ng KChIP2 cRNA coinjected: black) and based on the mean τ1 values from triple-exponential fits (i.e., the Ito component) of female myocytes (KChIP2+/+: grey, KChIP2+/-: orange). All currents were normalized to peak. C. Recovery from inactivation at -80 mV obtained for oocytes injected with different amounts of KChIP2 cRNA. Pooled recovery data are shown for oocytes injected with 1 ng Kv4.2 cRNA and 0 ng (empty symbols), 0.2 ng (grey symbols) and 0.4 ng KChIP2 cRNA (black symbols). Kv4.2/KChIP2 recovery kinetics were fitted by a single-exponential function. Black lines without symbols: Single-exponential fits for all other KChIP2 cRNA amounts (0.1, 0.8, 1.6, 3.2, 6.4 and 12.8 ng per oocyte); colored lines without symbols: Single-exponential functions representing the fast recovery component of female myocytes (see Fig 7A; KChIP2+/+: grey, KChIP2+/-: orange). D. Idealized current traces based on the same fitting procedures as the currents in B; black traces: currents obtained after consecutive injection of 1 ng Kv4.2 and 1 ng KChIP2 cRNA into the same oocyte; faster decay: 48 h Kv4.2 expression followed by 5 h KChIP2 expression (48+5); slower decay: 48 h Kv4.2 expression followed by 48 h KChIP2 expression (48+48). Red dotted traces represent the data for 0 and 12.8 ng KChIP2 cRNA from B. E. Recovery from inactivation for the two experimental paradigms (grey symbols: 48+5; black symbols: 48+48). The data were fitted by a single-exponential function. Red dotted lines: single exponential fits to the recovery data obtained with 0 and 12.8 ng KChIP2 cRNA per oocyte). Note the slow recovery component (~ 15%) in the 48+5 data, which was not captured by the single-exponential fit. F. Mean peak current amplitudes from A and from the experiments with consecutive cRNA injection (48+5 and 48+48). G. Inactivation time constants (τinact1 and τinact2) from B (0–12.8 ng KChIP2 cRNA per oocyte) and D (48+5 and 48+48). H. Recovery time constants (τrec) from C (0–12.8 ng KChIP2 cRNA per oocyte) and E (48+5 and 48+48). Image published in: Waldschmidt L et al. (2017) © 2017 Waldschmidt 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 license Larger Image Printer Friendly View

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