Fig. 3

Direct interaction between FMRP and Kv1.2 in a phosphorylation-specific manner. a Illustration of an alpha subunit of Kv1.2 channel with extensive details of intracellular C-terminus. b K⁺ current generated by a voltage ramp (−90 to 100 mV, top) from CHO cells expressing WT (Kv1.2-WT, middle) or truncated Kv1.2 (Kv1.2-Δ429-500, bottom) before and after infusion of N-terminus FMRP protein (n-FMRP, H00002332-P01, Novus Biologicals, 1:100 dilution). c The changes in amplitude of K⁺ current by n-FMRP is summarized for Kv1.2-WT (n = 8) and Kv1.2-Δ429-500 (n = 8) constructs. d Co-IP of Kv1.2 and FMRP in the absence or presence of three peptides targeting the sequence (436–457) of C-terminus of Kv1.2 as highlighted in a phosphorylated (PhosKv436-457), non-phosphorylated (Kv436-457), and phosphorylated scrambled peptide. e Summary of effect of the three peptides. Note that only PhosKv436-457 significantly reduces the production of Kv1.2 pull down as compared to the control conditions. f–h sIPSCs (left panels) recorded from PNs before and 20 min after infusion of the three peptides (2.5 mM) into WT synapses. The changes in the amplitude and frequency of sIPSCs are summarized in the right panels for PhosKv436-457 (n = 6, f), non-phosphorylated Kv436-457 (n = 6, g), and scrambled (n = 5, h) peptides. Consistent with the co-IP experiment, only PhosKv436-457 increases the amplitude and frequency of sIPSCs, acutely imparting a WT synapse with the KO phenotype. i Same quantifications for injecting PhosKv436-457 (2.5 mM) into KO synapses (n = 5) showing no effect on sIPSCs