KCNQ4 and pulmonary arterial hypertension: Several K+ channels have been reported to be downregulated in animal models of PAH including KV1.1, KV1.5, KV1.6, KV2.1, KV3.1b, KV7.1, KV7.4 and TASK1 while others were upregulated such as KV11.1, KCa1.1, KCa3.1 and KIR6.19,10.