ASIC2 and polycystic kidney disease: In recent decades, several ion channels have been reported to serve as molecular sensors for sour signal detection, which include acid-sensing ion channel 2 (ASIC2), hyperpolarization-activated cyclic nucleotide-gated channels (HCNs), two-pore domain K+ channels and polycystic kidney disease-like (PKD) channels [25,26,27,28,29] but no consensus about the main sourness sensor has been reached so far [2].