CFTR Cl− channels, one of the ABC transporter superfamily, play essential roles in: (1) water secretion in epithelial tissues, by generating Cl− secretion and prevention against infection of bacteria and viruses, and (2) maintenance of the plasma membrane depolarization by functioning as a Cl− efflux pathway, which causes glucose-induced insulin secretion by increasing the [Ca2+]c in pancreatic β cells. Here, ABCG2 is linked to infection.