Phospholipid-transporting ATPase IC (also known as ATP8B1 or ATPIC) belongs to subfamily IV of the P-type ATPases family, whose members transport phospholipids across the membrane. ATP8B1 can bind either CDC50A or CDC50B as its accessory protein for endoplasmic reticulum exit and plasma membrane lipid flippase activity [, , ].In hepatocytes, ATP8B1 localises in the canalicular membrane, where it may maintain the membrane integrity and to the function of ABCB4, an ABC floppase that play a role in bile export []. In the epithelial Caco-2 cells, ATP8B1 is required for apical protein expression and microvillus formation in polarised epithelial cells []. Mutations in ATP8B1 cause two forms of intrahepatic cholestasis, progressive familial intrahepatic cholestasis (PFIC) and benign recurrent intrahepatic cholestasis (BFIC) []. It is involved in the correct apical membrane localization of CDC42, CFTR and SLC10A2 [].
Cell cycle control protein 50B (CDC50B, also known as TMEM30B) is an accessory component of the phospholipid-transporting P4-ATPase flippase complex which catalyses the hydrolysis of ATP coupled to the transport of phospholipids across the membrane []. It can interact with several P4-ATPases, such as ATP8B1 and ATP8B2, and may perform broad functions in human physiology [].
