Phospholipid-transporting ATPase ID (also known as ATP8B2 or ATPID) belongs to the IV subfamily of the P-type ATPases family, whose members transport phospholipids across the membrane. The function of ATP8B2 is not clear. It can bind either CDC50A or CDC50B as its accessory protein required for its function []. ATP8B2 is expressed throughout the body [].
Probable phospholipid-transporting ATPase IM (also known as ATP8B4) belongs to subfamily IV of the P-type ATPases family, whose members transport phospholipids across the membrane. It appears to be a component of a P4-ATPase flippase complex and can bind either CDC50A or CDC50B as its accessory protein []. ATPase IM is expressed throughout the brain and may be involved in Alzheimer's disease [].
Cell cycle control protein 50C (CDC50C, also known as TMEM30C) is one of the CDC50 (CDC50A/B/C) proteins []. CDC50A and CDC50B are accessory components of the phospholipid-transporting ATPase (P4-ATPase) complex which catalyses the hydrolysis of ATP coupled to the transport of phospholipids across the membrane []. The function of CDC50C is not clear. Unlike the broad expression of CDC50A and CDC50B, CDC50C is expressed specifically in mouse testis [, ]. However, no full-length transcripts of CDC50C have been found in humans [].
Phospholipid-transporting ATPase IK (also known as ATP8B3 orATP1K) belongs to the subfamily IV of the P-type ATPases family, whose members transport phospholipids across the membrane. The function of ATP8B3 is not clear. Unlike other type IV members (ATP8B1,2,4), ATP8B3 does not seem to interact with either CDC50A or CDC50B []. It is exclusively expressed in the testis where it localises to the acrosomes of spermatids, the organelle which develops in the anterior half of the head of spermatozoa []. However, the disruption of ATP8B3 in mice does not affect sperm morphology or fertilisation rate [].
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 [].
