CDC50 proteins are critical components of the human class-1 P4-ATPase transport machinery.
Members of the P(4) subfamily of P-type ATPases catalyze phospholipid transport and create membrane lipid asymmetry in late secretory and endocytic compartments. P-type ATPases usually pump small cations and the transport mechanism involved appears conserved throughout the family. How this mechanism is adapted to flip phospholipids remains to be established. P(4)-ATPases form heteromeric complexes with CDC50 proteins. Dissociation of the yeast P(4)-ATPase Drs2p from its binding partner Cdc50p disrupts catalytic activity (Lenoir, G., Williamson, P., Puts, C. F., and Holthuis, J. C. (2009) J. Biol. Chem. 284, 17956-17967), suggesting that CDC50 subunits play an intimate role in the mechanism of transport by P(4)-ATPases. The human genome encodes 14 P(4)-ATPases while only three human CDC50 homologues have been identified. This implies that each human CDC50 protein interacts with multiple P(4)-ATPases or, alternatively, that some human P(4)-ATPases function without a CDC50 binding partner. Here we show that human CDC50 proteins each bind multiple class-1 P(4)-ATPases, and that in all cases examined, association with a CDC50 subunit is required for P(4)-ATPase export from the ER. Moreover, we find that phosphorylation of the catalytically important Asp residue in human P(4)-ATPases ATP8B1 and ATP8B2 is critically dependent on their CDC50 subunit. These results indicate that CDC50 proteins are integral part of the P(4)-ATPase flippase machinery.
Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584CH Utrecht, The Netherlands.
Susanne
S
Bryde
Hanka
H
Hennrich
Patricia M
PM
Verhulst
Philippe F
PF
Devaux
Guillaume
G
Lenoir
Joost C M
JC
Holthuis
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018938:Caco-2 Cells; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D055106:Genome-Wide Association Study; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D018411:Spodoptera
D008565:Membrane Proteins; D000251:Adenosine Triphosphatases; C111067:ATP8B1 protein, human