Proteomic analysis of the rat canalicular membrane reveals expression of a complex system of P4-ATPases in liver

ABSTRACT: Transport processes in the canalicular membrane are key elements in bile formation and are the driving force of the enterohepatic circulation of bile salts. The canalicular membrane is constantly exposed to the detergent action of bile salts. One potential element protecting the canalicular membrane from the high canalicular bile salt concentrations may be bile salt resistant microdomains, however additional factors are likely to play a role. To obtain insight into the molecular composition of the canalicular membrane, the proteome of highly purified rat canalicular membrane vesicles was determined. Isolated rat canalicular membrane vesicles were stripped from adhering proteins, deglycosylated and protease digested before shot gun proteomic analysis. Expression of individual candidates was studied by PCR, Western blotting and immunohistochemisty. A total of 2449 proteins were identified and 1282 were membrane or membrane associated proteins. About 50 % of the proteins identified here were absent from previously published liver proteomes. In addition to ATP8B1, four more P4-ATPases were identified. ATP8A1 and ATP9A shows expression specific to the canalicular membrane, ATP11C in the basolateral membrane and adjacent intracellular vesicles and ATP11A in an intracellular vesicular compartment partially colocalizing with RAB7A. This study helped to identify additional P4-ATPases from rat liver particularly in the canalicular membrane, previously not known to express in liver. These identified ATPases might be involved in transmembrane lipid homeostasis. The two newly identified P4-ATPases in the canalicular membrane may protect the canalicular membrane from the detergent action of bile salts.

INSTRUMENT(S): LTQ FT, LTQ Orbitrap

ORGANISM(S): Rattus Norvegicus (rat)

TISSUE(S): Liver

SUBMITTER: Pururawa Mayank Chaubey  

LAB HEAD: Bruno Stieger

PROVIDER: PXD003299 | Pride | 2016-07-05

REPOSITORIES: Pride