The plasma membrane polarity of human biliary epithelial cells: in situ immunohistochemical analysis and functional implications.
OBJECTIVE
In transporting epithelia, like the biliary epithelium, most plasma membrane proteins present a polarized distribution, essential for the maintenance of the structural and functional properties of the epithelium. We therefore analyzed the expression of polarized plasma membrane proteins by human biliary epithelial cells in order to compare them with other transporting epithelial cells and to search for differences in plasma membrane protein expression between their different anatomical subsets.


METHODS
We designed an in situ immunohistochemical study of the various anatomical compartments of the human biliary tract in order to assess the pattern of expression of selected polarized plasma membrane proteins, including integrin receptors, ectopeptidases, membrane transporters and GPI-linked proteins.


RESULTS
All biliary epithelial cells expressed the same repertoire of integrins, except for integrin chain alpha5, restricted to the intra-hepatic compartments. All biliary epithelial cells expressed the following apical ectopeptidases: aminopeptidase-N, neutral-endopeptidase, dipeptidyl-peptidase IV. All biliary epithelial cells expressed the membrane transporter Na+ K+-ATPase, restricted to the basolateral domain, and the apical transporters CFTR and MDR-1. The apical AE2 anion exchanger was restricted to the small intra-hepatic bile ducts and the gallbladder. The GPI-linked protein protectin was basolateral in the intrahepatic bile ducts and apical in the gallbladder.


CONCLUSIONS
The structural organization of the plasma membrane of biliary epithelial cells is very similar to that of other simple epithelia and exhibits a limited degree of heterogeneity.
Scoazec
J Y
JY
INSERM U327, Faculté de Médecine Xavier Bichat, Université Paris 7, France. u327@bichat.inserm.fr
Bringuier
A F
AF
Medina
J F
JF
Martínez-Ansó
E
E
Veissiere
D
D
Feldmann
G
G
Housset
C
C
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D001659:Biliary Tract / Q000166:cytology / Q000502:physiology*; D001692:Biological Transport; D018826:CD13 Antigens / Q000378:metabolism; D018958:CD55 Antigens / Q000378:metabolism; D018957:CD59 Antigens / Q000378:metabolism; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism; D004847:Epithelial Cells; D004848:Epithelium / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D016023:Integrins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D015260:Neprilysin / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018958:CD55 Antigens; D018957:CD59 Antigens; C505032:CFTR protein, human; D016023:Integrins; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D018826:CD13 Antigens; D018819:Dipeptidyl Peptidase 4; D015260:Neprilysin; D000254:Sodium-Potassium-Exchanging ATPase