Asymmetrical targeting of type II Na-P(i) cotransporters in renal and intestinal epithelial cell lines.
Targeting of newly synthesized transporters to either the apical or basolateral domains of polarized cells is crucial for the function of epithelia, such as in the renal proximal tubule or in the small intestine. Recently, different sodium-phosphate cotransporters have been identified. Type II cotransporters can be subdivided into two groups: type IIa and type IIb. Type IIa is predominantly expressed in renal proximal tubules, whereas type IIb is located on the intestinal and lung epithelia. To gain some insights into the polarized targeting of the type II cotransporters, we have transiently expressed type IIa and type IIb cotransporters in several epithelial cell lines: two lines derived from renal proximal cells (opossum kidney and LLC-PK(1)), one from renal distal cells (Madin-Darby canine kidney), and one from colonic epithelium (CaCo-2). We studied the expression of the transporters fused to the enhanced green fluorescent protein. Our data indicate that the polarized targeting is dependent on molecular determinants most probably located at the COOH terminus of the cotransporters as well as on the cellular context.
Hernando
N
N
Institute of Physiology, University of Zürich, Zürich CH-8057, Switzerland. hernando@physiol.unizh.ch
Sheikh
S
S
Karim-Jimenez
Z
Z
Galliker
H
H
Forgo
J
J
Biber
J
J
Murer
H
H
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D018374:LLC-PK1 Cells; D018613:Microscopy, Confocal; D009893:Opossums; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D050614:Sodium-Phosphate Cotransporter Proteins, Type IIb; D013552:Swine; D027981:Symporters; D014018:Tissue Distribution; D014162:Transfection
D002352:Carrier Proteins; C493554:SLC34A1 protein, human; C493557:SLC34A2 protein, human; D050608:Sodium-Phosphate Cotransporter Proteins; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D050614:Sodium-Phosphate Cotransporter Proteins, Type IIb; D027981:Symporters