title: Functional role of Na+-HCO3- cotransport in migration of transformed renal epithelial cells.
abstract: Cell migration is crucial for immune defence, wound healing or formation of tumour metastases. It has been shown that the activity of the Na(+)-H(+) exchanger (NHE1) plays an important role in cell migration. However, so far it is unknown whether Na(+)- HCO(3)(-) cotransport (NBC), which has similar functions in the regulation of intracellular pH (pH(i)) as NHE1, is also involved in cell migration. We therefore isolated NHE-deficient Madin-Darby canine kidney (MDCK-F) cells and tested whether NBC compensates for NHE in pH(i) and cell volume regulation as well as in migration. Intracellular pH was measured with the fluorescent pH indicator 2'7'-bis(carboxyethyl)-5-carboxyfluorescein (BCECF). The expression of NBC isoforms was determined with semiquantitative PCR. Migration was monitored with time-lapse video microscopy and quantified as the displacement of the cell centre. We found that MDCK-F cells express the isoform NBC1 (SLCA4A gene product) at a much higher level than the isoform kNBC3 (SLCA4A8 gene product). This difference is even more pronounced in NHE-deficient cells so that NBC1 is likely to be the major acid extruder in these cells and the major mediator of propionate-induced cell volume increase. NHE-deficient MDCK-F cells migrate more slowly than normal MDCK-F cells. NBC activity promotes migration during an acute intracellular acid load and increases migratory speed and displacement on a short timescale (< 30 min) whereas it has no effect on the long-term behaviour of migrating MDCK-F cells. Taken together, our results show that NBC actvity, despite many functional similarities, does not have the same importance for cell migration as NHE1 activity.
authors.affiliation: Institute of Physiology II, Münster, Germany. aschwab@uni-muenster.de
authors.forename: A
authors.initials: A
authors.lastname: Schwab
authors.forename: H
authors.initials: H
authors.lastname: Rossmann
authors.forename: M
authors.initials: M
authors.lastname: Klein
authors.forename: P
authors.initials: P
authors.lastname: Dieterich
authors.forename: B
authors.initials: B
authors.lastname: Gassner
authors.forename: C
authors.initials: C
authors.lastname: Neff
authors.forename: C
authors.initials: C
authors.lastname: Stock
authors.forename: U
authors.initials: U
authors.lastname: Seidler
mesh_terms: D000818:Animals; D002245:Carbon Dioxide; D002461:Cell Line, Transformed; D002465:Cell Movement; D048429:Cell Size; D002999:Clone Cells; D004285:Dogs; D006863:Hydrogen-Ion Concentration; D012333:RNA, Messenger / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
chemical_list: D012333:RNA, Messenger; C498898:SLC4A4 protein, human; C422022:SLC4A7 protein, human; D027982:Sodium-Bicarbonate Symporters; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D002245:Carbon Dioxide