Localization of TASK and TREK, two-pore domain K+ channels, in human cytotrophoblast cells.
OBJECTIVE
Two-pore domain K+ channels (K2P), an emerging K+ channel subfamily, contribute to setting membrane potential in both electrically excitable and nonexcitable cells and, as such, influence cellular function. The multinucleate syncytiotrophoblast of human placenta, formed from the fusion of mononucleate cytotrophoblast cells, is a transporting epithelium whose function likely depends on the activity of K+ channels. We have therefore investigated the gene expression of two members of this family, TASK and TREK, in cultured human cytotrophoblast cells, and have also investigated protein expression in cytotrophoblast cells and placenta.


METHODS
We used reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting, and immunocytochemistry to investigate the gene and protein expression of TASK and TREK isoforms in both isolated cytotrophoblast cells and term placental tissue.


RESULTS
In cytotrophoblast cells, mRNAs encoding TASK1, 2, 4, 5, and TREK1 were detected, whereas weak or no signals were observed for TASK3 and TREK2. Western blotting for TASK1 in cytotrophoblast cells gave two bands of approximately 78 and 150 kd; TREK1 gave bands of approximately 90 and 130 kd. TASK1 immunofluorescence in placenta colocalized with cytokeratin-7, a trophoblast-specific marker. TREK1 predominantly stained cells around the villous perimeter and this staining was colocalized with propidium iodide nuclear staining.


CONCLUSIONS
Human cytotrophoblast cells from term placenta are a site of expression for various K2P genes, two of which, namely, TASK1 and TREK1, are transcribed into protein.
Bai
Xilian
X
Maternal and Fetal Health Research Centre, University of Manchester, St. Mary's Hospital, Manchester, United Kingdom.
Greenwood
Susan L
SL
Glazier
Jocelyn D
JD
Baker
Philip N
PN
Sibley
Colin P
CP
Taggart
Michael J
MJ
Fyfe
Gregor K
GK
D015153:Blotting, Western; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D009419:Nerve Tissue Proteins; D010920:Placenta / Q000166:cytology / Q000378:metabolism*; D024683:Potassium Channels, Tandem Pore Domain / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism
D009419:Nerve Tissue Proteins; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger; C103742:potassium channel protein TREK-1; C420132:potassium channel subfamily K member 3