Publication Date:
2016-12-14
Description:
A Ca 2+ -activated nonselective cation channel (NSC Ca ) is found in principal cells of the mouse cortical collecting duct (CCD). However, the molecular identity of this channel remains unclear. We used mpkCCD c14 cells, a mouse CCD principal cell line, to determine whether NSC Ca represents the transient receptor potential (TRP) channel, the melastatin subfamily 4 (TRPM4). A Ca 2+ -sensitive single-channel current was observed in inside-out patches excised from the apical membrane of mpkCCD c14 cells. Like TRPM4 channels found in other cell types, this channel has an equal permeability for Na + and K + and has a linear current-voltage relationship with a slope conductance of ~23 pS. The channel was inhibited by a specific TRPM4 inhibitor, 9-phenanthrol. Moreover, the frequency of observing this channel was dramatically decreased in TRPM4 knockdown mpkCCD c14 cells. Unlike those previously reported in other cell types, the TRPM4 in mpkCCD c14 cells was unable to be activated by hydrogen peroxide (H 2 O 2 ). Conversely, after treatment with H 2 O 2 , TRPM4 density in the apical membrane of mpkCCD c14 cells was significantly decreased. The channel in intact cell-attached patches was activated by ionomycin (a Ca 2+ ionophore), but not by ATP (a purinergic P 2 receptor agonist). These data suggest that the NSC Ca current previously described in CCD principal cells is actually carried through TRPM4 channels. However, the physiological role of this channel in the CCD remains to be further determined.
Print ISSN:
1931-857X
Electronic ISSN:
1522-1466
Topics:
Medicine
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