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Electrophysiological characterization of mosquito NHE8 in Xenopus oocytes
Author(s) -
Piermarini Peter M,
Beyenbach Klaus W
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1239.16
Subject(s) - xenopus , extracellular , electrophysiology , voltage clamp , conductance , membrane potential , biophysics , chemistry , antiporter , intracellular , biology , biochemistry , membrane , gene , neuroscience , physics , condensed matter physics
Na/H exchangers (NHEs) mediate the antiport of Na + and/or K + for H + across cell membranes. In invertebrates and prokaryotes, some NHEs are electrogenic operating as nNa/H or Na/nH exchangers. In the yellow‐fever mosquito Aedes aegypti , a cDNA encoding an isoform of NHE8 ( Ae NHE8) was recently cloned and shown to mediate Na/H and K/H exchange when expressed in yeast and fibroblast cells (Kang’ethe et al., 2007, Am J Physiol Renal , 292: 1501). The goal of our study was to characterize the electrophysiology of Ae NHE8 when expressed in Xenopus oocytes ( Ae NHE8 oocytes). Measurements of membrane potential (V m ) and intracellular pH (pH i ) indicate that Ae NHE8 oocytes have a depolarized V m and a higher pH i compared to controls. In some batches of Ae NHE8 oocytes, reducing extracellular [Na + ] rapidly lowers pH i , which is reversed by returning [Na + ]. In all batches of Ae NHE8 oocytes, reducing extracellular [Na + ] consistently and reversibly hyperpolarizes V m . Two‐electrode voltage clamp studies show that Ae NHE8 oocytes have a higher conductance than controls and that the conductance is lowered by decreasing extracellular [Na + ]. Taken together, these observations indicate that Ae NHE8 induces a significant Na + ‐conductance when expressed in Xenopus oocytes. Whether the conductance is due to electrogenic nNa/H exchange remains to be determined. Supported by NSF Grant IOB‐0542797 to KWB.