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The α4 isoform of the Na + ,K + ‐ ATP ase is tuned for changing extracellular environments
Author(s) -
Voldsgaard Clausen Michael,
Nissen Poul,
Poulsen Hanne
Publication year - 2016
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13567
Subject(s) - gene isoform , extracellular , xenopus , oocyte , microbiology and biotechnology , atpase , biology , kinetics , chemistry , biochemistry , biophysics , enzyme , embryo , gene , physics , quantum mechanics
In their journey from the male to the female reproductive tract, spermatozoa are confronted with a constantly changing environment. To cope with the associated challenges, spermatozoa express a distinct set of transporters, channels and pumps. One of the membrane proteins unique to spermatozoa is the α4 isoform of the Na + ,K + ‐ ATP ase. In addition to α4, spermatozoa express the ubiquous α1 variant. To get a detailed understanding of how α1 and α4 differ, and why spermatozoa need an additional Na + ,K + ‐ ATP ase, we have conducted an electrophysiological comparison of the rodent isoforms (rat α4 versus mouse α1–3) using the Xenopus oocyte expression system. We demonstrate isoform‐specific differences in the voltage sensitivity of steady‐state turnover, with α2 being the more sensitive, and α1 and α2 having faster Na + release kinetics than α3 and α4. Our data further show that the α1 and α2 turnover rates are fast compared with those of α3 and α4. Finally, α4 is less influenced by changes in extracellular Na + and temperature than α1. Based on these findings, we discuss the possibility that evolution has selected robust activity rather than rapid turnover for α4.