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First published online on August 30, 2002.
 Copyright © 2002 by The Physiological Society
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2002.026047v1
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Received ,
Accepted after revision ,

Kir2.4 and Kir2.1 K+ channel subunits co-assemble: a potential new contributor to inward rectifier current heterogeneity

Gernot Schram1, Peter Melnyk2, Marc Pourrier3, Zhiguo Wang1, and S. Nattel4*

1 Department of Medicine and Research Center, Montreal Heart Institute and Department of Medicine, University of Montreal, Quebec, Canada
2 Department of Medicine and Research Center, Montreal Heart Institute, and Department of Pathology, McGill University, Quebec, Canada
3 Department of Medicine and Research Center, Montreal Heart Institute and Department of Pharmacology University of Montreal, Quebec, Canada
4 Montreal Heart Institute Research Center, 5000 Belanger Street East, Montreal, Quebec, Canada H1T 1C8

* To whom correspondence should be addressed. E-mail: nattel{at}icm.umontreal.ca.

Heteromeric channel assembly is a potential source of physiological variability. The potential significance of Kir2-subunit heterotetramerization has been controversial, but recent findings suggest that heteromultimerization of Kir2.1-3 may be significant. This study was designed to investigate whether the recently described Kir2.4 subunit can form heterotetramers with the important subunit Kir2.1, and if so, to investigate whether the resulting heterotetrameric channels are functional. Co-expression of either dominant negative Kir2.1 or Kir2.4 subunits in Xenopus oocytes with either wild-type Kir2.1 or 2.4 strongly decreased resulting current amplitude. To examine physical association between Kir2.1 and Kir2.4, Cos-7 cells were co-transfected with a His6-tagged Kir2.1 subunit (Kir2.1-His6) and a FLAG-tagged Kir2.4 subunit (Kir2.4-FLAG). After pulldown with a His6-binding resin, Kir2.4-FLAG could be detected in the eluted cell lysate by Western blotting, indicating co-assembly of Kir2.1-His6 and Kir2.4-FLAG. Expression of a tandem construct containing covalently linked Kir2.1 and 2.4 subunits led to robust current expression. Kir2.1-Kir2.4 tandem subunit expression, as well as co-injection of Kir2.1 and Kir2.4 cRNA into Xenopus oocytes, produced currents with barium sensitivity greater than that of Kir2.1 or Kir2.4 subunit expression alone. These results show that Kir2.4 subunits can co-assemble with Kir2.1 subunits, and that co-assembled channels are functional, with properties different from those of Kir2.4 or Kir2.1 alone. Since Kir2.1 and Kir2.4 mRNAs have been shown to co-localize in the CNS, Kir2.1 and Kir2.4 heteromultimers might play a role in the heterogeneity of native inward rectifier currents.




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