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J Physiol Volume 544, Number 2, 337-349, October 15, 2002 DOI: 10.1113/jphysiol.2002.026047
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Journal of Physiology (2002), 544.2, pp. 337-349
© Copyright 2002 The Physiological Society
DOI: 10.1113/jphysiol.2002.026047

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

Gernot Schram *†, Peter Melnyk *‡, Marc Pourrier *§, Zhiguo Wang *† and Stanley Nattel *†¶

* Department of Medicine and Research Center, Montreal Heart Institute, 5000 Belanger Street, Montreal, Quebec, Canada H1T 1C8, Departments of † Medicine and § Pharmacology, University of Montreal, C.P. 6128, succursale Centre-ville, Montreal, Quebec, Canada H3C 3J7 and Departments of ¶ Pharmacology and ‡ Pathology, McGill University, 3775 University, Montreal, Quebec, Canada H3A 2B4

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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