AtKC1, a conditionally targeted Shaker-type subunit, regulates the activity of plant K+ channels.
The Plant Journal. 2008-01-01; 53(1): 115-123
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1. Plant J. 2008 Jan;53(1):115-23. Epub 2007 Nov 1.
AtKC1, a conditionally targeted Shaker-type subunit, regulates the activity of
plant K+ channels.
Duby G(1), Hosy E, Fizames C, Alcon C, Costa A, Sentenac H, Thibaud JB.
(1)Biochimie et Physiologie Moléculaire des plantes,
CNRS(UMR-5004)-INRA-SupAgro-UM2, 2 place Viala, F-34060 Montpellier cedex 1,
Amongst the nine voltage-gated K(+) channel (Kv) subunits expressed in
Arabidopsis, AtKC1 does not seem to form functional Kv channels on its own, and
is therefore said to be silent. It has been proposed to be a regulatory subunit,
and to significantly influence the functional properties of heteromeric channels
in which it participates, along with other Kv channel subunits. The mechanisms
underlying these properties of AtKC1 remain unknown. Here, the transient
(co-)expression of AtKC1, AKT1 and/or KAT1 genes was obtained in tobacco
mesophyll protoplasts, which lack endogenous inward Kv channel activity. Our
experimental conditions allowed both localization of expressed polypeptides
(GFP-tagging) and recording of heterologously expressed Kv channel activity
(untagged polypeptides). It is shown that AtKC1 remains in the endoplasmic
reticulum unless it is co-expressed with AKT1. In these conditions heteromeric
AtKC1-AKT1 channels are obtained, and display functional properties different
from those of homomeric AKT1 channels in the same context. In particular, the
activation threshold voltage of the former channels is more negative than that of
the latter ones. Also, it is proposed that AtKC1-AKT1 heterodimers are preferred
to AKT1-AKT1 homodimers during the process of tetramer assembly. Similar results
are obtained upon co-expression of AtKC1 with KAT1. The whole set of data
provides evidence that AtKC1 is a conditionally-targeted Kv subunit, which
probably downregulates the physiological activity of other Kv channel subunits in
PMID: 17976154 [Indexed for MEDLINE]