Premium
A chimeric approach to identify trafficking signals in the Kir1.1(ROMK) channel
Author(s) -
Kim Boyoung,
Welling Paul A.
Publication year - 2007
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.21.6.a1332-b
Subject(s) - endoplasmic reticulum , xenopus , microbiology and biotechnology , phosphorylation , nuclear localization sequence , serine , cytoplasm , chemistry , potassium channel , nuclear transport , immunoprecipitation , amino acid , biology , biochemistry , biophysics , gene , cell nucleus
The cell surface density of Kir1.1 channels is precisely regulated to maintain potassium balance. Our recent studies in Xenopus oocytes indicate that phosphorylation of an N‐terminal residue, S44, stimulates forward trafficking to override endoplasmic reticulum localization (Yoo et al, JBC ‘05). In the present study, we have sought to identify the structural basis for ROMK ER‐localization in mammalian cells. A Chimeric strategy with Kir 1.1 and a related channel, Kir2.1, which is constitutively expressed on the plasmalemma, was employed. Swapping both cytoplasmic N‐ and C‐termini of Kir2.1 to ROMK were required to redirect Kir1.1 from the ER to plasmalemma. The C‐terminus of Kir 1.1 contains a basic amino‐acid cluster, resembling an ER‐localization signal, not found in Kir 2.1. Mutagenic neutralization of the basic‐residue motif caused a Kir 1.1/2.1 chimera, composed almost entirely of Kir 1.1 but containing the N‐terminus of Kir 2.1, to translocate to the plasmalemma. These observations suggest Kir 1.1 contains a C‐terminal ER‐localization signal and support our working model that phosphorylation of serine 44 drives an export step early in the secretory pathway to override an independent endoplasmic reticulum localization signal.