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The Role of Retromer in the Trafficking of the Ca 2+ ‐ activated K + channels KCa2.3 and KCa3.1
Author(s) -
Logue Matthew,
Cheung Tanya,
Devor Caitlin,
Devor Daniel,
McDonald Fiona,
Hamilton Kirk
Publication year - 2021
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.2021.35.s1.04094
Subject(s) - retromer , chemistry , endocytosis , microbiology and biotechnology , ion channel , population , biophysics , endosome , cell , biology , biochemistry , receptor , demography , sociology
The small‐ and intermediate‐conductance Ca 2+ ‐activated K + channels KCa2.3 ( KCNN3 ) and KCa3.1 ( KCNN4 ) regulate a plethora of physiological processes: including, water and electrolyte transport in polarised epithelia, neuronal firing, and vascular tone. Critical for KCa2.3 and KCa3.1 function is the regulation of the number of channels at the plasma membrane; however, the mechanisms that regulate the trafficking of KCa2.3 and KCa3.1 to and from the plasma membrane are still poorly understood. There are several marked differences in the trafficking pathways of these two channels, e.g. KCa2.3 has previously been established to recycle back to the plasma membrane after endocytosis; however, there are differences in opinion if KCa3.1 recycles in the literature. The highly conserved multi‐protein complex retromer has been demonstrated to regulate the retrieval and recycling of many membrane‐bound proteins, including ion channels. We hypothesised that retromer was required for the recycling of both KCa2.3 and KCa3.1. To test this hypothesis, we utilised a combination of biochemical and electrophysiological methods. Stabilisation of retromer with the pharmacological chaperone R55 increased the KCa2.3 population at the cell surface. Additionally, siRNA‐induced knockdown of the retromer subunit VPS35 decreased KCa2.3 levels at the cell surface. Surprisingly, even though KCa2.3 and KCa3.1 are in the same gene family, similar biochemical and Ussing chamber electrophysiological experiments demonstrated that R55 did not have an effect on KCa3.1 cell surface levels or current; suggesting, that retromer does not regulate the trafficking or recycling of KCa3.1. Cumulatively, these data suggest, for the first time, that retromer is involved in the recycling of KCa2.3, but not KCa3.1, a member of the same gene family.