title: Ankyrin-3 is a novel binding partner of the voltage-gated potassium channel Kv1.1 implicated in renal magnesium handling.
abstract: The voltage-gated potassium channel, Kv1.1, was recently identified as a causative gene in isolated dominant hypomagnesemia. The channel is situated in the distal convoluted tubule, where it participates in maintaining a favorable electrical gradient for driving magnesium ion into the cell through the transient receptor potential melastatin 6 channel. Pull-down experiments coupled to mass spectrometry using the carboxy-terminal domain of Kv1.1 as bait were used in mouse kidney lysates. Ankyrin-3 (ANK3) was identified as a binding partner of Kv1.1 and was enriched in isolated distal convoluted tubules as compared to whole kidney. Electrophysiology studies performed in HEK293 cells expressing Kv1.1 showed that ANK3 significantly inhibited Kv1.1-mediated currents (267 compared to 125 pA/pF) for control and ANK3, respectively. Finally, to evaluate a potential role of ANK3 in magnesium handling, the intrarenal abundance of ANK3 was measured in mice fed a low-, normal-, or high-magnesium diet for 10 days. Mice maintained on high dietary magnesium significantly doubled their fractional urinary excretion of magnesium, which coincided with a 1.8-fold increase in the renal expression of ANK3 compared to mice on a normal- or low-magnesium diet. Thus, our observations demonstrate a novel role for ANK3 in modulating the biophysical properties of Kv1.1. Such regulation appears to be particularly important in conditions of high dietary magnesium.
authors.affiliation: Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Pedro
authors.initials: P
authors.lastname: San-Cristobal
authors.affiliation: Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Sergio
authors.initials: S
authors.lastname: Lainez
authors.affiliation: Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Henrik
authors.initials: H
authors.lastname: Dimke
authors.affiliation: Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Mark J J
authors.initials: MJ
authors.lastname: de Graaf
authors.affiliation: Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Joost G J
authors.initials: JG
authors.lastname: Hoenderop
authors.affiliation: Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: René J M
authors.initials: RJ
authors.lastname: Bindels
mesh_terms: D000818:Animals; D017487:Ankyrins / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007150:Immunohistochemistry; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D051662:Kv1.1 Potassium Channel / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018408:Patch-Clamp Techniques; D011897:Random Allocation
chemical_list: C094681:Ank3 protein, mouse; D017487:Ankyrins; D051662:Kv1.1 Potassium Channel; D008274:Magnesium