Involvement of Golgin-160 in Cell Surface Transport of Renal ROMK Channel: Co-expression of Golgin-160 Increases ROMK Currents

Abstract

The weak inward rectifier potassium channel ROMKis important for water and salt reabsorption in thekidney. Here we identified Golgin-160 as a novelinteracting partner of the ROMK channel. By usingyeast two-hybrid assays and co-immunoprecipitationsfrom transfected cells, we demonstrate that Golgin-160associates with the ROMK C-terminus.Immunofluorescence microscopy confirmed that bothproteins are co-localized in the Golgi region. Theinteraction was further confirmed by the enhancementof ROMK currents by the co-expressed Golgin-160in Xenopus oocytes. The increase in ROMK currentamplitude was due to an increase in cell surfacedensity of ROMK protein. Golgin-160 also stimulatedcurrent amplitudes of the related Kir2.1, and ofvoltage-gated Kv1.5 and Kv4.3 channels, but not thecurrent amplitude of co-expressed HERG channel.These results demonstrate that the Golgi-associatedGolgin-160 recognizes the cytoplasmic C-terminus ofROMK, thereby facilitating the transport of ROMK to the cell surface. However, the stimulatory effect onthe activity of more distantly-related potassiumchannels suggests a more general role of Golgin-160in the trafficking of plasma membrane proteins.