Canonical Transient Receptor Potential Channel (TRPC) 3 and TRPC6 Associate with Large-Conductance Ca²⁺-Activated K⁺(BK_Ca) Channels: Role in BK_CaTrafficking to the Surface of Cultured Podocytes

Abstract

Large-conductance (BK Ca type) Ca 2ϩ -activated K ϩ channels encoded by the Slo1 gene and various canonical transient receptor potential channels (TRPCs) are coexpressed in many cell types, including podocytes (visceral epithelial cells) of the renal glomerulus. In this study, we show by coimmunoprecipitation and GST pull-down assays that BK Ca channels can associate with endogenous TRPC3 and TRPC6 channels in differentiated cells of a podocyte cell line. Both types of TRPC channels colocalize with Slo1 in podocytes and in human embryonic kidney (HEK) 293T cells transiently coexpressing the TRPC channels with Slo1. In HEK293T cells, coexpression of TRPC6 increased surface expression of a Slo1 subunit splice variant (Slo1 VEDEC ) that is typically retained in intracellular compartments, as assessed by cell-surface biotinylation assays and confocal microscopy. Corresponding currents through BK Ca channels were also increased with TRPC6 coexpression, as assessed by whole-cell and excised inside-out patch recordings. By contrast, coexpression of TRPC3 had no effect on the surface expression of BK Ca channels in HEK293T cells or on the amplitudes of currents in whole cells or excised patches. In podocytes, small interfering RNA knockdown of endogenous TRPC6 reduced steady-state surface expression of endogenous Slo1 channels, but knockdown of TRPC3 had no effect. TRPC6, but not TRPC3 knockdown also reduced voltageevoked outward current through podocyte BK Ca channels. These data indicate that TRPC6 and TRPC3 channels can bind to Slo1, and this colocalization may allow them to serve as a source of Ca 2ϩ for the activation of BK Ca channels. TRPC6 channels also play a role in the regulation of surface expression of a subset of podocyte BK Ca channels.

Regulation of BK-α expression in the distal nephron by aldosterone and urine pH

“…BK-␤4 localizes mostly in the cytosol of cultured neuron cells (34) but at the apical membrane of cultured IC cells (15). Moreover, Neph1, which expresses both in neurons and kidney podocytes, exhibited decreased surface BK-␣ expression in embryonic neurons, but increased expression in epithelial-like podocytes (20). In the present study, our data support the notion that BK-␤4 regulates BK-␣ expression in the plasma membrane by inhibiting its lysosomal degradation.…”

Nuclear factor of activated T cells mediates RhoA-induced fibronectin upregulation in glomerular podocytes

“…Also, albumin overload was shown to increase intracellular calcium ion concentration ([Ca 2ϩ ] i ) in podocytes both via the Ca 2ϩ influx and the release of the intracellular Ca 2ϩ stores (8). A number of cation channels have been identified to cause Ca 2ϩ influx in podocytes (16,35,58,68). Among them, TRPC6 has been attracting most attention.…”

New Insight on the Role of Transient Receptor Potential (TRP) Channels in Driven Gliomagenesis Pathways

“…Among ion channels contributing to Ca(2+) signaling, cytoskeleton changes, movement and migration, the TRPM and TRPC channel families seem to play an important role. Thus, triggering of TRPM8 by the specific agonist, menthol (Wondergem & Bartley, 2009), as TRPC3 and TRPC6 (Kim et al, 2009) increases glioma cell [Ca(2+)] i that in turn activates BK channels. Thus.…”