Figure 5.

Optical detection of surface hERG subunits with quantum dot in HEK293 cells. (A) Schematic of BBS- and YFP-tagged hERG 1a, CFP-tagged hERG 1b and YFP-tagged hERG 1a lacking the BBS tag. (B) Confocal images of non-permeabilized HEK293 cells expressing BBS-hERG 1a-YFP or hERG 1a-YFP alone and in combination with hERG 1b-CFP, and exposed to QD₆₅₅ to selectively label surface channels. Panels show hERG channels for YFP (total expression, left panel), CFP (middle panel), and QD₆₅₅ (surface channels, right panel). Scale bars represent 20 μm. (C) Normalized mean QD₆₅₅ signals from YFP-positive cells expressing BBS-hERG 1a-YFP alone (white column), BBS-hERG 1a-YFP/hERG 1b-CFP (black column), and hERG 1a-YFP/hERG 1b-CFP (gray column) represent relative surface density. hERG 1a-YFP/hERG 1b-CFP serves as negative control and shows negligible QD₆₅₅ signal consistent with lack of BBS-tag and therefore negligible channel surface density. (D) Compared to untreated HEK293 cells transiently expressing BBS-HERG 1a-YFP, pretreatment (≥1 h) with PA (1 mM) increased the surface density of hERG channels (~13%), while OA reduced (~20%, light gray column). Dotted line indicates 1. Numbers in parenthesis indicates the number of independent cell culture experiments.