Figure 3. Orai1-mediated Ca²⁺ entry induces plasma membrane insertion of TRPC1 channels.

Biotinylation of TRPC1 was determined in HSG cells (see Materials and Methods for details). (A) Detection of TRPC1 in the biotinylated fraction from control HSG cells and HSG cells treated with siOrai1 or expressing Orai1-E106Q in resting conditions or following treatment with Tg (see C for quantitation of the bands and average data from five individual experiments). (B) TRPC1 biotinylation in HSG cells treated with Tg either in the presence of Gd³⁺ or in Ca²⁺-free medium (see C for quantitation of data and average values obtained from four experiments). (C) Quantitation of TRPC1 surface expression shown in (A) and (B). ** indicates value significantly, p<0.01 from –Tg in control cells. All other values (unmarked) are represented relative to the –Tg condition in control cells and are not significantly different from each other. (D) TRPC1 biotinylation in HSG cells expressing Orai1-E106D with or without Tg treatment in either Ca²⁺-containing or nominally Ca²⁺-free medium (left panel). Average data (right panel, ** indicates values significantly, p<0.01, different from –Tg condition in controls, unmarked values are not different from each other). (E) TRPC1 biotinylation in HSG cells expressing STIM1(⁶⁸⁴EE⁶⁸⁵) with or without Tg treatment prior to surface biotinylation (left panel), average data (right panel, ** indicates values significantly, p<0.01, different from –Tg condition in controls; unmarked values are not different from each other).