Figure 3. TRPC1 functions as an endogenous SOCE channel, and knockdown of TRPC1 induces ER stress.

(A) Tg-induced currents (mean ± SEM) were evaluated in control siRNA– and TRPC1 siRNA–transfected cells. The holding potential for the recordings was –80 mV, and an I-V curve (mean current ± SEM) under these conditions is shown in B. (C) Analog plots of the 340/380 ratio from an average of 40–60 cells are shown. (D) Quantification (mean ± SEM) of fluorescence ratio. *P < 0.05 versus untreated control; numbers of cells imaged are indicated. (E) SH-SY5Y cells were transfected with control siRNA or TRPC1 siRNA, or treated with 50 or 100 μM SKF-96365 for 24 hours. Cells were lysed, subjected to SDS-PAGE, and immunoblotted with the respective antibodies. (F) SH-SY5Y cells transfected with control or STIM1 siRNA were lysed and immunoblotted with respective antibodies. (G) MTT assay was performed in control, TRPC1 siRNA–transfected, SKF-96365–treated (100 μM for 24 hours), or STIM1 siRNA–transfected cells. Values represent mean ± SD from at least 3 independent experiments. *P < 0.05 versus control. (H) Tissue lysates from the SNpc region of wild-type and Trpc1^–/– mice were subjected to SDS-PAGE and immunoblotted with the respective antibodies. (I and J) Endogenous currents (mean ± SEM) and relative I-V curves (mean currents ± SEM) upon Tg stimulation in DA neurons in the SNpc of Trpc1^+/+ and Trpc1^–/– mice. The currents shown were recorded at a holding potential of –70 mV. (K) DA neurons induced a large inward current by a hyperpolarizing pulse of 60 mV, indicating the electrical signature of DA neurons.