Functional Properties of Endogenous Receptor- and Store-operated Calcium Influx Channels in HEK293 Cells

Abstract

Activation of phospholipase C (PLC)-mediated signaling pathways in non-

STIM1 and STIM2 Proteins Differently Regulate Endogenous Store-operated Channels in HEK293 Cells

“…In control HEK293 cells, their activation after Tg application was observed in 14% of experiments (n ϭ 22) (Fig. 2, A, C, and F; Table 1), in agreement with our previous data on the properties of I NS channels in untreated HEK293 cells (56).…”

“…Store-operated TRPC3-containing I NS channels are nonselective channels with a conductance of 5 pS (39,56). No Tg- induced I NS channel activity was revealed in STIM1 knockdown cells (n ϭ 26).…”

“…Electrophysiological properties of calcium channels in this cell line have been studied in detail, which makes it a good model for analyzing mechanisms of storeoperated channel activation (56,57). HEK293 cells express endogenous STIM1 and STIM2 proteins (11,12,58), as was confirmed in our Western blot experiments (Fig.…”

“…In our previous studies, recordings in the cell-attached mode have shown that HEK293 cells contain three types of calcium channels, I max , I NS , and I min , differing in protein composition, conductance, selectivity to divalent ions, open time, and number per cell (56,57).…”

“…I min channels, the third calcium channel type in HEK293 cells, have a single-channel conductance of 1.2 pS, show high selectivity to divalent cations (P Ba/K ϭ 20), and are activated by extracellular UTP or intracellular IP 3 , but not by Tg (56). Regardless of store depletion by UTP, intracellular IP 3 at an increasing concentration is capable of activating I min channels through conformational coupling with the IP 3 receptor (IP 3 R) (59,60).…”