ABSTRACT
The identification of Orai and stromal interaction molecule (STIM) proteins has opened up new avenues of research in the field of receptor-regulated calcium signaling. The ligation of phospholipase C (PLC)-coupled receptors can activate either the common store-operated calcium entry (SOCE) pathway or store-independent calcium entry (SICE) pathway. The biophysical properties of LRC channels were identical to those of arachidonate-regulated Ca2+(ARC)-selective channels, prompting to undertake a side by side comparison in primary aortic vascular smooth muscle cells and HEK293 cells to determine whether these two conductances are mediated by the same or by different cellular pools of STIM and Orai proteins. A recording of ARC channel current in M3 muscarinic receptor-expressing HEK293 cells has revealed that, like Ca2+release-activated Ca2+, ARC channels possess a small, highly calcium-selective conductance. Proper grounding is essential for obtaining low-noise patch clamp recording from small conductance ARC/LRC channels.
