Figure 2. Location of key organelles and molecules involved in Ca²⁺ uptake at the base of pancreatic acinar cells.

EM picture of basal area of a pancreatic acinar cell showing areas in which the ER is devoid of ribosomes and comes very close to the plasma membrane (indicated with asterisk). This arrangement allows molecular interaction between STIM in the ER membrane and CRAC channels in the plasma membrane. A mitochondrion (m) is also seen near the plasma membrane. Arrowheads signpost ER–plasma membrane junctions where Ca²⁺ entry can take place. Indicative locations of the three key Ca²⁺ transporters at the base of the cell are shown. MCU, mitochondrial Ca²⁺ uniporter. Adapted from Lur et al. (2009).