Sentence: The depletion of ER Ca 2 + induces STIM1 to oligomerize and translocate from its reticular location in the bulk ER to specialized ER-PM junctions ( ≈ 20 nm ) where it forms STIM1 puncta and interacts with the pore-forming subunit of store-operated channels ( SOCs ) , Orai1 ( 8 ). 
 Section: background