On April 28, 2016, Harvard researcher Andrew Kruse and collaborators first revealed the molecular structure of the sigma-1 receptor (Sig1R), a cellular protein implicated in amyotrophic lateral sclerosis (ALS), which opened the door to potential therapeutic targets.

The Kruise lab revealed the crystal structure of Sig1R to be a single-pass transmembrane protein with residues 32–223 forming a carboxy-terminal/cytosolic domain consisting of a β-barrel and two flanking α-helices. To date, Sig1R remains an evolutionary isolate with no known homologous mammalian counterparts. The study was published in Nature.