Interactome of Ca2+-bound secretagogin in mouse embryonic (E13.5) pancreas

By using His6-tagged recombinant human secretagogin in the presence of Ca2+ (100 µM), we isolated its putative interacting partners from mouse embryonic (E13.5) pancreata and identified their amino acid sequences by mass spectrometry. Next to previously described interacting partners (participating in vesicle-mediated transport, cytoskeletal organization and members of chaperonin-containing complex), we found a substantial group of proteins involved in proteasomal catabolic process including 15 different subunits of the 26S proteasome. Our data support that secretagogin protects Pdx1 from proteasomal degradation to control a transcriptional program required for β cell specification.