Characterization of the γ-secretase subunit interactome in Arabidopsis thaliana

Gamma secretase is a multi-subunit complex with aspartic intramembrane protease activity that is involved in the pathogenesis of Alzheimer’s disease in humans. In Arabidopsis thaliana, γ-secretase subunits are localized to endomembrane system compartments and interact with each other in a similar manner to their human counterparts. Here, we identified the protein partners of two plant γ-secretase subunits, presenilin 2 and PEN-2, by tandem affinity purification and co-immunoprecipitation, respectively. Integral membrane proteins were found to interact with presenilin 2, whereas secreted proteins were found to interact with PEN-2. Microscopy screening revealed that the reticulon family protein, RTNLB1, and two single transmembrane domain proteins, TIR-X and the phytolongin PHYL1.1, interact with presenilins. Finally, we show that RTNLB1 interacts with TIR-X. These results represent a step toward elucidating the functions of γ-secretase subunits in plant cells.