In vitro analysis of SPP/SPPL proteases: mechanistic insights and facilitated drug discovery

• Applicant: Dr. Sabine Höppner
• Subject Area: Biochemistry
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 580443383

SPPL2a and SPPL2b are intramembrane aspartyl proteases structurally related to presenilins. While presenilins have been extensively studied in the context of Alzheimer’s disease, the distinct mechanistic and regulatory principles thought to govern SPPL proteases remain largely unknown. The aim of this project is to establish a deeper mechanistic understanding of SPPL2a and SPPL2b in order to close a key knowledge gap in the field of intramembrane proteolysis and to distinguish them from presenilins as specific targets for selective inhibitor development. The underlying hypothesis is that SPPL2a and SPPL2b are subject to previously uncharacterized regulatory mechanisms—such as multimerization, domain-specific interactions, and compartmentalized localization—which are essential for their physiological functions and pathological roles. Elucidating these mechanisms is expected to provide novel insights into disease-related dysfunctions. Based on a robust, established in vitro assay and the successful purification of SPPL2a, we aim to systematically investigate the enzymatic properties, structural features, and regulatory mechanisms of both SPPL2a and SPPL2b. This includes kinetic studies, the characterization of oligomeric states, and the identification of protein interaction partners. Building on these findings, we will analyze candidate Alzheimer’s drugs with respect to their potential off-target effects on SPPL2 proteases. The goal is to use the gained insights to establish a platform for testing the selectivity of aspartyl intramembrane protease inhibitors. In the long term, this project aims to lay the groundwork for the targeted development of selective therapeutics that address SPPL-dependent signaling pathways in immune and cancer-related diseases, while avoiding undesired SPPL-mediated side effects—particularly in the context of Alzheimer’s therapy.

• DFG Programme: Research Grants