Investigating the impact of amyotrophic lateral sclerosis-associated mutation in annexin A11 protein

Annexins, proteins that bind to phospholipids in a calcium-dependent manner, are essential for the health and homeostasis of the body. They are directly involved in several biological processes, such as anti-coagulation, cell signaling, cell growth regulation, apoptosis, inflammation, vesicle fusion and intracellular transport. In this project, our focus is on Annexin A11 (AnxA11), a unique member of this family, possesses an unusually long and intrinsically disordered N-terminal domain, which is essential for its ability to form biomolecular condensates, and has been linked to various pathological conditions such as systemic autoimmune diseases and sarcoidosis. Notably, multiple ALS-associated mutations have been identified within this disordered region of the protein, highlighting its potential relevance in neurodegenerative disease. These mutant proteins form intracellular aggregates and interfere with the interaction pattern with molecular partners. In this project, we propose to elucidate the molecular details of how the G38R mutation affects the biophysical and biochemical properties of AnxA11. The full-length AnxA11  undergoes a high level of proteolysis when expressed using conventional methodologies in E.coli. We successfully developed a procedure for expressing and purifying two constructs of the full-length AnxA11, one with the enhanced GFP at the C-terminus and other with SUMO protein at the N-terminus. We also analyse how the G38R mutation affects the protein secondary structure, Ca²⁺-binding and interaction with membranes. Our objective is to enhance our understanding of the pathology development caused by this inherited mutation. Additionally, we aim to delineate the characteristics of the aggregates formed by this mutation.