Annexin A11 and TDP-43: core players in neurodegeneration

Annexin A11 (ANXA11) is a Ca²⁺-dependent phospholipid-binding protein that has recently emerged as a key player in neurodegeneration. Rare pathogenic ANXA11 variants were initially identified in cases of amyotrophic lateral sclerosis (ALS). Since then, ANXA11 has been linked to a broader spectrum of related neurodegenerative diseases. Two independent studies demonstrated that ANXA11 co-aggregates with TDP-43 in all cases of frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP) type C, with cryo-EM revealing heteromeric ANXA11-TDP-43 filaments. These discoveries support the direct pathological interaction between the two proteins as an important feature of FTLD-TDP type C. We also described secondary ANXA11 pathology in related neurodegenerative diseases, including limbic-predominant age-related TDP-43 encephalopathy (LATE), and more rarely in ALS and FTLD-TDP types A and B. ANXA11 and TDP-43 co-aggregates are also a feature of a FTLD-TDP associated with primary lateral sclerosis. These advances have renewed interest in ANXA11 as a major player in ALS/FTLD pathogenesis in both genetic and sporadic neurodegenerative diseases. In this review, we summarize ANXA11 pathology across genetic and sporadic cases, highlighting its heterogeneous overlap with TDP-43 pathology. We synthesize current knowledge of ANXA11's physiological roles in phase separation, membrane repair, and RNA granule dynamics, integrating emerging evidence on how disruption of these processes may promote pathological aggregation and toxicity. Finally, we outline priorities for future research, with particular emphasis on elucidating ANXA11's mechanistic connection to TDP-43.