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The curious case of SARM1: Dr. Jekyll and Mr. Hyde in cell death and immunity?
Author(s) -
Sarkar Ankita,
Kumari Nripa,
Mukherjee Piyali
Publication year - 2023
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.16256
Subject(s) - signal transducing adaptor protein , biology , microbiology and biotechnology , immune system , innate immune system , death domain , trif , programmed cell death , genetics , signal transduction , toll like receptor , apoptosis
Sterile alpha and toll/interleukin‐1 receptor motif‐containing protein 1 (SARM1) was first identified as a novel ortholog of Drosophila protein CG7915 and was subsequently placed as the fifth member of the human TIR‐containing adaptor protein. SARM1 holds a unique position in this family where, unlike other members, it downregulates NFκB activity in response to immunogenic stimulation, interacts with another member of the family, TRIF, to negatively regulate its function, and it also mediates cell death responses. Over the past decade, SARM1 has emerged as one of the primary mediators of programmed axonal degeneration and this robust regulation of axonal degeneration—especially in models of peripheral neuropathy and traumatic injury—makes it an attractive target for therapeutic intervention. The TIR domain of SARM1 possesses an intrinsic NADase activity resulting in cellular energy deficits within the axons, a striking deviation from its other family members of human TLR adaptors. Interestingly, the TIR NADase activity, as seen in SARM1, is also observed in several prokaryotic TIR‐containing proteins where they are involved in immune evasion once within the host. Although the immune function of SARM1 is yet to be conclusively discerned, this closeness in function with the prokaryotic TIR‐domain containing proteins, places it at an interesting juncture of evolution raising questions about its origin and function in cell death and immunity. In this review, we discuss how a conserved immune adaptor protein like SARM1 switches to a pro‐neurodegenerative function and the evolutionarily significance of the process.