{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Fas Apoptosis Inhibitory Molecule (FAIM) is a multifunctional protein originally identified as a death receptor antagonist that exists in at least two alternatively spliced isoforms: a ubiquitously expressed short form (FAIM‐S) and a longer, neuron‐specific form (FAIM‐L). FAIM was first characterized in immune cells where its expression protects activated B cells from Fas‐induced apoptosis, thereby contributing to proper immune regulation; however, dysregulated FAIM expression may also promote the survival of malignant lymphocytes."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": " In the nervous system, FAIM‐L is expressed exclusively by neurons where it directly binds to the Fas receptor to impede the recruitment and activation of initiator caspase‐8 and interacts with X‐linked inhibitor of apoptosis protein (XIAP) to prevent its ubiquitination and degradation, thereby both blocking apoptotic cascades and modulating non‐apoptotic functions such as synaptic plasticity and receptor internalization."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": " Beyond its classical anti‐apoptotic roles, FAIM also participates in cancer metabolism; in lung adenocarcinoma cells, for example, FAIM promotes the formation and stabilization of GAC (a glutaminase isoform) through enhanced PKCε‐mediated phosphorylation and by sequestering GAC from proteolytic degradation. This activity leads to increased α‐ketoglutarate production and subsequent activation of the mTOR pathway, cumulatively supporting tumor growth and suppressing autophagy."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": " At the post‐transcriptional level, the expression of both FAIM isoforms is fine‐tuned by specific microRNAs (including miR‐206, miR‐1–3p, and miR‐133b), underscoring its role as an important node in the regulation of cell death pathways."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": " Studies in non‐mammalian systems further suggest that FAIM can positively influence NF‑κB signaling and inhibit apoptosis following pathogen challenges, thereby participating in innate immunity."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": " Likewise, genetic analyses in goats have indicated that while FAIM is expressed in ovarian tissue and may contribute to normal ovarian function by mitigating Fas‐triggered cell death, its expression appears not to be directly altered by nearby regulatory mutations."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": " Moreover, in bioreactor cell systems, targeting apoptotic regulators including FAIM has been shown to enhance viable cell numbers and productive culture longevity."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Collectively, these studies reveal that FAIM is a versatile modulator of cell fate whose functions vary according to cell type and context – from safeguarding neurons and immune cells against inappropriate apoptosis to influencing metabolic reprogramming in cancer – and highlight its potential as a target for therapeutic intervention.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "T L Rothstein "}, {"type": "b", "children": [{"type": "t", "text": "Inducible resistance to Fas-mediated apoptosis in B cells."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Cell Res (2000)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1038/sj.cr.7290053"}], "href": "https://doi.org/10.1038/sj.cr.7290053"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "11191348"}], "href": "https://pubmed.ncbi.nlm.nih.gov/11191348"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Miguel F Segura, Carme Sole, Marta Pascual, et al. 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