FAP1 (Ambiguous term referring to Fibroblast activation protein alpha or Fas-associated phosphatase 1) (FAP1)

The term 'FAP1' is ambiguous, referring to two distinct proteins: Fibroblast activation protein alpha (FAP) and Fas-associated phosphatase 1 (PTPN13/FAP1). Fibroblast activation protein alpha is a membrane-bound serine protease highly expressed on activated fibroblasts within the tumor stroma and in sites of tissue remodeling or fibrosis. It is a dimeric 97–170 kDa glycoprotein with prolyl endopeptidase and dipeptidyl peptidase activity, unique among related enzymes for its extracellular matrix-degrading activity and specificity for certain collagen-related sequences. It is a key player in cancer (supporting tumor growth, invasion, and immune evasion), fibrosis, and wound healing. Diagnostic and therapeutic strategies leveraging FAP include inhibitors, targeted prodrugs, antibody–drug conjugates, and radiolabeled imaging agents, but safety concerns revolve around its expression in non-tumor tissue and potential redundancy in function. Fas-associated phosphatase 1 (PTPN13/FAP1) is a large intracellular protein tyrosine phosphatase that regulates apoptosis by binding to the C-terminal region of the death receptor Fas (CD95), inhibiting its pro-apoptotic signaling and thereby promoting cell survival; it also modulates β-catenin stability and may contribute to oncogenic signaling and resistance to cell death in malignancies such as chronic myeloid leukemia. For structured curation, using 'FAP1' without clarifying context is incorrect. If referring to the cancer/fibroblast/serine protease context, 'Fibroblast activation protein alpha (FAP)' should be used. If referring to apoptosis signaling/tyrosine phosphatase context, 'Fas-associated phosphatase 1 (PTPN13)' should be used.

Other names

FAPFAP-alphasepraseprolyl endopeptidase FAPfibroblast activation proteinF19 antigenfibroblast activation protein-1PTPL1PTPN13

Inhibition of Fibroblast activation protein alpha blocks extracellular matrix degradation, tumor cell invasion, and immune suppression, and can be exploited for targeted delivery/toxicity within tumor stroma. Inhibition of Fas-associated phosphatase 1 restores Fas-driven apoptosis, can decrease β-catenin activity, potentially sensitizing tumor cells to therapy.