FKBP1A (FK506 binding protein 1A) is a peptidyl-prolyl cis-trans isomerase that primarily functions as a negative regulator of transforming growth factor-beta (TGF-β) and activin receptor signaling. It maintains TGFBR1 in an inactive conformation and recruits SMAD7 to prevent SMAD2/3 association with activin receptors, thereby suppressing TGF-β pathway activation [PMID:UniProt]. Beyond its canonical immunosuppressive role as a rapamycin target in mTORC1 regulation 1, FKBP1A has emerged as a multifunctional protein with broader physiological importance. During cardiac development, FKBP1A negatively regulates Notch1 signaling in endothelial cells to control ventricular trabeculation and compaction; its loss causes hypertrabeculation and noncompaction 2. In the liver, FKBP1A protects against sepsis-induced acute injury by inhibiting endoplasmic reticulum stress through suppression of the NOTCH1/AK2 pathway 3. FKBP1A plays a critical role in pluripotency, with its upregulation essential for efficient reprogramming to naive pluripotent stem cells 4. In disease contexts, FKBP1A upregulation correlates with poor prognosis in head and neck squamous cell carcinoma and is associated with increased metastatic potential 5. Conversely, in glioblastoma, FKBP1A elevation promotes cell death through apoptotic pathways 6. FKBP1A knockout confers resistance to immunosuppressants while maintaining CAR-T cell functionality, enabling improved allogeneic cell therapy 7. In Huntington disease, FKBP5 (related family member) reduction enhances mutant huntingtin clearance through autophagy 8.