The function of ENSG00000085982 (USP40, ubiquitin specific peptidase 40) is as follows. Deubiquitinating enzyme that plays a key role in maintaining endothelial cell (EC) barrier integrity and regulating apoptosis and inflammation. Stabilizes Claudin-1/CLDN1 by cleaving its polyubiquitin chains, thereby protecting tight junction structure (PubMed:38308285). Prevents EC barrier disruption by inhibiting RhoA activation and reducing phosphorylation of myosin light chain and cofilin. Suppresses EC inflammation by inhibiting NF-kappa-B activation, decreasing ICAM1 expression, and reducing leukocyte adhesion to ECs (PubMed:38307937). Mediates these protective effects in part via deubiquitination and inactivation of heat shock protein 90-beta/HSP90AB1 (PubMed:38307937). Targets CFLAR for 'Lys-48'-linked deubiquitination, stabilizing its protein levels. This interaction is facilitated by the adapter protein GMEB1, which enhances USP40-CFLAR binding. Through CFLAR stabilization, USP40 inhibits pro-caspase-8 activation and protects against apoptosis (PubMed:31046799). Additionally, USP40 stabilizes HINT1, an activator of p53/TP53, thereby maintaining p53/TP53 levels and sustaining the HINT1-p53/TP53 axis (By similarity). {ECO:0000250|UniProtKB:Q8BWR4, ECO:0000269|PubMed:31046799, ECO:0000269|PubMed:38307937, ECO:0000269|PubMed:38308285}.