protein
Apoptosis inhibitor 5
aka API-5
Gene
API5
Organism
Homo sapiens(9606)
Length
524 aa
Mass
59,005 Da
API5 (Apoptosis Inhibitor 5) is a 524-amino acid antiapoptotic protein that functions as a negative regulator of apoptosis through inhibition of ACIN1-mediated DNA fragmentation and suppression of E2F1-induced cell death (UniProt: Q9BZZ5). The protein plays a role in protein assembly and can enhance the cytotoxic effects of chemotherapeutic drugs when depleted, suggesting it acts as a cellular survival factor under stress conditions.
API5 is implicated in Alzheimer's Disease pathology. In post-mortem AD brain tissue compared to age-matched controls, API5 is significantly upregulated across subcellular fractions with a mean log2 fold-change of +0.626 (Chaparral AD proteomics). This upregulation was detected via TMT-labeled tandem mass spectrometry analysis across four subcellular fractions (P2, P3, S2, S3) in a discovery proteomics experiment. The increased expression of this antiapoptotic factor in AD brains may reflect a compensatory cellular response to neurodegeneration-associated stress or altered cell death signaling in the disease state.
Generated from the curated entity record below. May contain errors — verify against source links.
Proteomics Evidence · AD
↑ Up in ADP3
+0.847
P2
not detected
S2
not detected
S3
+0.405
Mean log₂FC across detected fractions: +0.626 (2 of 4 fractions detected)
Human post-mortem AD brain vs age-matched controls, TMT-labeled, 4 subcellular fractions (P2, P3, S2, S3), DDA proteomics.
Related Publications
Browse all →Tau molecular diversity contributes to clinical heterogeneity in Alzheimer's disease.
Dujardin Simon et al.Nature medicine2020PMID 32572268Deep Multilayer Brain Proteomics Identifies Molecular Networks in Alzheimer's Disease Progression.
Bai Bing et al.Neuron2020PMID 31926610A Multi-network Approach Identifies Protein-Specific Co-expression in Asymptomatic and Symptomatic Alzheimer's Disease.
Seyfried Nicholas T et al.Cell systems2017PMID 27989508Large-scale deep multi-layer analysis of Alzheimer's disease brain reveals strong proteomic disease-related changes not observed at the RNA level.
Johnson Erik C B et al.Nature neuroscience2022PMID 35115731Organization and regulation of gene transcription.
Cramer PatrickNature2019PMID 31462772
Function
Antiapoptotic factor that may have a role in protein assembly. Negatively regulates ACIN1. By binding to ACIN1, it suppresses ACIN1 cleavage from CASP3 and ACIN1-mediated DNA fragmentation. Also known to efficiently suppress E2F1-induced apoptosis. Its depletion enhances the cytotoxic action of the chemotherapeutic drugs
Sources
Last updated 5/8/2026, 6:31:39 AM