Signal transducer and activator of transcription 2

STAT2 (Signal Transducer and Activator of Transcription 2) is a transcription factor that mediates cellular responses to type I interferons (IFN-α and IFN-β) (UniProt: P52630). Upon IFN binding, STAT2 is phosphorylated by JAK kinases, dimerizes with STAT1, and associates with IRF9 to form the ISGF3 transcription factor complex that activates interferon-stimulated genes driving antiviral immunity. STAT2 also negatively regulates type I interferon signaling and modulates mitochondrial fission through DNM1L phosphorylation regulation (UniProt: P52630).

STAT2 is implicated in immune defense and developmental pathways. Genetic variants are associated with immunodeficiency disorders, including Immunodeficiency 44 (autosomal recessive, presenting with viral susceptibility and encephalopathy risk) and Pseudo-TORCH syndrome 3 (characterized by developmental delay, multisystemic involvement, and progressive intracranial calcifications) (UniProt: P52630).

In Alzheimer's disease, STAT2 is significantly down-regulated in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics; mean log2FC = −0.31). This downregulation may reflect diminished type I interferon signaling and impaired antiviral immune responses in the AD brain microenvironment.