Protein c-Fos (c-Fos)

Protein c-Fos is a proto-oncogene-encoded transcription factor that, together with c-Jun, forms the heterodimeric Activator protein 1 (AP-1) complex. This complex is a key regulator of gene expression in response to a variety of extracellular signals, integrating cellular responses such as proliferation, differentiation, and survival. c-Fos is rapidly and transiently induced as an immediate early gene after cell stimulation. Structurally, c-Fos contains a basic leucine zipper (bZIP) domain enabling it to dimerize with Jun proteins and bind DNA at AP-1 regulatory elements, driving changes in gene expression. Dysregulation and persistent overexpression of c-Fos are implicated in tumorigenesis, metastasis, and inflammatory diseases. In addition to its nuclear genomic role, c-Fos also has a non-genomic function in the cytoplasm, where it can regulate lipid synthesis for membrane biogenesis. Small-molecule inhibitors such as T-5224 have been developed to block AP-1/c-Fos function, showing therapeutic potential in rheumatoid arthritis, cancer, and pain models.

Other names

Fos proto-oncogene proteinProto-oncogene c-FosFosFosB (related family)AP-1 (when referring to the c-Fos-containing Activator protein 1 complex)Activator protein 1 (AP-1, specifically when as c-Fos/c-Jun heterodimer)

Inhibition of c-Fos/AP-1 prevents transcriptional activation of genes involved in inflammation, extracellular matrix degradation (MMPs), and cytokine production (e.g., IL-1β). AP-1 inhibitors disrupt c-Fos/c-Jun dimerization or DNA binding, block target gene expression implicated in disease.