Anthrax toxin receptor 1 (ANTXR1), also known as Tumor endothelial marker 8 (TEM8), is a glycoprotein of the Anthrax Toxin Receptor family that is expressed by endothelial cells. Anthrax toxin receptor 1 contains a 289 amino acid (aa) extracellular domain, a 21 aa transmembrane domain, and a 222 aa cytoplasmic domain. Type I transmembrane isoforms of 564 aa (80‑85 kDa) and 368 aa (60 kDa) and potentially secreted isoforms of 330 aa and 297 aa (45 kDa) are differentially expressed. All diverge at the C-terminal end but share the N-terminal extracellular domain . The extracellular domain shares structural similarity with von Willebrand factor type (vWFA) domains, which are characterized by their interactions with ECM components. The extracellular domain is involved in reorganization of cell actin cytoskeleton . Anthrax Receptor 1 binds Anthrax Protective Antigen with lesser affinity that Anthrax Receptor 2 and induces toxin internalization . Anthrax toxin receptor 1 has been implicated in tumor angiogenesis, as its expression has been shown to up-regulate in tumor blood vessels and is characterized as a tumor endothelial marker . ANTXR-1 was reported to be an amplifier of Wnt signaling in tumor microenvironment . Additionally, Anthrax toxin receptor 1 serves as the receptor for Seneca Valley virus, an oncolytic picornavirus affecting neuroendocrine cancers . Human ANTXR1 shares 99% aa identity with mouse and rat and 92% identity with dog and chick ANTXR1 within the extracellular domain.
