Cytoglobin (CYGB)

Cytoglobin is a recently discovered heme-containing globin protein predominantly found in fibroblast-like cells across numerous tissues. It has a classic globin alpha-helical structure and binds oxygen with an affinity similar to myoglobin, but exhibits wider tissue distribution and multiple alternative biological roles. Cytoglobin functions as a superoxide dismutase—unique among globins—effectively eliminating superoxide and contributing to cellular defense against oxidative stress. It also acts as a nitric oxide dioxygenase, participating in NO metabolism and redox signaling. Cytoglobin’s molecular switch (redox-sensitive cysteine residues forming disulfide bonds) enables dynamic regulation of oxygen affinity and ROS management. In cancer, cytoglobin correlates with aggressive phenotypes and mediates resistance to apoptosis triggered by chemotherapy (cisplatin, etoposide, doxorubicin), mainly by diminishing ROS and inhibiting p53 degradation. Elevated cytoglobin is linked to hepatic and kidney fibrosis via roles in stellate cell activation, and may protect against vascular and muscle injury. Overall, cytoglobin’s complex physiological functions, protective effects in stress and disease, involvement in cancer resistance, and potential impact on fibrosis and cardiovascular injury have made it a molecule of increasing interest as a therapeutic target and biomarker.

Other names

Stellate cell activation-associated proteinSTAPHistoglobinHGBNitric oxygen dioxygenase CYGBNODNitrite reductase CYGBPseudoperoxidase CYGBSuperoxide dismutase CYGB

Cytoglobin protects against cisplatin-induced apoptosis in cancer cells, provides protection against etoposide-induced apoptosis in myoblasts, and offers protection in osteosarcoma cells against doxorubicin. Its mechanisms include protection from ROS-mediated cellular damage through enzymatic dismutation of superoxide, NO dioxygenase activity—removing NO by converting it to nitrate, lipid peroxidase function—modulating cell signaling via lipid oxidation, inhibition of p53 ubiquitination—stabilizing p53 to resist apoptosis during chemotherapy, and redox regulation via cysteine disulfide bond formation—switching between conformational states that regulate oxygen and ROS affinity. No direct small-molecule inhibitors/activators are described; it primarily interacts through cytoprotective mechanisms rather than direct targeting by drugs.