Claudin 3 protein is a tight junction protein with a molecular weight of approximately 22 kDa. Tight junctions are important membrane-associated complexes between adjacent cells, and Claudin proteins form the main backbone of these structures. Along with other Claudin proteins, Claudin-3 protein stabilizes the structure of intercellular junctions by interacting with each other. It helps maintain the stability of cell gaps and facilitates transmembrane transport/enrichment functions. Claudin-3 protein can also alter the permeability of intercellular junctions, controlling the passage of substances. Claudin-3 protein is often overexpressed in certain cancers, such as ovarian cancer and breast cancer. This increased expression level is associated with the enhancement of tumor cell invasiveness and vitality. Therefore, Claudin-3 may become a target for the treatment of prostate cancer and other malignancies. In cell susceptibility and demyelinating anatomical phenotypes, inhibition of Claudin-3 expression is associated with neurotoxicity.