The function of CLDN9 (claudin 9, ENSG00000213937) is as follows. Plays a major role in tight junction-specific obliteration of the intercellular space, through calcium-independent cell-adhesion activity. . (Microbial infection) Acts as a receptor for hepatitis C virus (HCV) entry into hepatic cells. {ECO:0000269|PubMed:17804490, ECO:0000269|PubMed:20375010}.