CD82 is a 45-90 kD type III tetraspan membrane protein which is encoded by the KAI1 gene. CD82 forms a complex with CD37, CD53, CD81, ECM and MHC molecules. CD82 is a member of the tetraspanin family of proteins, which are evolutionarily conserved proteins present in most eukaryotes and function in many aspects of cell physiology as mediators of cell adhesion, membrane trafficking, and cell signaling (1). One of the most distinct features of tetraspanins is their ability to associate in cis with other tetraspanins, integrins, members of the immunoglobulin superfamily of cell adhesion molecules, and signaling receptors, thereby forming tetraspanin-enriched microdomains (1,2). Expression of this gene has been shown to be downregulated in tumor progression of human cancers and can be activated by p53 through a consensus binding sequence in the promoter. Its expression and that of p53 are strongly correlated, and the loss of expression of these two proteins is associated with poor survival for prostate cancer patients. Two alternatively spliced transcript variants encoding distinct isoforms have been found for this gene.

1. Charrin S, le Naour F, Silvie O, Milhiet PE, Boucheix C, Rubinstein E. Lateral organization of membrane proteins: tetraspanins spin their web. Biochem J. 2009;420:133–154.
2. Hemler ME. Targeting of tetraspanin proteins—potential benefits and strategies. Nat Rev Drug Discov. 2008;7:747–758.