Tetraspanins

The first tetraspanins were discovered on surface of human leucocytes, but it was rapidly demonstrated that they had a wider tissue expression. Twenty -six molecules display sufficient homology to belong to the same superfamil y. Their function is not precisely known, but data coming from biochemical studies or knockout mice suggest that they play a major role in membrane bi ology. One of their outstanding properties is their ability to form a netwo rk of multimolecular complexes, the 'tetraspanin web', in which integrins a re included. The structure of these complexes is under investigation, but s ome of the rules that govern their organization have already been unraveled . The challenge is to determine how the organization of the 'tetraspanin we b' modifies the function of its constitutive molecules and consequently inf luences cellular behaviour. The implications may be considerable for the un derstanding of basic cellular processes such as migration and also of disea ses related to loss or mutation of a single tetraspanin.