The tetraspan molecule CD151, a novel constituent of hemidesmosomes, associates with the integrin alpha 6 beta 4 and may regulate the spatial organization of hemidesmosomes

CD151 is a cell surface protein that belongs to the tetraspan superfamily. It associates with other tetraspan molecules and certain integrins to form large complexes at the cell surface. CD151 is expressed by a variety of epi thelia and mesenchymal cells. We demonstrate here that in human skin CD151 is codistributed with alpha 3 beta 1 and alpha 6 beta 4 at the basolateral surface of basal keratinocytes, Immunoelectron microscopy showed that CD151 is concentrated in hemidesmosomes. By immunoprecipitation from transfected K562 cells, we established that CD151 associates with alpha 3 beta 1 and a lpha 6 beta 4. In beta 4-deficient pyloric atresia associated with junction al epidermolysis bullosa (PA-JEB) keratinocytes, CD151 and alpha 3 beta 1 a re clustered together at the basal cell surface in association with patches of laminin-5. Focal adhesions are present at the periphery of these cluste rs, connected with actin filaments, and they contain both CD151 and alpha 3 beta 1. Transient transfection studies of PA-JEB cells with beta 4 reveale d that the integrin alpha 6 beta 4 becomes incorporated into the alpha 3 be ta 1-CD151 clusters where it induces the formation of hemidesmosomes. As a result, the amount of alpha 3 beta 1 in the clusters diminishes and the pro tein becomes restricted to the peripheral focal adhesions. Furthermore, CD1 51 becomes predominantly associated with alpha 6 beta 4 in hemidesmosomes, whereas its codistribution with alpha 3 beta 1 in focal adhesions becomes p artial. The localization of alpha 6 beta 4 in the pre-hemidesmosomal cluste rs is accompanied by a strong upregulation of CD151, which is at least part ly due to increased cell surface expression. Using beta 4 chimeras containi ng the extracellular and transmembrane domain of the IL-2 receptor and the cytoplasmic domain of beta 4, we found that for recruitment of CD151 into h emidesmosomes, the beta 4 subunit must be associated with alpha 6, confirmi ng that integrins associate with tetraspans via their or subunits. CD151 is the only tetraspan identified in hemidesmosomal structures. Others, such a s CD9 and CD81, remain diffusely distributed at the cell surface. In conclusion, we show that CD151 is a major component of (pre)-hemidesmoso mal structures and that its recruitment into hemidesmosomes is regulated by the integrin alpha 6 beta 4. We suggest that CD151 plays a role in the for mation and stability of hemidesmosomes by providing a framework for the spa tial organization of the different hemidesmosomal components.