Type XVII collagen is a component of hemidesmosomes (HDs) (Has & Kern 2010). It associates with integrin alpha6beta4 (a6b4) (Hopkinson et al. 1999). The extracellular region of a6b4 extends from the cell membrane into the basement membrane to bind laminins, with a preference for laminin-332 (Hopkinson & Jones 2000, Sugawara et al. 2008), which is a component of anchoring fibrils. Laminins are complex glycoproteins, consisting of alpha, beta and gamma chains bound into a cross-shaped molecule. Laminin-332 is a complex of alpha-3, beta-2 and gamma-2 subunits. The cytoplasmic domain of integrin beta-4 interacts with other hemidesmosomal components, plectrin and BPAG1. The interaction of a6b4 and plectrin is likely to be the initial step in HD formation (de Pereda et al. 2009). The cytoplasmic domain of collagen type XVII (BP180) binds to integrin beta-4, plectin and BPAG1 (Hopkinson & Jones 2000, Koster et al. 2003). The transmembrane protein CD151 (tetraspanin-24) associates with a6b4 (Sterk et al. 2002) and is essential for the correct assembly of basement membranes in human kidney and skin, possibly having a role in integrin alpha-3 maturation and cell surface expression (Karamatic Crew et al. 2003).