Collagen type XVII, identified as the 180-kDa bullous pemphigoid antigen or BP180, is a transmembrane protein forming a family with collagen type XIII. It is an important structural component of hemidesmosomes, complexes found in the dermal-epidermal basement membrane zone that mediate adhesion of keratinocytes to the underlying membrane (Franzke et al. 2005). The intracellular ligands of collagen XVII include Beta 4-integrins, plectin and BP230 in the hemidesmosomal plaque (Koster et al. 2003). Extracellular ligands include alpha 6-integrin and laminin-5 in anchoring filaments (Hopkinson et al. 1995, Tasanen et al. 2004). Mutations in the human collagen XVII gene COL17A1 lead to diminished epidermal adhesion and skin blistering in response to minimal shearing forces, a disorder called junctional epidermolysis bullosa (JEB).
A soluble ectodomain form of collagen type XVII referred to as LAD-1 is generated by proteolytic processing of the full length form (Hirako et al. 1988, Schäcke et al. 1998). Collagen XVII has a furin consensus sequence but is cleaved by proteinases of the ADAM family rather than furin convertases. ADAM-17 (TACE) appears to be the major physiologically-relevant sheddase for collagen XVII, though ADAM-9 and -10 may substitute (Franzke et al. 2002). These proteinases are activated by furin (Franzke et al. 2005).