Collagen XVII, also known as COL17 or BP180, is a transmembrane protein that plays a crucial role in maintaining the adhesion between the epidermis and the basement membrane in the skin. It is a component of hemidesmosomes, which are multiprotein complexes that mediate the adhesion of keratinocytes to the underlying membrane. It is involved in cell-cell adhesion and signaling, particularly in immune cell transmigration and angiogenesis. The extracellular domain of COL17 can be physiologically cleaved from the cell surface by ADAM family proteins in a process known as ectodomain shedding, which is thought to be associated with the migration and proliferation of keratinocytes. The C-terminal cleavage of COL17 may be associated with basement membrane formation. Collagen XVII is involved in skin homeostasis, aging, and wound repair. It mediates the interactions of stem cells with surrounding cells and the matrix to regulate these processes. Changes in COL17 expression and function are associated with skin aging, as it affects the balance of symmetric and asymmetric cell divisions in epidermal stem cells. COL17 has also been implicated in skin cancers, such as squamous cell carcinoma, basal cell carcinoma, and malignant melanocytic tumors.