Component of intercellular desmosome junctions. Involved in the interaction of plaque proteins and intermediate filaments mediating cell-cell adhesion.Defects in DSG1 are the cause of palmoplantar keratoderma striate type 1 (SPPK1) [MIM:148700]; also known as keratosis palmoplantaris striata I. SPPK1 is a dermatoligical disorder characterized by thickening of the skin on the palms and soles, and longitudinal hyperkeratotic lesions on the palms, running the length of each finger.