We have established a monoclonal antibody K114 (mAbK114) against hamster keratinocytes. The mAbK114 recognizes a 50-95 kDa cell-surface protein that is expressed restrictedly in the dermal sheath cells near the bulge area of the hair follicle and in the differentiated sebocytes of the normal adult hamster skin. Upon being cultured in vitro, however, the keratinocytes strongly and transiently expressed this novel K114 antigen (AgK114) in spite of low expression level of AgK114 by the freshly prepared keratinocytes. The cDNA of AgK114 was isolated by expression cloning using mAbK114. Sequence analysis revealed that it had 242 amino acid residues with a signal peptide at the N terminus, potential six N-glycosylation sites, a characteristic repetitive threonine rich domain, and a possible glycosylphosphatidylinositol (GPI) anchoring site near the C terminus. We examined various conditions in which expression of AgK114 was enhanced in vivo. Interestingly, AgK114 molecule was expressed accompanying tissue damages of the skin. It was transiently induced in basal epidermal keratinocytes after UV exposure. In addition, AgK114 was also induced in elongating edge epidermal keratinocytes during tissue regeneration after an excised wounding. These results suggest that AgK114 is involved in the recovering process from injury.