Epsin 3 is a novel extracellular matrix-induced transcript specific to wounded epithelia

Using an in vitro model of keratinocyte activation by the extracellular mat rix following injury, we have identified epsin 3, a novel protein closely r elated to, but distinct from previously described epsins. Epsin 3 contains a domain structure common to this gene family, yet demonstrates novel diffe rences in its regulation and pattern of expression. Epsin 3 mRNA and protei n were undetectable in keratinocytes isolated from unwounded skin, but indu ced in cells following contact with fibrillar type I collagen. The native t riple helical structure of collagen was required to mediate this response a s cells failed to express epsin 3 when plated on gelatin. Consistent with t he reported function of other epsins, epsin 3 was evident in keratinocytes as punctate vesicles throughout the cytoplasm that partially co-localized w ith clathrin. In addition, epsin 3 exhibited nuclear accumulation when mr. clear export was inhibited. In contrast to other known epsins, epsin 3 was restricted to keratinocytes migrating across collagen and down-regulated fo llowing cell differentiation, suggesting that expression was spatially and temporally regulated. Indeed, epsin 3 was localized specifically to migrati ng keratinocytes in cutaneous wounds, but not found in intact skin. Intrigu ingly, Northern hybridization and reverse transcriptase-polymerase chain re action experiments indicated that epsin 3 expression was restricted to epit helial wounds or pathologies exhibiting altered cell-extracellular matrix i nteractions. Thus, we have identified a novel type I collagen-induced epsin that demonstrates structural and behavioral similarity to this gene family , yet exhibits restricted and regulated expression, suggesting that epsin 3 may serve an important function in activated epithelial cells during tissu e morphogenesis.