9.B.329. The Resistin-like Molecule (RELM) Family
Vitamin A deficiency increases susceptibility to skin infection. Harris et al. 2019 showed that resistin-like molecule α (RELMα), a small secreted cysteine-rich protein, is expressed by epidermal keratinocytes and sebocytes and serves as an antimicrobial protein that is required for vitamin-A-dependent resistance to skin infection. RELMα is induced by microbiota colonization of the murine skin, is bactericidal in vitro, and protects against bacterial infection of the skin in vivo. RELMα expression requires dietary vitamin A and is induced by the therapeutic vitamin A analog isotretinoin, which protects against skin infection in a RELMα-dependent manner. The RELM family member Resistin was expressed in human skin, was induced by vitamin A analogs, and killed skin bacteria, indicating a conserved function for RELM proteins in skin innate immunity. These findings provide insight into how vitamin A promotes resistance to skin infection (Harris et al. 2019). This family may be distantly related to the Dermaseptin Family (1.C.52), and therefore part of the Cecropin Superfamily.