Description
Epigen is a member of the epidermal growth factor family and is expressed by several tissues, including the testis, liver, heart and in certain tumor cells. It is strongly mitogenic for fibroblasts and epithelial cells, despite its relatively weak affinity for its main receptor, ErbB1. The mitogenic potential of Epigen is enhanced by its unusually long persistence on the membrane before ubiquitylation and receptor-mediated depletion. The gene of human Epigen encodes a 154 amino acid (a.a.) residue type I transmembrane precursor glycoprotein which contains a 22 a.a. signal peptide, an 88 a.a. extracellular domain, a 21 a.a. transmembrane domain and a 23 a.a. cytoplasmic domain. By alternative splicing of the gene, Epigen has several isoforms. The mature, shed form of human Epigen (54 – 104a.a.) shares 92 %, 94 % and 94 % a.a. sequence identity with mouse, rat and equine Epigen, respectively