function:May be involved in macrophage-mediated cellular proliferation. It is mitogenic for fibroblasts and smooth muscle but not endothelial cells. It is able to bind EGF receptors with higher affinity than EGF itself and is a far more potent mitogen for smooth muscle cells than EGF. Also acts as a diphtheria toxin receptor.,PTM:O-linked glycan attachment sites were determined by Edman degradation, O-glycanase digest suggests mucin-type glycosylation (done in HB-EGF purified from histiocytic lymphoma cell line U-937).,PTM:Several N-termini have been identified by direct sequencing. The forms with N-termini 63, 73 and 74 have been tested and found to be biologically active.,similarity:Contains 1 EGF-like domain.,subcellular location:Mature HB-EGF is released into the extracellular space and probably binds to a receptor.,