Neuregulin-1/Heregulin-b1, human recombinant (rHuNRG1-B1)

Recombinant human Neuregulin-1/Heregulin-b1 produced in E. coli is a single, non-glycosylated, polypeptide chain containing 65 amino acids (177-241) and having a total molecular mass of 7.5 kDa. Neuregulin/Heregulin is a family of structurally related polypeptide growth factors which are stemmed from alternatively spliced genes (NRG1, NRG2, NRG3 and NRG4). Thus far, there are more than 14 soluble and transmembrane proteins derived from the NRG1 gene. Proteolytic processing of the extracellular domain of the transmembrane NRG1 isoforms release soluble growth factors. HRG1-b1 is comprised of an Ig domain and an EGF-like domain which is necessary for direct binding to receptor tyrosine kinases erb3 and erb4. This binding stimulates erb3 and erb4 heterodimerization with erb2, promoting intrinsic kinase activity, which results in tyrosine phosphorylation. Even though HRG1-b1 biological effects are still unclear, it has been discovered to advance motility and invasiveness of breast cancer cells which in addition might entail up-regulation of expression and function of the autocrine motility-promoting factor (AMF). The ED50 was determined by the dose-dependent stimulation of the proliferation of human MCF-7 cells is less than 0.5 ng/ml, corresponding to a specific activity of > 2.0 × 106 units/mg.