Chemically synthesized SDF-1 alpha analogue, N33A, is a potent chemotactic agent for CXCR4/Fusin/LESTR-expressing human leukocytes

Stromal cell-derived factor (SDF) 1 is a potent chemoattractant for leukocytes through activation of the receptor CXCR4/Fusin/LESTR, which is a fusion co-factor for the entry of T lymphocytotropic human immunodeficiency virus type 1 (HIV-1), This CXCR4-mediated HIV-1 fusion can be inhibited by SDF-1, Because of its importance in the study of immunity and AIDS, large scale production of SDF-1 is desirable, In addition to recombinant technology, chemical synthesis provides means by which biologically active proteins can be produced not only in large quantity but also with a variety of designed modifications, In this study, we investigated the binding and function of an SDF-1 alpha analogue, N33A, synthesized by a newly developed native chemical ligation approach, Radioiodinated N33A showed high affinity binding to human monocytes, T lymphocytes, as well as neutrophils, and competed equally well with native recombinant SDF-1 alpha for binding sites on leukocytes. N33A also showed equally potent chemoattractant activity as native recombinant SDF-1 alpha for human leukocytes. Further study with CXCR4/Fusin/LESTR transfected HEK 293 cells showed that N33A binds and induces directional migration of these cells in vitro. These results demonstrate that the chemically synthesized SDF-1 alpha analogue, N33A, which can be produced rapidly in large quantity, possesses the same capacity as native SDF-1 alpha to activate CXCR4-expressing cells and will provide a valuable agent for research on the host immune response and AIDS.