Platelet tropomyosin binding protein is identical with serum albumin

We have shown that the platelet tropomyosin binding protein described in the accompanying paper (Gerhard, M. D., DiGirolamo, P. M., and Hitchcock-DeGregori, S. E. (1985) J. Biol. Chem. 260, 3221-3227) is identical with human serum albumin. The immunological determinants are completely shared; the tryptic peptide maps are the same; the proteins comigrate on two-dimensional gels; and the amino acid sequences of the first 33 amino acids are the same. Although human serum albumin in plasma or commercially prepared protein will not bind tropomyosin-Affi-Gel 15, it will bind following purification from plasma by chromatography on hydroxylapatite.     

Development of membrane-potential responsiveness by myeloid leukemia cells during neutrophilic differentiation

The ability of a myeloid leukemia cell line (HL-60) to undergo membrane electrical potential changes was followed during neutrophilic differentiation induced by 2 compounds. Membrane-potential changes were induced with 12-O-tetradecanoylphorbol 13-acetate (TPA) or formyl-methionyl-leucyl-phenylalanine (FMLP) and were monitored by flow cytometry. The magnitude of the membrane-potential response to TPA increased in a more uniform manner as the population of cells matured than did acquisition of mature morphology or ability to undergo the respiratory burst in response to TPA. The response to TPA and FMLP of HL-60 cells, maximally induced to differentiate by dimethylsulfoxide, closely resembled that of neutrophils. Thus, HL-60 cells may be a useful tool in the study of the relation between membrane depolarization and subsequent cellular activation.