title: Increased growth promoting but not mast cell degranulation potential of a covalent dimer of c-Kit ligand.
abstract: The native form of soluble c-kit ligand (KL) is a noncovalent dimer. We have isolated a soluble, disulfide-linked dimer of murine KL (KL-CD) by expressing KL in Escherichia coli and refolding the denatured protein under conditions that promote the formation of both noncovalent dimers (KL-NC) and KL-CD. KL-CD exhibits a 10- to 15-fold increase in the ability to stimulate the growth of both the human megakaryocytic cell line MO7e and murine bone marrow-derived mast cells relative to KL-NC. Colony-forming assays of murine bone marrow progenitor cells also reflected this increased potency. However, KL-CD and KL-NC are equally able to prime mast cells for enhanced IgE-dependent degranulation in vitro and activate mast cells in vivo. Improving the growth-promoting activity of KL without changing its mast cell activation potential suggests that KL-CD or a related molecule could be administered in the clinic at doses that stimulate hematopoietic recovery while avoiding significant mast cell activation.
authors.affiliation: CytoMed Inc, Cambridge, MA 02139, USA.
authors.forename: K H
authors.initials: KH
authors.lastname: Nocka
authors.forename: B A
authors.initials: BA
authors.lastname: Levine
authors.forename: J L
authors.initials: JL
authors.lastname: Ko
authors.forename: P M
authors.initials: PM
authors.lastname: Burch
authors.forename: B E
authors.initials: BE
authors.lastname: Landgraf
authors.forename: R
authors.initials: R
authors.lastname: Segal
authors.forename: R
authors.initials: R
authors.lastname: Lobell
mesh_terms: D000818:Animals; D015550:Cell Degranulation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D019281:Dimerization; D004926:Escherichia coli; D006801:Humans; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008533:Megakaryocytes / Q000187:drug effects* / Q000473:pathology; D051379:Mice; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry / Q000494:pharmacology; D019089:Stem Cell Factor / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D011994:Recombinant Proteins; D019089:Stem Cell Factor