title: Baseline and stimulated turnover of cell surface c-Kit expression in different types of human mast cells.
abstract: The receptor tyrosine kinase c-Kit is fundamental to mast cell (MC) development and maintenance. Its regulation can occur at various levels, but nothing is known about how this is accomplished in normal human tissue MC. Likewise, the baseline turnover of c-Kit has not been addressed yet. We used mature MC from human skin, along with the MC lines LAD-2 and HMC-1 and treated them with stem cell factor (SCF), cycloheximide, actinomycin D (AD) and combinations thereof, and determined expression levels of c-Kit and other surface receptors by flow cytometry. Ligand-induced internalization of c-Kit was found to be a universal mechanism and detectable in all MC subtypes. By Western blot analysis of LAD-2 cells, c-Kit was found to nearly disappear 3 h after the addition of SCF to slowly recover thereafter. Investigations into the baseline turnover of c-Kit expression revealed that c-Kit is strongly affected by the inhibition of de novo translation in all MC subsets, while a suppression of transcription had a weaker effect and displayed greater cell-to-cell variation. Only a minor impact on other cell surface receptors (CD29, CD50 and CD54) was noted. On combined treatment, cycloheximide, AD and SCF displayed additive effects, resulting in a complete disappearance of c-Kit from the cell surface. In conclusion, c-Kit represents a rapidly cycling cell surface receptor. It is not only immediately internalized upon binding of its ligand, but it is also heavily affected by the inhibition of translation or transcription when viewed against an average background. Interestingly, c-Kit regulation seems largely independent of the MC subtype.
authors.affiliation: Department of Dermatology and Allergy, Universitätsmedizin Berlin, Berlin, Germany. magda.babina@charite.de
authors.forename: Magda
authors.initials: M
authors.lastname: Babina
authors.forename: Claudia
authors.initials: C
authors.lastname: Rex
authors.forename: Sven
authors.initials: S
authors.lastname: Guhl
authors.forename: Friedrich
authors.initials: F
authors.lastname: Thienemann
authors.forename: Metin
authors.initials: M
authors.lastname: Artuc
authors.forename: Beate M
authors.initials: BM
authors.lastname: Henz
authors.forename: Torsten
authors.initials: T
authors.lastname: Zuberbier
mesh_terms: D015703:Antigens, CD / Q000378:metabolism; D001549:Benzamides; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D004705:Endocytosis / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D000068877:Imatinib Mesylate; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D019089:Stem Cell Factor / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D001549:Benzamides; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D019089:Stem Cell Factor; D003609:Dactinomycin; D000068877:Imatinib Mesylate; D003513:Cycloheximide; D019009:Proto-Oncogene Proteins c-kit; D013755:Tetradecanoylphorbol Acetate