Transmembrane signaling: tumor promoter distribution

• Published in: Biochimica et biophysica acta Vol. 982; no. 2; pp. 237 - 244
• Main Authors: FISHER, K. A, YANAGIMOTO, K. C
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 10.07.1989; North-Holland
• Subjects: Biological and medical sciences; Cell membranes. Ionic channels. Membrane pores; Cell structures and functions; Cytosol - metabolism; Erythrocyte Membrane - drug effects; Erythrocyte Membrane - metabolism; Fundamental and applied biological sciences. Psychology; Humans; Lipid Bilayers - metabolism; Molecular and cellular biology; Pharmaceutical Vehicles; Phosphorylation; Protein Kinase C - physiology; Tetradecanoylphorbol Acetate - pharmacokinetics; Tetradecanoylphorbol Acetate - pharmacology; Human; Signal transduction; Blood cell; Protein kinase C; Enzyme; Transcription promoter; Tumor promotor; Plasma membrane; Red blood cell; Molecular interaction; Lipids; Localization
• ISSN: 0006-3002; 1878-2434
• DOI: 10.1016/0005-2736(89)90060-6

Diacylglycerol plays a critical role in transmembrane signaling by activating protein kinase C (PKC). The tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) mimics that action, and in the human erythrocyte, TPA-activated PKC phosphorylates membrane proteins. Although molecular aspects of this process have been investigated, details of the interaction of TPA with plasma membranes remain elusive. Because TPA is hydrophobic, it has been assumed that it associates with the lipid bilayer. However, there is no direct evidence for its transbilayer distribution. Because knowledge of its location would limit molecular models proposed to explain its mode of action, we have used membrane-splitting techniques, based on freeze-fracture of planar cell monolayers, to quantify transmembrane partitioning of [3H]TPA. Under conditions where PKC-mediated phosphorylation was stimulated by [3H]TPA and where more than 90% of the [3H]TPA was associated with the human red cell plasma membrane, two-thirds of the TPA partitioned with the cytoplasmic leaflet after bilayer splitting. This represents the first direct topographic localization of TPA in a biological membrane and supports the hypothesis that the mechanism of TPA activation requires its association with the cytoplasmic leaflet of the bilayer.