Procyclin gene expression and loss of the variant surface glycoprotein during differentiation of Trypanosoma brucei

• Published in: The Journal of cell biology 1989-02, Vol.108 (2), p.737-746
• Main Authors: Roditi, I, Schwarz, H, Pearson, T.W, Beecroft, R.P, Liu, M.K, Richardson, J.P, Buhring, H.J, Pleiss, J, Bulow, R, Williams, R.O, Overath, P
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Antibodies; Biological and medical sciences; Bloodstream forms; Cell Differentiation; Cell membranes; DIFERENCIACION; DIFFERENCIATION; DIFFERENTIATION; DNA Probes; Electrophoresis, Polyacrylamide Gel; Flow Cytometry; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Gels; GENE; Gene expression; Gene Expression Regulation; GENES; GLICOPROTEINAS; GLYCOPROTEINE; GLYCOPROTEINS; Kinetics; Membrane glycoproteins; Messenger RNA; Microscopy; Microscopy, Electron; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Molecular Structure; Nucleic Acid Hybridization; Procyclic forms; Protein Conformation; RNA; RNA, Messenger - biosynthesis; TRYPANOSOMA; Trypanosoma brucei; Trypanosoma brucei brucei - genetics; Trypanosoma brucei brucei - growth & development; Trypanosoma brucei brucei - metabolism; Trypanosome; Variant Surface Glycoproteins, Trypanosoma - metabolism
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.108.2.737

In the mammalian host, the unicellular flagellate Trypanosoma brucei is covered by a dense surface coat that consists of a single species of macro-molecule, the membrane form of the variant surface glycoprotein (mfVSG). After uptake by the insect vector, the tsetse fly, bloodstream-form trypanosomes differentiate to procyclic forms in the fly midgut. Differentiation is characterized by the loss of the mfVSG coat and the acquisition of a new surface glycoprotein, procyclin. In this study, the change in surface glycoprotein composition during differentiation was investigated in vitro. After triggering differentiation, a rapid increase in procyclin-specific mRNA was observed. In contrast, there was a lag of several hours before procyclin could be detected. Procyclin was incorporated and uniformly distributed in the surface coat. The VSG coat was subsequently shed. For a single cell, it took 12-16 h to express a maximum level of procyclin at the surface while the loss of the VSG coat required ∼4 h. The data are discussed in terms of the possible molecular arrangement of mfVSG and procyclin at the cell surface. Molecular modeling data suggest that a (Asp-Pro)2 (Glu-Pro)22-29 repeat in procyclin assumes a cylindrical shape 14-18 nm in length and 0.9 nm in diameter. This extended shape would enable procyclin to interdigitate between the mfVSG molecules during differentiation, exposing epitopes beyond the 12-15-nm-thick VSG coat.