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Degradation, Recycling, and Shedding of Trypanosoma brucei Variant Surface Glycoprotein
Author(s) -
SEYFANG ANDREAS,
MECKE DIETER,
DUSZENKO MICHAEL
Publication year - 1990
Publication title -
the journal of protozoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 0022-3921
DOI - 10.1111/j.1550-7408.1990.tb01263.x
Subject(s) - trypanosoma brucei , antigenic variation , endocytosis , biology , glycoprotein , antigen , microbiology and biotechnology , membrane glycoproteins , incubation , biochemistry , gene , genetics , cell
.Trypanosoma brucei bloodstream forms express a densely packed surface coat consisting of identical variant surface glycoprotein (VSG) molecules. This surface coat is subject to antigenic variation by sequential expression of different VSG genes and thus enables the cells to escape the mammalian host's specific immune response. VSG turnover was investigated and compared with the antigen switching rate. Living cells were radiochemically labeled with either 125 I‐Bolton‐Hunter reagent or 35 S‐methionine, and immunogold‐surface labeled for electron microscopy studies. The fate of labeled VSG was studied during subsequent incubation or cultivation of labeled trypanosomes. Our data show that living cells slowly released VSG into the medium with a shedding rate of 2.2 ± 0.6% h −1 (t 1/2 = 33 ± 9 h). In contrast, VSG degradation accounted for only 0.3 ± 0.06% h −1 (t 1/2 = 237 ± 45 h) and followed the classical lysosomal pathway as judged by electron microscopy. Since VSG uptake by endocytosis was rather high, our data suggest that most of the endocytosed VSG was recycled to the surface membrane. These results indicate that shedding of VSG at a regular turnover rate is sufficient to remove the old VSG coat within one week, and no increase of the VSG turnover rate seems to be necessary during antigenic variation.