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Procyclins and free GPIs are not required for the survival of procyclic form Trypanosoma brucei
Author(s) -
Guther Lucia Sampaio,
Ferguson Michael Anthony
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a514-a
Subject(s) - trypanosoma brucei , biology , biochemistry , gene
Glycosylphosphatidylinositol (GPI) anchors are essential for the survival of bloodstream form Trypanosoma brucei , but not procyclic form T.brucei . The procyclic cell surface is dominated by about 3x10 6 procyclin molecules, each of which has an average of about 10 LacNAc units attached to the GPI anchor, and about 1x10 6 free GPIs that contain about 4 LacNAc units. Procyclin‐free mutants of procyclic form T.brucei have been generated previously by deleting procyclin genes and by disrupting late‐stage GPI biosynthesis. In all cases the procyclins were replaced by an increase in free GPIs. These data suggest that, in the absence of procyclins, free LacNAc‐containing GPIs might compensate for surface occupancy. On the other hand, galactose‐starvation (using a conditional null mutant of UDP‐Glc 4′ epimerase) causes 10‐fold up‐regulation in (LacNAc‐free) procyclin expression but this fails to compensate for the global loss of surface LacNAc expression and growth ceases. Based on these observations, we expected that a block in an early step in GPI biosynthesis (one that would prevent GPI anchoring of procyclin and the expression of LacNAc‐containing free GPIs) would be lethal. However, we were able to generate null mutants of TbGPI12 , the gene that encodes the enzyme that catalyses the second step in GPI biosynthesis. Analysis of these cell suggests that they are devoid of procyclins and free GPIs. We suggest that procyclins and free GPI glycolipids are not essential for the growth of procyclic form T. brucei in culture. Work is in progress to identify molecules that might have taken the place of procyclins and free GPIs in these mutants.