- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- Analysis and expression of Leishmania surface proteinase...
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
Analysis and expression of Leishmania surface proteinase and glycoproteins Macdonald, Mary Helen
Abstract
Leishmania is a protozoan parasite transmitted by a sandfly vector to humans and other mammalian hosts causing chronic infection. Leishmania exists in two distinct life stages: the promastigote which replicates in the insect gut, and the amastigote which replicates in macrophage cells of the mammalian host. There is considerable evidence that Leishmania cell surface molecules play critical roles in the initiation and establishment of macrophage infection, evasion of non-specific immune defenses, and in stimulation of a cellular and humoral immune response. Relative to promastigotes, the amastigote cell surface is largely uncharacterized. The major surface glycoprotein of Leishmania promastigotes, referred to as GP63, is a zinc metalloproteinase of 63,000 Mr containing a glycosyiphosphatidylinositol (GPI) membrane anchor. GP63 has been predicted to be synthesized as a 602 amino acid precursor protein containing an NH₂-terminal leader sequence of 39 amino acids, a putative regulatory pro region of 61 amino acids, the mature protein of 477 amino acids, and a C00H-terminal GPI attachment signal sequence of 25 amino acids. Recent studies demonstrated that recombinant GP63 (rGP63) expressed by the baculovirus insect cell system was secreted as a glycosylated latent proteinase that required activation for full proteinase activity (Button,L.L. et al. Gene 134:75-81, 1993). The overall objectives of this study were to determine the activation mechanism of recombinant GP63 (rGP63), using both secreted and cell surface expression systems, and to identify novel glycoproteins expressed on the surface of L. mexicana amastigotes. The activation of secreted latent rGP63 (rGP63s) was found to be consistent with the cysteine switch mechanism described for mammalian matrix metalloproteinases. NH₂- terminal sequence analysis revealed that activation of rGP63s with HgCl₂ resulted in progressive autolytic removal of the predicted pro region, ultimately generating the mature NH₂-terminus. This processing included the removal of a conserved Cys residue (Cys-48) and occurred by a cis mechanism since the addition of previously activated rGP63s did not lead to an enhancement of latent rGP63s proteinase activation. rGP63s expressed in COS- 7 cells was also secreted as a latent proteinase and appeared to be activated by the same mechanism. rGP63 expressed on the surface of COS-7 cells as either a GPI-linked protein (rGP63gpi) or as a transmembrane fusion protein (rGP63tm) was produced as an active proteinase without the requirement for activation with HgCl₂ Expression of GP63 as an active proteinase, therefore, is not linked specifically to the GPI pathway and does not require a factor or microenvironment unique to Leishmania. The potential of glycoprotein purification to enrich for cell surface proteins was exploited in a search to identify novel amastigote surface molecules. The strategy was to isolate candidate glycoproteins, by lectin affinity chromatography and SDS-PAGE, for NH₂-terminal amino acid sequence analysis in order to design oligonucleotide probes to isolate a corresponding cDNA clone. The most abundant glycoproteins were identified by NH₂-terminal sequence analysis as Cys proteinases, GP63, and fragments thereof. Of 12 sequences obtained, 5 appeared to be unique and provide a basis for further studies to isolate the corresponding genes.
Item Metadata
Title |
Analysis and expression of Leishmania surface proteinase and glycoproteins
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
1995
|
Description |
Leishmania is a protozoan parasite transmitted by a sandfly vector to humans and
other mammalian hosts causing chronic infection. Leishmania exists in two distinct life
stages: the promastigote which replicates in the insect gut, and the amastigote which
replicates in macrophage cells of the mammalian host. There is considerable evidence that
Leishmania cell surface molecules play critical roles in the initiation and establishment of
macrophage infection, evasion of non-specific immune defenses, and in stimulation of a
cellular and humoral immune response. Relative to promastigotes, the amastigote cell
surface is largely uncharacterized. The major surface glycoprotein of Leishmania
promastigotes, referred to as GP63, is a zinc metalloproteinase of 63,000 Mr containing a
glycosyiphosphatidylinositol (GPI) membrane anchor. GP63 has been predicted to be
synthesized as a 602 amino acid precursor protein containing an NH₂-terminal leader
sequence of 39 amino acids, a putative regulatory pro region of 61 amino acids, the mature
protein of 477 amino acids, and a C00H-terminal GPI attachment signal sequence of 25
amino acids. Recent studies demonstrated that recombinant GP63 (rGP63) expressed by
the baculovirus insect cell system was secreted as a glycosylated latent proteinase that
required activation for full proteinase activity (Button,L.L. et al. Gene 134:75-81, 1993).
The overall objectives of this study were to determine the activation mechanism of
recombinant GP63 (rGP63), using both secreted and cell surface expression systems, and
to identify novel glycoproteins expressed on the surface of L. mexicana amastigotes.
The activation of secreted latent rGP63 (rGP63s) was found to be consistent with
the cysteine switch mechanism described for mammalian matrix metalloproteinases. NH₂-
terminal sequence analysis revealed that activation of rGP63s with HgCl₂ resulted in
progressive autolytic removal of the predicted pro region, ultimately generating the mature
NH₂-terminus. This processing included the removal of a conserved Cys residue (Cys-48)
and occurred by a cis mechanism since the addition of previously activated rGP63s did not
lead to an enhancement of latent rGP63s proteinase activation. rGP63s expressed in COS-
7 cells was also secreted as a latent proteinase and appeared to be activated by the same
mechanism. rGP63 expressed on the surface of COS-7 cells as either a GPI-linked protein
(rGP63gpi) or as a transmembrane fusion protein (rGP63tm) was produced as an active
proteinase without the requirement for activation with HgCl₂ Expression of GP63 as an
active proteinase, therefore, is not linked specifically to the GPI pathway and does not
require a factor or microenvironment unique to Leishmania.
The potential of glycoprotein purification to enrich for cell surface proteins was exploited in
a search to identify novel amastigote surface molecules. The strategy was to isolate candidate
glycoproteins, by lectin affinity chromatography and SDS-PAGE, for NH₂-terminal amino acid
sequence analysis in order to design oligonucleotide probes to isolate a corresponding cDNA
clone. The most abundant glycoproteins were identified by NH₂-terminal sequence analysis as
Cys proteinases, GP63, and fragments thereof. Of 12 sequences obtained, 5 appeared to be
unique and provide a basis for further studies to isolate the corresponding genes.
|
Extent |
4808546 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-06-09
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
|
DOI |
10.14288/1.0088874
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
1995-05
|
Campus | |
Scholarly Level |
Graduate
|
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.