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Leishmania gp63 molecule implicated in cellular adhesion lacks an Arg-Gly-Asp sequence
R A Miller1, S G Reed, M Parsons
1Seattle Biomedical Research Institute, WA 98109.
Abstract:
The parasitic protozoa Leishmania are intracellular pathogens which enter host cells through largely undefined mechanisms. One molecule thought to play an important role in this process is gp63, the major glycoprotein on the surface of the infective promastigote form. We have cloned and analyzed the gp63 gene from Leishmania chagasi, an etiologic agent of acute visceral leishmaniasis. The predicted amino acid sequence is highly homologous to that reported for Leishmania major, with the exception of a 56-amino-acid region. This region in L. major was predicted to contain an arginine-glycine-aspartic acid (RGD) sequence that was subsequently hypothesized to be involved in binding to the host cell. The L. chagasi gene lacks this sequence or indeed any RGD sequence, and further studies failed to confirm the existence of an RGD sequence in the L. major gp63 gene. Binding to the host cell surface must therefore be mediated by other sequences in gp63 or by other components of the Leishmania promastigote.
Insights
The gp63 protein on Leishmania chagasi is crucial for host cell entry. Researchers found it lacks the arginine-glycine-aspartic acid (RGD) sequence previously thought essential for parasitic protozoa infection.
Area of Science:
- Parasitology
- Molecular Biology
- Infectious Diseases
Background:
- Leishmania are parasitic protozoa that cause leishmaniasis.
- Host cell entry mechanisms for Leishmania remain largely unknown.
- gp63, a surface glycoprotein, is implicated in Leishmania invasion.
Purpose of the Study:
- To clone and analyze the gp63 gene from Leishmania chagasi.
- To investigate the role of the arginine-glycine-aspartic acid (RGD) sequence in gp63-mediated host cell binding.
Main Methods:
- Gene cloning and sequencing of Leishmania chagasi gp63.
- Amino acid sequence prediction and comparison with Leishmania major gp63.
- Bioinformatic analysis to identify potential binding motifs.
Main Results:
- The Leishmania chagasi gp63 sequence is homologous to Leishmania major gp63, with a notable 56-amino-acid difference.
- The L. chagasi gp63 gene lacks an RGD sequence.
- RGD sequence was not confirmed in L. major gp63, challenging previous hypotheses.
Conclusions:
- The RGD sequence is not essential for Leishmania gp63 binding to host cells.
- Host cell attachment by Leishmania likely involves other gp63 sequences or surface components.
- Further research is needed to elucidate the precise mechanisms of Leishmania invasion.