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Developmental induction of Golgi structure and function in the primitive eukaryote Giardia lamblia
H D Luján1, A Marotta, M R Mowatt
1Laboratory of Parasitic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892.
The Journal of Biological Chemistry
|March 3, 1995
Summary
Giardia lamblia, a primitive eukaryote, develops a Golgi complex during cyst differentiation. Its protein secretion machinery functions similarly to higher eukaryotes, even without a visible Golgi in non-cyst cells.
Area of Science:
- Cell Biology
- Eukaryotic Evolution
- Parasitology
Background:
- Eukaryotic cells possess membrane-bound compartments, with the Golgi complex central to protein processing and secretion.
- Giardia lamblia, an early-branching eukaryote, provides insights into the evolution of eukaryotic cellular complexity.
- The presence and function of the Golgi complex in primitive eukaryotes are not fully understood.
Purpose of the Study:
- To investigate the presence and function of the Golgi complex during the life cycle of Giardia lamblia.
- To determine if Giardia lamblia possesses a functional secretory pathway despite its unique cellular structure.
- To understand the evolutionary origins of the Golgi complex and its associated machinery.
Main Methods:
- Analysis of Golgi enzyme activities during Giardia lamblia differentiation.
- Morphological assessment of the Golgi complex during encystation.
- Treatment with brefeldin A to assess protein secretion inhibition and associated protein localization.
- Detection of ADP-ribosylation factor and beta-COP association with membranes.
Main Results:
- Giardia trophozoites exhibit induced Golgi enzyme activities and a morphologically identifiable Golgi complex upon differentiation into cysts.
- Non-encysting trophozoites lack a morphologically or biochemically identifiable Golgi complex.
- Protein secretion in both non-encysting and encysting trophozoites is sensitive to brefeldin A.
- Brefeldin A-sensitive association of ADP-ribosylation factor and beta-COP with membranes was observed in Giardia.
Conclusions:
- Giardia lamblia possesses a functional secretory machinery resembling that of higher eukaryotes, despite the absence of a discernible Golgi complex in non-encysting stages.
- These findings suggest a minimal requirement for Golgi structure in maintaining basic eukaryotic secretory functions.
- The study sheds light on the biogenesis of Golgi structure and function and its evolutionary trajectory.