Developmental induction of Golgi structure and function in the primitive eukaryote Giardia lamblia.
A fundamental characteristic of eukaryotic cells is the presence of membrane-bound compartments and membrane transport pathways in which the Golgi complex plays a central role in the selective processing, sorting, and secretion of proteins. The parasitic protozoan Giardia lamblia belongs to the earliest identified lineage among eukaryotes and therefore offers unique insight into the progression from primitive to more complex eukaryotic cells. Here, we report that Giardia trophozoites undergo a developmental induction of Golgi enzyme activities, which correlates with the appearance of a morphologically identifiable Golgi complex, as they differentiate to cysts. Prior to this induction, no morphologically or biochemically identifiable Golgi complex exists within nonencysting cells. Remarkably, protein secretion in both nonencysting and encysting trophozoites is inhibited by brefeldin A, and brefeldin A-sensitive membrane association of ADP-ribosylation factor and beta-COP is observed. These results suggest that the secretory machinery of Giardia resembles that of higher eukaryotes despite the absence of a Golgi complex in nonencysting trophozoites. These findings have implications both for defining the minimal machinery for protein secretion in eukaryotes and for examining the biogenesis of Golgi structure and function.
Luján
H D
HD
Laboratory of Parasitic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892.
Marotta
A
A
Mowatt
M R
MR
Sciaky
N
N
Lippincott-Schwartz
J
J
Nash
T E
TE
D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000494:pharmacology; D020727:ADP-Ribosylation Factors; D000135:Acid Phosphatase / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D020126:Brefeldin A; D002518:Ceramides / Q000494:pharmacology; D020756:Coatomer Protein; D003517:Cyclopentanes / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D016829:Giardia lamblia / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000201:enzymology / Q000378:metabolism*; D008291:Malate Dehydrogenase / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000378:metabolism
D002518:Ceramides; D020756:Coatomer Protein; D003517:Cyclopentanes; D008869:Microtubule-Associated Proteins; D015800:Protozoan Proteins; D020126:Brefeldin A; C037974:N-(7-(4-nitrobenzo-2-oxa-1,3-diazole))-6-aminocaproyl sphingosine; D008291:Malate Dehydrogenase; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D019204:GTP-Binding Proteins; D020727:ADP-Ribosylation Factors; D009327:4-Chloro-7-nitrobenzofurazan