Developmental Induction of Golgi Structure and Function in the Primitive Eukaryote Giardia lamblia

doi:10.1074/jbc.270.9.4612

Developmental Induction of Golgi Structure and Function in the Primitive Eukaryote Giardia lamblia(*)

From the (1)Laboratory of Parasitic Diseases, NIAID and the
(2)Cell Biology and Metabolism Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892

^§ To whom correspondence should be addressed:
Laboratory of Parasitic Diseases, NIAID, NIH, 9000 Rockville Pike, Bldg. 4, Rm. 126, Bethesda, MD 20892-0425.
Tel.: 301-496-6920; Fax: 301-402-2689; hdl{at}4.niaid.nih.gov

Abstract

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 β-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.

Footnotes

↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

ER

endoplasmic reticulum

ARF

ADP-ribosylation factor

gARF

Giardia ARF

rgARF

recombinant gARF

BFA

brefeldin A

VSP

variant-specific surface protein

CWP

cyst wall protein

PBS

phosphate-buffered saline

NBD

N-(-7-nitrobenz-2-oxa-1,3-diazol-4-yl-aminocaproyl).
↵²Mowatt, H. D., Cotten, D. B., Bowers, B., Yee, J., Nash, T. E., Stibbs, H. H.,(1995) Mol. Microbiol., in press.
↵³H. D. Luján, M. R. Mowatt, J. J. Wu, Y. Lu, A. Lees, M. R. Chance, and T. E. Nash, submitted for publication.
- Received October 3, 1994.
- Revision received November 10, 1994.