title: Assembly and export of a Toxoplasma microneme complex in Giardia lamblia.
abstract: The microneme proteins of Toxoplasma gondii belong to a large family of adhesins of apicomplexan parasites involved in motility and host cell invasion. During secretory transport, soluble micronemes associate with membrane-bound carriers/escorters and become exposed on the parasite surface as complexes with an array of adhesive domains. Previously, we have exploited the intestinal protozoan Giardia lamblia as an expression system to produce correctly folded and unglycosylated monomeric surface proteins of T. gondii. Here, we report assembly and export of a trimeric microneme (MIC1/4/6) adhesin complex from Toxoplasma. Co-expressed, recombinant microneme proteins were used to investigate structural requirements for microneme complex formation. In addition, export of a microneme subunit induced development of novel Golgi-like compartments demonstrating the existence of post endoplasmic reticulum structures involved in constitutive secretion in this 'Golgi-less' cell. Recreation of the trimeric microneme escorter-cargo system in Giardia is a versatile tool to analyse universal requirements for complex assembly, receptor-ligand interactions and Golgi neogenesis in the basal Giardia secretory system.
authors.affiliation: Institute of Parasitology, University of Zürich, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
authors.forename: Verena
authors.initials: V
authors.lastname: Gaechter
authors.forename: Adrian B
authors.initials: AB
authors.lastname: Hehl
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D018274:Electroporation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005822:Genetic Vectors; D016829:Giardia lamblia / Q000378:metabolism* / Q000502:physiology; D006056:Golgi Apparatus / Q000502:physiology; D006790:Host-Parasite Interactions / Q000502:physiology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014122:Toxoplasma / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D015815:Cell Adhesion Molecules; C105877:MIC1 protein, Toxoplasma gondii; C428323:MIC4 protein, Toxoplasma gondii; C512738:MIC6 protein, Toxoplasma gondii; D015800:Protozoan Proteins; D011994:Recombinant Proteins