title: The single dynamin family protein in the primitive protozoan Giardia lamblia is essential for stage conversion and endocytic transport.
abstract: Dynamins are universally conserved large guanosine triphosphatases, which function as mechanoenzymes in membrane scission. The primitive protozoan Giardia lamblia has a single dynamin-related protein (GlDRP) with an unusual domain structure. Giardia lacks a Golgi apparatus but generates transient Golgi-like delay compartments dubbed encystation-specific vesicles (ESVs), which serve to accumulate and mature cyst wall proteins during differentiation to infectious cyst forms. Here, we analyze the function of GlDRP during growth and encystation and demonstrate that it relocalizes from peripheral endosomal-lysosomal compartments to nascent ESVs. We show that GlDRP is necessary for secretion of the cyst wall material and ESV homeostasis. Expression of a dominant-negative GlDRP variant does not interfere with ESV formation but blocks cyst formation completely prior to regulated exocytosis. GlDRP colocalizes with clathrin at the cell periphery and is necessary for endocytosis of surface proteins to endosomal-lysosomal organelles in trophozoites. Electron microscopy and live cell imaging reveal gross morphological changes as well as functional impairment of the endocytic system in cells expressing the dominant-negative GlDRP. Thus, giardial DRP plays a key role in two distinct trafficking pathways and in organelle homeostasis, both essential functions for the proliferation of the parasite in the gut and its transmission to a new host.
authors: Institute of Parasitology, University of Zürich, Winterthurerstrasse 266a, 8057 Zürich, Switzerland.
authors: Verena
authors: V
authors: Gaechter
authors: Elisabeth
authors: E
authors: Schraner
authors: Peter
authors: P
authors: Wild
authors: Adrian B
authors: AB
authors: Hehl
mesh_terms: D000818:Animals; D034281:Dynamins / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D016829:Giardia lamblia / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D008018:Life Cycle Stages; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D021381:Protein Transport; D015800:Protozoan Proteins / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D015800:Protozoan Proteins; D034281:Dynamins