Role for the flagellum attachment zone in Leishmania anterior cell tip morphogenesis.

Clare Halliday,Katerina Pruzinova,Jack D Sunter,Flavia Moreira-Leite,Petr Volf,Carolina Moura Costa Catta-Preta,Jitka Myskova,Ryuji Yanase,Jeremy C Mottram,Kent L Hill

doi:10.1371/journal.ppat.1008494

Clare Halliday, Katerina Pruzinova + Show 8 more

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https://doi.org/10.1371/journal.ppat.1008494

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Abstract

The shape and form of the flagellated eukaryotic parasite Leishmania is sculpted to its ecological niches and needs to be transmitted to each generation with great fidelity. The shape of the Leishmania cell is defined by the sub-pellicular microtubule array and the positioning of the nucleus, kinetoplast and the flagellum within this array. The flagellum emerges from the anterior end of the cell body through an invagination of the cell body membrane called the flagellar pocket. Within the flagellar pocket the flagellum is laterally attached to the side of the flagellar pocket by a cytoskeletal structure called the flagellum attachment zone (FAZ). During the cell cycle single copy organelles duplicate with a new flagellum assembling alongside the old flagellum. These are then segregated between the two daughter cells by cytokinesis, which initiates at the anterior cell tip. Here, we have investigated the role of the FAZ in the morphogenesis of the anterior cell tip. We have deleted the FAZ filament protein, FAZ2 and investigated its function using light and electron microscopy and infection studies. The loss of FAZ2 caused a disruption to the membrane organisation at the anterior cell tip, resulting in cells that were connected to each other by a membranous bridge structure between their flagella. Moreover, the FAZ2 null mutant was unable to develop and proliferate in sand flies and had a reduced parasite burden in mice. Our study provides a deeper understanding of membrane-cytoskeletal interactions that define the shape and form of an individual cell and the remodelling of that form during cell division.

Highlights

The kinetoplastid parasites have a defined shape and form, which varies during their life cycle depending on the specific ecological niche
Leishmania parasites have an elongated cell shape with a flagellum extending from one end and this shape is due to a protein skeleton beneath the cell membrane
When we deleted FAZ2 we found that the cell membrane at the end of the cell was distorted resulting in unusual connections between the flagella of different cells

Summary

Introduction

The kinetoplastid parasites have a defined shape and form, which varies during their life cycle depending on the specific ecological niche. These different shapes and forms of Leishmania spp and Trypanosoma brucei are determined by their highly organised sub-pellicular microtubule array. At the distal end of the bulbous lumen is the flagellar pocket collar, a cytoskeletal structure that cinches in the cell membrane to form this bulbous domain [3] Distal to this point, within the flagellar pocket neck region, the cell body membrane is closely apposed to the flagellum membrane until the flagellum exits the cell body. Since the Leishmania promastigote flagellum extends from the anterior cell tip it has traditionally been described as ‘free’; the basal region is firmly attached to the cell body within the flagellar pocket neck region [3]

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