title: Malaria IMC1 membrane skeleton proteins operate autonomously and participate in motility independently of cell shape.
abstract: Plasmodium IMC1 (inner membrane complex 1) proteins comprise components of the subpellicular network, a lattice of intermediate filaments that form a structural part of the pellicle in the zoite stages of malaria parasites. Family members IMC1a and IMC1b are differentially expressed in sporozoites and ookinetes, respectively, but have functionally equivalent roles affecting cell morphology, strength, motility, and infectivity. Because of the coincident effects of previous imc1 gene disruptions on both zoite shape and locomotion, it has been impossible to ascribe a direct involvement in motility to these proteins. We show here that a third family member, IMC1h, has a distinct differential expression pattern and localizes to the pellicle of both ookinetes and sporozoites. Knock-out of IMC1h mimics the loss-of-function phenotypes of IMC1a and IMC1b in their respective life stages, indicating that IMC1 proteins could be operating co-dependently. By generating double null mutant parasites for IMC1h and IMC1b, we tested this hypothesis: double knock-out exacerbated the phenotypes of the single knock-outs in terms of ookinete strength, motility, and infectivity but did not further affect ookinete morphology. These findings provide the first genetic evidence that IMC1 proteins can function independently of each other and contribute to gliding motility independently of cell shape.
authors.affiliation: Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom.
authors.forename: Annie Z
authors.initials: AZ
authors.lastname: Tremp
authors.forename: Johannes T
authors.initials: JT
authors.lastname: Dessens
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation / Q000502:physiology; D055786:Gene Knockout Techniques; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010962:Plasmodium berghei / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D034101:Sporozoites / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D015800:Protozoan Proteins