ADF/cofilin-driven actin dynamics in early events ofLeishmaniacell division

Abstract

ADF/cofilin is an actin-dynamics-regulating protein that is required for several actin-based cellular processes such as cell motility and cytokinesis. A homologue of this protein has recently been identified in the protozoan parasite Leishmania, which has been shown to be essentially required in flagellum assembly and cell motility. However, the role of this protein in cytokinesis remains largely unknown. We show here that deletion of the gene encoding ADF/cofilin in these organisms results in several aberrations in the process of cell division. These aberrations include delay in basal body and kinetoplast separation, cleavage furrow progression and flagellar pocket division. In addition to these changes, the intracellular trafficking and actin dynamics are also adversely affected. All these abnormalities are, however, reversed by episomal complementation. Together, these results indicate that actin dynamics regulates early events in Leishmania cell division.

Overexpression of S4D Mutant of Leishmania donovani ADF/Cofilin Impairs Flagellum Assembly by Affecting Actin Dynamics

“…LdCof has been implicated in regulation of multiple cellular events in Leishmania, such as flagellum elongation, paraflagellar rod (PFR) assembly (52), flagellar pocket duplication, intracellular vesicular trafficking, and the cell cycle (51). In principle, LdCof possesses two major biochemical activities akin to those of ADF/cofilin proteins (40), viz., F-actin depolymerization and nucleotide exchange activities.…”

“…In Leishmania cells, actin is diffusely distributed throughout the cell body, including the flagellum, kinetoplast, and nucleus, and sometimes shows filament bundles and patches (30,47). However, upon complete ablation of LdCof in these cells, most of actin accumulates in the form of bundles, and no actin is seen in the residual flagellum by immunofluorescence (51,52). As the S4D protein overexpression phenotypes closely resembled those of the LdCof gene deletion mutants, we also analyzed the distribution of actin in these cells.…”

“…Actin dynamics are also involved in intracellular vesicular trafficking and cell division in Leishmania cells (33,51). Therefore, S4D protein-overexpressing cells were assessed for trafficking of endocytic vesicles using FM4-64 dye, which is known to be internalized by the endocytic activity and to traffic down toward the posterior pole with time (37,48).…”

Morphological Events during the Cell Cycle of Leishmania major

“…These include the nucleus, the Golgi apparatus, the basal body, the mitochondrion (which incorporates the kinetoplast), and the flagellum, which protrudes from the cell body via the flagellar pocket. The generation of viable progeny relies upon precise control of the duplication and segregation of these organelles (11,17,29,32).The cell cycle of procyclic form Trypanosoma brucei has been characterized extensively and forms a basis for comparison with other trypanosomatids, including Leishmania. Notably, in T. brucei, replication of the nuclear and kinetoplast DNAs (S phase) starts almost synchronously, whereas the division and segregation periods for the nucleus (M and C phases, respectively) and kinetoplast (D and A phases, respectively) are separated in time.…”

“…These include the nucleus, the Golgi apparatus, the basal body, the mitochondrion (which incorporates the kinetoplast), and the flagellum, which protrudes from the cell body via the flagellar pocket. The generation of viable progeny relies upon precise control of the duplication and segregation of these organelles (11,17,29,32).…”