Actin‐depolymerizing factor, ADF/cofilin, is essentially required in assembly of Leishmania flagellum

Abstract

SummaryADF/cofilins are ubiquitous actin dynamics-regulating proteins that have been mainly implicated in actinbased cell motility. Trypanosomatids, e.g. Leishmania and Trypanosoma, which mediate their motility through flagellum, also contain a putative ADF/cofilin homologue, but its role in flagellar motility remains largely unexplored. We have investigated the role of this protein in assembly and motility of the Leishmania flagellum after knocking out the ADF/cofilin gene by targeted gene replacement. The resultant mutants were completely immotile, short and stumpy, and had reduced flagellar length and severely impaired beat. In addition, the assembly of the paraflagellar rod was lost, vesicle-like structures were seen throughout the length of the flagellum and the state and distribution of actin were altered. However, episomal complementation of the gene restored normal morphology and flagellar function. These results for the first time indicate that the actin dynamics-regulating protein ADF/ cofilin plays a critical role in assembly and motility of the eukaryotic flagellum.

The other side of the coin: Functional and structural versatility of ADF/cofilins

“…in Pfam, which is considered to be one of the most reliable domain databases, the seed sequence alignment is shifted in the case of the N-terminal end of human cofilin-1, which results in a less descriptive domain definition for the ADF-H domain. (Tammana et al, 2008;Yeoh et al, 2002) M. musculus ADF YES (RbskACT, platelet) YES (RbskACT, platelet) YES (platelet) ND (Vartiainen et al, 2002) M. musculus cofilin-1 (nm)…”

“…NO (human platelet) ND ND (Singh et al, 2011) T. gondii TgADF (Tammana et al, 2008;Yeoh et al, 2002) M. musculus ADF YES/ADP (RbskACT) ND (Vartiainen et al, 2002) M. musculus cofilin 1 (nm) YES/ADP (RbskACT) ND (Vartiainen et al, 2002) M. musculus cofilin 2 (m) YES/ADP (RbSKACT) ND (Vartiainen et al, 2002) stimulation (human platelet, bovine beta, PfACT) (Schüler et al, 2005a;Singh et al, 2011) P. berghei PbADF2 YES/? (human platelet) stimulation (human platelet) (Singh et al, 2011) T. gondii TgADF YES/?…”

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

“…Detailed characterization of Leishmania ADF/cofilin (Cof) revealed that it readily binds both the monomeric and filamentous (Kapoor et al, 2008) forms of Leishmania actin and also depolymerizes filamentous actin into monomers (Tammana et al, 2008). Furthermore, it displays high nucleotide exchange but weak actin-filament-severing activities (Tammana et al, 2008).…”

“…Leishmania parasites express only one isoform of ADF/cofilin, which is essentially required in flagellar assembly and motility (Tammana et al, 2008). Detailed characterization of Leishmania ADF/cofilin (Cof) revealed that it readily binds both the monomeric and filamentous (Kapoor et al, 2008) forms of Leishmania actin and also depolymerizes filamentous actin into monomers (Tammana et al, 2008).…”

“…Detailed characterization of Leishmania ADF/cofilin (Cof) revealed that it readily binds both the monomeric and filamentous (Kapoor et al, 2008) forms of Leishmania actin and also depolymerizes filamentous actin into monomers (Tammana et al, 2008). Furthermore, it displays high nucleotide exchange but weak actin-filament-severing activities (Tammana et al, 2008). As the distributions of Cof and actin in Leishmania cells are largely polarized towards the flagellar pocket region where the basal body is located (Tammana et al, 2008), and as the cell division in trypanosomatids is initiated with basal body duplication followed by flagellum formation and flagellar pocket division (Ralston and Hill, 2008), we investigated the role of Cof-driven actin dynamics in Leishmania cell division.…”