Isolation of Leishmania Promastigote Flagella.

Eukaryotic flagella are conserved multifunctional organelles with roles in motility, intercellular interactions, and signal transduction. Leishmania possess a single flagellum at all stages of their life cycle. Flagella of promastigote forms in the fly are long and motile, with a canonical 9 + 2 microtubule axoneme and an extra-axonemal paraflagellar rod (PFR). This protocol describes a simple method for the isolation of Leishmania mexicana promastigote flagella, optimized to yield intact flagella that retain both the cytoskeletal elements (9 + 2 axoneme and PFR) and the surrounding membrane. The isolated flagella and deflagellated cell bodies are suitable for analysis by electron microscopy, protein mass spectrometry, and lipidomics.

Genetic dissection of a Leishmania flagellar proteome demonstrates requirement for directional motility in sand fly infections.

The protozoan parasite Leishmania possesses a single flagellum, which is remodelled during the parasite's life cycle from a long motile flagellum in promastigote forms in the sand fly to a short immotile flagellum in amastigotes residing in mammalian phagocytes. This study examined the protein composition and in vivo function of the promastigote flagellum. Protein mass spectrometry and label free protein enrichment testing of isolated flagella and deflagellated cell bodies defined a flagellar proteome for L. mexicana promastigote forms (available via ProteomeXchange with identifier PXD011057). This information was used to generate a CRISPR-Cas9 knockout library of 100 mutants to screen for flagellar defects. This first large-scale knockout screen in a Leishmania sp. identified 56 mutants with altered swimming speed (52 reduced and 4 increased) and defined distinct mutant categories (faster swimmers, slower swimmers, slow uncoordinated swimmers and paralysed cells, including aflagellate promastigotes and cells with curled flagella and disruptions of the paraflagellar rod). Each mutant was tagged with a unique 17-nt barcode, providing a simple barcode sequencing (bar-seq) method for measuring the relative fitness of L. mexicana mutants in vivo. In mixed infections of the permissive sand fly vector Lutzomyia longipalpis, paralysed promastigotes and uncoordinated swimmers were severely diminished in the fly after defecation of the bloodmeal. Subsequent examination of flies infected with a single paralysed mutant lacking the central pair protein PF16 or an uncoordinated swimmer lacking the axonemal protein MBO2 showed that these promastigotes did not reach anterior regions of the fly alimentary tract. These data show that L. mexicana need directional motility for successful colonisation of sand flies.

Complementation of a manganese-dependent superoxide dismutase-deficient yeast strain with Pneumocystis carinii sod2 gene.

Manganese-dependent superoxide dismutase (MnSOD) is one of the key enzymes involved in the cellular defense against oxidative stress. Previously, the Pneumocystis carinii sod2 gene (Pcsod2) was isolated and characterized. Based on protein sequence comparison, Pcsod2 was suggested to encode a putative MnSOD protein likely to be targeted into the mitochondrion. In this work, the Pcsod2 was cloned and expressed as a recombinant protein in EG110 Saccharomyces cerevisiae strain lacking the MnSOD-coding gene (Scsod2) in order to investigate the function and subcellular localization of P. carinii MnSOD (PcMnSOD). The Pcsod2 gene was amplified by PCR and cloned into the pYES2.1/V5-His-TOPO(®) expression vector. The recombinant construct was then transformed into EG110 strain. Once its expression had been induced, PcMnSOD was able to complement the growth defect of EG110 yeast cells that had been exposed to the redox-cycling compound menadione. N-term sequencing of the PcMnSOD protein allowed identifying the cleavage site of a mitochondrial targeting peptide. Immune-colocalization of PcMnSOD and yeast CoxIV further confirmed the mitochondrial localization of the PcMnSOD. Heterologous expression of PcMnSOD in yeast indicates that Pcsod2 encodes an active MnSOD, targeted to the yeast mitochondrion that allows the yeast cells to grow in the presence of reactive oxygen species (ROS).