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Profiling proteome changes during polyamine depletion within the Leishmania donovani polyamine pathway gene deletion mutants, del-odc (ornithine decarboxylase) and del-spdsyn (spermidine synthase)

ABSTRACT: Polyamines are aliphatic polycations that have emerged as important determinants of cell growth and viability in rapidly proliferating cells, including in the pathogenic protozoan parasite Leishmania donovani. In L. donovani, the polyamine spermidine is synthesized by the successive conversion of ornithine into putrescine (catalyzed by ornithine decarboxylase or ODC) and putrescine into spermidine (catalyzed by spermidine synthase or SPDSYN). Deletion of either ODC (del-odc) or SPDSYN (del-spdsyn) from the L. donovani genome renders these parasites auxotrophic for polyamines and these mutants are impaired in their ability to survive both in culture and within the mammalian host without the addition of exogenous polyamine supplementation. Significantly, del-odc parasites immediately cease proliferation after putrescine is removed from the culture media and perish within two weeks, while spermidine starved del-spdsyn mutants, which retain intracellular putrescine pools, show a slow-growth phenotype, and persist for several weeks in culture. To elucidate the key differences within the proteome of putrescine-starved del-odc cells and spermidine-starved del-spdsyn parasites, a shotgun quantitative proteomics approach was undertaken using TMT labeling and LC-MS/MS analysis. Briefly, three biological replicates each for mid-log phase del-odc and del-spdsyn promastigotes grown in the presence of exogenous putrescine (for del-odc) or spermidine (for del-spdsyn) supplementation were washed to remove the exogenous polyamine supplementation and incubated in polyamine-free media. At 24 and 48 h, cells from each biological replicate were isolated and prepared for tandem mass tag (TMT) labeling and downstream LC-MS/MS analyses. Peptides were identified using a database generated from the reference genome of L. donovani BPK282A1 strain. Changes in relative protein abundance for the polyamine-starved del-odc and del-spdsyn cell lines at 24 and 48 h were calculated by comparing aggregate total reporter ion intensities for each protein to that of the corresponding polyamine-supplemented 0-h timepoint.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Leishmania Donovani Bpk282a1

TISSUE(S): Promastigote

DISEASE(S): Leishmaniasis

SUBMITTER: Phillip Wilmarth

LAB HEAD: Nicola S. Carter

PROVIDER: PXD036349 | Pride | 2022-08-29

REPOSITORIES: Pride

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Project description:Polyamines (putrescine, spermidine, and spermine) are major organic polycations essential for a wide spectrum of cellular processes. The cells require mechanisms to maintain homeostasis of intracellular polyamines to prevent otherwise severe adverse effects. We performed a detailed transcriptome profile analysis of P. aeruginosa in response to agmatine and putrescine with an emphasis in polyamine catabolism. Agmatine serves as precursor compound for putrescine (and hence spermidine and spermine), which was proposed to convert into GABA and succinate before entering the TCA cycle in support of cell growth as the sole source of carbon and nitrogen. Two acetylpolyamine amidohydrolases, AphA and AphB, were identified to be involved in the conversion of agmatine into putrescine. Enzymatic products of AphA were confirmed by mass spectrometry analysis. Interestingly, the alanine-pyruvate cycle was shown indispensable for polyamine utilization. The newly identified dadRAX locus, encoding the regulator, alanine transaminase and racemase respectively, coupled with SpuC, the major putrescine-pyruvate transaminase, were key components to maintain alanine homeostasis. Corresponding mutant strains were severely hampered in polyamine utilization. On the other hand, the alternative gamma-glutamylation pathway for the conversion of putrescine into GABA was also discussed. Subsequently, GabD, GabT and PA5313 were identified for GABA utilization. Growth defect of PA5313 gabT double mutant in GABA suggested the importance of these two transaminases. The succinic-semialdehyde dehydrogenase activity of GabD and its induction by GABA was also demonstrated in vitro. Polyamine utilization in general was proven independent of the PhoPQ two-component system even the expression of which was induced by polyamines. Multiple potent catabolic pathways as depicted in this study could serve pivotal roles in control of intracellular polyamine levels. Experiment Overall Design: P. aeruginosa PAO1 was grown aerobically in minimal medium P with 350 rpm shaking at 37C, in the presence of L-glutamate alone or with the addition of putrescine, agmatine or GABA at 20 mM. Cells were harvested when the optical density at 600 nm reached 0.5~0.6 by centrifugation for 5 minutes at 4C. Total RNA samples were isolated by RNeasy purification kit following instructions of the manufacturer (Qiagen). Reverse transcription for cDNA synthesis, fragmentation by DNase I treatment, cDNA probe labeling and hybridization were performed according to the instructions of GeneChip manufacturer (Affymetrix). Data were processed by Microarray Suite 5.0 software normalizing the absolute expression signal values of all chips to a target intensity of 500. GeneSpring software (Silicon Genetics) was used for expression pattern analysis and comparison. Only genes showing consistent expression profiles in duplicates were selected for further analysis.

Dataset Information

Profiling proteome changes during polyamine depletion within the Leishmania donovani polyamine pathway gene deletion mutants, del-odc (ornithine decarboxylase) and del-spdsyn (spermidine synthase)

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