Phospholipase D (PLD) is Present in Leishmania donovani and its Activity Increases in Response to Acute Osmotic Stress

• Published in: The Journal of eukaryotic microbiology Vol. 48; no. 1; pp. 102 - 110
• Main Authors: BLUM, J. JOSEPH, LEHMAN, JASON A, HORN, JEFF M, GOMEZ-CAMBRONERO, JULIAN
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2001; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Blotting, Western; Cell volume changes; Culture Media; cytoskelcton; cytoskeleton; Fundamental and applied biological sciences. Psychology; immune complex enzyme assay; Leishmania; Leishmania donovani - enzymology; Leishmania donovani - growth & development; Leishmania donovani - physiology; Osmolar Concentration; Osmotic Pressure; phospholipase D; Phospholipase D - metabolism; phospholipase D, PLD; PLD; Precipitin Tests; Protozoa. Invertebrata; Kinetoplastida; Protozoa; Host parasite relation; Protozoal disease; Molecular form; Enzyme; Leishmania donovani; Parasite; Environmental factor; Esterases; Parasitosis; Phosphoric diester hydrolases; Leishmaniasis; Phospholipase D; Stress; Infection; Osmotic shock; Regulation(control); Enzymatic activity; Hydrolases; Cytoskeleton; Cell volume; Immune complex
• ISSN: 1066-5234; 1550-7408
• DOI: 10.1111/j.1550-7408.2001.tb00421.x

We report here that the signaling molecule phospholipase D (PLD) is present in the parasitic protozoan Leishmania donovani. In vitro enzymatic activity is dependent on Ca2+ and Mg2+ ions, its basal activity is stimulated by phosphatidyl-inositol-4,5-bisphosphate (PIP2), and its pH optima are pH 8.0 and pH 6.0. PLD activity increases 3-fold about 5 min after an abrupt decrease in osmolality from 317 mOsm (isosmotic) to 155 mOsm and increases 1.5-fold in response to an abrupt increase in osmolality to 617 mOsM. Cells grown for > 24 h under the anisosmotic conditions showed only marginal changes in activity compared to the controls grown under isosmotic conditions, indicating an adaptation to long-term exposure to hypo- or hyper-osmolarity. Immunologically, two isoforms, PLD1 and PLD2, are present. An analysis of in vitro PLD activity in anti-PLD immunocomplexes revealed that either hypotonic (cell swelling) or hypertonic stress (cell shrinking) causes an increase in PLD1 activation but a reduction in PLD2 activity. The interplay between these two isoforms results in a predominance for PLD1 in the observed increase when measuring total PLD activity. Finally, the increase in enzymatic activity in acute hyposmotic shock is accompanied by tyrosyl phosphorylation of the PLD1 isoform, suggesting a role for protein tyrosine kinase in the control of PLD activity in response to osmotic stress.