Uptake and cellular localization of exogenous lipids by Giardia lamblia, a primitive eukaryote

Tamara L. Stevens, George R. Gibson, Rodney Adam, Julie Maier, Melissa Allison-Ennis, Siddhartha Das

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)

Abstract

Giardia lamblia trophozoites are unable to carry out de novo lipid synthesis. It is therefore likely that lipids are acquired from the small intestine of the host, in which the trophozoites are exposed to free and conjugated fatty acids, various sterols, phospholipids, bile acids, and bile- lipid mixed micelles. Here we show that G. lamblia is capable of taking up exogenous phosphatidylcholine (PC), phosphatidylinositol (PI), sphingomyelin (SM), cholesterol, ceramide (Cer), and fatty acids. Results from epifluorescence and high-resolution confocal microscopy suggest that fluorescent analogs of SM and PC were accumulated in the plasma membranes, whereas palmitic acid and Cer were localized intracellularly. Interestingly, many of these analogs were also concentrated in perinuclear regions. Similar labeling patterns were observed when the fluorescent analogs were delivered to the parasite via liposomes. To test whether G. lamblia was capable of esterifying exogenous fatty acids into membrane or cellular phospholipids, trophozoites were pulse-labeled with 3H-labeled palmitic or myristic acids and the phospholipids analyzed by thin-layer chromatography. Results document that G. lamblia was able to incorporate exogenous fatty acids into various phospholipids, i.e., PI, PC, PE, and PG. Interestingly, a major portion of radiolabeled fatty acids was incorporated into PG, a phospholipid characteristic of prokaryotic membranes.

Original languageEnglish
Pages (from-to)133-143
Number of pages11
JournalExperimental Parasitology
Volume86
Issue number2
DOIs
Publication statusPublished - Jun 1997
Externally publishedYes

Keywords

  • BODIPY, 4,4-difluoro-1,3,5,7,8-pentamethyl- 4-bora-3a, 4a-diaza-s-indacene
  • BSA, bovine serum albumin
  • Cer, ceramide
  • Cho, cholesterol
  • DPH, 2-3- [diphenylhexatrienyl]propanyl
  • ESV
  • Fluorescent lipid probes
  • Giardia lamblia
  • Lipid trafficking
  • MVL, multilamellar vesicles
  • NBD, N-7-nitrobenz-2-oxa-1,3-diazole
  • PBS, phosphate-buffered saline
  • PC, phosphatidylcholine
  • PE, phosphatidylethanolamine
  • PG, phosphatidylglycerol
  • PI, phosphatidylinositol
  • Plasma and nuclear membranes
  • Pyrene- PI, 4-(1-pyrenebutyl)-myo-inositol-1-phosphate
  • SM, sphingomyelin
  • TLC, thin-layer chromatography
  • Trophozoites

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