TY - JOUR
T1 - Uptake and cellular localization of exogenous lipids by Giardia lamblia, a primitive eukaryote
AU - Stevens, Tamara L.
AU - Gibson, George R.
AU - Adam, Rodney
AU - Maier, Julie
AU - Allison-Ennis, Melissa
AU - Das, Siddhartha
N1 - Funding Information:
We are grateful to Dr. Claire Payne (University of Arizona, Tucson) and Dr. Charles Kuszynski (University of Nebraska Medical Center, Omaha) for capturing confocal images. Epifluorescence microscope experiments were carried out in Analytical Cytology Core Facility at the University of Texas at El Paso. We are thankful to Drs. Louis Irwin (UTEP), Stephen B. Aley (UTEP), Frances D. Gillin (UCSD), and Michael Lehker (UTEP) for critically reviewing the manuscript. We appreciate the technical help from Mr. Richard Flores and Mr. David Ramirez. This work was supported by Grants AI 136597, GM 08012, and RR 08124 from the National Institute of Health.
PY - 1997/6
Y1 - 1997/6
N2 - 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.
AB - 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.
KW - BODIPY, 4,4-difluoro-1,3,5,7,8-pentamethyl- 4-bora-3a, 4a-diaza-s-indacene
KW - BSA, bovine serum albumin
KW - Cer, ceramide
KW - Cho, cholesterol
KW - DPH, 2-3- [diphenylhexatrienyl]propanyl
KW - ESV
KW - Fluorescent lipid probes
KW - Giardia lamblia
KW - Lipid trafficking
KW - MVL, multilamellar vesicles
KW - NBD, N-7-nitrobenz-2-oxa-1,3-diazole
KW - PBS, phosphate-buffered saline
KW - PC, phosphatidylcholine
KW - PE, phosphatidylethanolamine
KW - PG, phosphatidylglycerol
KW - PI, phosphatidylinositol
KW - Plasma and nuclear membranes
KW - Pyrene- PI, 4-(1-pyrenebutyl)-myo-inositol-1-phosphate
KW - SM, sphingomyelin
KW - TLC, thin-layer chromatography
KW - Trophozoites
UR - http://www.scopus.com/inward/record.url?scp=0031171677&partnerID=8YFLogxK
U2 - 10.1006/expr.1997.4162
DO - 10.1006/expr.1997.4162
M3 - Article
C2 - 9207743
AN - SCOPUS:0031171677
SN - 0014-4894
VL - 86
SP - 133
EP - 143
JO - Experimental Parasitology
JF - Experimental Parasitology
IS - 2
ER -