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Start Date

April 2021

Document Type

Oral Presentation

Department

Biological Sciences

Faculty Mentor

Ilka Pinz, PhD

Keywords

caveolae, caveolae structure, lipid composition, LION, lipid ontology

Abstract

Caveolae are plasma membrane microdomains with specific lipid species signature. The loss of caveolae’s function is associated with cardiovascular disease and diabetes. Caveolae membranes are enriched in sphingolipids, cholesterol, and small cone-shaped lipids to enable the specific flask-shaped membrane curvatures. Caveolin proteins insert into the inner membrane leaflet and provide anchoring sites for membrane-localized receptor tyrosine kinases, such as the insulin receptor. In this study, we investigated how the lipid composition of the caveolar membrane microdomain affects caveolin protein localization. We hypothesized that exposure of cells to a saturated lipid changes the lipid composition of the caveolae membrane microdomain, preventing caveolae from forming, leading to loss of function of cell signaling. Lung epithelial (LE2) cells were grown to 80% confluency in normal growth medium; then, they were switched to a medium containing 0.2 mM or 0.4 mM palmitate (saturated-lipid) for 28 hours. We used oleate (mono-unsaturated lipid) at the same concentrations and normal growth medium as control. After harvesting cells at 100% confluency, caveolae were isolated by sucrose gradient centrifugation. Caveolin-1 protein levels were determined by Western blotting, and lipid profiles were determined by mass spectrometry in each gradient fraction. Lipidomic data were assessed using the LION lipid ontology software. We found that exposure to palmitate changes the localization of caveolin-1 away from the plasma membrane to higher density membrane fractions. In addition, the lipidomic signature of all membrane fractions changed significantly compared to control medium. In particular, the caveolin fraction of cells exposed to palmitate showed an increase in sphingolipid species, decreased ceramide species, and higher levels of saturated lipids compared to control and oleate exposed cells. Our study shows that the lipid composition of the caveolae membrane microdomain is an important determinant of the caveolae structure and the caveolin protein's ability to insert into the membrane and form the flask-like invagination.

Thinking Matters 2021 Presentation Dawood Jimale.pptx (13426 kB)
Saturated lipid-induced changes in the lipidomic signature and structure of caveolae - Slides

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Saturated lipid-induced changes in the lipidomic signature and structure of caveolae - transcript

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Apr 30th, 12:00 AM

Saturated lipid-induced changes in the lipidomic signature and structure of caveolae

Caveolae are plasma membrane microdomains with specific lipid species signature. The loss of caveolae’s function is associated with cardiovascular disease and diabetes. Caveolae membranes are enriched in sphingolipids, cholesterol, and small cone-shaped lipids to enable the specific flask-shaped membrane curvatures. Caveolin proteins insert into the inner membrane leaflet and provide anchoring sites for membrane-localized receptor tyrosine kinases, such as the insulin receptor. In this study, we investigated how the lipid composition of the caveolar membrane microdomain affects caveolin protein localization. We hypothesized that exposure of cells to a saturated lipid changes the lipid composition of the caveolae membrane microdomain, preventing caveolae from forming, leading to loss of function of cell signaling. Lung epithelial (LE2) cells were grown to 80% confluency in normal growth medium; then, they were switched to a medium containing 0.2 mM or 0.4 mM palmitate (saturated-lipid) for 28 hours. We used oleate (mono-unsaturated lipid) at the same concentrations and normal growth medium as control. After harvesting cells at 100% confluency, caveolae were isolated by sucrose gradient centrifugation. Caveolin-1 protein levels were determined by Western blotting, and lipid profiles were determined by mass spectrometry in each gradient fraction. Lipidomic data were assessed using the LION lipid ontology software. We found that exposure to palmitate changes the localization of caveolin-1 away from the plasma membrane to higher density membrane fractions. In addition, the lipidomic signature of all membrane fractions changed significantly compared to control medium. In particular, the caveolin fraction of cells exposed to palmitate showed an increase in sphingolipid species, decreased ceramide species, and higher levels of saturated lipids compared to control and oleate exposed cells. Our study shows that the lipid composition of the caveolae membrane microdomain is an important determinant of the caveolae structure and the caveolin protein's ability to insert into the membrane and form the flask-like invagination.

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