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Published on: June 3, 2016
Lipoprotein lipase degradation by adipocytes: receptor-associated protein (RAP)-sensitive and proteoglycan-mediated
J C Obunike1, P Sivaram, L Paka
1Department of Medicine, Columbia University College of Physicians & Surgeons, New York, NY 10032, USA.
Journal of Lipid Research
|November 1, 1996
Summary
Adipocytes degrade cell surface lipoprotein lipase (LPL) via proteoglycans and RAP-sensitive receptors. This study investigates LPL metabolism and its regulation in adipocytes.
Area of Science:
- Biochemistry
- Cell Biology
- Metabolic Regulation
Background:
- Lipoprotein lipase (LPL) is crucial for triglyceride hydrolysis, synthesized by adipocytes and myocytes.
- Cell surface LPL degradation is a key regulatory mechanism for enzyme production.
Purpose of the Study:
- To investigate LPL metabolism in adipocytes (BFC-1 beta cell line).
- To determine the roles of heparan sulfate proteoglycans (HSPG), LRP, and GPI-linked proteins in LPL uptake and degradation.
Main Methods:
- Studied 125I-labeled LPL degradation in adipocytes.
- Assessed inhibition by 39 kDa receptor associated protein (RAP) and phosphatidylinositol-specific phospholipase C (PIPLC).
- Investigated HSPG involvement using heparinase/heparitinase and proteoglycan metabolism via 35SO4 labeling.
Main Results:
- Adipocytes degraded 23-28% of cell surface LPL in 4 h.
- LPL degradation involved both RAP-sensitive (LRP-mediated) and non-RAP-sensitive pathways.
- Heparan sulfate proteoglycans (HSPG) were essential for most LPL degradation, with rapid turnover of pericellular proteoglycans.
Conclusions:
- Adipocytes actively degrade cell surface LPL.
- LPL degradation is mediated by a combination of proteoglycans and RAP-sensitive receptors.
- HSPG plays a significant role in LPL uptake and degradation kinetics.
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