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The intrinsic instability of the hydrolase domain of lipoprotein lipase facilitates its inactivation by ANGPTL4-catalyzed unfolding.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2021 Mar 23; Vol. 118 (12). - Publication Year :
- 2021
-
Abstract
- The complex between lipoprotein lipase (LPL) and its endothelial receptor (GPIHBP1) is responsible for the lipolytic processing of triglyceride-rich lipoproteins (TRLs) along the capillary lumen, a physiologic process that releases lipid nutrients for vital organs such as heart and skeletal muscle. LPL activity is regulated in a tissue-specific manner by endogenous inhibitors (angiopoietin-like [ANGPTL] proteins 3, 4, and 8), but the molecular mechanisms are incompletely understood. ANGPTL4 catalyzes the inactivation of LPL monomers by triggering the irreversible unfolding of LPL's α/β-hydrolase domain. Here, we show that this unfolding is initiated by the binding of ANGPTL4 to sequences near LPL's catalytic site, including β2, β3-α3, and the lid. Using pulse-labeling hydrogen‒deuterium exchange mass spectrometry, we found that ANGPTL4 binding initiates conformational changes that are nucleated on β3-α3 and progress to β5 and β4-α4, ultimately leading to the irreversible unfolding of regions that form LPL's catalytic pocket. LPL unfolding is context dependent and varies with the thermal stability of LPL's α/β-hydrolase domain ( T <subscript> m </subscript> of 34.8 °C). GPIHBP1 binding dramatically increases LPL stability ( T <subscript> m </subscript> of 57.6 °C), while ANGPTL4 lowers the onset of LPL unfolding by ∼20 °C, both for LPL and LPL•GPIHBP1 complexes. These observations explain why the binding of GPIHBP1 to LPL retards the kinetics of ANGPTL4-mediated LPL inactivation at 37 °C but does not fully suppress inactivation. The allosteric mechanism by which ANGPTL4 catalyzes the irreversible unfolding and inactivation of LPL is an unprecedented pathway for regulating intravascular lipid metabolism.<br />Competing Interests: The authors declare no competing interest.
- Subjects :
- Amino Acid Sequence
Binding Sites
Catalysis
Catalytic Domain
Disease Susceptibility
Humans
Kinetics
Lipolysis
Mass Spectrometry
Protein Binding
Protein Stability
Protein Unfolding
Temperature
Angiopoietin-Like Protein 4 chemistry
Angiopoietin-Like Protein 4 metabolism
Hydrolases chemistry
Hydrolases metabolism
Lipoprotein Lipase chemistry
Lipoprotein Lipase metabolism
Protein Domains
Subjects
Details
- Language :
- English
- ISSN :
- 1091-6490
- Volume :
- 118
- Issue :
- 12
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 33723082
- Full Text :
- https://doi.org/10.1073/pnas.2026650118