Dataset Information

ANGPTL3/8 is an atypical unfoldase that regulates intravascular lipolysis by catalyzing unfolding of lipoprotein lipase as measured by hydrogen/deuterium exchange mass spectrometry (HDX-MS)

ABSTRACT: Lipoprotein lipase (LPL) carries out the lipolytic processing of triglyceride-rich lipoproteins (TRL) along the luminal surface of capillaries. LPL activity is regulated by angiopoietin-like proteins (ANGPTL3, ANGPTL4, and ANGPTL8), which control the delivery of TRL-derived lipid nutrients to tissues in a temporal and spatial fashion. This regulation mediates the partitioning of lipid delivery to storage and metabolic tissues according to nutritional status. A complex between ANGPTL3 and ANGPTL8 (ANGPTL3/8) inhibits LPL activity in oxidative tissues, but its mode-of-action has remained unknown. Here, we used biophysical techniques to define how ANGPTL3/8 and ANGPTL3 interact with LPL and how they drive LPL inactivation. We demonstrate, by mass photometry, that ANGPTL3/8 is a heterotrimer with a 2:1 stoichiometry between ANGPTL3 and ANGPTL8 and that ANGPTL3 is a homotrimer. Hydrogen–deuterium exchange mass spectrometry (HDX-MS) studies revealed that both ANGPTL3/8 and ANGPTL3 use the proximal portion of their N-terminal α-helices to interact with sequences surrounding the catalytic pocket in LPL. That binding event triggers unfolding of LPL’s α/β- hydrolase domain and irreversible loss of LPL catalytic activity. The binding of LPL to its endothelial transporter protein (GPIHBP1) or to heparan-sulfate proteoglycans protects LPL from inactivation by unfolding, particularly against the unfolding triggered by ANGPTL3. Pulse-labelling HDX-MS studies revealed that ANGPTL3/8 and ANGPTL3 catalyze LPL unfolding in an ATP-independent fashion, which categorize these LPL inhibitors as atypical unfoldases. The catalytic nature of LPL unfolding by ANGPTL3/8 explains why low plasma concentrations of ANGPTL3/8 are effective in inhibiting a molar excess of LPL in capillaries.

INSTRUMENT(S): Synapt G2 HDMS

ORGANISM(S): Homo Sapiens (human) Bos Taurus (bovine)

SUBMITTER: Signe Bondesen

LAB HEAD: Thomas J. D. Jørgensen

PROVIDER: PXD060125 | Pride | 2025-03-26

REPOSITORIES: Pride

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ANGPTL3/8 is an atypical unfoldase that regulates intravascular lipolysis by catalyzing unfolding of lipoprotein lipase.

Kumari Anni A Larsen Sanne W R SWR Bondesen Signe S Qian Yuewei Y Tian Hao D HD Walker Sydney G SG Davies Brandon S J BSJ Remaley Alan T AT Young Stephen G SG Konrad Robert J RJ Jørgensen Thomas J D TJD Ploug Michael M

Proceedings of the National Academy of Sciences of the United States of America 20250320 12

Lipoprotein lipase (LPL) carries out the lipolytic processing of triglyceride-rich lipoproteins (TRL) along the luminal surface of capillaries. LPL activity is regulated by the angiopoietin-like proteins (ANGPTL3, ANGPTL4, ANGPTL8), which control the delivery of TRL-derived lipid nutrients to tissues in a temporal and spatial fashion. This regulation of LPL mediates the partitioning of lipid delivery to adipose tissue and striated muscle according to nutritional status. A complex between ANGPTL3 ...[more]

PMID: 40112106

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Project description:Lipoprotein lipase (LPL) is responsible for the intravascular catabolism of triglyceride-rich lipoproteins and plays a central role in whole-body energy balance and lipid homeostasis. As such, LPL is subject to tissue-specific regulation in different physiological conditions, but the mechanisms of this regulation remain incompletely characterized. Previous work revealed that LPL comprises a set of proteoforms with different isoelectric points, but their regulation and functional significance have not been studied thus far. Here we studied the distribution of LPL proteoforms in different rat tissues and their regulation under physiological conditions. First, analysis by two-dimensional electrophoresis and Western blot showed different patterns of LPL proteoforms (i.e., different pI or relative abundance of LPL proteoforms) in different rat tissues under basal conditions, which could be related to the tissue-specific regulation of the enzyme. Next, the comparison of LPL proteoforms from heart and brown adipose tissue between adults and 15-day-old rat pups, two conditions with minimal regulation of LPL in these tissues, yielded virtually the same tissue-specific patterns of LPL proteoforms. In contrast, the pronounced down-regulation of LPL activity observed in white adipose tissue during fasting is accompanied by a prominent reconfiguration of the LPL proteoform pattern. Furthermore, refeeding reverts this down-regulation of LPL activity and restores the pattern of LPL proteoforms in this tissue. Importantly, this reversible proteoform-specific regulation during fasting and refeeding indicates that LPL proteoforms are functionally diverse. Further investigation of potential differences in the functional properties of LPL proteoforms showed that all proteoforms exhibit lipolytic activity and have similar heparin-binding affinity, although other functional aspects remain to be investigated. Overall, this study demonstrates the ubiquity, differential distribution and specific regulation of LPL proteoforms in rat tissues and underscores the need to consider the existence of LPL proteoforms for a complete understanding of LPL regulation under physiological conditions.