Electrostatic sheathing of lipoprotein lipase is essential for its movement across capillary endothelial cells
Wenxin Song, … , Loren G. Fong, Stephen G. Young
Wenxin Song, … , Loren G. Fong, Stephen G. Young
Published March 1, 2022
Citation Information: J Clin Invest. 2022;132(5):e157500. https://doi.org/10.1172/JCI157500.
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Research Article Metabolism

Electrostatic sheathing of lipoprotein lipase is essential for its movement across capillary endothelial cells

Abstract

GPIHBP1, an endothelial cell (EC) protein, captures lipoprotein lipase (LPL) within the interstitial spaces (where it is secreted by myocytes and adipocytes) and transports it across ECs to its site of action in the capillary lumen. GPIHBP1’s 3-fingered LU domain is required for LPL binding, but the function of its acidic domain (AD) has remained unclear. We created mutant mice lacking the AD and found severe hypertriglyceridemia. As expected, the mutant GPIHBP1 retained the capacity to bind LPL. Unexpectedly, however, most of the GPIHBP1 and LPL in the mutant mice was located on the abluminal surface of ECs (explaining the hypertriglyceridemia). The GPIHBP1-bound LPL was trapped on the abluminal surface of ECs by electrostatic interactions between the large basic patch on the surface of LPL and negatively charged heparan sulfate proteoglycans (HSPGs) on the surface of ECs. GPIHBP1 trafficking across ECs in the mutant mice was normalized by disrupting LPL-HSPG electrostatic interactions with either heparin or an AD peptide. Thus, GPIHBP1’s AD plays a crucial function in plasma triglyceride metabolism; it sheathes LPL’s basic patch on the abluminal surface of ECs, thereby preventing LPL-HSPG interactions and freeing GPIHBP1-LPL complexes to move across ECs to the capillary lumen.

Authors

Wenxin Song, Anne P. Beigneux, Anne-Marie L. Winther, Kristian K. Kristensen, Anne L. Grønnemose, Ye Yang, Yiping Tu, Priscilla Munguia, Jazmin Morales, Hyesoo Jung, Pieter J. de Jong, Cris J. Jung, Kazuya Miyashita, Takao Kimura, Katsuyuki Nakajima, Masami Murakami, Gabriel Birrane, Haibo Jiang, Peter Tontonoz, Michael Ploug, Loren G. Fong, Stephen G. Young

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Figure 8

Assessing movement of the GPIHBP1-specific antibody 11A12 from the abluminal plasma membrane (APM) to the luminal plasma membrane (LPM) in brown adipose tissue (BAT) capillary endothelial cells of living mice.

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Assessing movement of the GPIHBP1-specific antibody 11A12 from the ablum...
Alexa Fluor 488–11A12 (green) was injected into the interscapular BAT of Gpihbp1+/+ and Gpihbp1S/S mice. After 15 or 90 minutes, images of capillary cross sections containing an endothelial cell nucleus (blue) were recorded by fluorescence microscopy. The presence of the cell nucleus made it possible to visualize 11A12 on the APM (blue arrowhead) and the LPM (magenta arrowhead). Shown here is a representative capillary cross section for each experimental condition. On the right, we show the number of capillary cross sections (from a total of 50 counted) in which Alexa Fluor 488–11A12 was detectable at the capillary lumen. Three additional cross sections per experimental condition are shown in Supplemental Figure 9. (A and B) Capillary cross sections in BAT from Gpihbp1+/+ and Gpihbp1S/S mice 15 minutes (A) or 90 minutes (B) after the injection of Alexa Fluor 488–11A12. (C) Capillary cross sections in BAT 90 minutes after an injection of Alexa Fluor 488–11A12, 0.75 U heparin, and 15 μg dextran sulfate. (D and E) Capillary cross sections in BAT 90 minutes after an injection of Alexa Fluor 488–11A12 and 34 μmol of a synthetic peptide corresponding to the WT GPIHBP1 AD (EDGDADPEPENYNYDDDDDEEEEEE) (D) or the S-protein tag (KETAAAKFERQHMDS) (E). Scale bars: 2 μm.