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Unexpected expression pattern for glycosylphosphatidylinositol-anchored HDL-binding protein 1 (GPIHBP1) in mouse tissues revealed by positron emission tomography scanning
Journal article   Open access   Peer reviewed

Unexpected expression pattern for glycosylphosphatidylinositol-anchored HDL-binding protein 1 (GPIHBP1) in mouse tissues revealed by positron emission tomography scanning

Tove Olafsen, Stephen G Young, Brandon S J Davies, Anne P Beigneux, Vania E Kenanova, Constance Voss, Glen Young, Koon-Pong Wong, Richard H Barnes II, Yiping Tu, …
The Journal of biological chemistry, Vol.285(50), pp.39239-39248
12/10/2010
DOI: 10.1074/jbc.M110.171041
PMCID: PMC2998116
PMID: 20889497
url
https://doi.org/10.1074/jbc.M110.171041View
Published (Version of record) Open Access

Abstract

Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1), a GPI-anchored endothelial cell protein, binds lipoprotein lipase (LPL) and transports it into the lumen of capillaries where it hydrolyzes triglycerides in lipoproteins. GPIHBP1 is assumed to be expressed mainly within the heart, skeletal muscle, and adipose tissue, the sites where most lipolysis occurs, but the tissue pattern of GPIHBP1 expression has never been evaluated systematically. Because GPIHBP1 is found on the luminal face of capillaries, we predicted that it would be possible to define GPIHBP1 expression patterns with radiolabeled GPIHBP1-specific antibodies and positron emission tomography (PET) scanning. In Gpihbp1(-/-) mice, GPIHBP1-specific antibodies were cleared slowly from the blood, and PET imaging showed retention of the antibodies in the blood pools (heart and great vessels). In Gpihbp1(+/+) mice, the antibodies were cleared extremely rapidly from the blood and, to our surprise, were taken up mainly by lung and liver. Immunofluorescence microscopy confirmed the presence of GPIHBP1 in the capillary endothelium of both lung and liver. In most tissues with high levels of Gpihbp1 expression, Lpl expression was also high, but the lung was an exception (very high Gpihbp1 expression and extremely low Lpl expression). Despite low Lpl transcript levels, however, LPL protein was readily detectable in the lung, suggesting that some of that LPL originates elsewhere and then is captured by GPIHBP1 in the lung. In support of this concept, lung LPL levels were significantly lower in Gpihbp1(-/-) mice than in Gpihbp1(+/+) mice. In addition, Lpl(-/-) mice expressing human LPL exclusively in muscle contained high levels of human LPL in the lung.
 Gene Expression Regulation Mice, Transgenic Positron-Emission Tomography - methods Receptors, Lipoprotein - chemistry Animals Endothelium - metabolism Glycosylphosphatidylinositols - metabolism Models, Biological Cell Membrane - metabolism Lung - metabolism Mice Kinetics Binding Sites Capillaries - metabolism

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