Posttranscriptional regulation of the human LDL receptor by the U2-spliceosome

Paolo Zanoni, Grigorios Panteloglou, Alaa Othman, Joel T Haas, Roger Meier, Antoine Rimbert, Marta Futema, Yara Abou Khalil, Simon F Norrelykke, Andrzej J Rzepiela, Szymon Stoma, Michael Stebler, Freerk van Dijk, Melinde Wijers, Justina C Wolters, Nawar Dalila, Nicolette C A Huijkman, Marieke Smit, Antonio Gallo, Valérie CarreauAnne Philippi, Jean-Pierre Rabès, Catherine Boileau, Michele Visentin, Luisa Vonghia, Jonas Weyler, Sven Francque, An Verrijken, Ann Verhaegen, Luc Van Gaal, Adriaan van der Graaf, Belle V van Rosmalen, Jerome Robert, Srividya Velagapudi, Mustafa Yalcinkaya, Michaela Keel, Silvija Radosavljevic, Andreas Geier, Anne Tybjaerg-Hansen, Mathilde Varret, Lucia Rohrer, Steve E Humphries, Bart Staels, Bart van de Sluis, Jan Albert Kuivenhoven, Arnold von Eckardstein

Abstract

BACKGROUND: The LDLR (low-density lipoprotein receptor) in the liver is the major determinant of LDL-cholesterol levels in human plasma. The discovery of genes that regulate the activity of LDLR helps to identify pathomechanisms of hypercholesterolemia and novel therapeutic targets against atherosclerotic cardiovascular disease.

METHODS: We performed a genome-wide RNA interference screen for genes limiting the uptake of fluorescent LDL into Huh-7 hepatocarcinoma cells. Top hit genes were validated by in vitro experiments as well as analyses of data sets on gene expression and variants in human populations.

RESULTS: The knockdown of 54 genes significantly inhibited LDL uptake. Fifteen of them encode for components or interactors of the U2-spliceosome. Knocking down any one of 11 out of 15 genes resulted in the selective retention of intron 3 of LDLR. The translated LDLR fragment lacks 88% of the full length LDLR and is detectable neither in nontransfected cells nor in human plasma. The hepatic expression of the intron 3 retention transcript is increased in nonalcoholic fatty liver disease as well as after bariatric surgery. Its expression in blood cells correlates with LDL-cholesterol and age. Single nucleotide polymorphisms and 3 rare variants of one spliceosome gene, RBM25, are associated with LDL-cholesterol in the population and familial hypercholesterolemia, respectively. Compared with overexpression of wild-type RBM25, overexpression of the 3 rare RBM25 mutants in Huh-7 cells led to lower LDL uptake.

CONCLUSIONS: We identified a novel mechanism of posttranscriptional regulation of LDLR activity in humans and associations of genetic variants of RBM25 with LDL-cholesterol levels.

OriginalsprogEngelsk
TidsskriftCirculation Research
Vol/bind130
Udgave nummer1
Sider (fra-til)80-95
Antal sider16
ISSN0009-7330
DOI
StatusUdgivet - 7 jan. 2022

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