Functional interrogation of cellular Lp(a) uptake by genome-scale CRISPR screening

Area of Science:

• Cardiovascular Biology
• Lipid Metabolism
• Molecular Genetics

Background:

• Elevated lipoprotein(a) (Lp(a)) is a causal risk factor for atherosclerotic cardiovascular disease and calcific aortic valve stenosis.
• Understanding the mechanism of Lp(a) clearance is crucial, but the specific receptor(s) responsible for Lp(a) uptake have remained elusive.
• Lipoprotein steady-state levels are determined by synthesis and clearance rates, with clearance being a key regulatory point.

Purpose of the Study:

• To identify the primary receptor(s) mediating lipoprotein(a) (Lp(a)) uptake in liver cells.
• To functionally validate the role of identified regulators in Lp(a) metabolism.
• To investigate the association between genetic variants in candidate genes and circulating Lp(a) levels in a human cohort.

Main Methods:

• Genome-scale CRISPR screen in HuH7 cells to identify regulators of Lp(a) uptake.
• Functional validation through gene disruption and overexpression, and in vitro binding assays (biolayer interferometry).
• Analysis of human genetic variants and Lp(a) levels in the UK Biobank cohort.

Main Results:

• The LDL receptor (LDLR) and its regulator MYLIP (IDOL) were identified as top regulators of Lp(a) uptake.
• LDLR expression directly influenced Lp(a) uptake in cells, and direct binding between LDLR and Lp(a) was confirmed.
• Loss-of-function LDLR variants were associated with increased Lp(a) levels in the UK Biobank cohort.

Conclusions:

• The LDL receptor (LDLR) plays a central role in mediating lipoprotein(a) (Lp(a)) uptake by hepatocytes.
• These findings clarify a key mechanism in Lp(a) metabolism and its link to cardiovascular risk.
• The LDLR is a potential therapeutic target for managing elevated Lp(a) levels.