A new study published in Nature shows that chronic intake of dietary cholesterol activates Ral GTPases, setting off a cascade that hastens the removal of low‑density lipoprotein receptors (LDLR) from cell surfaces. The research identifies the RalBP1–REPS1 complex and the lysosomal enzyme cathepsin A (CTSA) as key mediators of LDLR internalization and degradation, a process that diminishes the body’s ability to clear circulating cholesterol. Inhibiting CTSA, the authors report, restores LDLR function and could represent a novel therapeutic avenue for cardiovascular disease.
The investigators fed mice a high‑cholesterol diet and observed sustained activation of Ral‑A and Ral‑B GTPases in liver cells. Using genetic and pharmacologic tools, they demonstrated that activated Ral proteins recruit the adaptor protein RalBP1, which in turn couples with REPS1 to direct LDLR toward lysosomes. Once inside the lysosome, CTSA facilitates receptor degradation. Mice lacking REPS1 or treated with a CTSA inhibitor retained higher levels of LDLR on hepatocyte surfaces, leading to increased clearance of LDL particles from the bloodstream.
“Chronic dietary cholesterol appears to hijack a Ral‑dependent trafficking route that accelerates LDLR turnover,” the authors wrote. “Targeting CTSA reverses this effect and restores receptor-mediated LDL uptake.”
The findings add a mechanistic layer to the long‑standing observation that high dietary cholesterol can blunt the efficacy of LDL‑lowering strategies such as statins, which rely on up‑regulating LDLR expression. By revealing a post‑translational checkpoint that reduces receptor availability, the study suggests that combining CTSA inhibition with existing lipid‑lowering drugs might enhance therapeutic outcomes.
Analysis: While the mouse models provide compelling evidence of a Ral‑CTSA axis controlling LDLR stability, translation to human physiology will require careful validation. The study does not address potential off‑target effects of CTSA inhibition, nor does it explore whether long‑term suppression of this lysosomal enzyme could impact other cellular processes. Moreover, dietary patterns in humans are more complex than the controlled high‑cholesterol feeding used in the experiments. Future clinical trials will be needed to determine whether CTSA inhibitors can safely and effectively augment LDL clearance in patients at risk for atherosclerotic cardiovascular disease.
Sources
Nature, “Dietary cholesterol activates a Ral‑dependent pathway driving LDLR turnover,” June 24 2026, https://www.nature.com/articles/s41586-026-10697-z
Source: Nature – Original article
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Story synopsis gathered from: Nature — source
