Background and Aims: We recently found that the CCC and WASH complexes coordinate endosomal LDLR recycling. In vitro studies have implicated that both complexes are recruited to endosomes trough a binding with the retromer subunit VPS35. Remarkably, a recent study has shown that CCC and WASH localize to endosomes independently of VPS35. Furthermore, a dominant-negative mutation in VPS35 is correlated with Parkinson’s disease and, to our knowledge, has not been associated with dyslipidemia. These controversial results made us decide to assess the contribution of VPS35 to LDL metabolism.
Methods: Somatic CRISPR/Cas9 gene editing approach was used to generate liver specific Vps35 knockout mice. Plasma cholesterol concentrations were measured and the lipoprotein profiles were determined by FPLC. Hepatic VLDL-TG secretion was measured using poloxamer-407. Additionally, Vps35 was ablated in Hepa1-6 cells using CRISPR/Cas9 technology. Control and Vps35 knockout (KO) cells were characterized for LDLR and LRP1 receptor levels with Western blot.
Results: Hepatic VPS35 inactivation did not alter body weight, liver weight, or cause overt liver pathology, but it increased plasma cholesterol levels by ~15% compared to control mice. Lipoprotein fractionation revealed that elevated plasma cholesterol levels were due to increased plasma LDL cholesterol. Interestingly, hepatic VPS35 ablation decreased plasma triglyceride levels while hepatic VLDL-TG secretion was not significantly altered. VPS35 deficiency slightly increased LDLR levels in Hepa1-6 hepatocytes.
Conclusions: VPS35 regulates plasma LDL-C and TG levels. In contrast to ablation of WASH or CCC, VPS35 deficiency does not reduce LDLR at the cell surface. These data suggest that different components of the endosomal sorting machinery have different functions in the regulation of plasma lipid levels, but further studies are needed to unravel the underlying mechanism.

03 - THE PARKINSON’S DISEASE GENE VPS35 REGULATES PLASMA LDL CHOLESTEROL LEVELS IN A CCC/WASH-DEPENDENT MANNER