Biology subjects

Kakava, S.

Publications and source records attributed to Kakava, S..

4 recordsLinked to original sources

bioRxiv2026

The COPI coatomer influences LDL receptor activity, hepatic lipid storage, and apoB secretion

BackgroundDecreased hepatic removal of low density lipoproteins (LDL) and increased apolipoprotein B (apoB) production cause hypercholesterolemia, a major causal risk factor of atherosclerotic cardiovascular disease (ASCVD). By a genome-wide siRNA screen, we previously identified subunits of the Coat protein I (COPI) complex to limit LDL uptake into Huh-7 hepatocarcinoma cells. MethodsThese findings were validated by targeted in vitro experiments as well as genetic association studies in humans and three mouse models with mutated or disrupted COPI genes. ResultsSilencing of COPA, COPB1, COPB2, ARCN1, COPG1, and COPZ1 in Huh-7 cells resulted in decreased uptake of LDL and aberrant glycosylation and altered cell surface abundance of the LDL receptor (LDLR) as well as increased apoB secretion and cellular lipid storage. Single nucleotide polymorphisms of ARCN1 were associated with lower ARCN1 expression and higher levels of LDL-cholesterol (LDL-C). Rare variants of COPA and COPG1 were enriched among patients with LDL-C > 5 mmol/L. Patients and mice carrying other rare immunopathogenic missense variants of COPA and COPG1 did not present with elevated plasma levels of LDL-C, while hepatic knockdown of murine Copg1 increased the concentrations of non-HDL-cholesterol in plasma and triglycerides in the liver. ConclusionsThe COPI coatomer regulates LDLR activity and apoB secretion as well as lipid content of liver cells. Loss of function of some variants of COPI genes are associated with higher LDL-C levels.

cell biology↗

bioRxiv2025

Both the low-density lipoprotein receptor and apolipoprotein E define blood-borne high-density lipoprotein entry into the brain.

Data from epidemiological and genetic studies as well as animal experiments indicate that high-density lipoproteins (HDL) play a role in the pathogenesis of central nervous system (CNS) diseases. Apolipoprotein A-I, the major protein of HDL, has been immunolocalized in the brain although it is produced exclusively by the liver and intestine. We therefore investigated how HDL cross the blood-brain barrier (BBB), using both in vitro and in vivo approaches. In vitro, we found that HDL bind to, are internalized by, and are transported through human brain endothelial cells via mechanisms involving the scavenger receptor BI (SR-BI) and the low-density lipoprotein receptor (LDLR). Notably, we discovered that LDLR facilitates only the transport of HDL particles containing apolipoprotein E (apoE). In vivo, HDL injected into the bloodstream enter into the brain through brain endothelial cells, and accumulated in medulla, cerebellum, olfactory bulb, hippocampus and cortex. Further investigation in Ldlr-/- mice revealed region-specific changes in HDL accumulation with reduced levels in the medulla and mixture of midbrain/cortex/hippocampus, no change in the olfactory bulb, and increased levels in the cerebellum. Together, these findings provide new insight on the interaction of the lipoprotein metabolism between the periphery and CNS. For the first time, we show that brain endothelial receptors and HDL composition jointly dictate HDLs crossing through the BBB and their localization within the brain.

neuroscience↗

bioRxiv2025

Metabolic Origins of Neurotoxic 1-deoxySphingolipids in Type 2 Diabetes

Type 2 diabetes (T2D) and diabetic peripheral neuropathy (DPN) are associated with disruptions in sphingolipid (SL) metabolism, including an increased formation of neurotoxic 1-deoxysphingolipids (1-deoxySL). Here we report data from an untargeted proteomics, lipidomics and metabolomics profiling in plasma and skin samples of a carefully characterized T2D cohort and age-matched healthy controls. We investigated the association between plasma and skin amino acids and the sphingolipidome in blood and skin of T2D patients and several diabetic rodent models. We developed a hypothesis on how changes in the metabolism of the two amino acids relates to SL formation and DPN. To test this hypothesis and identify key enzymes responsible for the 1-deoxySL formation we developed stable isotope based SL flux assays, using UC13Glucose, 15NGlutamine, D4-Palmitic acid, D4-Alanine and D3N15-Serine as tracers. In combination with genetic interference approaches, we identified pathways that are responsible for shifting between the formation of 1-deoxySL and canonical SL in T2D. Furthermore, we verified these findings in vivo in several rodent models. This study links disturbances in amino acids, lipids, and protein homeostasis to DPN in T2D.

neuroscience↗

bioRxiv2020

Loss of RNF43/ZNRF3 predisposes to Hepatocellular carcinoma by impairing liver regeneration and altering liver fat metabolism

The homologous E3 ubiquitin ligases RNF43/ZNRF3 negatively regulate WNT signalling activation. Recently, both genes have been found mutated in several types of cancers. Specifically, loss-of-function mutations result in adenoma formation in mouse small intestine. However, their role in liver cancer has not been explored yet. Here we describe that hepatocyte-specific deletion of both Rnf43/Znrf3 results in altered lipid metabolism and a non-alcoholic steatohepatitis (NASH) phenotype in mouse, in the absence of exogenous fat supplementation. The effect is cell-autonomous, as evidenced by the intracellular lipid accumulation detected in mutant liver organoids. Upon chronic liver damage, Rnf43/Znrf3 deletion results in impaired hepatocyte regeneration, subsequent to an imbalance between hepatocyte differentiation and proliferation, which leads to hepatocellular carcinoma. Remarkably, hepatocellular carcinoma patients with mutations in ZNRF3 also present altered lipid metabolism and poorer survival. Our findings imply that Wnt activation through the RNF43/ZNRF3 module predisposes to liver cancer by altering the liver lipid metabolic ground-state and impairing liver regeneration, which combined, facilitate the progression towards malignancy. Our results highlight the requirement for personalized therapeutic or dietary interventions for those RNF43/ZNRF3 mutated individuals at risk of developing steatosis, NASH and/or liver cancer.

cancer biology↗