Biology subjects

Heffer, M.

Publications and source records attributed to Heffer, M..

2 recordsLinked to original sources

bioRxiv2026

GD3 synthase deficiency disrupts Na+/K+-ATPase and plasma membrane Ca2+-ATPase function in mouse brain

GD3 synthase (GD3S) is a key enzyme in the production of gangliosides, sialylated membrane glycosphingolipids with essential physiological roles in mammalian brains. To elucidate the molecular bases of neuropathological findings associated with GD3S deficiency, we performed a multilayered analysis focused on the functionality of ion transporters Na +/K+-ATPase (NKA) and plasma membrane Ca2+-ATPase (PMCA) in the cortex and cerebellum of GD3S-deficient mice (GD3S-/-). We examined global transcriptomes, NKA and PMCA gene and protein expression, the influence of membrane lipid composition on lipid raft integrity, and the activity of both ATPases, pairing them with an exploratory principal component analysis. Transcriptomic data reveal that sets of genes involved in ion transport and membrane dynamics are differentially expressed in the absence of GD3S, whereas qRT-PCR data confirm changes in gene expression of specific NKA and PMCA subunits or isoforms. Altered protein expression and significantly lower activity of both NKA and PMCA were found in the cerebral cortex of GD3S-/- mice. Detailed lipidomic analysis revealed segregation of cholesterol into lipid rafts, which may lead to disordered membrane lipid architecture in GD3S deficiency. Additionally, altered ganglioside composition was found to affect the activities of NKA and PMCA in the brain tissue of GD3S-/- mice. Our results confirm that an imbalance in membrane ganglioside composition leads to significant alterations in ion transporter function. Experimental restoration of ATPase activity in cortical homogenates by administering exogenous b-series gangliosides may aid in developing therapeutic strategies targeting deficits in GD3S and other enzymes of ganglioside biosynthesis.

neuroscience↗

bioRxiv2025

Hepatic management of toxic sterols after acute deletion of Cyp51 from cholesterol synthesis

Lanosterol 14-demethylase (CYP51) is an enzyme involved in cholesterol synthesis, crucial for the normal liver function. Diminished activity of CYP51 leads to metabolism associated liver disease, ending in hepatocellular carcinoma. It is still not clear which processes are most affected in the hepatocytes and how they communicate with other cells towards the progressive liver pathology. Herein we describe a new inducible, liver-specific Cyp51 knockout mouse model (iLKO), developed to study how acute disruption of cholesterol synthesis is managed in the adult liver. Doxycycline inducible deletion avoided developmental confounders of albumin-Cre models and enabled isolation of viable primary hepatocytes. iLKO hepatocytes and liver tissue showed CYP51 depletion with accumulation of lanosterol and 24,25-dihydrolanosterol, while hepatic cholesterol levels remained largely unchanged, indicating compensatory uptake and/or pathway rerouting. Histological examination and transmission electron microscopy (TEM) revealed hepatomegaly with mild portal inflammation and ductular reaction but no overt fibrosis at the studied time points. iLKO hepatocytes displayed increased nuclear lipid droplets (LD) that might be involved in adaptation to endoplasmic reticulum (ER) stress. Additionally, we discovered crystal-like inclusions, especially in Kupffer cells. MALDI-TOF MSI could not resolve their composition, but their occurrence alongside sterol overload implicates non-cholesterol sterol crystallization as a potential trigger of inflammation. In summary, iLKO is a suitable model for dissection of sterol toxicity, clearly separated from developmental effects of Cyp51 depletion. Future examinations could reveal how toxic sterol intermediates are buffered in adult liver and how they might be connected to inflammation driven pathologies, relevant also to human health.

biochemistry↗