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

Abstract

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.