Mutations in the acid β-glucocerebrosidase (GBA1) gene, responsible for the lysosomal storage disorder Gaucher’s disease (GD), are the strongest genetic risk factor for Parkinson’s disease (PD) known to date. Here we generate induced pluripotent stem cells from subjects with GD and PD harbouring GBA1 mutations, and differentiate them into midbrain dopaminergic neurons followed by enrichment using fluorescence-activated cell sorting. Neurons show a reduction in glucocerebrosidase activity and protein levels, increase in glucosylceramide and α-synuclein levels as well as autophagic and lysosomal defects. Quantitative proteomic profiling reveals an increase of the neuronal calcium-binding protein 2 (NECAB2) in diseased neurons. Mutant neurons show a dysregulation of calcium homeostasis and increased vulnerability to stress responses involving elevation of cytosolic calcium. Importantly, correction of the mutations rescues such pathological phenotypes. These findings provide evidence for a link between GBA1 mutations and complex changes in the autophagic/lysosomal system and intracellular calcium homeostasis, which underlie vulnerability to neurodegeneration.

Membrane microdomains (lipid rafts) are now recognized as critical for proper compartmentalization of insulin signaling. We previously demonstrated that, in adipocytes in a state of TNFα-induced insulin resistance, the inhibition of insulin metabolic signaling and the elimination of insulin receptors (IR) from the caveolae microdomains were associated with an accumulation of the ganglioside GM3. To gain insight into molecular mechanisms behind interactions of IR, caveolin-1 (Cav1), and GM3 in adipocytes, we have performed immunoprecipitations, cross-linking studies of IR and GM3, and live cell studies using total internal reflection fluorescence microscopy and fluorescence recovery after photobleaching techniques. We found that ( i ) IR form complexes with Cav1 and GM3 independently; ( ii ) in GM3-enriched membranes the mobility of IR is increased by dissociation of the IR–Cav1 interaction; and ( iii ) the lysine residue localized just above the transmembrane domain of the IR β-subunit is essential for the interaction of IR with GM3. Because insulin metabolic signal transduction in adipocytes is known to be critically dependent on caveolae, we propose a pathological feature of insulin resistance in adipocytes caused by dissociation of the IR–Cav1 complex by the interactions of IR with GM3 in microdomains.

Cell membrane components are organized as specialized domains involved in membrane-associated events such as cell signaling, cell adhesion, and protein sorting. These membrane domains are enriched in sphingolipids and cholesterol but display a low protein content. Theoretical considerations and experimental data suggest that some properties of gangliosides play an important role in the formation and stabilization of specific cell lipid membrane domains. Gangliosides are glycolipids with strong amphiphilic character and are particularly abundant in the plasma membranes, where they are inserted into the external leaflet with the hydrophobic ceramide moiety and with the oligosaccharide chain protruding into the extracellular medium. The geometry of the monomer inserted into the membrane, largely determined by the very large surface area occupied by the oligosaccharide chain, the ability of the ceramide amide linkage to form a network of hydrogen bonds at the water–lipid interface of cell membranes, the Δ⁴ double bond of sphingosine proximal to the water–lipid interface, the capability of the oligosaccharide chain to interact with water, and the absence of double bonds into the double-tailed hydrophobic moiety are the ganglioside features that will be discussed in this review, to show how gangliosides are responsible for the formation of cell lipid membrane domains characterized by a strong positive curvature.

Tumor-infiltrating immune cells can be conditioned by molecules released within the microenvironment to thwart antitumor immune responses, thereby facilitating tumor growth. Among immune cells, neutrophils play an important protumorigenic role by favoring neoangiogenesis and/or by suppressing antitumor immune responses. Tumor-derived oxysterols have recently been shown to favor tumor growth by inhibiting dendritic cell migration toward lymphoid organs. We report that tumor-derived oxysterols recruit protumor neutrophils in a liver X receptor (LXR)–independent, CXCR2-dependent manner, thus favoring tumor growth by promoting neoangiogenesis and immunosuppression. We demonstrate that interfering with the oxysterol–CXCR2 axis delays tumor growth and prolongs the overall survival of tumor-bearing mice. These results identify an unanticipated protumor function of the oxysterol–CXCR2 axis and a possible target for cancer therapy.