The lipid-modulating effects of a CD4-specific recombinant antibody correlate with ZAP-70 segregation outside membrane rafts

Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease

Essential polyunsaturated fatty acids (PUFAs) have profound effects on brain development and function. Abnormalities of PUFA status have been implicated in neuropsychiatric diseases such as major depression, bipolar disorder, schizophrenia, Alzheimer's disease, and attention deficit hyperactivity disorder. Pathophysiologic mechanisms could involve not only suboptimal PUFA intake, but also metabolic and genetic abnormalities, defective hepatic metabolism, and problems with diffusion and transport. This article provides an overview of physiologic factors regulating PUFA utilization, highlighting their relevance to neuropsychiatric disease.

Possible protective effect of membrane lipid rafts against interleukin-1β-mediated anti-proliferative effect in INS-1 cells

We recently reported that pancreatic islets from pre-diabetic rats undergo an inflammatory process in which IL-1β takes part and controls β-cell function. In the present study, using the INS-1 rat pancreatic β-cell line, we investigated the potential involvement of membrane-associated cholesterol-enriched lipid rafts in IL-1β signaling and biological effects on insulin secretion, β-cell proliferation and apoptosis. We show that, INS-1 cells exposure to increasing concentrations of IL-1β leads to a progressive inhibition of insulin release, an increase in the number of apoptotic cells and a dose-dependent decrease in pancreatic β-cell proliferation. Disruption of membrane lipid rafts markedly reduced glucose-stimulated insulin secretion but did not affect either cell apoptosis or proliferation rate, demonstrating that membrane lipid raft integrity is essential for β-cell secretory function. In the same conditions, IL-1β treatment of INS-1 cells led to a slight further decrease in insulin secretion for low concentrations of the cytokine, and a more marked one, similar to that observed in normal cells for higher concentrations. These effects occurred together with an increase in iNOS expression and surprisingly with an upregulation of tryptophane hydroxylase and protein Kinase C in membrane lipid rafts suggesting that compensatory mechanisms develop to counteract IL-1β inhibitory effects. We also demonstrate that disruption of membrane lipid rafts did not prevent cytokine-induced cell death recorded after exposure to high IL-1β concentrations. Finally, concerning cell proliferation, we bring strong evidence that membrane lipid rafts exert a protective effect against IL-1β anti-proliferative effect, possibly mediated at least partly by modifications in ERK and PKB expression/activities. Our results 1) demonstrate that IL-1β deleterious effects do not require a cholesterol-dependent plasma membrane compartmentalization of IL-1R1 signaling and 2) confer to membrane lipid rafts integrity a possible protective function that deserves to be considered in the context of inflammation and especially T2D pathogenesis.

CD4 ligation excludes the Carma1-Bcl10-MALT1 complex from GM1-positive membrane rafts in CD3/CD28 activated T cells

The antibody 13B8.2, which is directed against the CDR3-like loop on the D1 domain of CD4, induces CD4/ZAP-70 reorganization and ceramide release in membrane rafts. Here, we investigated whether CD4/ZAP-70 compartmentalization could be mediated by an effect of 13B8.2 on the Carma1-Bcl10-MALT1 complex in membrane rafts. We report that treatment of CD3/CD28-activated Jurkat T cells with 13B8.2, but not rituximab, excluded Carma1-Bcl10-MALT1 proteins from GM1(+) membrane rafts and concomitantly decreased NF-κB activation. Fluorescence confocal imaging confirmed that Carma1-Bcl10 and Carma1-MALT1 co-patching, observed in GM1(+) membrane rafts following CD3/CD28 activation, were abrogated after a 24h-treatment with 13B8.2. The CD4/ZAP-70 compartmentalization in membrane rafts induced by 13B8.2 is thus related to Carma1-Bcl10-MALT1 raft exclusion.