Acyl-CoA-binding protein (ACBP) localizes to the endoplasmic reticulum and Golgi in a ligand-dependent manner in mammalian cells

International audienceIn the present study, we microinjected fluorescently labelled liver bovine ACBP (FACI-50), into HeLa and bovine mammary gland epithelial (BMGE) cell lines to characterize the localization and dynamics of ACBP in living cells. Results showed that ACBP targeted to the endoplasmic reticulum (ER) and Golgi in a ligand-binding dependent manner. A variant Y28F/K32A-FACI-50, which is unable to bind acyl-CoA, did no longer show association with ER and became segregated from Golgi, as analysed by intensity correlation calculations. Depletion of fatty acids from cells by addition of fatty acid free BSA (FAFBSA) significantly decreased FACI-50 association with Golgi, while fatty acid overloading increased Golgi-association, strongly supporting that ACBP associates with Golgi in a ligand-dependent manner. Fluorescence recovery after photobleaching (FRAP) showed that the fatty acid induced targeting of FACI-50 to Golgi resulted in a 5-fold reduction in FACI-50 mobility. We suggest that ACBP is targeted to ER and Golgi in a ligand-binding dependent manner in living cells, and propose that ACBP may be involved in vesicular trafficking

Phosphoproteomic analysis of cells treated with longevity-related autophagy inducers

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The Adiponectin Receptor Homologs in C. elegans Promote Energy Utilization and Homeostasis

Adiponectin is an adipokine with insulin-sensitising actions in vertebrates. Its receptors, AdipoR1 and AdipoR2, are PAQR-type proteins with 7-transmembrane domains and topologies reversed that of GPCR's, i.e. their C-termini are extracellular. We identified three adiponectin receptor homologs in the nematode C. elegans, named paqr-1, paqr-2 and paqr-3. These are differently expressed in the intestine (the main fat-storing tissue), hypodermis, muscles, neurons and secretory tissues, from which they could exert systemic effects. Analysis of mutants revealed that paqr-1 and -2 are novel metabolic regulators in C. elegans and that they act redundantly but independently from paqr-3. paqr-2 is the most important of the three paqr genes: mutants grow poorly, fail to adapt to growth at low temperature, and have a very high fat content with an abnormal enrichment in long (C20) poly-unsaturated fatty acids when combined with the paqr-1 mutation. paqr-2 mutants are also synthetic lethal with mutations in nhr-49, sbp-1 and fat-6, which are C. elegans homologs of nuclear hormone receptors, SREBP and FAT-6 (a Δ9 desaturase), respectively. Like paqr-2, paqr-1 is also synthetic lethal with sbp-1. Mutations in aak-2, the C. elegans homolog of AMPK, or nhr-80, another nuclear hormone receptor gene, suppress the growth phenotype of paqr-2 mutants, probably because they restore the balance between energy expenditure and storage. We conclude that paqr-1 and paqr-2 are receptors that regulate fatty acid metabolism and cold adaptation in C. elegans, that their main function is to promote energy utilization rather than storage, and that PAQR class proteins have regulated metabolism in metazoans for at least 700 million years

Acyl-CoA binding protein is an essential protein in mammalian cell lines.

In the present work, small interference RNA was used to knock-down acyl-CoA binding protein (ACBP) in HeLa, HepG2 and Chang cells. Transfection with ACBP-specific siRNA stopped growth, detached cells from the growth surface and blocked thymidine and acetate incorporation. The results show that depletion of ACBP in mammalian cells results in lethality, suggesting that ACBP is an essential protein

Elimination of the last reactions in ergosterol biosynthesis alters the resistance of Saccharomyces cerevisiae to multiple stresses

The sterol composition of membranes is known to influence many phenotypes of yeast. However, a systematic study of the relationship between sterol composition and stress resistances has not been conducted. Here, we therefore constructed single or double gene deletion mutants of the last four enzymes in ergosterol biosynthesis in a prototrophic genetic background of Saccharomyces cerevisiae. Identification of the sterol composition of these mutants revealed a high flexibility of the sterol-processing steps instead of the previously proposed sequential conversion. Compared with the wild type, the mutants showed altered resistances to different exogenous stresses regarding the specific growth rate and duration of lag phase. The erg5 deletion mutant whose sterol has a saturated side chain exhibited overall robust growth under the tested stress conditions. The thermotolerant phenotype of erg5 deletion mutant was reproduced in filamentous fungus Penicillium oxalicum. These results highlight the important role of sterols in the response of yeast cells to environmental stresses, and suggest the possibility of improving the robustness of industrial yeast strains by engineering their sterol composition

Serotonin Regulates C. elegans Fat and Feeding through Independent Molecular Mechanisms

SummaryWe investigated serotonin signaling in C. elegans as a paradigm for neural regulation of energy balance and found that serotonergic regulation of fat is molecularly distinct from feeding regulation. Serotonergic feeding regulation is mediated by receptors whose functions are not required for fat regulation. Serotonergic fat regulation is dependent on a neurally expressed channel and a G protein-coupled receptor that initiate signaling cascades that ultimately promote lipid breakdown at peripheral sites of fat storage. In turn, intermediates of lipid metabolism generated in the periphery modulate feeding behavior. These findings suggest that, as in mammals, C. elegans feeding behavior is regulated by extrinsic and intrinsic cues. Moreover, obesity and thinness are not solely determined by feeding behavior. Rather, feeding behavior and fat metabolism are coordinated but independent responses of the nervous system to the perception of nutrient availability