Biology

Mammalian acetyl-CoA carboxylase (ACC) isoforms, ACC-1 and ACC-2, catalyze the formation of malonyl-CoA, a substrate for fatty acid synthesis and fatty acyl chain elongation, and a potent inhibitor of beta-oxidation. Based on the phenotype of knockout mice, ACC contributes significantly to overall body energy metabolism and is a potential drug target for the treatment of obesity and type II diabetes. Highly-purified ACC-1 undergoes a dramatic increase in mass following treatment with allosteric activators such as citrate, apparently due to linear polymerization of ACC dimers. The current studies were undertaken to explore (a) the extent to which ACC-2 undergoes polymerization and (b) to investigate whether other cellular proteins associate with and perhaps regulate the polymerization process. Size exclusion chromatography and sucrose gradient sedimentation studies show that ACC-2 undergoes very modest changes in molecular size upon allosteric activation, although the extent of polymerization of ACC-2 is enhanced in the presence of ACC-1. Isolation of the largest molecular forms of ACC, followed by mass spectrometry analysis, reveals that ACC "polymers" are multi-protein complexes. The proteins most reliably detected in ACC polymer fractions include tubulin, actin, fatty acid synthase, and heat shock proteins. The significance of the additional components of ACC complexes is evaluated from effects on the kinetics of the ACC reaction and of the polymerization process, as well as by cellular colocalization using fluorescence microscopy and co-immunoprecipitation studies. [ABSTRACT FROM AUTHOR]

Conference presentation delivered at the 15th <a href="http://www.aegeanconferences.org/src/App/conferences">Aegean Innate Immunity Conference (Chania, Crete, Greece, 2018)</a>. <p>Phagocytosis is a fundamental cellular activity preserved in a broad spectrum of eukaryotic organisms, from simple unicellular protists where it is used for the ingestion of food particles, to complex multicellular organisms where phagocytosis is an essential component of innate immunity against invading microorganisms. In this study, we report on the effect of glucose on phagocytosis in the model protist Tetrahymena pyriformis. Initial experiments examined the effects of temperature and contact time with the phagocytic target India ink, on phagocytosis by Tetrahymena. Phagocytosis was assessed by counting the number of phagocytic vacuoles in cells fixed with glutaraldehyde and visualized by light microscopy. Phagocytosis was maximal at room temperature and after 30 min of incubation with India ink. Glucose suppressed phagocytosis in a concentration-dependent manner. In addition, we demonstrated that exposure of cells to other hypertonic solutions, including sucrose, fructose, galactose and mannitol, used at 25mM concentrations, respectively, suppressed phagocytosis. Furthermore, we showed that hypotonic conditions, including incubation of cells in distilled water or diluted proteose peptone culture medium, had little effect on phagocytosis of India ink by Tetrahymena. Our studies may be relevant in elucidating the role of glucose and/or hypertonicity in contributing to impaired phagocytosis, and possibly enhanced risk of infections, in patients with untreated or poorly controlled diabetes mellitus, a condition associated with hyperglycemia.</p>