17 research outputs found
Ubiquitous presence of gluconeogenic regulatory enzyme, fructose-1,6-bisphosphatase, within layers of rat retina
To shed some light on gluconeogenesis in mammalian retina, we have focused on fructose-1,6-bisphosphatase (FBPase), a regulatory enzyme of the process. The abundance of the enzyme within the layers of the rat retina suggests that, in mammals in contrast to amphibia, gluconeogenesis is not restricted to one specific cell of the retina. We propose that FBPase, in addition to its gluconeogenic role, participates in the protection of the retina against reactive oxygen species. Additionally, the nuclear localization of FBPase and of its binding partner, aldolase, in the retinal cells expressing the proliferation marker Ki-67 indicates that these two gluconeogenic enzymes are involved in non-enzymatic nuclear processes
Nuclear localization of aldolase A in pig cardiomyocytes
The subcellular localization of the muscle
aldolase (aldolase A) in cardiomyocytes was determined
immunocytochemically by light and electron
microscopy. The enzyme was localized in the cytoplasm
and also in cardiomyocyte nuclei. Inside the nuclei it
was preferentially localized in the heterochromatin
region. The nuclear localization was confirmed by the
measurement of aldolase activity in subcellular fractions
of a heart muscle, and in isolated nuclei of
cardiomyocytes. There was no detectable aldolase
activity in isolated cardiomyocyte nuclei fractions if the
fraction was not preincubated with a solution containing
Triton X-100 and KCl. The calculated concentration of
aldolase in the nucleus was about 0.6 µM. This paper is
the first report on the localization of aldolase A inside
cardiomyocyte nuclei
Astrocyte-Neuron Crosstalk Regulates the Expression and Subcellular Localization of Carbohydrate Metabolism Enzymes
Astrocytes releasing glucose- and/or glycogen-derived lactate and glutamine play a crucial role in shaping neuronal function and plasticity. Little is known, however, how metabolic functions of astrocytes, e.g., their ability to degrade glucosyl units, are affected by the presence of neurons. To address this issue we carried out experiments which demonstrated that co-culturing of rat hippocampal astrocytes with neurons significantly elevates the level of mRNA and protein for crucial enzymes of glycolysis (phosphofructokinase, aldolase, and pyruvate kinase), glycogen metabolism (glycogen synthase and glycogen phosphorylase), and glutamine synthetase in astrocytes. Simultaneously, the decrease of the capability of neurons to metabolize glucose and glutamine is observed. We provide evidence that neurons alter the expression of astrocytic enzymes by secretion of as yet unknown molecule(s) into the extracellular fluid. Moreover, our data demonstrate that almost all studied enzymes may localize in astrocytic nuclei and this localization is affected by the co-culturing with neurons which also reduces proliferative activity of astrocytes. Our results provide the first experimental evidence that the astrocyte-neuron crosstalk substantially affects the expression of basal metabolic enzymes in the both types of cells and influences their subcellular localization in astrocytes. GLIA 2015;63:328-34
Insulin/IGF1-PI3K-dependent nucleolar localization of a glycolytic enzyme - phosphoglycerate mutase 2, is necessary for proper structure of nucleolus and RNA synthesis
Phosphoglycerate mutase (PGAM), a conserved, glycolytic enzyme has been found in nucleoli of cancer cells. Here, we present evidence that accumulation of PGAM in the nucleolus is a universal phenomenon concerning not only neoplastically transformed but also non-malignant cells. Nucleolar localization of the enzyme is dependent on the presence of the PGAM2 (muscle) subunit and is regulated by insulin/IGF-1-PI3K signaling pathway as well as drugs influencing ribosomal biogenesis. We document that PGAM interacts with several 40S and 60S ribosomal proteins and that silencing of PGAM2 expression results in disturbance of nucleolar structure, inhibition of RNA synthesis and decrease of the mitotic index of squamous cell carcinoma cells. We conclude that presence of PGAM in the nucleolus is a prerequisite for synthesis and initial assembly of new pre-ribosome subunits