Predominance of the Cytoplasmic Form of Brain Hexokinase in Cultured Astrocytes

Lusk, James A.; Manthorpe, C. Marston; Kao‐Jen, Judy; Wilson, John E.

doi:10.1111/j.1471-4159.1980.tb11221.x

Cited by 23 publications

(19 citation statements)

References 24 publications

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“…It dges not seem likely that the relative distribution of hexokinase between cytoplasm and mitochondria can be directly correlated with cell type, i.e., neurons versus glia. Recently Roth-Schecter et al (1979) have reported that, in agreement with Lusk et al (1980), the predominant form of hexokinase in cultured astrocytes has a cytoplasmic location; addition of pentobarbital to the cultures, however, resulted in increased levels of hexokinase in the cells with the bulk of the increase seen in the mitochondrial-bound enzyme. Thus it would appear that, even in a given cell type, the relative distribution of hexokinase between cytoplasm and mitochondria may be influenced by environmental factors.…”

Section: J Kao-jen and J E Wilsonmentioning

confidence: 78%

“…In view of the marginal improvement from using the Vibratome and the considerably greater time requirement for preparing sections in this manner, we did not routinely use this method. modification of a method described previously (Lusk et al, 1980). All dilutions were prepared with 0.05 M-Tris-HCl buffer-0.9% NaCI, pH 7.6, containing 0.5% normal goat serum.…”

Section: Methodsmentioning

confidence: 99%

“…It has also been suggested that the hexokinase is localized predominantly in the cytoplasm of glia, but on the mitochondria of neurons (Bigl et al, 1971). Previous work (Lusk et al, 1980) had indicated that most of the hexokinase in cultured astroctyes could be assigned a cytoplasmic location. The extensive staining of the cytoplasmic regions of the astrocytes in situ seen in the present study is consistent with these earlier results; i.e., although intense staining of mitochondria1 profiles, particularly in the glial end feet, was seen, the deposits of peroxidase reaction product throughout the cytoplasm clearly indicated the presence of substantial nonmitochondrial activity in these cells.…”

Section: J Kao-jen and J E Wilsonmentioning

confidence: 99%

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Localization of Hexokinase in Neural Tissue: Electron Microscopic Studies of Rat Cerebellar Cortex

Kao‐Jen

Wilson

1980

Journal of Neurochemistry

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The distribution of hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) in the rat cerebellar cortex has been studied at the electron microscopic level using the peroxidase-antiperoxidase procedure. Extensive staining of cytoplasmic regions, with some increased staining at mitochondrial profiles, was seen in the cell bodies of both neurons (basket, stellate, Lugaro, Golgi, and granule cells) and astrocytes. Oligodendrocytes showed little or no detectable staining. Purkinje cell perikarya were much less intensely stained than were the perikarya of other neurons. The initial portion of the Purkinje dendrite was, like the perikaryon from which it emerged, lightly stained. More intense staining was seen in the secondary and tertiary branches of the Purkinje dendrite, but the terminal branches were devoid of stain. Granule cell dendrites were well stained in their initial portions but devoid of stain in their terminal dendritic digits which form part of the cerebellar glomeruli. In contrast to the unstained granule cell dendritic digits, the central mossy fiber nerve terminal of the glomerulus exhibited intense staining of the mitochondrial profiles and of synaptic vesicles adjacent to the mitochondria. Axons of basket cells showed intense staining in the segments adjacent to the Purkinje cell soma, while terminal twigs of the basket axons in the pinceau surrounding the (unstained) initial segment of the Purkinje axon showed markedly decreased staining intensity. These results indicate that there may be substantial variation in hexokinase levels between the various regions of neuronal processes. Hexokinase was seen at both cytoplasmic and mitochondrial locations in a variety of cells. It does not appear likely that location of hexokinase can be directly correlated with cell type, i.e., with neurons versus glia.

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Section: J Kao-jen and J E Wilsonmentioning

confidence: 78%

Section: Methodsmentioning

confidence: 99%

Section: J Kao-jen and J E Wilsonmentioning

confidence: 99%

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Localization of Hexokinase in Neural Tissue: Electron Microscopic Studies of Rat Cerebellar Cortex

Kao‐Jen

Wilson

1980

Journal of Neurochemistry

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“…Astroglial cells express hexokinase I, the primary isoform of hexokinase found in brain. The early report on the predominance of soluble hexokinase in white matter of the cat brain (Bigl et al, 1971) corresponded well with the finding that in homogenates of cultured astrocytes about 80% of hexokinase activity was found in the soluble fraction (Lusk et al, 1980). However, in a recent study, astroglial cells were fixed with paraformaldehyde, incubated with monoclonal antibody against hexokinase I, and the localization of immunoreactivity was investigated with confocal laser microscopy (Lynch et al, 1991).…”

Section: Phosphorylation Of Carbohydrates By Astrocytesmentioning

confidence: 81%

Metabolic pathways for glucose in astrocytes

Wiesinger

Hamprecht

Dringen

1997

Glia

167

110

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Cultured astroglial cells are able to utilize the monosaccharides glucose, mannose, or fructose as well as the sugar alcohol sorbitol as energy fuel. Astroglial uptake of the aldoses is carrier‐mediated, whereas a non‐saturable transport mechanism is operating for fructose and sorbitol. The first metabolic step for all sugars, including fructose being generated by enzymatic oxidation of sorbitol, is phosphorylation by hexokinase. Besides glucose only mannose may serve as substrate for build‐up of astroglial glycogen. Whereas glycogen synthase appears to be present in astrocytes as well as neurons, the exclusive localization of glycogen phosphorylase in astrocytes and ependymal cells of central nervous tissue correlates well with the occurrence of glycogen in these cells. The identification of lactic acid rather than glucose as degradation product of astroglial glycogen appears to render the presence of glucose‐6‐phosphatase in cultured astrocytes an enigma. The colocalization of pyruvate carboxylase, phosphenolpyruvate carboxykinase and fructose‐1,6‐bisphosphatase points to astrocytes as being the gluconeogenic cell type of the CNS. GLIA 21:22–34, 1997. © 1997 Wiley‐Liss, Inc.

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“…However, no differentiation could be made between the hepatic and ␤-cell forms of this enzyme, since the PCR primers were specifically designed to cover a region homologous to both. This issue may be of some importance, because only hepatic GK expression is reduced by fasting and reinstated by refeeding (50). Such responsiveness to the metabolic state of the animal plays an important regulatory role in the expression of both pro-opiomelanocortin (POMC) and NPY in the ARC.…”

Section: Discussionmentioning

confidence: 99%

Localization of glucokinase gene expression in the rat brain.

et al. 2000

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The brain contains a subpopulation of glucosensing neurons that alter their firing rate in response to elevated glucose concentrations. In pancreatic ␤-cells, glucokinase (GK), the rate-limiting enzyme in glycolysis, mediates glucose-induced insulin release by regulating intracellular ATP production. A similar role for GK is proposed to underlie neuronal glucosensing. Via in situ hybridization, GK mRNA was localized to hypothalamic areas that are thought to contain relatively large populations of glucosensing neurons (the arcuate, ventromedial, dorsomedial, and paraventricular nuclei and the lateral area). GK also was found in brain areas without known glucosensing neurons (the lateral habenula, the bed nucleus stria terminalis, the inferior olive, the retrochiasmatic and medial preoptic areas, and the thalamic posterior paraventricular, interpeduncular, oculomotor, and anterior olfactory nuclei). Conversely, GK message was not found in the nucleus tractus solitarius, which contains glucosensing neurons, or in ependymal cells lining the third ventricle, where others have described its presence. In the arcuate nucleus, >75% of neuropeptide Y-positive neurons also expressed GK, and most GK + neurons also expressed KIR6.2 (the pore-forming subunit of the ATP-sensitive K + channel). The anatomic distribution of GK mRNA was confirmed in micropunch samples of hypothalamus via reverse transcription-polymerase chain reaction (RT-PCR). Nucleotide sequencing of the recovered PCR product indicated identity with nucleotides 1092-1411 (within exon 9 and 10) of hepatic and ␤-cell GK. The specific anatomic localization of GK mRNA in hypothalamic areas known to contain glucosensing neurons and the coexpression of KIR6.2 and NPY in GK + neurons support a role for GK as a primary determinant of glucosensing in neuropeptide neurons that integrate multiple signals relating to peripheral energy metabolism. Diabetes 49:693-700, 2000 M ammalian feeding behavior and general energy homeostasis appear to be regulated by circulating levels of nutrients (glucose) and peptides (e.g., leptin, insulin). Sensors to detect levels of these factors have been found to reside within specific nuclei of the hypothalamus (1-8), where central regulation of energy homeostasis is believed to be coordinated. For example, large changes in blood glucose are correlated with centrally mediated responses such as thermogenesis through activation of the sympathetic nervous system. These changes are monitored by the brain (9-11), and such responses are altered in obesity-prone animals (11-13). Moreover, lesions of the ventromedial hypothalamus (VMH) prevent the hypoglycemic activation of the sympathetic response (14). Thus, available data indicate that glucose detection by hypothalamic neurons may play an important role in regulating energy homeostasis.Glucosensing neurons are among the best characterized of such metabolic sensors. Unlike most neurons, they use glucose as a signaling molecule to alter their firing rate in response to changes in ambient glucose le...

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Predominance of the Cytoplasmic Form of Brain Hexokinase in Cultured Astrocytes

Cited by 23 publications

References 24 publications

Localization of Hexokinase in Neural Tissue: Electron Microscopic Studies of Rat Cerebellar Cortex

Localization of Hexokinase in Neural Tissue: Electron Microscopic Studies of Rat Cerebellar Cortex

Metabolic pathways for glucose in astrocytes

Localization of glucokinase gene expression in the rat brain.

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