ABSTRACT
The glutamate uptake transporter GLT-1 is best understood for its critical role in preventing brain seizures. Increasing evidence argues that GLT-1 also modulates, and is modulated by, metabolic processes that influence glucose homeostasis. To investigate further the potential role of GLT-1 in these regards, the authors examined GLT-1 expression in pancreas and found that mature multimeric GLT-1 protein is stably expressed in the pancreas of wild-type, but not GLT-1 knockout, mice. There are three primary functional carboxyl-terminus GLT-1 splice variants, called GLT-1a, b, and c. Brain and liver express all three variants; however, the pancreas expresses GLT-1a and GLT-1b but not GLT-1c. Quantitative real time-PCR further revealed that while GLT-1a is the predominant GLT-1 splice variant in brain and liver, GLT-1b is the most abundant splice variant expressed in pancreas. Confocal microscopy and immunohistochemistry showed that GLT-1a and GLT-1b are expressed in both islet ß- and α-cells. GLT-1b was also expressed in exocrine ductal domains. Finally, glutamine synthetase was coexpressed with GLT-1 in islets, which suggests that, as with liver and brain, one possible role of GLT-1 in the pancreas is to support glutamine synthesis.
Subject(s)
Excitatory Amino Acid Transporter 2/genetics , Pancreas/metabolism , Animals , Excitatory Amino Acid Transporter 2/deficiency , Excitatory Amino Acid Transporter 2/metabolism , Gene Expression Profiling , Immunohistochemistry , Mice , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Confocal , Pancreas/cytology , Real-Time Polymerase Chain ReactionABSTRACT
The clinical hallmark of Alzheimer's disease (AD) is impairment of cognition associated with loss of synapses, accumulation of amyloid-beta (Abeta) both within neurons and as extracellular deposits, and neurofibrillary degeneration composed of phospho-tau. Neurons in the hippocampus are among those that are most vulnerable. The purpose of this study was to investigate the expression of genes associated with cognition, synapse, and mitochondrial function in hippocampal neurons of AD compared to normal individuals. Neurons from the hippocampus with intraneuronal Abeta immunoreactivity were captured with laser microdissection; RNA was extracted; and levels of brain-derived neurotrophic factor (BDNF), TrkB (BDNF receptor), dynamin-1 (DYN), and cytochrome C oxidase subunit II (COX2) were assessed with quantitative real-time polymerase chain reaction. We found no significant differences in the expression of these genes in AD between neurons associated with Abeta compared to those lacking Abeta immunoreactivity. Double immunofluorescence microscopy showed the number of hippocampal neurons coexpressing Abeta or phospho-tau and either BDNF, TrkB, or DYN was similar in AD and controls. Our results suggest that neither intraneuronal Abeta nor phospho-tau has obligatory effects on reducing the expression of genes important for memory and cognition in hippocampus of AD.
Subject(s)
Alzheimer Disease/genetics , Alzheimer Disease/metabolism , Amyloid beta-Peptides/genetics , Gene Expression Regulation , Intracellular Fluid/metabolism , Neurons/metabolism , tau Proteins/genetics , Aged , Aged, 80 and over , Alzheimer Disease/pathology , Amyloid beta-Peptides/biosynthesis , Cognition/physiology , Hippocampus/metabolism , Hippocampus/pathology , Humans , Longitudinal Studies , Mitochondrial Proteins/genetics , Neurons/pathology , Prospective Studies , Synapses/genetics , tau Proteins/biosynthesisABSTRACT
Infection of the brain by HIV-1 often results in cognitive- motor disorders, the most severe form being HIV-1 associated dimentia (HAD). However, the etiology and pathogenesis of neuroAIDS at the molecular level is still not fully understood and controversial issues remain, including the significance of abortive infection and localized viral load. This paper proposes that quantitative comparison of HIV-1 proviral and RNAloads across the brain will clarify some of these issues. It was hypothesized that there are differences in ratios of multispliced and unspliced HIV RNA in different regions of brain by analogy with prior findings of brain regional differences in virus and strains of HIV-1. A competitive RT-PCR method was used to compare ratios of multispliced to unspliced HIV-1 RNA's across brain regions of one case with HAD. Statistical analysis results showed that data obtained by repeated assays for each RNA preparation were not significantly different. Significant differences were detected between specimens obtained from different regions of the brain. The ratio of MS/US RNA in the frontal lobe was significantly greater than in the basal ganglia, medial temporal lobe, and another site in the temporal lobe. It must be noted that our approach has been the analysis of macroscopic brain regions separated by several centimeters; future studies will analyze microscopic analysis of these brain regions. The current study was preformed to produce results on gross differences in neuroanatomical locations at cm distances. Future studies will be performed to compare different regions with microscopic anatomic specificity.