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Protection against HIV-1 gp120-induced brain damage by neuronal expression of human amyloid precursor protein.

ABSTRACT: Expression of the HIV-1 envelope protein gp120 in brains of transgenic (tg) mice induces extensive neurodegeneration (Toggas, S. M., E. Masliah, E. M. Rockenstein, G. F. Rall, C. R. Abraham, and L. Mucke. 1994. Nature [Lond.]. 367:188-193.). To further analyze the pathogenesis of gp120-induced neurotoxicity and to assess the neuroprotective potential of human amyloid precursor proteins (hAPPs) in vivo, different hAPP isoforms were expressed in neurons of gp120/hAPP-bigenic mice: hAPP751, which contains a Kunitz-type protease inhibitor domain, or hAPP695, which lacks this domain. Bigenic mice overexpressing hAPP751 at moderate levels showed significantly less neuronal loss, synapto-dendritic degeneration, and gliosis than singly tg mice expressing gp120 alone. In contrast, higher levels of hAPP695 expression in bigenic mice failed to prevent gp120-induced brain damage. These data indicate that hAPP can exert important neuroprotective functions in vivo and that the efficiency of this protection may depend on the hAPP isoform expressed and/or on the level of neuronal hAPP expression. Hence, molecules that mimic beneficial APP activities may be useful in the prevention/treatment of HIV-1-associated nervous system damage and, perhaps, also of other types of neural injury.

SUBMITTER: Mucke L

PROVIDER: S-EPMC2191956 | biostudies-other | 1995 Apr

REPOSITORIES: biostudies-other

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Protection against HIV-1 gp120-induced brain damage by neuronal expression of human amyloid precursor protein.

Mucke L L Abraham C R CR Ruppe M D MD Rockenstein E M EM Toggas S M SM Mallory M M Alford M M Masliah E E

The Journal of experimental medicine 19950401 4

Expression of the HIV-1 envelope protein gp120 in brains of transgenic (tg) mice induces extensive neurodegeneration (Toggas, S. M., E. Masliah, E. M. Rockenstein, G. F. Rall, C. R. Abraham, and L. Mucke. 1994. Nature [Lond.]. 367:188-193.). To further analyze the pathogenesis of gp120-induced neurotoxicity and to assess the neuroprotective potential of human amyloid precursor proteins (hAPPs) in vivo, different hAPP isoforms were expressed in neurons of gp120/hAPP-bigenic mice: hAPP751, which c ...[more]

PMID: 7699335

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Project description:The chemokine receptor CCR5 is a major co-receptor for human immunodeficiency virus 1 (HIV-1) mediating infection of target cells1,2. Beyond its function as co-receptor, CCR5 also influences the course of HIV disease and progression to AIDS3. However, it is unclear how CCR5 affects HIV-associated damage to the central nervous system (CNS) and development of HIV-associated neurocognitive disorders (HAND) independently of its co-receptor function. Here we show in a transgenic model of brain damage induced by HIV envelope protein gp1204 that genetic ablation of CCR5 prevents neuronal injury and loss and limits microglial activation, but fails to abrogate astrocytosis. CCR5 deficiency also protected gp120-transgenic mice against impairment of spatial learning and memory. Thus, CCR5-deficiency revealed that astrocytosis, a prominent pathological feature of AIDS brains5, can occur independently from neuronal demise and behavioral impairment. Since the viral envelope protein expressed in the transgenic mouse model originated from HIV-1 LAV4, a CXCR4-preferring virus that can infect macrophages6, CCR5 appeared to exert its control of neuronal injury predominantly in an indirect fashion and independently from its function as a co-receptor. Using analysis of genome-wide CNS gene expression we identified a subset of 734 genes that were differentially regulated in association with neuronal injury in the presence of CCR5. This subset of genes indicated that neuronal injury was associated with activation of macrophages and microglia. A set of 1305 genes was only differentially regulated in association with gp120 in the absence of CCR5 and indicated changes to leukocyte function and the anti-viral immune response besides a down-regulation of components in the GABAergic neurotransmission system. Interestingly, the most significantly differentially expressed genes were observed in a separate subset of 461 genes that was regulated in association with gp120 but independently of the CCR5 genotype. The finding that differential regulation of the 461 and 1305 gene sets was not necessarily linked to neuronal damage and loss suggested that altered expression of at least some of these factors may represent a protective adaptive response of the brain to the presence of viral gp120. Additional experiments using quantitative RT-PCR, protein assays and flow cytometry further supported the notion that CCR5 deficiency blunted microglial activation, a hallmark of HIV-associated brain injury7-9 without significantly affecting the expression of viral gp120. These results provide in vivo evidence for a significant role of CCR5 in HIV-associated CNS injury and behavioral impairment that is independent of the molecules’ function as HIV co-receptor. To characterize the neuroprotective effect of CCR5 ablation in the presence of HIV gp120, we next performed a genome-wide gene expression analysis using whole brain RNA preparations of mice from lines 1 and 2. We decided to collect samples from two time points before and after the ages of when we analyzed histopathology (6 months) and behavior (8 to 9 months) in order to identify genes for which differential regulation may be affected by an interaction of HIVgp120 expression and age. Accordingly, we collected brain tissue of gp120tg, CCR5KO x gp120tg, WT and CCR5KO mice at five different ages: 1.5, 3, 6, 12, and 20 (line 1) or 16 (line 2) months.

Project description:UnlabelledAmyloid precursor protein (APP) was originally identified as the source of β-amyloid peptides that accumulate in Alzheimer's disease (AD), but it also has been implicated in the control of multiple aspects of neuronal motility. APP belongs to an evolutionarily conserved family of transmembrane proteins that can interact with a variety of adapter and signaling molecules. Recently, we showed that both APP and its insect ortholog [APPL (APP-Like)] directly bind the heterotrimeric G-protein Goα, supporting the model that APP can function as an unconventional Goα-coupled receptor. We also adapted a well characterized assay of neuronal migration in the hawkmoth, Manduca sexta, to show that APPL-Goα signaling restricts ectopic growth within the developing nervous system, analogous to the role postulated for APP family proteins in controlling migration within the mammalian cortex. Using this assay, we have now identified Manduca Contactin (MsContactin) as an endogenous ligand for APPL, consistent with previous work showing that Contactins interact with APP family proteins in other systems. Using antisense-based knockdown protocols and fusion proteins targeting both proteins, we have shown that MsContactin is selectively expressed by glial cells that ensheath the migratory neurons (expressing APPL), and that MsContactin-APPL interactions normally prevent inappropriate migration and outgrowth. These results provide new evidence that Contactins can function as authentic ligands for APP family proteins that regulate APP-dependent responses in the developing nervous system. They also support the model that misregulated Contactin-APP interactions might provoke aberrant activation of Goα and its effectors, thereby contributing to the neurodegenerative sequelae that typify AD.Significance statementMembers of the amyloid precursor protein (APP) family participate in many aspects of neuronal development, but the ligands that normally activate APP signaling have remained controversial. This research provides new evidence that members of the Contactin family function as authentic ligands for APP and its orthologs, and that this evolutionarily conserved class of membrane-attached proteins regulates key aspects of APP-dependent migration and outgrowth in the embryonic nervous system. By defining the normal role of Contactin-APP signaling during development, these studies also provide the framework for investigating how the misregulation of Contactin-APP interactions might contribute to neuronal dysfunction in the context of both normal aging and neurodegenerative conditions, including Alzheimer's disease.

Dataset Information

Protection against HIV-1 gp120-induced brain damage by neuronal expression of human amyloid precursor protein.

Publications

Protection against HIV-1 gp120-induced brain damage by neuronal expression of human amyloid precursor protein.

Similar Datasets

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