Human angiogenin is a neuroprotective factor and amyotrophic lateral sclerosis associated angiogenin variants affect neurite extension/pathfinding and survival of motor neurons

Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
Human Molecular Genetics (Impact Factor: 6.39). 02/2008; 17(1):130-49. DOI: 10.1093/hmg/ddm290
Source: PubMed


Amyotrophic lateral sclerosis (ALS) is a late onset neurodegenerative disorder affecting upper and lower motor neurons (MNs). The molecular mechanisms underlying ALS are poorly understood. Mutations in SOD1 is one of the known causes of ALS but occur only in a very small number of cases of ALS. Interestingly, mutations in human angiogenin (hANG), a member of the ribonuclease A (RNase A) superfamily known to be involved in neovascularization, have been recently reported in patients with ALS, but the effects of these mutations on MN differentiation and survival has not been investigated. We have used the well-characterized pluripotent P19 embryonal carcinoma (EC) cell culture model of neuro-ectodermal differentiation to study the effects of hANG-ALS variants on MN differentiation and survival. Here we report that P19 EC cells induced to differentiate in the presence of hANG and hANG-ALS-associated variants internalize the wild-type and variant proteins. The P19 EC cells differentiate to form neurons but the ability of the neurites to extend and make contacts with neighbouring neurites is compromised when treated with the hANG-ALS variants. In addition, hANG-ALS variants also have a cytotoxic effect on MNs leading to their degeneration. hANG was able to protect neurons from hypoxia-induced cell death, but the variants of hANG implicated in ALS lacked the neuroprotective activity. Our findings show that ANG plays an important role in neurite extension/pathfinding and survival providing a causal link between mutations in hANG and ALS.

  • Source
    • "It has been shown that wild-type ANG (WT-ANG) has a wide tissue distribution and is strongly expressed in both endothelial cells, and MNs in fetal and adult spinal cord of humans8. WT-ANG acts as a neuroprotective factor because it determines the physiology and health of MNs by inducing angiogenesis, stimulating neurite outgrowth and path-finding and protecting MNs from hypoxia-induced death89. Several reports on heterozygous missense mutations of ANG and consequent experimental functional assays have shown that ANG insufficiency and loss-of-functions due to these mutations lead to ALS pathogenesis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Several missense mutations in the coding region of angiogenin (ANG) gene have been identified in Amyotrophic Lateral Sclerosis (ALS) patients. These mutations lead to loss of either ribonucleolytic activity or nuclear translocation activity or both of ANG (protein encoded by ANG gene) causing ALS. We present here a cohesive and comprehensive picture of the molecular origins of functional loss of all ALS associated ANG mutants, emerging via extensive molecular dynamics simulations. Our method effectively predicts that conformational change of His114 results in loss of ribonucleolytic activity and that reduction of solvent accessible surface area of nuclear localization signal residues (31)RRR(33) results in loss of nuclear translocation activity. These predictions hold true, without exception, for all ANG mutants studied and can be employed to infer whether a new ANG mutation is causative of ALS or benign ahead of experimental findings.
    Full-text · Article · Feb 2013 · Scientific Reports
  • Source
    • "The ALS-associated mutant K40I lacks neuroprotective effects compared to wildtype angiogenin in ALS models including hypoxia and serum deprivation [10], [11], [31]. While the mechanism whereby K40I is ineffective compared to wild-type angiogenin is not fully understood, it has been postulated to be a result of its inability to phosphorylate Akt [10], [11]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The angiogenic factor, angiogenin, has been recently linked to both Amyotrophic Lateral Sclerosis (ALS) and Parkinson Disease (PD). We have recently shown that endogenous angiogenin levels are dramatically reduced in an alpha-synuclein mouse model of PD and that exogenous angiogenin protects against cell loss in neurotoxin-based cellular models of PD. Here, we extend our studies to examine whether activation of the prosurvival Akt pathway is required for angiogenin's neuroprotective effects against 1-methyl-4-phenylpyridinium (MPP+), as observed in ALS models, and to test the effect of virally-mediated overexpression of angiogenin in an in vivo PD model. Using a dominant negative Akt construct, we demonstrate that inhibition of the Akt pathway does not reduce the protective effect of angiogenin against MPP+ toxicity in the dopaminergic SH-SY5Y cell line. Furthermore, an ALS-associated mutant of angiogenin, K40I, which fails to induce Akt phosphorylation, was similar to wildtype angiogenin in protection against MPP+. These results confirm previous work showing neuroprotective effects of angiogenin against MPP+, and indicate that Akt is not required for this protective effect. We also investigated whether adeno-associated viral serotype 2 (AAV2)-mediated overexpression of angiogenin protects against dopaminergic neuron loss in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model. We found that angiogenin overexpression using this approach does not reduce the MPTP-induced degeneration of dopaminergic cells in the substantia nigra, nor limit the depletion of dopamine and its metabolites in the striatum. Together, these findings extend the evidence for protective effects of angiogenin in vitro, but also suggest that further study of in vivo models is required to translate these effects into meaningful therapies.
    Full-text · Article · Feb 2013 · PLoS ONE
  • Source
    • "Angiogenin is expressed at high levels in the developing nervous system both in the brain and spinal cord, predominantly in neurons, and its activity has been shown to be necessary for neurite extension/pathfinding in differentiated motoneuron-like cells derived from pluripotent P19 carcinoma cells (Subramanian and Feng, 2007; Figure 1A and Table 2). Interestingly, ALS-associated angiogenin mutants failed to show the same activity (Subramanian et al., 2008). Angiogenin is also expressed and enriched in adult motoneurons (Greenway et al., 2006), and has been shown to protect mature, cultured motoneurons against different ALS-associated insults, such as excitotoxicity (Ca2+ mediated injury resulting from glutamate receptor overactivation), hypoxia, and endoplasmic reticulum stress. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Amyotrophic lateral sclerosis is a fatal neurodegenerative disease caused by the loss of motoneurons. The precise molecular and cellular basis for neuronal death is not yet well established, but the contemporary view is that it is a culmination of multiple aberrant biological processes. Among the proposed mechanisms of motoneuron degeneration, alterations in the homeostasis of RNA binding proteins (RBP) and the consequent changes in RNA metabolism have received attention recently. The ribonuclease, angiogenin was one of the first RBPs associated with familial and sporadic ALS. It is enriched in motoneurons under physiological conditions, and is required for motoneuron survival under stress conditions. Furthermore, delivery of angiogenin protects cultured motoneurons against stress-induced injury, and significantly increases the survival of motoneurons in SOD(G93A) mice. In this overview on the role of angiogenin in RNA metabolism and in the control of motoneuron survival, we discuss potential pathogenic mechanisms of angiogenin dysfunction relevant to ALS and other neurodegenerative disorders. We also discuss recent evidence demonstrating that angiogenin secreted from stressed motoneurons may alter RNA metabolism in astrocytes.
    Full-text · Article · Nov 2012 · Frontiers in Neuroscience
Show more