title: Motoneurons secrete angiogenin to induce RNA cleavage in astroglia.
abstract: Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disorder affecting motoneurons. Mutations in angiogenin, encoding a member of the pancreatic RNase A superfamily, segregate with ALS. We previously demonstrated that angiogenin administration shows promise as a neuroprotective therapeutic in studies using transgenic ALS mice and primary motoneuron cultures. Its mechanism of action and target cells in the spinal cord, however, are largely unknown. Using mixed motoneuron cultures, motoneuron-like NSC34 cells, and primary astroglia cultures as model systems, we here demonstrate that angiogenin is a neuronally secreted factor that is endocytosed by astroglia and mediates neuroprotection in paracrine. We show that wild-type angiogenin acts unidirectionally to induce RNA cleavage in astroglia, while the ALS-associated K40I mutant is also secreted and endocytosed, but fails to induce RNA cleavage. Angiogenin uptake into astroglia requires heparan sulfate proteoglycans, and engages clathrin-mediated endocytosis. We show that this uptake mechanism exists for mouse and human angiogenin, and delivers a functional RNase output. Moreover, we identify syndecan 4 as the angiogenin receptor mediating the selective uptake of angiogenin into astroglia. Our data provide new insights into the paracrine activities of angiogenin in the nervous system, and further highlight the critical role of non-neuronal cells in the pathogenesis of ALS.
authors.affiliation: Department of Physiology and Medical Physics, Centre for Study of Neurological Disorders, Royal College of Surgeons in Ireland, Dublin 2, Ireland.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Skorupa
authors.forename: Matthew A
authors.initials: MA
authors.lastname: King
authors.forename: Isabela M
authors.initials: IM
authors.lastname: Aparicio
authors.forename: Heiko
authors.initials: H
authors.lastname: Dussmann
authors.forename: Karen
authors.initials: K
authors.lastname: Coughlan
authors.forename: Bridget
authors.initials: B
authors.lastname: Breen
authors.forename: Dairin
authors.initials: D
authors.lastname: Kieran
authors.forename: Caoimhin G
authors.initials: CG
authors.lastname: Concannon
authors.forename: Philippe
authors.initials: P
authors.lastname: Marin
authors.forename: Jochen H M
authors.initials: JH
authors.lastname: Prehn
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000502:physiology*; D015153:Blotting, Western; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D002966:Clathrin / Q000502:physiology; D017077:Culture Media, Conditioned; D004705:Endocytosis / Q000502:physiology; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009046:Motor Neurons / Q000378:metabolism*; D018696:Neuroprotective Agents; D019899:Paracrine Communication / Q000502:physiology; D011485:Protein Binding; D059367:RNA Cleavage / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D012259:Ribonuclease, Pancreatic / Q000378:metabolism* / Q000502:physiology*; D053671:Syndecan-4 / Q000378:metabolism; D014162:Transfection
chemical_list: D002966:Clathrin; D017077:Culture Media, Conditioned; D018696:Neuroprotective Agents; D053671:Syndecan-4; C046366:angiogenin; D012259:Ribonuclease, Pancreatic