Motoneurons secrete angiogenin to induce RNA cleavage in astroglia.
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.
This research was supported by a Co-Tutelle PhD studentship provided by the National Biophotonics and Imaging Platform Ireland (funded by the Irish Government's Programme for Research in Third Level Institutions, Cycle 4, National Development Plan 2007–2013′), and by grants from Enterprise Ireland (TD 20090107), Science Foundation Ireland (08/IN1/B1949), and the Fondation Thierry Latran (AAP2011/PREHN) to J.H.M.P. We thank Sarah Cannon for technical assistance and Dr. Guo Fu Hu (Harvard Medical School.) for kindly providing anti-human angiogenin antiserum.
CommentsThis article is also available at http://www.jneurosci.org/content/32/15/5024.full.pdf+html
Published CitationSkorupa A, King MA, Aparicio IM, Dussmann H, Coughlan K, Breen B, Kieran D, Concannon CG, Marin P, Prehn JH. Motoneurons secrete angiogenin to induce RNA cleavage in astroglia. Journal of Neuroscience. 2012;32(15):5024-38.
- Physiology and Medical Physics