Cholinergic Regulation of hnRNPA2/B1 Translation by M1 Muscarinic Receptors.
Cholinergic vulnerability, characterized by loss of acetylcholine (ACh), is one of the hallmarks of Alzheimer's disease (AD). Previous work has suggested that decreased ACh activity in AD may contribute to pathological changes through global alterations in alternative splicing. This occurs, at least partially, via the regulation of the expression of a critical protein family in RNA processing, heterogeneous nuclear ribonucleoprotein (hnRNP) A/B proteins. These proteins regulate several steps of RNA metabolism, including alternative splicing, RNA trafficking, miRNA export, and gene expression, providing multilevel surveillance in RNA functions. To investigate the mechanism by which cholinergic tone regulates hnRNPA2/B1 expression, we used a combination of genetic mouse models and in vivo and in vitro techniques. Decreasing cholinergic tone reduced levels of hnRNPA2/B1, whereas increasing cholinergic signaling in vivo increased expression of hnRNPA2/B1. This effect was not due to decreased hnRNPA2/B1 mRNA expression, increased aggregation, or degradation of the protein, but rather to decreased mRNA translation by nonsense-mediated decay regulation of translation. Cell culture and knock-out mice experiments demonstrated that M1 muscarinic signaling is critical for cholinergic control of hnRNPA2/B1 protein levels. Our experiments suggest an intricate regulation of hnRNPA2/B1 levels by cholinergic activity that interferes with alternative splicing in targeted neurons mimicking deficits found in AD.



In Alzheimer's disease, degeneration of basal forebrain cholinergic neurons is an early event. These neurons communicate with target cells and regulate their long-term activity by poorly understood mechanisms. Recently, the splicing factor hnRNPA2/B, which is decreased in Alzheimer's disease, was implicated as a potential mediator of long-term cholinergic regulation. Here, we demonstrate a mechanism by which cholinergic signaling controls the translation of hnRNPA2/B1 mRNA by activation of M1 muscarinic type receptors. Loss of cholinergic activity can have profound effects in target cells by modulating hnRNPA2/B1 levels.
Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A5K8, and Graduate Program in Neuroscience.
Benjamin
B
Kolisnyk
Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A5K8, and Anatomy and Cell Biology.
Mohammed A
MA
Al-Onaizi
Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A5K8, and Anatomy and Cell Biology.
Jason
J
Xu
Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A5K8, and.
Gustavo M
GM
Parfitt
Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A5K8, and Departments of Physiology and Pharmacology and.
Valeriy G
VG
Ostapchenko
The Edmond and Lily Safra Center for Brain Sciences, and The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel 91904.
Geula
G
Hanin
The Edmond and Lily Safra Center for Brain Sciences, and The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel 91904.
Hermona
H
Soreq
Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A5K8, and Graduate Program in Neuroscience, Departments of Physiology and Pharmacology and Anatomy and Cell Biology, mprado@robarts.ca vprado@robarts.ca.
Marco A M
0000-0002-3028-5778
MA
Prado
Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A5K8, and Graduate Program in Neuroscience, Departments of Physiology and Pharmacology and Anatomy and Cell Biology, mprado@robarts.ca vprado@robarts.ca.
Vania F
0000-0003-4994-6393
VF
Prado
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D002795:Choline O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D018678:Cholinergic Agents / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology*; D004622:Embryo, Mammalian; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000235:genetics; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects*; D043643:Receptor, Muscarinic M1 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects / Q000235:genetics; D050494:Vesicular Acetylcholine Transport Proteins / Q000235:genetics / Q000378:metabolism
D018678:Cholinergic Agents; D018679:Cholinergic Agonists; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D009687:Nuclear Proteins; D043643:Receptor, Muscarinic M1; C493460:Slc18a3 protein, mouse; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; D050494:Vesicular Acetylcholine Transport Proteins; C439768:hnRNP A2; D002217:Carbachol; D002795:Choline O-Acetyltransferase
Alzheimer's disease; VAChT; acetylcholine; alternative splicing; hippocampus