The Cellular Prion Protein Interacts with the Tissue Non-Specific Alkaline Phosphatase in Membrane Microdomains of Bioaminergic Neuronal Cells

BACKGROUND: The cellular prion protein, PrP(C), is GPI anchored and abundant in lipid rafts. The absolute requirement of PrP(C) in neurodegeneration associated to prion diseases is well established. However, the function of this ubiquitous protein is still puzzling. Our previous work using the 1C11 neuronal model, provided evidence that PrP(C) acts as a cell surface receptor. Besides a ubiquitous signaling function of PrP(C), we have described a neuronal specificity pointing to a role of PrP(C) in neuronal homeostasis. 1C11 cells, upon appropriate induction, engage into neuronal differentiation programs, giving rise either to serotonergic (1C11(5-HT)) or noradrenergic (1C11(NE)) derivatives. METHODOLOGY/PRINCIPAL FINDINGS: The neuronal specificity of PrP(C) signaling prompted us to search for PrP(C) partners in 1C11-derived bioaminergic neuronal cells. We show here by immunoprecipitation an association of PrP(C) with an 80 kDa protein identified by mass spectrometry as the tissue non-specific alkaline phosphatase (TNAP). This interaction occurs in lipid rafts and is restricted to 1C11-derived neuronal progenies. Our data indicate that TNAP is implemented during the differentiation programs of 1C11(5-HT) and 1C11(NE) cells and is active at their cell surface. Noteworthy, TNAP may contribute to the regulation of serotonin or catecholamine synthesis in 1C11(5-HT) and 1C11(NE) bioaminergic cells by controlling pyridoxal phosphate levels. Finally, TNAP activity is shown to modulate the phosphorylation status of laminin and thereby its interaction with PrP. CONCLUSION/SIGNIFICANCE: The identification of a novel PrP(C) partner in lipid rafts of neuronal cells favors the idea of a role of PrP in multiple functions. Because PrP(C) and laminin functionally interact to support neuronal differentiation and memory consolidation, our findings introduce TNAP as a functional protagonist in the PrP(C)-laminin interplay. The partnership between TNAP and PrP(C) in neuronal cells may provide new clues as to the neurospecificity of PrP(C) function

Déviation du métabolisme énergétique et neurodégénérescence dans les maladies à prions

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The Cellular Prion Protein—ROCK Connection: Contribution to Neuronal Homeostasis and Neurodegenerative Diseases

International audienceAmyloid-based neurodegenerative diseases such as prion, Alzheimer's, and Parkinson's diseases have distinct etiologies and clinical manifestations, but they share common pathological events. These diseases are caused by abnormally folded proteins (pathogenic prions PrP Sc in prion diseases, β-amyloids/Aβ and Tau in Alzheimer's disease, α-synuclein in Parkinson's disease) that display β-sheet-enriched structures, propagate and accumulate in the nervous central system, and trigger neuronal death. In prion diseases, PrP Sc -induced corruption of the physiological functions exerted by normal cellular prion proteins (PrP C ) present at the cell surface of neurons is at the root of neuronal death. For a decade, PrP C emerges as a common cell surface receptor for other amyloids such as Aβ and α-synuclein, which relays, at least in part, their toxicity. In lipid-rafts of the plasma membrane, PrP C exerts a signaling function and controls a set of effectors involved in neuronal homeostasis, among which are the RhoA-associated coiled-coil containing kinases (ROCKs). Here we review (i) how PrP C controls ROCKs, (ii) how PrP C -ROCK coupling contributes to neuronal homeostasis, and (iii) how the deregulation of the PrP C -ROCK connection in amyloid-based neurodegenerative diseases triggers a loss of neuronal polarity, affects neurotransmitter-associated functions, contributes to the endoplasmic reticulum stress cascade, renders diseased neurons highly sensitive to neuroinflammation, and amplifies the production of neurotoxic amyloids

Production of seedable Amyloid-β peptides in model of prion diseases upon PrPSc-induced PDK1 overactivation

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Axon diodes for the reconstruction of oriented neuronal networks in microfluidic chambers

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PDK1 decreases TACE-mediated alpha-secretase activity and promotes disease progression in prion and Alzheimer's diseases

α-secretase–mediated cleavage of amyloid precursor protein (APP) precludes formation of neurotoxic amyloid-β (Aβ) peptides, and α-cleavage of cellular prion protein (PrPC) prevents its conversion into misfolded, pathogenic prions (PrPSc). The mechanisms leading to decreased α-secretase activity in Alzheimer's and prion disease remain unclear. Here, we find that tumor necrosis factor-α–converting enzyme (TACE)-mediated α-secretase activity is impaired at the surface of neurons infected with PrPSc or isolated from APP-transgenic mice with amyloid pathology. 3-phosphoinositide–dependent kinase-1 (PDK1) activity is increased in neurons infected with prions or affected by Aβ deposition and in the brains of individuals with Alzheimer's disease. PDK1 induces phosphorylation and caveolin-1–mediated internalization of TACE. This dysregulation of TACE increases PrPSc and Aβ accumulation and reduces shedding of TNF-α receptor type 1 (TNFR1). Inhibition of PDK1 promotes localization of TACE to the plasma membrane, restores TACE-dependent α-secretase activity and cleavage of APP, PrPC and TNFR1, and attenuates PrPSc- and Aβ-induced neurotoxicity. In mice, inhibition or siRNA-mediated silencing of PDK1 extends survival and reduces motor impairment following PrPSc infection and in APP-transgenic mice reduces Alzheimer's disease-like pathology and memory impairment.8 page(s

The expression of a functional TNAP is restricted to differentiated serotonergic and noradrenergic 1C11 derived-cells.

<p>In (A), the presence of TNAP in 1 µg of lipid rafts prepared from 1C11 induced or not to differentiate was revealed by western blot analysis using an anti-TNAP specific antibody. In (B), the expression of TNAP mRNAs was evaluated by PCR analysis. TNAP (upper panel) or GAPDH (lower panel) specific fragments were obtained after amplification by PCR of cDNA synthesized from mRNA isolated from the 1C11 precursor and the differentiated 1C11^5-HT and 1C11^NE cells. In (C), phosphatase activity at the surface of 1C11 and 1C11^5-HT cells was measured by luminescence using the CSPD substrate and expressed as relative luminescent unit (RLU). White bars correspond to total phosphatase activities, black bars to the activity measured in the presence of 1 mM orthovanadate and grey bars in the presence of 5 mM tetramisol.</p