Notch activation induces neurite remodeling and functional modifications in SH‐SY5Y neuronal cells

Abstract

Notch proteins are definitely recognized as key regulators of the neuronal fate during embryo development, but their function in the adult brain is still largely unknown. We have previously demonstrated that Notch pathway stimulation increases microtubules stability followed by the remodeling of neuronal morphology with neurite varicosities loss, thicker neuritis, and enlarged growth cones. Here we show that the neurite remodeling is a dynamic event, dependent on transcription and translation, and with functional implications. Exposure of differentiated human SH-SY5Y neuroblastoma cells to the Notch ligand Jagged1 induces varicosities loss all along the neurites, accompanied by the redistribution of presynaptic vesicles and the decrease in neurotransmitters release. As evaluated by time lapse digital imaging, dynamic changes in neurite morphology were rapidly reversible and dependent on the activation of the Notch signaling pathway. In fact, it was prevented by the inhibition of the proteolytic c-secretase enzyme or the transcription machinery, and was mimicked by the transfection of the intracellular domain of Notch. One hour after treatment with Jagged1, several genes were downregulated. Many of these genes encode proteins that are known to be involved in protein synthesis. These data suggest that in adult neurons, Notch pathway activates a transcriptional program that regulates the equilibrium between varicosities formation and varicosities loss in the neuronal presynaptic compartment involving the expression and redistribution of both structural and functional proteins.

Notch signaling and neural connectivity

“…Analyses of mammalian neurons in a variety of primary culture and cell line paradigms have provided insights into mechanisms by which Notch may control neurite growth [17–19]. These include stabilization of microtubules[20], turnover of varicosities and filopodia on neurites, and changes in the expression of a variety of cytoskeletal and signaling proteins that modulate neurite growth[21]. Consistent with in vitro studies, Notch and its ligands are present on both axons and dendrites of mammalian neurons in vivo [22, 23].…”

Nuclear Factor κB-Dependent Neurite Remodeling Is Mediated by Notch Pathway

“…They are regarded as presynaptic, dynamic structures that are able to remodel their morphology in response to a variety of stimuli (De Paola et al, 2003;Nikonenko et al, 2003;Udo et al, 2005;Umeda et al, 2005;Ferrari-Toninelli et al, 2009). Varicosities appear as membrane swellings of various size.…”

Forced Notch Signaling Inhibits Commissural Axon Outgrowth in the Developing Chick Central Nerve System

“…A group of studies over the past decade have provided in vitro evidence for a function of canonical Notch signaling in the regulation of neurite outgrowth in the nervous system [9], [10], [17], [18], [19], [22]; however, our study is the first to use an in vivo model to show that the canonical Notch pathway plays a vital role in axonal growth in the vertebrate nervous system. We found that ectopically expressing NICD in newly differentiated post-mitotic commissural neurons decreased axon midline crossing by about 87% compared to controls, indicating that activation of Notch signaling severely hinders axon outgrowth.…”

“…Notch signaling is also known to promote dendritic branching [9], and to inhibit neurite extension in cultured rodent cortical neurons [9], [10], [18], N2a neuroblastoma cells [19] and PC12 cells [20]. Furthermore, in cultured murine cortical neurons and differentiated human SH-SY5Y neuroblastoma cells, Notch signaling can induce microtubule stabilization in neurites and thereby promote neurite outgrowth and branching as well as growth cone enlargement [21], [22]. However, in vivo evidence demonstrating the effects of Notch signaling on axon outgrowth is still lacking.…”