NGF FLIPs TrkA onto the death TRAIL in neuroblastoma cells

NTRK1-mediated protection against manganese-induced neurotoxicity and cell apoptosis via IGF2 in SH-SY5Y cells

BACKGROUND

Excessive manganese (Mn) exposure has been linked to neurotoxicity, cognitive impairments. Neurotrophic Receptor Kinase 1 (NTRK1) encodes Tropomyosin kinase A (TrkA), a neurotrophic receptor, as a mediator of neuron differentiation and survival. Insulin-like growth factor 2 (IGF2), a pivotal member of the insulin gene family, plays a crucial role in brain development and neuroprotection. Despite this knowledge, the precise mechanisms through which NTRK1 and IGF2 influence cell responses to Mn-induced neuronal damage remain elusive.

METHODS

Cell apoptosis was assessed using CCK8, TUNEL staining, and Western blot analysis of cleaved Caspase-3. Lentiviral vectors facilitated NTRK1 overexpression, while small interfering RNAs (siRNAs) facilitated IGF2 knockdown. Real-time Quantitative PCR (qPCR) determined gene expression levels, while Western blotting measured protein expression.

RESULTS

The study reveals that NTRK1 inhibits MnCl2-induced apoptosis in SH-SY5Y cells. NTRK1 overexpression significantly upregulated IGF2 expression, and subsequent siRNA-IGF2 experiments confirmed IGF2's pivotal role in NTRK1-mediated neuroprotection. Notably, the study identifies that NTRK1 regulates the expression of IGF2 in the neuroprotective mechanism with the involvement of ER stress pathways.

DISCUSSION

The study reveals NTRK1's neuroprotective role via IGF2 against Mn-induced neurotoxicity and ER stress modulation in SH-SY5Y cells. These findings offer insights into potential therapies for neurodegenerative disorders related to Mn exposure and NTRK1 dysfunction, driving future research in this domain.

TRAIL induces pro-apoptotic crosstalk between the TRAIL-receptor signaling pathway and TrkAIII in SH-SY5Y cells, unveiling a potential therapeutic "Achilles heel" for the TrkAIII oncoprotein in neuroblastoma

TrkAIII expression in neuroblastoma (NB) associates with advanced stage disease, worse prognosis, post therapeutic relapse, and in NB models TrkAIII exhibits oncogenic activity and promotes chemotherapeutic-resistance. Here, we report a potential therapeutic “Achilles heel” for the TrkAIII oncoprotein in a SH-SY5Y NB model that is characterised by one-way TRAIL-induced, pro-apoptotic crosstalk between the TRAIL receptor signaling pathway and TrkAIII that results in the delayed induction of apoptosis. In TrkAIII SH-SY5Y cells, blocked in the intrinsic apoptosis pathway by elevated constitutive Bcl-2, Bcl-xL and Mcl-1 expression, TRAIL induced delayed caspase-dependent apoptosis via the extrinsic pathway and completely abrogated tumourigenic capacity in vitro. This effect was initiated by TRAIL-induced SHP-dependent c-Src activation, the induction of TrkAIII/SHP-1/c-Src complexing leading to SHP-mediated TrkAIII de-phosphorylation, subsequent induction of complexing between de-phosphorylated TrkAIII and cFLIP associated with a time-dependent increase the caspase-8 to cFLIP ratio at activated death receptors, resulting in delayed caspase cleavage and caspase-dependent apoptosis. We also confirm rate-limiting roles for c-FLIP and Mcl-1 in regulating the sensitivity of TrkAIII SH-SY5Y cells to TRAIL-induced apoptosis via the extrinsic and intrinsic pathways, respectively. Our study unveils a novel mechanism for the TRAIL-induced apoptosis of TrkAIII expressing NB cells that depends upon SHP/Src-mediated crosstalk between the TRAIL-receptor signaling pathway and TrkAIII, and supports a novel potential pro-apoptotic therapeutic use for TRAIL in TrkAIII expressing NB.

Gene expression and molecular pathway activation signatures of MYCN-amplified neuroblastomas

Neuroblastoma is a pediatric cancer arising from sympathetic nervous system. Remarkable heterogeneity in outcomes is one of its widely known features. One of the traits strongly associated with the unfavorable subtype is the amplification of oncogene MYCN. Here, we performed cross-platform biomarker detection by comparing gene expression and pathway activation patterns from the two literature reports and from our experimental dataset, combining profiles for the 761 neuroblastoma patients with known MYCN amplification status. We identified 109 / 25 gene expression / pathway activation biomarkers strongly linked with the MYCN amplification. The marker genes/pathways are involved in the processes of purine nucleotide biosynthesis, ATP-binding, tetrahydrofolate metabolism, building mitochondrial matrix, biosynthesis of amino acids, tRNA aminoacylation and NADP-linked oxidation-reduction processes, as well as in the tyrosine phosphatase activity, p53 signaling, cell cycle progression and the G1/S and G2/M checkpoints. To connect molecular functions of the genes involved in MYCN-amplified phenotype, we built a new molecular pathway using known intracellular protein interaction networks. The activation of this pathway was highly selective in discriminating MYCN-amplified neuroblastomas in all three datasets. Our data also suggest that the phosphoinositide 3-kinase (PI3K) inhibitors may provide new opportunities for the treatment of the MYCN-amplified neuroblastoma subtype.

Epileptic Encephalopathy Caused by Mutations in the Guanine Nucleotide Exchange Factor DENND5A

Epileptic encephalopathies are a catastrophic group of epilepsies characterized by refractory seizures and cognitive arrest, often resulting from abnormal brain development. Here, we have identified an epileptic encephalopathy additionally featuring cerebral calcifications and coarse facial features caused by recessive loss-of-function mutations in DENND5A. DENND5A contains a DENN domain, an evolutionarily ancient enzymatic module conferring guanine nucleotide exchange factor (GEF) activity to multiple proteins serving as GEFs for Rabs, which are key regulators of membrane trafficking. DENND5A is detected predominantly in neuronal tissues, and its highest levels occur during development. Knockdown of DENND5A leads to striking alterations in neuronal development. Mechanistically, these changes appear to result from upregulation of neurotrophin receptors, leading to enhanced downstream signaling. Thus, we have identified a link between a DENN domain protein and neuronal development, dysfunction of which is responsible for a form of epileptic encephalopathy.

Nerve growth factor: role in growth, differentiation and controlling cancer cell development

Recent progress in the Nerve Growth Factor (NGF) research has shown that this factor acts not only outside its classical domain of the peripheral and central nervous system, but also on non-neuronal and cancer cells. This latter observation has led to divergent hypothesis about the role of NGF, its specific distribution pattern within the tissues and its implication in induction as well as progression of carcinogenesis. Moreover, other recent studies have shown that NGF has direct clinical relevance in certain human brain neuron degeneration and a number of human ocular disorders. These studies, by suggesting that NGF is involved in a plethora of physiological function in health and disease, warrant further investigation regarding the true role of NGF in carcinogenesis. Based on our long-lasting experience in the physiopathology of NGF, we aimed to review previous and recent in vivo and in vitro NGF studies on tumor cell induction, progression and arrest. Overall, these studies indicate that the only presence of NGF is unable to generate cell carcinogenesis, both in normal neuronal and non-neuronal cells/tissues. However, it cannot be excluded the possibility that the co-expression of NGF and pro-carcinogenic molecules might open to different consequence. Whether NGF plays a direct or an indirect role in cell proliferation during carcinogenesis remains to demonstrate.