Neurotrophins regulate the development, maintenance, and function of vertebrate nervous systems by activating two classes of receptors: the Trk family of receptor tyrosine kinases and p75NTR, a member of the TNF receptor superfamily. These receptors activate various signaling pathways, including those involving ras, cdc-42/ras/rho G proteins, and cascades like MAP kinase, PI-3 kinase, and Jun kinase. During development, neurotrophins act as survival factors, ensuring a balance between the number of surviving neurons and the need for appropriate target innervation. They also regulate cell fate decisions, axon growth, dendrite pruning, innervation patterning, and the expression of proteins crucial for neuronal function, such as neurotransmitters and ion channels. In the mature nervous system, neurotrophins control synaptic function and plasticity while continuing to modulate neuronal survival. Neurotrophins include NGF, BDNF, NT-3, and NT-4, derived from a common ancestral gene. They are synthesized and secreted by various tissues, including sympathetic and sensory target organs. Neurotrophins are also produced by macrophages and mast cells in response to nerve injury. They are expressed in regions invaded by sensory axons during development, providing trophic support to neurons that have not yet contacted their targets. Many neurons also synthesize neurotrophins, such as sensory neurons producing BDNF. Neurotrophins bind to Trk receptors (TrkA, TrkB, TrkC) and p75NTR. Trk receptors are tyrosine kinases that activate signaling pathways involved in survival, differentiation, axon growth, and synaptic function. p75NTR, a member of the TNF receptor family, can either promote or inhibit survival and differentiation depending on the context. It can also induce apoptosis through the Jun kinase pathway. The interaction between Trk and p75NTR receptors is complex, with Trk receptors often promoting survival and differentiation, while p75NTR can induce apoptosis. Neurotrophins regulate signaling through various pathways, including Ras-ERK, PI-3 kinase, and PLC-γ1. These pathways are involved in cell survival, differentiation, and synaptic plasticity. The Trk receptors are regulated by membrane trafficking, with internalization of the NGF-TrkA complex being essential for prolonged signaling. p75NTR also influences signaling through interactions with adapter proteins like TRAF-6, which activate NF-κB and other pathways. Adapter proteins such as NRIF, NRAGE, and SC-1 also interact with p75NTR, influencing cell survival and differentiation. The regulation of neurotrophin signaling is complex, involving multiple pathways and interactions. Trk receptors and p75NTR receptors have reciprocal regulatory roles, with Trk receptors often promoting survival andNeurotrophins regulate the development, maintenance, and function of vertebrate nervous systems by activating two classes of receptors: the Trk family of receptor tyrosine kinases and p75NTR, a member of the TNF receptor superfamily. These receptors activate various signaling pathways, including those involving ras, cdc-42/ras/rho G proteins, and cascades like MAP kinase, PI-3 kinase, and Jun kinase. During development, neurotrophins act as survival factors, ensuring a balance between the number of surviving neurons and the need for appropriate target innervation. They also regulate cell fate decisions, axon growth, dendrite pruning, innervation patterning, and the expression of proteins crucial for neuronal function, such as neurotransmitters and ion channels. In the mature nervous system, neurotrophins control synaptic function and plasticity while continuing to modulate neuronal survival. Neurotrophins include NGF, BDNF, NT-3, and NT-4, derived from a common ancestral gene. They are synthesized and secreted by various tissues, including sympathetic and sensory target organs. Neurotrophins are also produced by macrophages and mast cells in response to nerve injury. They are expressed in regions invaded by sensory axons during development, providing trophic support to neurons that have not yet contacted their targets. Many neurons also synthesize neurotrophins, such as sensory neurons producing BDNF. Neurotrophins bind to Trk receptors (TrkA, TrkB, TrkC) and p75NTR. Trk receptors are tyrosine kinases that activate signaling pathways involved in survival, differentiation, axon growth, and synaptic function. p75NTR, a member of the TNF receptor family, can either promote or inhibit survival and differentiation depending on the context. It can also induce apoptosis through the Jun kinase pathway. The interaction between Trk and p75NTR receptors is complex, with Trk receptors often promoting survival and differentiation, while p75NTR can induce apoptosis. Neurotrophins regulate signaling through various pathways, including Ras-ERK, PI-3 kinase, and PLC-γ1. These pathways are involved in cell survival, differentiation, and synaptic plasticity. The Trk receptors are regulated by membrane trafficking, with internalization of the NGF-TrkA complex being essential for prolonged signaling. p75NTR also influences signaling through interactions with adapter proteins like TRAF-6, which activate NF-κB and other pathways. Adapter proteins such as NRIF, NRAGE, and SC-1 also interact with p75NTR, influencing cell survival and differentiation. The regulation of neurotrophin signaling is complex, involving multiple pathways and interactions. Trk receptors and p75NTR receptors have reciprocal regulatory roles, with Trk receptors often promoting survival and