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Ligand-induced dynamics of neurotrophin receptors investigated by single-molecule imaging approaches.

Marchetti L, Luin S, Bonsignore F, de Nadai T, Beltram F, Cattaneo A - Int J Mol Sci (2015)

Bottom Line: Nevertheless, a comprehensive description of the ligand-induced nanoscale details of NRs dynamics and interactions spanning from the initial lateral movements triggered at the plasma membrane to the internalization and transport processes is still missing.Here we discuss requirements, potential and practical implementation of these novel approaches for the study of neurotrophin trafficking and signalling, in the framework of current knowledge available also for other ligand-receptor systems.We shall especially highlight the correlation between the receptor dynamics activated by different neurotrophins and the respective signalling outcome, as recently revealed by single-molecule tracking of NRs in living neuronal cells.

View Article: PubMed Central - PubMed

Affiliation: National Enterprise for nanoScience and nanoTechnology (NEST) Laboratory, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza San Silvestro 12, Pisa I-56127, Italy. teresa.denadai@sns.it.

ABSTRACT
Neurotrophins are secreted proteins that regulate neuronal development and survival, as well as maintenance and plasticity of the adult nervous system. The biological activity of neurotrophins stems from their binding to two membrane receptor types, the tropomyosin receptor kinase and the p75 neurotrophin receptors (NRs). The intracellular signalling cascades thereby activated have been extensively investigated. Nevertheless, a comprehensive description of the ligand-induced nanoscale details of NRs dynamics and interactions spanning from the initial lateral movements triggered at the plasma membrane to the internalization and transport processes is still missing. Recent advances in high spatio-temporal resolution imaging techniques have yielded new insight on the dynamics of NRs upon ligand binding. Here we discuss requirements, potential and practical implementation of these novel approaches for the study of neurotrophin trafficking and signalling, in the framework of current knowledge available also for other ligand-receptor systems. We shall especially highlight the correlation between the receptor dynamics activated by different neurotrophins and the respective signalling outcome, as recently revealed by single-molecule tracking of NRs in living neuronal cells.

Show MeSH
Schematic picture of tropomyosin receptor kinases (Trks) and the p75 neurotrophin receptors (p75NTR). (A) Structure of the two receptors: The intracellular (on top) and extracellular (on bottom) domains are highlighted. The following abbreviations are used: CRD (cystein-rich domain); LRR (leucine-rich domain); IgL-D (immunoglobulin-like domain); TKD (tyrosine-kinase domain); CD (chopper domain); DD (death domain); (B) Modified residues of the Trks (on top) and of p75NTR (on bottom) receptors. The following abbreviations are used: TM (transmembrane domain); JM (juxta-membrane domain); N (N-terminus); C (C-terminus). The following symbols are used: Grey ↓ (N- or O-glycosylation sites); green ↓ (ATP-binding site); red ↓ (site of covalent homo-dimerization due to the disulfide bond formed by Cys257 [32,33]). U (ubiquitination-related lysine residues, as derived from studies mainly performed on the TrkA receptor [34,35,36,37]); Y (phosphorylated tyrosine residues, their numeration and function is described in Figure 2); P (palmitoylated Cys residue [38]).
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ijms-16-01949-f001: Schematic picture of tropomyosin receptor kinases (Trks) and the p75 neurotrophin receptors (p75NTR). (A) Structure of the two receptors: The intracellular (on top) and extracellular (on bottom) domains are highlighted. The following abbreviations are used: CRD (cystein-rich domain); LRR (leucine-rich domain); IgL-D (immunoglobulin-like domain); TKD (tyrosine-kinase domain); CD (chopper domain); DD (death domain); (B) Modified residues of the Trks (on top) and of p75NTR (on bottom) receptors. The following abbreviations are used: TM (transmembrane domain); JM (juxta-membrane domain); N (N-terminus); C (C-terminus). The following symbols are used: Grey ↓ (N- or O-glycosylation sites); green ↓ (ATP-binding site); red ↓ (site of covalent homo-dimerization due to the disulfide bond formed by Cys257 [32,33]). U (ubiquitination-related lysine residues, as derived from studies mainly performed on the TrkA receptor [34,35,36,37]); Y (phosphorylated tyrosine residues, their numeration and function is described in Figure 2); P (palmitoylated Cys residue [38]).

Mentions: More than fifty years after the discovery of the nerve growth factor (NGF) [16,17], the first and best characterized NT, and thirty years after the discovery of its retrograde transport [18,19], it is still surprising that these factors exert their multitude of biological functions mostly by binding only two types of membrane receptors, hereafter referred to as neurotrophin receptors (NRs): the tropomyosin receptor kinases (Trks) and the p75 neurotrophin receptor (p75NTR) [20,21,22,23,24,25,26]. Figure 1 schematically shows these two NRs and highlights the lack of relation between their structures. Trks belong to the receptor tyrosine kinase (RTK) family: these are traditionally known to dimerize upon ligand binding, thus activating the trans-phosphorylation of the intracellular kinase domains, and additional phosphorylation of intracellular effectors; alternatively, there is increasing evidence that many RTK members exist as dimers or clusters also in the absence of ligands, and the dimers can be active, eventually stabilized by ligand binding and/or primed for ligand-induced activation [27]. For the Trks such activation mechanisms ensue in mostly neurotrophic and survival responses [22]. On the other hand, p75NTR is a member of the tumor necrosis factor receptor (TNFR) superfamily: It has no intracellular enzymatic activity and is best known for mediating neural-cell death during development as well as in the adult following injury [25,28,29]. The specification of differential neuron-specific actions is achieved by NT binding to NRs using a number of different but interlaced molecular mechanisms, the main of which will be listed in the following.


Ligand-induced dynamics of neurotrophin receptors investigated by single-molecule imaging approaches.

Marchetti L, Luin S, Bonsignore F, de Nadai T, Beltram F, Cattaneo A - Int J Mol Sci (2015)

Schematic picture of tropomyosin receptor kinases (Trks) and the p75 neurotrophin receptors (p75NTR). (A) Structure of the two receptors: The intracellular (on top) and extracellular (on bottom) domains are highlighted. The following abbreviations are used: CRD (cystein-rich domain); LRR (leucine-rich domain); IgL-D (immunoglobulin-like domain); TKD (tyrosine-kinase domain); CD (chopper domain); DD (death domain); (B) Modified residues of the Trks (on top) and of p75NTR (on bottom) receptors. The following abbreviations are used: TM (transmembrane domain); JM (juxta-membrane domain); N (N-terminus); C (C-terminus). The following symbols are used: Grey ↓ (N- or O-glycosylation sites); green ↓ (ATP-binding site); red ↓ (site of covalent homo-dimerization due to the disulfide bond formed by Cys257 [32,33]). U (ubiquitination-related lysine residues, as derived from studies mainly performed on the TrkA receptor [34,35,36,37]); Y (phosphorylated tyrosine residues, their numeration and function is described in Figure 2); P (palmitoylated Cys residue [38]).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4307343&req=5

ijms-16-01949-f001: Schematic picture of tropomyosin receptor kinases (Trks) and the p75 neurotrophin receptors (p75NTR). (A) Structure of the two receptors: The intracellular (on top) and extracellular (on bottom) domains are highlighted. The following abbreviations are used: CRD (cystein-rich domain); LRR (leucine-rich domain); IgL-D (immunoglobulin-like domain); TKD (tyrosine-kinase domain); CD (chopper domain); DD (death domain); (B) Modified residues of the Trks (on top) and of p75NTR (on bottom) receptors. The following abbreviations are used: TM (transmembrane domain); JM (juxta-membrane domain); N (N-terminus); C (C-terminus). The following symbols are used: Grey ↓ (N- or O-glycosylation sites); green ↓ (ATP-binding site); red ↓ (site of covalent homo-dimerization due to the disulfide bond formed by Cys257 [32,33]). U (ubiquitination-related lysine residues, as derived from studies mainly performed on the TrkA receptor [34,35,36,37]); Y (phosphorylated tyrosine residues, their numeration and function is described in Figure 2); P (palmitoylated Cys residue [38]).
Mentions: More than fifty years after the discovery of the nerve growth factor (NGF) [16,17], the first and best characterized NT, and thirty years after the discovery of its retrograde transport [18,19], it is still surprising that these factors exert their multitude of biological functions mostly by binding only two types of membrane receptors, hereafter referred to as neurotrophin receptors (NRs): the tropomyosin receptor kinases (Trks) and the p75 neurotrophin receptor (p75NTR) [20,21,22,23,24,25,26]. Figure 1 schematically shows these two NRs and highlights the lack of relation between their structures. Trks belong to the receptor tyrosine kinase (RTK) family: these are traditionally known to dimerize upon ligand binding, thus activating the trans-phosphorylation of the intracellular kinase domains, and additional phosphorylation of intracellular effectors; alternatively, there is increasing evidence that many RTK members exist as dimers or clusters also in the absence of ligands, and the dimers can be active, eventually stabilized by ligand binding and/or primed for ligand-induced activation [27]. For the Trks such activation mechanisms ensue in mostly neurotrophic and survival responses [22]. On the other hand, p75NTR is a member of the tumor necrosis factor receptor (TNFR) superfamily: It has no intracellular enzymatic activity and is best known for mediating neural-cell death during development as well as in the adult following injury [25,28,29]. The specification of differential neuron-specific actions is achieved by NT binding to NRs using a number of different but interlaced molecular mechanisms, the main of which will be listed in the following.

Bottom Line: Nevertheless, a comprehensive description of the ligand-induced nanoscale details of NRs dynamics and interactions spanning from the initial lateral movements triggered at the plasma membrane to the internalization and transport processes is still missing.Here we discuss requirements, potential and practical implementation of these novel approaches for the study of neurotrophin trafficking and signalling, in the framework of current knowledge available also for other ligand-receptor systems.We shall especially highlight the correlation between the receptor dynamics activated by different neurotrophins and the respective signalling outcome, as recently revealed by single-molecule tracking of NRs in living neuronal cells.

View Article: PubMed Central - PubMed

Affiliation: National Enterprise for nanoScience and nanoTechnology (NEST) Laboratory, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza San Silvestro 12, Pisa I-56127, Italy. teresa.denadai@sns.it.

ABSTRACT
Neurotrophins are secreted proteins that regulate neuronal development and survival, as well as maintenance and plasticity of the adult nervous system. The biological activity of neurotrophins stems from their binding to two membrane receptor types, the tropomyosin receptor kinase and the p75 neurotrophin receptors (NRs). The intracellular signalling cascades thereby activated have been extensively investigated. Nevertheless, a comprehensive description of the ligand-induced nanoscale details of NRs dynamics and interactions spanning from the initial lateral movements triggered at the plasma membrane to the internalization and transport processes is still missing. Recent advances in high spatio-temporal resolution imaging techniques have yielded new insight on the dynamics of NRs upon ligand binding. Here we discuss requirements, potential and practical implementation of these novel approaches for the study of neurotrophin trafficking and signalling, in the framework of current knowledge available also for other ligand-receptor systems. We shall especially highlight the correlation between the receptor dynamics activated by different neurotrophins and the respective signalling outcome, as recently revealed by single-molecule tracking of NRs in living neuronal cells.

Show MeSH