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Understanding cell signalling systems: paving the way for new therapies.

Jones EY - Philos Trans A Math Phys Eng Sci (2015)

Bottom Line: Importantly, we can complement protein crystallographic results with biophysical and cellular studies to dovetail structural information with functional impact.The generic architecture of a semaphorin-plexin complex is characterized by the dimeric semaphorin cross-linking two copies of the plexin receptor.For specific family members, the co-receptor neuropilin serves to bolster this architecture, but in all cases, the dimeric interaction lies at the core of the ligand receptor complex, providing the essential trigger for signalling.

View Article: PubMed Central - PubMed

Affiliation: Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK yvonne.jones@strubi.ox.ac.uk.

ABSTRACT
The cell-to-cell signalling mechanisms of multi-cellular organisms orchestrate human development during embryogenesis and control homeostasis in adult tissues. These are mechanisms vital to human health and perturbation of cell-to-cell signalling is a contributing factor in many pathologies including cancer. The semaphorin cell guidance cues and their cognate plexin receptors exemplify a cell-to-cell signalling system for which insights into mechanistic principles are emerging. X-ray crystallographic data from Diamond beam lines have enabled us to probe the inner workings of semaphorin-plexin signalling to atomic-level resolutions. Importantly, we can complement protein crystallographic results with biophysical and cellular studies to dovetail structural information with functional impact. The signature seven-bladed β propeller 'sema' domain of the semaphorins forms a dimer; in contrast the equivalent domain in the plexins is monomeric. The generic architecture of a semaphorin-plexin complex is characterized by the dimeric semaphorin cross-linking two copies of the plexin receptor. For specific family members, the co-receptor neuropilin serves to bolster this architecture, but in all cases, the dimeric interaction lies at the core of the ligand receptor complex, providing the essential trigger for signalling.

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Related in: MedlinePlus

The semaphorin–neuropilin–plexin complex. The schematic domain organization of mouse Sema3A, PlxnA2 and Nrp1 is presented above two orthogonal views of the structure of a semaphorin–neuropilin–plexin complex. Sema3A sema domain (green) and PlxnA21−4 (blue) structures are shown in ribbon representation and Nrp1 domain a1 structures (red) in surface representation. (Adapted from [15].)
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RSTA20130155F3: The semaphorin–neuropilin–plexin complex. The schematic domain organization of mouse Sema3A, PlxnA2 and Nrp1 is presented above two orthogonal views of the structure of a semaphorin–neuropilin–plexin complex. Sema3A sema domain (green) and PlxnA21−4 (blue) structures are shown in ribbon representation and Nrp1 domain a1 structures (red) in surface representation. (Adapted from [15].)

Mentions: We determined a crystal structure of mNrp11−4 (2.7 Åresolution; Diamond I04-1) [15], and so had high-resolution structures in hand for all the components of the semaphorin–neuropilin–plexin complex (mPlxnA21−4 at 2.3 Åfrom our earlier studies [12], and a 2.8 Åsema domain dimer structure for mSema3A from the laboratory of Dimitar Nikolov [11]). These well-characterized individual structures proved essential for our structure determination and analysis of the complex [15]. After extensive crystal optimization and screening, the final diffraction dataset we were able to generate for the semaphorin–neuropilin–plexin complex extended to 7 Å resolution and was the result of merging the diffraction data collected from three crystals, one each on Diamond beamlines I04-1, I02 and I03. The crystal structure was solved by molecular replacement revealing an asymmetric unit containing six copies of PlxnA21−4 and one copy each of the Sema3A sema domain and Nrp11−4 (Nrp1 domains a2, b1 and b2 were omitted from the model because of disorder). Given the low resolution of the diffraction data, the model was only subjected to rigid-body refinement, with each domain treated as a rigid group (26 groups in total: four for each PlxnA2 molecule and one each for Sema3A and Nrp1) and a single B factor per domain. Twofold crystallographic symmetry generates the biologically relevant 330 kDa complex which comprises the semaphorin dimer, two neuropilin a1 domains and two plexins (figure 3).Figure 3.


Understanding cell signalling systems: paving the way for new therapies.

Jones EY - Philos Trans A Math Phys Eng Sci (2015)

The semaphorin–neuropilin–plexin complex. The schematic domain organization of mouse Sema3A, PlxnA2 and Nrp1 is presented above two orthogonal views of the structure of a semaphorin–neuropilin–plexin complex. Sema3A sema domain (green) and PlxnA21−4 (blue) structures are shown in ribbon representation and Nrp1 domain a1 structures (red) in surface representation. (Adapted from [15].)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4308982&req=5

RSTA20130155F3: The semaphorin–neuropilin–plexin complex. The schematic domain organization of mouse Sema3A, PlxnA2 and Nrp1 is presented above two orthogonal views of the structure of a semaphorin–neuropilin–plexin complex. Sema3A sema domain (green) and PlxnA21−4 (blue) structures are shown in ribbon representation and Nrp1 domain a1 structures (red) in surface representation. (Adapted from [15].)
Mentions: We determined a crystal structure of mNrp11−4 (2.7 Åresolution; Diamond I04-1) [15], and so had high-resolution structures in hand for all the components of the semaphorin–neuropilin–plexin complex (mPlxnA21−4 at 2.3 Åfrom our earlier studies [12], and a 2.8 Åsema domain dimer structure for mSema3A from the laboratory of Dimitar Nikolov [11]). These well-characterized individual structures proved essential for our structure determination and analysis of the complex [15]. After extensive crystal optimization and screening, the final diffraction dataset we were able to generate for the semaphorin–neuropilin–plexin complex extended to 7 Å resolution and was the result of merging the diffraction data collected from three crystals, one each on Diamond beamlines I04-1, I02 and I03. The crystal structure was solved by molecular replacement revealing an asymmetric unit containing six copies of PlxnA21−4 and one copy each of the Sema3A sema domain and Nrp11−4 (Nrp1 domains a2, b1 and b2 were omitted from the model because of disorder). Given the low resolution of the diffraction data, the model was only subjected to rigid-body refinement, with each domain treated as a rigid group (26 groups in total: four for each PlxnA2 molecule and one each for Sema3A and Nrp1) and a single B factor per domain. Twofold crystallographic symmetry generates the biologically relevant 330 kDa complex which comprises the semaphorin dimer, two neuropilin a1 domains and two plexins (figure 3).Figure 3.

Bottom Line: Importantly, we can complement protein crystallographic results with biophysical and cellular studies to dovetail structural information with functional impact.The generic architecture of a semaphorin-plexin complex is characterized by the dimeric semaphorin cross-linking two copies of the plexin receptor.For specific family members, the co-receptor neuropilin serves to bolster this architecture, but in all cases, the dimeric interaction lies at the core of the ligand receptor complex, providing the essential trigger for signalling.

View Article: PubMed Central - PubMed

Affiliation: Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK yvonne.jones@strubi.ox.ac.uk.

ABSTRACT
The cell-to-cell signalling mechanisms of multi-cellular organisms orchestrate human development during embryogenesis and control homeostasis in adult tissues. These are mechanisms vital to human health and perturbation of cell-to-cell signalling is a contributing factor in many pathologies including cancer. The semaphorin cell guidance cues and their cognate plexin receptors exemplify a cell-to-cell signalling system for which insights into mechanistic principles are emerging. X-ray crystallographic data from Diamond beam lines have enabled us to probe the inner workings of semaphorin-plexin signalling to atomic-level resolutions. Importantly, we can complement protein crystallographic results with biophysical and cellular studies to dovetail structural information with functional impact. The signature seven-bladed β propeller 'sema' domain of the semaphorins forms a dimer; in contrast the equivalent domain in the plexins is monomeric. The generic architecture of a semaphorin-plexin complex is characterized by the dimeric semaphorin cross-linking two copies of the plexin receptor. For specific family members, the co-receptor neuropilin serves to bolster this architecture, but in all cases, the dimeric interaction lies at the core of the ligand receptor complex, providing the essential trigger for signalling.

Show MeSH
Related in: MedlinePlus