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Identifying Function Determining Residues in Neuroimmune Semaphorin 4A

Semaphorin 4A (Sema4A) exerts a stabilizing effect on human Treg cells in PBMC and CD4+ T cell cultures by engaging Plexin B1. Sema4A deficient mice display enhanced allergic airway inflammation accompanied by fewer Treg cells, while Sema4D deficient mice displayed reduced inflammation and increased...

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Autores principales: Chapoval, Svetlana P., Lee, Mariah, Lemmer, Aaron, Ajayi, Oluwaseyi, Qi, Xiulan, Neuwald, Andrew F., Keegan, Achsah D.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8953949/
https://www.ncbi.nlm.nih.gov/pubmed/35328445
http://dx.doi.org/10.3390/ijms23063024
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author Chapoval, Svetlana P.
Lee, Mariah
Lemmer, Aaron
Ajayi, Oluwaseyi
Qi, Xiulan
Neuwald, Andrew F.
Keegan, Achsah D.
author_facet Chapoval, Svetlana P.
Lee, Mariah
Lemmer, Aaron
Ajayi, Oluwaseyi
Qi, Xiulan
Neuwald, Andrew F.
Keegan, Achsah D.
author_sort Chapoval, Svetlana P.
collection PubMed
description Semaphorin 4A (Sema4A) exerts a stabilizing effect on human Treg cells in PBMC and CD4+ T cell cultures by engaging Plexin B1. Sema4A deficient mice display enhanced allergic airway inflammation accompanied by fewer Treg cells, while Sema4D deficient mice displayed reduced inflammation and increased Treg cell numbers even though both Sema4 subfamily members engage Plexin B1. The main objectives of this study were: 1. To compare the in vitro effects of Sema4A and Sema4D proteins on human Treg cells; and 2. To identify function-determining residues in Sema4A critical for binding to Plexin B1 based on Sema4D homology modeling. We report here that Sema4A and Sema4D display opposite effects on human Treg cells in in vitro PBMC cultures; Sema4D inhibited the CD4+CD25+Foxp3+ cell numbers and CD25/Foxp3 expression. Sema4A and Sema4D competitively bind to Plexin B1 in vitro and hence may be doing so in vivo as well. Bayesian Partitioning with Pattern Selection (BPPS) partitioned 4505 Sema domains from diverse organisms into subgroups based on distinguishing sequence patterns that are likely responsible for functional differences. BPPS groups Sema3 and Sema4 into one family and further separates Sema4A and Sema4D into distinct subfamilies. Residues distinctive of the Sema3,4 family and of Sema4A (and by homology of Sema4D) tend to cluster around the Plexin B1 binding site. This suggests that the residues both common to and distinctive of Sema4A and Sema4D may mediate binding to Plexin B1, with subfamily residues mediating functional specificity. We mutated the Sema4A-specific residues M198 and F223 to alanine; notably, F223 in Sema4A corresponds to alanine in Sema4D. Mutant proteins were assayed for Plexin B1-binding and Treg stimulation activities. The F223A mutant was unable to stimulate Treg stability in in vitro PBMC cultures despite binding Plexin B1 with an affinity similar to the WT protein. This research is a first step in generating potent mutant Sema4A molecules with stimulatory function for Treg cells with a view to designing immunotherapeutics for asthma.
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spelling pubmed-89539492022-03-26 Identifying Function Determining Residues in Neuroimmune Semaphorin 4A Chapoval, Svetlana P. Lee, Mariah Lemmer, Aaron Ajayi, Oluwaseyi Qi, Xiulan Neuwald, Andrew F. Keegan, Achsah D. Int J Mol Sci Article Semaphorin 4A (Sema4A) exerts a stabilizing effect on human Treg cells in PBMC and CD4+ T cell cultures by engaging Plexin B1. Sema4A deficient mice display enhanced allergic airway inflammation accompanied by fewer Treg cells, while Sema4D deficient mice displayed reduced inflammation and increased Treg cell numbers even though both Sema4 subfamily members engage Plexin B1. The main objectives of this study were: 1. To compare the in vitro effects of Sema4A and Sema4D proteins on human Treg cells; and 2. To identify function-determining residues in Sema4A critical for binding to Plexin B1 based on Sema4D homology modeling. We report here that Sema4A and Sema4D display opposite effects on human Treg cells in in vitro PBMC cultures; Sema4D inhibited the CD4+CD25+Foxp3+ cell numbers and CD25/Foxp3 expression. Sema4A and Sema4D competitively bind to Plexin B1 in vitro and hence may be doing so in vivo as well. Bayesian Partitioning with Pattern Selection (BPPS) partitioned 4505 Sema domains from diverse organisms into subgroups based on distinguishing sequence patterns that are likely responsible for functional differences. BPPS groups Sema3 and Sema4 into one family and further separates Sema4A and Sema4D into distinct subfamilies. Residues distinctive of the Sema3,4 family and of Sema4A (and by homology of Sema4D) tend to cluster around the Plexin B1 binding site. This suggests that the residues both common to and distinctive of Sema4A and Sema4D may mediate binding to Plexin B1, with subfamily residues mediating functional specificity. We mutated the Sema4A-specific residues M198 and F223 to alanine; notably, F223 in Sema4A corresponds to alanine in Sema4D. Mutant proteins were assayed for Plexin B1-binding and Treg stimulation activities. The F223A mutant was unable to stimulate Treg stability in in vitro PBMC cultures despite binding Plexin B1 with an affinity similar to the WT protein. This research is a first step in generating potent mutant Sema4A molecules with stimulatory function for Treg cells with a view to designing immunotherapeutics for asthma. MDPI 2022-03-11 /pmc/articles/PMC8953949/ /pubmed/35328445 http://dx.doi.org/10.3390/ijms23063024 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Chapoval, Svetlana P.
Lee, Mariah
Lemmer, Aaron
Ajayi, Oluwaseyi
Qi, Xiulan
Neuwald, Andrew F.
Keegan, Achsah D.
Identifying Function Determining Residues in Neuroimmune Semaphorin 4A
title Identifying Function Determining Residues in Neuroimmune Semaphorin 4A
title_full Identifying Function Determining Residues in Neuroimmune Semaphorin 4A
title_fullStr Identifying Function Determining Residues in Neuroimmune Semaphorin 4A
title_full_unstemmed Identifying Function Determining Residues in Neuroimmune Semaphorin 4A
title_short Identifying Function Determining Residues in Neuroimmune Semaphorin 4A
title_sort identifying function determining residues in neuroimmune semaphorin 4a
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8953949/
https://www.ncbi.nlm.nih.gov/pubmed/35328445
http://dx.doi.org/10.3390/ijms23063024
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