Lymphocyte receptor cis interactions in immune cell signaling
Lymphocytes express a wide range of surface receptors that transduce important signals, including by binding to other proteins expressed at the same membrane (in cis). Such interactions are typically studied with biochemical tools like immunoprecipitation, in which interaction equilibria are disturb...
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| Format: | Thesis |
| Language: | English |
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2023
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| _version_ | 1826316285635461120 |
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| author | Mørch, A |
| author_facet | Mørch, A |
| author_sort | Mørch, A |
| collection | OXFORD |
| description | Lymphocytes express a wide range of surface receptors that transduce important signals, including by binding to other proteins expressed at the same membrane (in cis). Such interactions are typically studied with biochemical tools like immunoprecipitation, in which interaction equilibria are disturbed by cell lysis, or through fixed high-resolution imaging, in which all dynamics are lost. Here, we adapt and implement a form of fluctuation spectroscopy, called scanning fluorescence cross-correlation spectroscopy (sFCCS), to study the diffusion and interactions of proteins expressed at the surface of living cells. This system is used to test three different instances of important receptor cis interactions. In Chapter 4, we demonstrate the presence of intermolecular PD-1/PD-1 cis binding (i.e., transient dimerization) and validate this novel and unexpected finding with other biophysical methods. Using genetic engineering and in vivo models of disease, we find that PD-1 dimers are important for the functional inhibition of T cells. Next, in Chapter 5, we address the controversy surrounding the coupling between T-cell coreceptors (CD4 and CD8αβ) and the signal-initiating kinase Lck at the cell surface. sFCCS experiments show that coreceptor/Lck occupancy is much higher than claimed by previous reports. In addition, we find that differences between CD4 and CD8αβ are especially pronounced when they are co-expressed and need to compete for limiting amounts of Lck, which may be relevant for models of thymopoiesis. Finally, in Chapter 6, we turn to the study of cis interactions between an inhibitory NK-cell receptor and class I MHC molecules. Guided by structural biology, we determine how novel malarial surface antigens have evolved to bind inhibitory molecules even when ‘masked’ by MHC-I binding in cis. Together, our results shed light on this puzzling class of receptor interactions and provide important context for understanding lymphocyte signaling in infection, immunology and translational biology. |
| first_indexed | 2024-03-07T07:43:36Z |
| format | Thesis |
| id | oxford-uuid:35e97747-a59d-4f90-b21a-1986affd96b7 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:42:05Z |
| publishDate | 2023 |
| record_format | dspace |
| spelling | oxford-uuid:35e97747-a59d-4f90-b21a-1986affd96b72024-12-07T13:18:38ZLymphocyte receptor cis interactions in immune cell signalingThesishttp://purl.org/coar/resource_type/c_db06uuid:35e97747-a59d-4f90-b21a-1986affd96b7biophysicsmolecular immunologyEnglishHyrax Deposit2023Mørch, ALymphocytes express a wide range of surface receptors that transduce important signals, including by binding to other proteins expressed at the same membrane (in cis). Such interactions are typically studied with biochemical tools like immunoprecipitation, in which interaction equilibria are disturbed by cell lysis, or through fixed high-resolution imaging, in which all dynamics are lost. Here, we adapt and implement a form of fluctuation spectroscopy, called scanning fluorescence cross-correlation spectroscopy (sFCCS), to study the diffusion and interactions of proteins expressed at the surface of living cells. This system is used to test three different instances of important receptor cis interactions. In Chapter 4, we demonstrate the presence of intermolecular PD-1/PD-1 cis binding (i.e., transient dimerization) and validate this novel and unexpected finding with other biophysical methods. Using genetic engineering and in vivo models of disease, we find that PD-1 dimers are important for the functional inhibition of T cells. Next, in Chapter 5, we address the controversy surrounding the coupling between T-cell coreceptors (CD4 and CD8αβ) and the signal-initiating kinase Lck at the cell surface. sFCCS experiments show that coreceptor/Lck occupancy is much higher than claimed by previous reports. In addition, we find that differences between CD4 and CD8αβ are especially pronounced when they are co-expressed and need to compete for limiting amounts of Lck, which may be relevant for models of thymopoiesis. Finally, in Chapter 6, we turn to the study of cis interactions between an inhibitory NK-cell receptor and class I MHC molecules. Guided by structural biology, we determine how novel malarial surface antigens have evolved to bind inhibitory molecules even when ‘masked’ by MHC-I binding in cis. Together, our results shed light on this puzzling class of receptor interactions and provide important context for understanding lymphocyte signaling in infection, immunology and translational biology. |
| spellingShingle | biophysics molecular immunology Mørch, A Lymphocyte receptor cis interactions in immune cell signaling |
| title | Lymphocyte receptor cis interactions in immune cell signaling |
| title_full | Lymphocyte receptor cis interactions in immune cell signaling |
| title_fullStr | Lymphocyte receptor cis interactions in immune cell signaling |
| title_full_unstemmed | Lymphocyte receptor cis interactions in immune cell signaling |
| title_short | Lymphocyte receptor cis interactions in immune cell signaling |
| title_sort | lymphocyte receptor cis interactions in immune cell signaling |
| topic | biophysics molecular immunology |
| work_keys_str_mv | AT mørcha lymphocytereceptorcisinteractionsinimmunecellsignaling |