Biology subjects

Baldwin, T. A.

Publications and source records attributed to Baldwin, T. A..

9 recordsLinked to original sources

bioRxiv2024

RasGRP1 Signalling Programs Developing γδ-Thymocytes towards the γδT17 Lineage Through Control of c-Maf Expression

The {gamma}{delta} TCR instructively directs both lineage specification and effector programming of developing {gamma}{delta} T cells. However, the manner in which different TCR signal strengths and other auxiliary signals coordinate downstream of the {gamma}{delta} TCR to regulate {gamma}{delta} T cell development remains unclear. In this study we characterized the role of Ras guanyl-releasing protein 1 (RasGRP1) in the development and effector programming of {gamma}{delta} T cells. While RasGRP1 was not necessary for bulk {gamma}{delta} T cell generation, we found it required for efficient generation of V{gamma}4+ thymocytes, and lineage-committed CD73+ {gamma}{delta} T cells in the thymus and periphery. Despite a decrease in immature CD73+ {gamma}{delta} thymocytes, we report an expansion of the perinatal wave of CD8+IFN{gamma}+ {gamma}{delta} T cell population in the absence of RasGRP1. IL-17 producing {gamma}{delta} T cells were significantly reduced in RasGRP1 KO mice, with a specific loss of V{gamma}2+ {gamma}{delta} T cells that corresponds to a loss of c-Maf expression as early as the DN1d thymocyte stage. Critically, these adult-programmed {gamma}{delta}T17s could express c-Maf in response to CCR9 stimulation, with RasGRP1 being required for CCR9-induced c-Maf expression. Thus, RasGRP1 activation serves as an important signalling hub in the effector programming of {gamma}{delta} T cells, which integrates signals from both non-TCR and TCR inputs to direct differentiation.

immunology↗

bioRxiv2024

Oncolytic vaccinia virus as a precision cancer vaccine platform

Oncolytic viruses are immunotherapeutic agents that selectively replicate in and kill tumour cells with the goal of promoting anti-cancer immune responses. Vaccinia virus (VACV) is a strong oncolytic virus candidate as it infects a wide range of cancer cells, is amenable to genetic tailoring and induces potent, long-lasting immunity. Here, we examine the use of genetically engineered oncolytic VACVs (oVACV) to express a variety of MHC-I complexes and the co-stimulatory ligand CD80 to stimulate anti-tumour CD8+ T cell responses in two syngeneic cancer models. Tumour antigen specific CD8+ T cells were detected in both the tumour and spleen following oVACV treatment, demonstrating the ability to induce tumour targeted T cell responses with viral therapy. oVACV expression of peptide-MHC-I complexes enhanced the efficacy of primary tumour clearance with tumour specific antigen targeting showing the greatest efficacy. Initial tumour clearance following treatment with oVACVs led to variable anti-tumour immune memory depending on the tumour model. Depletion of CD8+ T cells prevented therapeutic efficacy of oVACV while combination with PD-L1 immune checkpoint blockade enhanced tumour clearance. Overall, we demonstrate the ability to generate an oncolytic virus capable of inducing recognition and elimination of tumour cells through VACV-mediated expression of defined peptide-MHC-I complexes.

immunology↗

bioRxiv2024

Internal regulation between constitutively expressed T cell coinhibitory receptors BTLA and CD5 and tolerance in recent thymic emigrants

Several coinhibitory receptors are upregulated upon activation, whereas a small number of coinhibitory receptors are expressed constitutively by naive T cells. The relationship between constitutively expressed coinhibitors is unknown. We found an inverse relationship between two constitutively expressed coinhibitors, CD5 and BTLA; BTLA expression was low in the thymus and high in the periphery, corresponding respectively with high and low CD5 expression. Germline or induced deletion of Btla in somatic cells demonstrated a causal relationship between BTLA expression and CD5 levels in T cells of central and peripheral lymphoid tissues. The effect of BTLA on CD5 expression on thymic and peripheral CD4 T cells was due to BTLA signaling, rather than signaling by its ligand, the herpes virus mediator (HVEM). Regulation was maintained in mice with a non-signaling HVEM mutant but was lost in Tnfrsf14-/- (Hvem-/-) mice. Increased CD5 levels have been positively associated with increased recognition of self-peptide MHC complexes. Thus, control of CD5 expression by BTLA signals early in T cell ontogeny suggested that BTLA might be important for establishing self-tolerance in newly generated T cells. Consistent with this concept, we found that BTLA, as well as the inducible coinhibitor PD-1, were needed post thymic selection in recent thymic emigrants (RTE) to establish self-tolerance. RTE lacking BTLA caused a multiorgan autoimmune disease whose development required CD4 T cells and MHC class II. Together, our findings identify a negative regulatory pathway allowing constitutively expressed coinhibitory receptors to calibrate their expression in thymic T cell differentiation. Expression of constitutive and induced coinhibitory receptors is needed to establish tolerance in the periphery for RTE.

immunology↗

bioRxiv2022

Establishment of CD8+ T cell thymic central tolerance to tissue-restricted antigen requires PD-1

Highly self-reactive T cells are censored from the repertoire by both central and peripheral tolerance mechanisms upon receipt of high-affinity TCR signals. Clonal deletion is considered a major driver of central tolerance; however, other mechanisms such as induction of regulatory T cells and functional impairment have been described. An understanding of the interplay between these different central tolerance mechanisms is still lacking. We previously showed that impaired clonal deletion to a model tissue-restricted antigen (TRA) did not compromise tolerance. In this study, we determined that murine T cells that failed clonal deletion were rendered functionally impaired in the thymus. PD-1 was induced in the thymus and was required to establish cell-intrinsic tolerance to TRA in CD8+ thymocytes independently of clonal deletion. PD-1 signaling in developing thymocytes was sufficient for tolerance induction, however in some cases the absence of PD-L1-mediated signaling in the periphery resulted in broken tolerance at late time points. Finally, we showed that chronic exposure to high affinity antigen supported the long-term maintenance of tolerance. Taken together, our study identifies a critical role for PD-1 in establishing central tolerance in autoreactive T cells that escape clonal deletion. It also sheds light on potential mechanisms of action of anti-PD-1 pathway immune checkpoint blockade and the development of immune-related adverse events. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=161 SRC="FIGDIR/small/502412v2_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1e3d786org.highwire.dtl.DTLVardef@15aaaaaorg.highwire.dtl.DTLVardef@17ab803org.highwire.dtl.DTLVardef@1c6e23b_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2021

Popeye Domain-Containing Protein 1 Scaffolds a Complex of Adenylyl Cyclase 9 and the Two-Pore-Domain Potassium Channel TREK-1 in Heart

The establishment of macromolecular complexes by scaffolding proteins such as A-kinase anchoring proteins is key to the local production of cAMP by anchored adenylyl cyclase (AC) and the subsequent cAMP signaling necessary for many cardiac functions. We have identified herein a novel AC scaffold, the Popeye domain-containing (POPDC) protein. Unlike other AC scaffolding proteins, POPDC1 binds cAMP with high affinity. The POPDC family of proteins are important for cardiac pacemaking and conduction, due in part to their cAMP-dependent binding and regulation of TREK-1 potassium channels. TREK-1 binds the AC9:POPDC1 complex and co-purifies in a POPDC1-dependent manner with AC9-associated activity in heart. Although the interaction of AC9 and POPDC1 is cAMP independent, TREK-1 association with AC9 and POPDC1 is reduced in an isoproterenol-dependent manner, requiring an intact cAMP binding Popeye domain and AC activity within the complex. We show that deletion of Adcy9 (AC9) gives rise to bradycardia at rest and stress-induced heart rate variability. The phenotype for deletion of Adcy9 is milder than previously observed upon loss of Popdc1, but similar to loss of Kcnk2 (TREK-1). Thus, POPDC1 represents a novel scaffolding protein for AC9 to regulate heart rate control. ONE-SENTENCE SUMMARYAdenylyl cyclase type 9 binds in an isoproterenol-dependent manner to the POPDC1:TREK-1 complex regulating heart rate.

biochemistry↗

bioRxiv2021

S-Palmitoylation-Dependent Regulation of Cardiomyocyte Rac1 Signaling Activity and Cardiac Hypertrophy

S-palmitoylation is a reversible lipid modification that regulates trafficking, localization, activity, and/or stability of protein substrates by serving as a fatty acid anchor to cell membranes. However, S-palmitoylation-dependent control of signal transduction in cardiomyocytes and its effects on cardiac physiology are not well understood. We performed an in vivo gain-of-function screen of zinc finger Asp-His-His-Cys (zDHHC) family S-acyl transferases that catalyze S-palmitoylation and identified the Golgi-localized enzyme zDHHC3 as a critical regulator of cardiac maladaptation. The closely-related enzyme, zDHHC7, also induced severe cardiomyopathy but this effect was not observed with overexpression of plasma membrane enzyme zDHHC5, endoplasmic reticulum enzyme zDHHC6, or Golgi enzyme zDHHC13. To identify effectors that may underlie zDHHC3-induced cardiomyopathy we performed quantitative site-specific S-acyl proteomics in zDHHC3-overexpressing cells that revealed the small GTPase Rac1 as a novel substrate. We generated cardiomyocyte-specific transgenic mice overexpressing zDHHC3, which develop severe cardiac disease. Cardiomyopathy and congestive heart failure in zDHHC3 transgenic mice are preceded by enhanced S-palmitoylation of Rac1 and induction of additional Rho family small GTPases including RhoA, Cdc42, and the Rho family-specific chaperone RhoGDI. In contrast, transgenic mice overexpressing an enzymatically-dead mutant of zDHHC3 do not exhibit this profound induction of RhoGTPase signaling or develop cardiac disease. Rac1 S-palmitoylation, plasma membrane localization, activity, and downstream hypertrophic signaling were substantially increased in zDHHC3 overexpressing hearts. Taken together, these data suggest inhibition of zDHHC3/7 S-acyl transferase activity at the cardiomyocyte Golgi or disruption of Rac1 S-palmitoylation as novel therapeutic strategies to treat cardiac disease or other diseases associated with enhanced RhoGTPase signaling.

molecular biology↗

bioRxiv2021

γδ-Thymocyte Maturation and Emigration

The thymus is the site of both {beta} and {gamma}{delta}-T cell development. After several unique waves of {gamma}{delta}-T cells are generated in, and exported from, the fetal/neonatal thymus, the adult thymus continues to produce a stream of {gamma}{delta}-T cells throughout life. One intriguing feature of {gamma}{delta} T cell development is the coordination of differentiation and acquisition of effector function within the fetal thymus, however, it is less clear whether this paradigm holds true in adult animals. To investigate the relationship between maturation and time since V(D)J recombination in adult-derived {gamma}{delta}-thymocytes, we used the Rag2pGFP model. Immature (CD24+) {gamma}{delta}-thymocytes expressed high levels of GFP while only a small minority of mature (CD24-) {gamma}{delta}-thymocytes were GFP+. Similarly, most GFP+ {gamma}{delta}-splenocytes were immature, while some were mature. Analysis of {gamma}{delta}-recent thymic emigrants (RTEs) indicated that most {gamma}{delta}-T cell RTEs were CD24+ and GFP+ and adoptive transfer experiments showed that immature {gamma}{delta}-thymocytes could be maintained in the periphery for at least 3 days over which time they matured. With respect to the mature {gamma}{delta}-thymocytes that were GFP-, parabiosis experiments demonstrated that mature {gamma}{delta}-T cells did not recirculate from the periphery. Instead, a population of mature {gamma}{delta}-thymocytes remained resident in the thymus for at least 60 days while mature {gamma}{delta}-thymocytes derived solely from adult hematopoiesis were mostly lost from the thymus within 60 days. Collectively, these data demonstrate two streams of actively developing {gamma}{delta}-T cells in adult mice: an immature subset that quickly leaves the thymus and matures in the periphery, and one that completes maturation within the thymus over a longer period of time. Furthermore, there is a fetal-derived and heterogeneous population of resident {gamma}{delta}-thymocytes of unknown functional importance.

immunology↗

bioRxiv2020

G protein-regulated endocytic trafficking of adenylyl cyclase type 9

GPCRs are increasingly recognized to initiate signaling via heterotrimeric G proteins as they move through the endocytic network, but little is known about how relevant G protein effectors are localized. Here we report dynamic trafficking of adenylyl cyclase type 9 (AC9) from the plasma membrane to endosomes, while adenylyl cyclase type 1 (AC1) remains in the plasma membrane, and stimulation of AC9 trafficking by ligand-induced activation of Gs-coupled GPCRs or Gs. AC9 transits a similar dynamin-dependent early endocytic pathway as activated GPCRs but, in contrast to GPCR trafficking which is regulated by {beta}-arrestin but not Gs, AC9 trafficking is regulated by Gs but not {beta}-arrestin. We also show that AC9, but not AC1, contributes to cAMP production from endosomes. These results reveal dynamic and isoform-specific trafficking of adenylyl cyclase in the endocytic network, and a discrete role of a heterotrimeric G protein in controlling subcellular location of a relevant effector.

cell biology↗

bioRxiv2018

Dynamin binding protein is required for Xenopus laevis kidney development

The adult human kidney contains over one million nephrons, with each nephron consisting of a tube containing segments that have specialized functions in nutrient and water absorption and waste excretion. The embryonic kidney of Xenopus laevis consists of a single functional nephron composed of regions that are analogous to those found in the human nephron, making it a simple model for the study of nephrogenesis. The exocyst complex, which traffics proteins to the cell membrane in vesicles via CDC42, is essential for normal kidney development. Here, we show that the CDC42-GEF, dynamin binding protein (Dnmbp/Tuba), is essential for nephrogenesis in Xenopus. dnmbp is expressed in Xenopus embryo kidneys during development, and knockdown of Dnmbp using two separate morpholino antisense oligonucleotides results in reduced expression of late pronephric markers, whereas the expression of early markers of nephrogenesis remains unchanged. A greater reduction in expression of markers of differentiated distal and connecting tubules was seen in comparison to proximal tubule markers, indicating that Dnmbp reduction may have a greater impact on distal and connecting tubule differentiation. dnmbp knockout using CRISPR results in a similar reduction of late markers of pronephric tubulogenesis. Overexpression of dnmbp in the kidney also resulted in disrupted pronephric tubules, suggesting that dnmbp levels in the developing kidney are tightly regulated, with either increased or decreased levels leading to developmental defects. Together, these data suggest that Dnmbp is required for nephrogenesis.

developmental biology↗