Biology subjects

Hogan, P. G.

Publications and source records attributed to Hogan, P. G..

5 recordsLinked to original sources

bioRxiv2026

Mechanisms determining Schistosoma mansoni CRAC channel activation

Schistosoma mansoni and its schistosome relatives are parasitic worms that impose a substantial disease burden on human populations and livestock. On the rationale that calcium signalling is a critical process in multicellular organisms, we have examined wildtype and engineered S. mansoni STIM and ORAI-- orthologues of STIM and ORAI known in mammals and other species for their central role in cellular calcium signalling-- by imaging their localization, interactions, and contribution to ion currents and calcium influx in living cells. The ER membrane protein S. mansoni STIM recapitulates the essential functions of mammalian STIM1, namely, calcium-sensing by its ER-luminal domain, targeting to ER-plasma membrane junctions through interactions with the plasma membrane and with plasma membrane S. mansoni ORAI channels, and an ability to gate the S. mansoni ORAI channel. S. mansoni ORAI is a plasma membrane calcium channel that exhibits striking parallels with mammalian ORAI1 in its pore architecture and gating mechanism. The schistosome and human proteins are not completely interchangeable, however, and schistosome-human ORAI chimeras point to a special role of the ORAI N terminus in channel gating. Importantly, we demonstrate pharmacological differences between the schistosome and human channels that may offer an opportunity for selective therapeutic targeting of schistosome STIM-ORAI-dependent calcium entry. Author SummaryCalcium channels represent potential targets to parasitic helminths. We investigated Schistosoma mansoni CRAC channel activation through the expression of its proteins. We have established that the fundamental protein conformational changes and protein-protein interactions underlying STIM-ORAI signaling are shared between humans and schistosome proteins. Importantly, a key finding is that evolutionary divergence in residues that are not implicated in the basic mechanisms of STIM-ORAI activation appears to offer a window for pharmacological inhibitors that would be selective for the schistosome ORAI channel. We identified pharmacological differences for two compounds tested. These differences open avenues for the development of selective drugs that can target the S. mansoni CRAC channel without affecting human physiology, thus offering the prospect of new treatments for schistosomiasis.

biochemistry↗

bioRxiv2026

The atypical IκB factor IκBδ enhances CD8 T cell accumulation and effector functions in solid tumors

Two prominent mechanisms by which tumors fend off immune control are by constraining the ability of T cells and CAR T cells to survive and expand in the tumor, and by restraining their ability to sustain full cytotoxic capacity. We identified I{kappa}B{delta}, encoded by Nfkbid, a poorly characterized I{kappa}B family member, as a molecular lever that overcomes both of these constraints on anti-tumor CD8+ tumor-infiltrating lymphocytes (TILs). Nfkbid is an NFAT target gene that is expressed in CD8+ effector T cells and, at modest levels, in CD8+ TILs. We found that Nfkbid depletion impaired TIL accumulation, exacerbating the growth of solid tumors. On the other hand, ectopic I{kappa}B{delta} overexpression enhanced TIL expansion, reduced the expression of exhaustion-associated transcription factors and inhibitory receptors, and elevated cytotoxic molecule production, leading to enhanced tumor control. I{kappa}B{delta} has a shorter protein isoform that is identical in a core region spanning the ankyrin-repeat domain known to interact with NF{kappa}B proteins, but that lacks the [~]150-residue N-terminal region. We showed that the shared core region is sufficient to drive T cell accumulation, whereas the N-terminal peptide region is required for robust effector function and to counter exhaustion, underscoring that tumor-infiltrating CD8+ T cell accumulation and effector differentiation are separable programs. Our current study provides evidence that I{kappa}B{delta}, an atypical member of the NF{kappa}B family, is a lever to overcome two cardinal deficits that limit CD8+ TIL anti-tumor efficacy: impaired accumulation in the tumor and diminished effector function.

immunology↗

bioRxiv2026

Reversible control of T cell exhaustion by NR4A transcription factors revealed through targeted protein degradation

Tumor-infiltrating CD8+ T cells (TILs) show progressive loss of effector function and upregulation of inhibitory receptors. NR4A transcription factors have emerged as key regulators of this dysfunctional state. Here we developed degron-based systems enabling rapid degradation of endogenous NR4A proteins in both mouse and primary human T cells. We demonstrate that the continuous presence of each NR4A protein is required to maintain suppression of effector cytokines and expression of co-inhibitory receptors; degradation of individual NR4A proteins rapidly restored these functional features, with each NR4A protein exerting prominent effects on distinct as well as overlapping subsets of genes and surface markers associated with effector, memory and exhaustion programs. Transcriptional profiling of phenotypically defined populations revealed both shared and unique gene programs across NR4A family members. Through CRISPR-mediated endogenous gene editing in primary human CD8+ T cells, we show that targeted degradation of NR4A proteins with a small molecule degrader can maintain cytokine expression and suppress inhibitory receptor expression in cells subjected to chronic stimulation, providing a framework for a powerful strategy for therapeutic intervention. One Sentence SummaryTargeted degradation of endogenous NR4A proteins reveals that individual family members maintain features of T cell dysfunction through overlapping as well as non-redundant mechanisms, providing a therapeutic strategy to restore anti-tumor function.

immunology↗

bioRxiv2025

Loss of TET function in T regulatory cells yields ex-Treg cells biased toward T follicular helper cells, causingautoimmune diseases through autoantibody production

T regulatory cells (Treg cells) express the transcription factor FOXP3 and maintain immune homeostasis by attenuating effector responses. Treg cells are prone to lose FOXP3 and convert to pathological ex-Treg cells under conditions of strong or chronic inflammation. One mechanism for loss of FOXP3 expression involves increased DNA methylation of intronic enhancers CNS1 and CNS2 in the Foxp3 locus; these enhancers are maintained in a demethylated state by TET enzymes, 5-methylcytosine (5mC) dioxygenases that generate 5-hydroxymethylcytosine (5hmC) and other oxidized methylcytosines that are essential intermediates in all pathways of DNA demethylation. We previously showed that FOXP3+ Treg cells from Tet2/3-deficient (Tet2/3 DKO) mice displayed increased methylation of CNS1 and CNS2 and converted to FOXP3-negative ex-Treg cells considerably more efficiently than WT Treg cells. Here we extend our previous analysis of Foxp3-Cre Tet2/3fl/fl mice. We classified the mice as DKO- moderate or DKO-severe based on the total number of leukocytes in the spleen and peripheral lymph nodes and investigated the phenotypic and molecular basis for the progressive inflammation occurring in these mice. RNA-seq as well as histological and immunocytochemical analyses showed a striking expansion of T follicular helper (Tfh) cells and plasma cells in Tet2/3 DKO-severe mice. RNA-seq analyses also revealed increased induction of interferon-stimulated genes (ISGs) in CD4+ FOXP3- T cells from these mice, and single-cell (sc) RNA-seq analyses suggested strongly that this was due to skewed differentiation of both Tet2/3 DKO FOXP3+ Treg cells and Tet2/3 DKO FOXP3- ex-Treg cells into Tfh-like cells. Base-resolution "6-base" sequencing showed the expected loss of 5hmC and increased 5mC in Tfh cells purified from Tet2/3 DKO-severe mice, and suggested that the observed bias in gene expression patterns could arise both from a direct increase in methylation of essential enhancers stemming from TET deficiency, or because methylation interfered with binding of methylation-sensitive transcriptional regulators including CTCF.

immunology↗

bioRxiv2023

Proteome-wide base editor screens to assess phosphorylation site functionality in high-throughput

Signaling pathways that drive gene expression are typically depicted as having a dozen or so landmark phosphorylation and transcriptional events. In reality, thousands of dynamic post-translational modifications (PTMs) orchestrate nearly every cellular function, and we lack technologies to find causal links between these vast biochemical pathways and genetic circuits at scale. Here, we describe "signaling-to-transcription network" mapping through the development of PTM-centric base editing coupled to phenotypic screens, directed by temporally-resolved phosphoproteomics. Using T cell activation as a model, we observe hundreds of unstudied phosphorylation sites that modulate NFAT transcriptional activity. We identify the phosphorylation-mediated nuclear localization of the phosphatase PHLPP1 which promotes NFAT but inhibits NF{kappa}B activity. We also find that specific phosphosite mutants can alter gene expression in subtle yet distinct patterns, demonstrating the potential for fine-tuning transcriptional responses. Overall, base editor screening of PTM sites provides a powerful platform to dissect PTM function within signaling pathways.

systems biology↗