Biology subjects

Alarcon, B.

Publications and source records attributed to Alarcon, B..

6 recordsLinked to original sources

bioRxiv2026

An ER Retrieval-and-Release System Reveals Ligand-Independent Basal Signaling by Cell Surface TCRs

The T cell receptor (TCR) machinery comprises the ligand-binding TCR{beta} and the CD3 signaling dimers. Individual subunits are synthesized in the endoplasmic reticulum (ER) and only the fully assembled TCRs reach the cell surface. We engineered a system to retained CD3{varepsilon} is in the ER. This allowed only partial TCR assembly, while continuous retrieval of CD3{varepsilon} from the Golgi back to the ER enabled complete assembly. Synchronous TCR release by biotin addition caused a transient increase in surface TCR abundance that gradually returned to steady-state levels. Mathematical modeling revealed that TCR levels were controlled by feedback mechanisms. Notably, surface-localized, but not ER-localized, TCRs spontaneously generated ligand-independent basal signaling. Phosphoproteomic analyses revealed that this signal is similar, but not identical, to ligand-induced TCR activation signals, with distinct phosphorylation patterns already evident at the CD3 subunits. Our findings establish the TCR retrieval-and-release system as a tool to investigate ligand-independent basal TCR signaling.

immunology↗

bioRxiv2024

TAF1-dependent transcriptional dysregulation underlies multiple sclerosis

A major conceptual and clinical challenge in multiple sclerosis (MS) is understanding the mechanisms that drive the central nervous system (CNS)-resident neuroinflammation and neurodegeneration underneath disease progression. Genome-wide association studies (GWAS) have implicated RNA polymerase II (RNAPII) promoter-proximal pausing in oligodendrocyte pathology, but the causal mechanisms remain unclear. Here we find that the C-terminal region of TAF1, a core component of the general transcription factor TFIID, is underdetected in progressive MS brains, which can be explained by endoproteolysis due to extralysosomal cathepsin B (CTSB). Mice lacking the C-terminal TAF1 domain (Taf1d38) exhibit MS-like brain transcriptomic signature, alongside CNS-resident inflammation, progressive demyelination, and motor disability. Mechanistically, C-terminal TAF1 interacts with MS-linked factors that cooperate to regulate RNAPII pausing, particularly affecting oligodendroglial myelination genes. These findings uncover a previously unrecognized transcriptional mechanism underlying MS progression and establish a tractable in vivo model for therapeutic development.

neuroscience↗

bioRxiv2024

Pre-TCR-Targeted Immunotherapy for T-cell Acute Lymphoblastic Leukemia

Targeted immunotherapy for T-cell acute lymphoblastic leukemia (T-ALL), an aggressive tumor of developing T-cell progenitors, is an urgent unmet need, especially for relapsed/refractory (r/r) disease. Selective T-ALL targeting is challenging due to the shared antigen expression between leukemic and normal T cells. Here we identify the pre-TCR, a surface receptor essential for T-cell development, as a biomarker of leukemia-initiating cells (LICs) in human T-ALL. Loss-of-function genetic approaches demonstrate that pre-TCR signaling is necessary for LIC activity and tumor progression in pre-TCR+ T-ALL patients xenografts. Furthermore, we demonstrate the specific therapeutic targeting of pre-TCR with a monoclonal antibody against the invariant pT subunit of the human pre-TCR, and validate an anti-pT antibody-drug conjugate treatment as a potent immunotherapy for inhibiting LIC activity and tumor progression of T-ALL in vivo. These findings reveal the suitability of pre-TCR targeting as a promising therapy for the treatment of (r/r) patients with T-ALL expressing the pre-TCR.

immunology↗

bioRxiv2020

Astrocyte to microglia cross-talk in acute and chronic neuroinflammation is shaped by SFRP1

Neuroinflammation is a common feature of many neurodegenerative diseases, which fosters a dysfunctional neuron-microglia-astrocyte crosstalk that, in turn, maintains microglial cells into a perniciously reactive state that often enhance neuronal damage. The molecular components that mediate this critical communication are however not fully explored. Here, we have asked whether Secreted-Frizzled-Related-Protein-1 (SFRP1), a multifunctional regulator of cell-to-cell communication, is part of the cellular crosstalk underlying neuroinflammation. We show that in mouse models of acute and chronic neuroinflammation, astrocyte-derived SFRP1 is sufficient to promote and sustain microglial activation, and thus a chronic inflammatory state. SFRP1 allows the upregulation of components of Hypoxia Induced Factors-dependent inflammatory pathway and, to a lower extent, of those downstream of the Nuclear Factor-kappaB. We thus propose that SFRP1 acts as a critical astrocyte to microglia amplifier of neuroinflammation, representing a potential valuable therapeutic target for counteracting the harmful effect of chronic inflammation present in several neurodegenerative diseases.

neuroscience↗

bioRxiv2020

Recreation of an antigen-driven germinal center in vitro by providing B cells with phagocytic antigen

Successful vaccines rely on activating a functional humoral response that results from generating class-switched high affinity immunoglobulins (Igs) with a superior capacity to neutralize infection. Key to this process is the germinal center (GC) reaction, in which B cells are selected in their search for antigen and T cell help. A major hurdle to understanding the mechanisms of B cell:T cell cooperation has been the lack of an in vitro system to recreate GCs in an antigen-specific manner. Here we report the generation of functional antigen-specific high affinity Igs of different isotypes in simple 2-cell type cultures of naive B and T cells. It is crucial for this process for B cells to take up antigen by a phagocytic mechanism, which results in stronger and more sustained BCR signals compared to stimulation with a soluble antigen. We also show the applicability of the system to generate antibodies of potential clinical interest.

immunology↗

bioRxiv2020

CCR5 deficiency impairs CD4+ T cell memory responses and antigenic sensitivity through increased ceramide synthesis

In CD4+ T cells, CCR5 is not only a coreceptor for HIV-1 infection, but also contributes to their functional fitness. Here we show that by limiting GATA-1-induced transcription of specific ceramide synthases, CCR5 signaling reduces ceramide levels and thereby increases T cell antigen receptor (TCR) nanoclustering in antigen-experienced mouse and human CD4+ T cells. This activity is CCR5-specific and independent of CCR5 costimulatory activity. CCR5-deficient mice showed reduced production of high affinity class-switched antibodies, but only after antigen rechallenge, which implies an impaired memory CD4+ T cell response. This study identifies a CCR5 function in the generation of CD4+ T cell memory responses, and establishes an antigen-independent mechanism that regulates TCR nanoclustering by altering specific lipid species.

immunology↗