Biology subjects

Hernandez-Perez, S.

Publications and source records attributed to Hernandez-Perez, S..

8 recordsLinked to original sources

bioRxiv2025

Dynamic Micropatterning Reveals Spatial Dynamics of B Cell Receptor Signaling and Immune Synapse Formation

B cell activation by foreign antigens, recognized by the B cell receptor (BCR), is the key prerequisite for cell differentiation for antibody production. B cells typically encounter antigens bound to the surface of antigen presenting cells (APCs), leading to the formation of the immunological synapse (IS). To gain a deeper understanding of lymphocyte activation, we developed a dynamic micropatterning technique that enables the modeling of IS formation with exceptional spatial and temporal control. Using this method, we can image B cells before and after BCR engagement, in both fixed and live samples. We compared the activation of different BCR proximal signaling proteins in activatory and non-activatory areas of the synapse and found that the activated signaling proteins exhibited distinct spatial distributions. While pCD79A was strongly localized in the antigen-tethered area, surprisingly, pPLC{gamma}2 was enriched in regions lacking BCR ligands. We also visualized the formation of the IS in living cells using enhanced-resolution microscopy in 3D. We identified different cell behaviors during this process, including the repurposing of pre-existing actin-based protrusions as ready-made building blocks for the IS -- a feature uniquely detectable with this highly controllable system. Extending our approach to include a co-stimulatory B cell ligand, ICAM-1, and T cell system using CD3 and CD28 antibodies as ligands, we demonstrate the broader applicability of this method. Overall, our results highlight the power of dynamic micropatterning in elucidating the rapid and dynamic earliest steps of the IS formation with high spatial and temporal precision.

immunology↗

bioRxiv2025

Fusion of Complement Fragment C3d Enhances Germinal Center Responses to HIV-1 Envelope Glycoproteins

Eliciting sustained germinal center (GC) responses is critical for the development of an effective HIV-1 vaccine, yet HIV-1 envelope glycoprotein (Env) immunogens often fail to elicit GC responses required for the maturation of cognate B cells that secrete broadly neutralizing antibodies (bNAbs). Effective antigen recognition is important for initial B cell priming, activation, and GC engagement. Since complement opsonization contributes to antigen recognition, we investigated whether C3d fusion could enhance the GC response of the stabilized HIV-1 Env immunogen based on a consensus sequence (ConM Env). Our results demonstrate that ConM Env-C3d induced potent HIV-specific B cell activation in vitro compared to ConM Env alone. We also observed that the C3d fusion enhanced antigen presentation by human tonsil-derived follicular dendritic cells (FDCs) to HIV-specific B cell lines. Moreover, mouse immunization studies combining ConM Env-C3d with the AddaS03 adjuvant revealed significantly enhanced early GC formation and prolonged antigen display and retention on FDCs for up to 56 days, highlighting improved antigen persistence within GCs. These immunological enhancements, including a more focused early antibody response, correlated with improved virus neutralization. Additionally, we observed sex-based differences in immune responses, with female mice showing stronger antibody responses and enhanced antigen retention compared to males. These findings suggest that C3d fusion can enhance GC engagement and improve the immunogenicity of HIV-1 vaccines.

immunology↗

bioRxiv2023

Spatiotemporal control of microtubule acetylation by mechanical cues regulates lysosome dynamics at the immune synapse of B cells to promote antigen presentation

The capacity of B cells to extract immobilized antigens through the formation of an immune synapse can be tuned by the physical characteristics of the surface where antigens are encountered. However, the underlying mechanisms that couple mechanosensing by B cells to antigen extraction and processing remain poorly understood. We show that B cells activated by antigens associated with stiffer substrates exhibit enhanced spreading responses and higher tubulin acetylation at the center of the immune synapse, where less motile lysosomes preferentially localize. This process is coupled to the translocation of the microtubule acetylase, ATAT1 to the cytoplasm of B cells, which occurs as a mechano-response during BCR stimulation. Accordingly, B cells silenced for ATAT1 are unable to stabilize lysosomes at the synaptic interface and display a lower capacity to extract and present immobilized antigens to T cells. Overall, these findings highlight how BCR-dependent mechano-responses trigger microtubule network modifications to precisely orchestrate lysosome positioning to promote antigen extraction and presentation in B cells.

cell biology↗

bioRxiv2023

Proteomic profiling of isolated immune synapses from primary mouse B cells

The immune synapse (IS) is a cell-cell interaction platform critical in lymphocyte activation by specific antigens. Despite of B cells being able to also respond to soluble antigens, in particular the in vivo importance of the IS and surface-tethered antigen recognition has strongly emerged in the recent years. The IS serves as a dynamic hub for multiple cellular actions but the molecular details of these functions, especially beyond the B cell antigen receptor (BCR) signalling, remain poorly understood. Here, to address the lack in the systems level understanding of the IS, we setup methodology for comprehensive investigation of the composition of the primary mouse B cells IS at proteome level. Utilizing functionalized magnetic beads to mimic antigen presenting cells and trigger IS formation on them, we developed a method to specifically and robustly extract the cell adhesions on the beads, namely the IS or transferrin receptor mediated adhesion as a control. Our data revealed 661 proteins exclusively present in the IS at 15 minutes after BCR engagement, 13 exclusively in the control adhesions and 365 proteins shared between the samples. We got strong coverage of the known components of the IS as well as identified a plethora of unknown proteins and functional pathways with hitherto unknown roles in B cell IS. Thus, in this work, we validated the IS isolation method as a valuable tool to study early B cell activation by surface-bound antigens as well as unveil several novel proteins and pathways suggestive of new functional aspects in the IS.

immunology↗

bioRxiv2022

Loss of Rab8a in B cells leads to increased antibody responses and class-switch recombination

Rab8a is a small GTPase with a wide range of reported functions in different cell types, including vesicle recycling, vesicle traffic to cilia, cell ruffling, migration, neurite outgrowth, Toll-like receptor signalling and T cell receptor docking at the immune synapse. However, the role of Rab8a in B lymphocytes has not been described to date. Here, using a conditional B cell-specific Rab8a knockout mouse model, we investigate the role of Rab8a both in vivo and in vitro. Rab8a KO mice present enhanced antibody responses to both T-dependent and T-independent immunisations. Rab8a KO cells showed normal BCR trafficking and antigen processing and presentation but however, increased class-switch recombination. While the early BCR signalling responses, such as proximal kinase activation and calcium-flux, were normal, the signalling via AKT and ERK1/2 was decreased. We propose that the lack of Rab8a alters cellular signalling leading to enhanced antibody responses and increased class-switch recombination potentially via downmodulation of the PI3K/AKT/mTOR pathway.

immunology↗

bioRxiv2020

APEX2 proximity biotinylation reveals protein dynamics triggered by B cell receptor activation

Successful B cell activation, critical for high-affinity antibody production, is controlled by the B cell antigen receptor (BCR). However, we still lack a comprehensive protein-level view of the very dynamic multi-branched cellular events triggered by antigen binding. Here, we employed APEX2 proximity biotinylation to study antigen-induced changes, 5-15 min after receptor activation, at the vicinity of the plasma membrane lipid rafts, wherein BCR enriches upon activation. The data reveals dynamics of signaling proteins, as well as various players linked to the subsequent processes, such as actin cytoskeleton remodelling and endocytosis. Interestingly, our differential expression analysis identified dynamic responses in various proteins previously not linked to early B cell activation. We demonstrate active SUMOylation at the sites of BCR activation in various conditions and report its functional role in BCR signaling through Akt and MAPK axes.

immunology↗

bioRxiv2019

Missing-In-Metastasis / Metastasis Suppressor 1 modulates B cell receptor signaling, B cell metabolic potential and T cell-independent immune responses.

Efficient generation of antibodies by B cells is one of the prerequisites of protective immunity. B cell activation by cognate antigens via B cell receptors (BCR), or pathogen-associated molecules through pattern-recognition receptors, such as Toll-like receptors (TLRs), leads to transcriptional and metabolic changes that ultimately transform B cells into antibody producing plasma cells or memory cells. BCR signaling and a number of steps downstream of it rely on coordinated action of cellular membranes and the actin cytoskeleton, tightly controlled by concerted action of multiple regulatory proteins, some of them exclusive to B cells. Here, we dissect the role of Missing-In-Metastasis (MIM), or Metastasis suppressor 1 (MTSS1), a cancer-associated membrane and actin cytoskeleton regulating protein, in B cell-mediated immunity by taking advantage of MIM knockout mouse strain. We show undisturbed B cell development and largely normal composition of B cell compartments in the periphery. Interestingly, we found that MIM-/- B cells are defected in BCR signaling in response to surface-bound antigens but, on the other hand, show increased metabolic activity after stimulation with LPS or CpG. In vivo, MIM knockout animals exhibit impaired IgM antibody responses to immunization with T cell-independent antigen. This study provides the first comprehensive characterization of MIM in B cells, demonstrates its regulatory role for B cell-mediated immunity, as well as proposes new functions for MIM in tuning receptor signaling and cellular metabolism, processes which may also contribute to the poorly understood functions of MIM in cancer.

immunology↗

bioRxiv2019

Fast targeting of antigen and surface-derived MHCII into degradative compartments implies endosomal prewiring for antigen presentation in B cells.

In order to mount high-affinity antibody responses, B cells internalise specific antigens and process them into peptides loaded onto MHCII for presentation to TO_SCPLOWHC_SCPLOW cells. While the biochemical principles of antigen processing and MHCII loading have been well dissected, how the endosomal vesicle system is wired to enable these specific functions remains much less studied. Here, we performed a systematic microscopy-based analysis of antigen trafficking in B cells to reveal its route to the MHCII peptide-loading compartment (MIIC). Surprisingly, we detected fast targeting of internalised antigen into peripheral acidic compartments that possessed the hallmarks of MIIC and also showed degradative capacity. In these vesicles, internalised antigen converged rapidly with membrane-derived MHCII and partially overlapped with Cathepsin-S and H2-M, both required for peptide loading. These early compartments appeared heterogenous and atypical as they contained a mixture of both early and late markers, indicating specialized endosomal route. Together, our data suggests that, in addition to previously-reported perinuclear late endosomal MIICs, antigen processing and peptide loading could start already in these specialized early peripheral acidic vesicles (eMIIC) to support fast peptide-MHCII presentation.

immunology↗