Biology subjects

Fackler, O.

Publications and source records attributed to Fackler, O..

5 recordsLinked to original sources

bioRxiv2025

HIV-1 Reprograms CD4 T Cell Responses by Impairing Antigen-specific Communication with Dendritic Cells

HIV-1 infection causes general dysfunction of adaptive immune cells that persists even under therapy but the underlying mechanisms remain elusive. Antigen-specific interactions of the main target cells of HIV, CD4 T cells, with dendritic cells (DCs) orchestrate global T cell responses and convey help to CD8 T cells. Here we report that HIV-1, by virtue of its pathogenesis factor Nef, impairs activation and transcriptionally reprograms CD4 T cells to dampen Th1 differentiation in response to antigen-specific stimulation by DCs. These alterations also disrupt functional communication to DCs to reduce DC activation and limit Th1 helper cytokine production. Mechanistically, Nef achieves this modulation of antigen-specific CD4 T cell function by reducing T cell surface levels of CD4. These results define modulation of CD4 T cell-DC communication as pathogenic principle by which HIV-1 disrupts adaptive immunity and emphasize the direct role of CD4 in immune cell communication. One Sentence SummaryHIV-1 suppresses Th1 polarization by disrupting the communication between CD4 T cells and Dendritic cells through cell surface CD4 downregulation by the viral pathogenesis factor Nef.

immunology↗

bioRxiv2022

Genomic profiling of HIV-1 integration in microglia links viral insertions to TAD organization

HIV-1 persists in anatomically distinct cellular and tissue reservoirs as a stably integrated provirus that is a major barrier to HIV-1 cure. Proviral insertions are largely characterized in blood cells, while HIV-1 integration patterns remain unexplored in microglia, the major brain reservoir. Here, we employ genomics approaches to obtain the first HIV-1 integration site (IS) profiling in microglia and perform in-depth analysis of transcriptome, specific histone signatures and chromatin accessibility on different genomic scales. We show that HIV-1 follows genic insertion patterns into introns of actively transcribed genes, characteristic of blood reservoirs. HIV-1 insertional hotspot analysis by non-negative matrix factorization (NMF)-based approach clusters IS signatures with genic- and super-enhancers. Chromatin accessibility transcription factor (TF) footprints reveal that increased CTCF binding marks latently infected microglia compared to productively infected one. We identify CTCF-enriched topologically associated domain (TAD) borders with signatures of active chromatin as a neighborhood for HIV-1 integration in microglia and CD4+ T cells. Our findings further strengthen the notion that HIV-1 follows the patterns of host cell genome organization to integrate and to establish the silent proviral state and reveal that these principles are largely conserved in different anatomical latent reservoirs.

genomics↗

bioRxiv2022

ARPC5 Isoforms Drive Distinct Arp2/3-dependant Actin Remodeling Events in CD4 T Cells

Arp2/3-dependent formation of nuclear F-actin networks of different morphology and stability is observed in an increasing number of biological processes. In CD4 T cells, T cell receptor (TCR) signaling induces cytoplasmic and nuclear F-actin assembly via Arp2/3 to strengthen contacts to antigen presenting cells and to regulate gene expression, respectively. How Arp2/3 complex is regulated to mediate these distinct actin polymerization events in response to a common stimulus is unknown. Arp2/3-complex consists of 7 subunits where ARP3, ARPC1 and ARPC5 exist as two different isoforms in humans that can assemble in complexes with different properties. Examining whether specific Arp2/3 subunit isoforms govern distinct actin remodeling events in CD4 T cells, we find that the ARPC5L isoform drives nuclear actin polymerization, while cytoplasmic actin dynamics and TCR proximal signalling selectively relies on ARPC5. In contrast, formation of stable nuclear F-actin networks triggered by DNA replication stress in CD4 T cells requires ARPC5 and is independent of ARPC5L. Moreover, nuclear actin polymerization induced by TCR signaling but not by DNA replication stress is controlled by nuclear calcium-calmodulin signalling and N-WASP. Specific ARPC5 isoforms thus govern Arp2/3 complex activity in distinct actin polymerization events. ARPC5 isoform diversity thus emerges as a mechanism to tailor Arp2/3 activity to different physiological stimuli.

immunology↗

bioRxiv2020

Cellular Protrusions Engage Viral Infection Enhancing EF-C Peptide Nanofibrils

Self-assembling peptide nanofibrils (PNF) have gained increasing attention as versatile molecules in material science and biomedicine. One important application of PNF is to enhance retroviral gene transfer, a technology that has been central to the development of gene therapy. The best-investigated and commercially available PNF is derived from a 12-mer peptide termed EF-C. The mechanism of transduction enhancement depends on the polycationic surface of EF-C PNF, which binds to the negatively charged membranes of viruses and cells thereby overcoming electrostatic repulsion and increasing virion attachment and fusion. Assuming an even distribution of charges at the surfaces of virions and cells would result in an evenly distributed interaction of the virions with the cell surface. However, we here report that PNF do not randomly bind at the cell surface but are actively engaged by cellular protrusions. Chemical suppression of protrusion formation in cell lines and primary CD4+ T cells greatly reduced fibril binding and hence virion binding. Thus, the mechanism of PNF-mediated viral transduction enhancement involves active engagement of virus-loaded fibrils by cellular protrusions.

cell biology↗

bioRxiv2019

Salivary gland macrophages assist tissue-resident CD8+ T cell immune surveillance

Tissue macrophages and tissue resident memory CD8+ T cells (TRM) play important roles for pathogen sensing and rapid protection of barrier tissues. To date, it is incompletely understood how these two cell types cooperate for efficient organ surveillance during homeostasis. Here, we used intravital imaging to show that TRM dynamically crawled along tissue macrophages in murine submandibular salivary glands (SMG) during the memory phase following a viral infection. Ex vivo confined SMG TRM integrated an unexpectedly wide range of migration modes: in addition to chemokine-and adhesion receptor-driven motility, SMG TRM displayed a remarkable capacity of autonomous motility in the absence of chemoattractants and adhesive ligands. This unique intrinsic SMG TRM motility was transmitted by friction and adaptation to microenvironmental topography through protrusion insertion into permissive gaps. Analysis of extracellular space in SMG using super-resolution shadow imaging showed discontinuous attachment of tissue macrophages to neighboring epithelial cells, offering paths of least resistance for patrolling TRM. Upon tissue macrophage depletion, intraepithelial SMG TRM showed decreased motility and reduced epithelial crossing events, and failed to cluster in response to local inflammatory chemokine stimuli. In sum, our data uncover a continuum of SMG TRM migration modes and identify a new accessory function of tissue macrophages to facilitate TRM patrolling of the complex exocrine gland architecture.\n\nOne sentence summaryCombined in vitro and in vivo imaging of salivary gland-resident tissue memory CD8+ T cells (TRM) uncovers their unique migratory behavior and describes a novel accessory function of tissue macrophages to assist TRM surveillance.

immunology↗