Biology subjects

Paoletti, A.

Publications and source records attributed to Paoletti, A..

3 recordsLinked to original sources

bioRxiv2024

P2Y2 purinergic receptor and DNA sensor cGAS dictate ionizing radiation-mediated proinflammatory macrophage activation

The reprogramming of tumor-associated macrophages (TAMs) by radiotherapy is associated with cancer patients response and sensitization to immune checkpoint blockade, but the molecular mechanisms involved remain largely unknown. Here, we show that following ionizing radiation (IR), macrophages accumulate single and double strand-DNA breaks and fragmented mitochondria in their cytosol, and stabilize the DNA sensor cyclic GMP-AMP synthase (cGAS). We demonstrate that mitochondrial fragmentation is induced by the activation of the dynamin-related protein 1 (DRP1), and controls the stabilization of cGAS and the proinflammatory activation of irradiated macrophages. Furthermore, pharmacological and genetic inhibitions of cGAS impair the proinflammatory activation of irradiated macrophages, thus revealing that cGAS is a central effector of IR-mediated proinflammatory macrophage activation. Interestingly, we also report that the purinergic receptor P2Y2 acts as an endogenous repressor of the proinflammatory macrophage activation and demonstrate that P2Y2 inactivation enhances the capacity of irradiated macrophages to undergo a proinflammatory activation. Our results thus define a new signaling pathway elicited in macrophages by IR directing mitochondrial dynamics, cytosolic DNA recognition by cGAS and proinflammatory phenotype, which is enhanced following P2Y2 inactivation.

immunology↗

bioRxiv2024

Distinct tissue-niche localization and function of synovial tissue myeloid DC subsets in health, and in active and remission Rheumatoid Arthritis

Current rheumatoid arthritis (RA) treatments do not restore immune tolerance. Investigating dendritic cell (DC) populations in human synovial tissue (ST) may reveal pathways to re-instate tolerance in RA. With single-cell and spatial-transcriptomics of synovial tissue biopsies, validated by micro co-culture systems, we identified condition and niche-specific myeloid DC clusters with distinct differentiation trajectories and functions. Healthy synovium contains a unique tolerogenic AXLpos DC2 cluster in the superficial sublining layer. In active RA, a macrophage-rich lining-layer niche becomes populated with inflammatory DC3 clusters that specifically activate memory CCL5pos TEM and CCL5posCXCL13pos TPH, promoting synovitis. In the sublining lymphoid niche, CCR7pos DC2 mReg specifically interact with naive-T-cells, potentially driving the local expansion of new effector T-cells. Sustained remission sees the resolution of these niches but lacks the recovery of tolerogenic AXLpos DC2, indicating latent potential for disease flare. A human RA disease-flare model showed that the activation of blood predecessor of ST-DC3 clusters precedes the onset of inflammation in joints. Therapeutic strategies targeting pathogenic ST-DC3 clusters, or reinstating tolerogenic AXLpos DC2, may restore immune homeostasis in RA. In briefDeconstruction of human RA synovium, using single-cell spatial transcriptomics and micro-culture systems, reveals distinct neighbourhoods within the synovial architecture across health, and RA patients with active disease or sustained remission. Discrete niches are identified that contain distinct myeloid DC clusters that differ in frequency, differentiation trajectories, and effector functions. HighlightsO_LIHuman RA synovium exhibits condition and niche specific myeloid DC clusters that vary in their tissue differentiation trajectories and functions. C_LIO_LIST-CD14pos DC3 (iDC3) support inflammatory CCL5pos TEM and CCL5pos TPH cell activation in the hyperplastic lining layer. C_LIO_LIST-CCR7pos DC2 (mReg), driven by MIR155, interact with naive-T-cells in sublining lymphoid niches. C_LIO_LIA specific inflammatory signature of blood predecessors of ST-DC3s predict flare in RA. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=199 HEIGHT=200 SRC="FIGDIR/small/600758v1_ufig1.gif" ALT="Figure 1"> View larger version (74K): org.highwire.dtl.DTLVardef@27ab01org.highwire.dtl.DTLVardef@4be238org.highwire.dtl.DTLVardef@1f10734org.highwire.dtl.DTLVardef@1102056_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2021

SFI1 and centrin form a distal end complex critical for proper centriole architecture and ciliogenesis

Over the course of evolution, the function of the centrosome has been conserved in most eukaryotes, but its core architecture has evolved differently in some clades, as illustrated by the presence of centrioles in humans and a spindle pole body in yeast (SPB). Consistently, the composition of these two core elements has diverged greatly, with the exception of centrin, a protein known to form a complex with Sfi1 in yeast to structurally initiate SPB duplication. Even though SFI1 has been localized to human centrosomes, whether this complex exists at centrioles and whether its function has been conserved is still unclear. Here, using conventional fluorescence and super-resolution microscopies, we demonstrate that human SFI1 is a bona fide centriolar protein localizing to the very distal end of the centriole, where it associates with a pool of distal centrin. We also found that both proteins are recruited early during procentriole assembly and that depletion of SFI1 results in the specific loss of the distal pool of centrin, without altering centriole duplication in human cells, in contrast to its function for SPB. Instead, we found that SFI1/centrin complexes are essential for correct centriolar architecture as well as for ciliogenesis. We propose that SFI1/centrin complexes may guide centriole growth to ensure centriole integrity and function as a basal body.

cell biology↗