Biology subjects

Jorge, A. M.

Publications and source records attributed to Jorge, A. M..

3 recordsLinked to original sources

bioRxiv2023

The role of GpsB in cell morphogenesis of Staphylococcus aureus

For decades, cells of the gram-positive bacterial pathogen Staphylococcus aureus were thought to lack a dedicated elongation machinery. However, S. aureus cells were recently shown to elongate before division, in a process that requires a SEDS (Shape Elongation Division and Sporulation) / PBP (Penicillin Binding Protein) pair for peptidoglycan synthesis, consisting of the glycosyltransferase RodA and the transpeptidase PBP3. In ovococci and rod-shaped bacteria the elongation machinery, known as elongasome, is composed of various proteins besides a dedicated SEDS/PBP pair. To identify proteins involved in the elongation of S. aureus, we screened the Nebraska Transposon Mutant Library, which contains transposon mutants in virtually all non-essential staphylococcal genes, for mutants with modified cell shape. We confirmed the roles of RodA/PBP3 in S. aureus elongation and identified GpsB, SsaA, and RodZ as additional proteins involved in this process. The gpsB mutant showed the strongest phenotype, mediated by the partial delocalization from the division septum of PBP2, the only bifunctional PBP in S. aureus, with both glycosyltransferase and transpeptidase activity, and of the PBP4 transpeptidase. Increased levels of these PBPs at the cell periphery result in higher levels of peptidoglycan insertion throughout the entire cell, overriding the RodA/PBP3-mediated peptidoglycan synthesis at the outer edge of the septum, which leads to cell elongation. As a consequence, in the absence of GpsB, S. aureus cells become more spherical.

microbiology↗

bioRxiv2021

SCARF1-induced efferocytosis plays an immunomodulatory role in humans, and autoantibodies targeting SCARF1 are produced in patients with systemic lupus erythematosus

Deficiency in the clearance of cellular debris is a major pathogenic factor in the emergence of autoimmune diseases. We previously demonstrated that mice deficient for scavenger receptor class F member 1 (SCARF1) develop a lupus-like autoimmune disease with symptoms similar to human systemic lupus erythematosus (SLE), including a pronounced accumulation of apoptotic cells (ACs). Therefore, we hypothesized that SCARF1 will be important for clearance of ACs and maintenance of self-tolerance in humans, and that dysregulation of this process could contribute to SLE. Here, we show that SCARF1 is highly expressed on phagocytic cells, where it functions as an efferocytosis receptor. In healthy individuals, we discovered that engagement of SCARF1 by ACs on BDCA1+ dendritic cells (DCs) initiates an interleukin-10 (IL-10) anti-inflammatory response mediated by the phosphorylation of signal transducer and activator of transcription 1 (STAT1). Unexpectedly, there was no significant difference in SCARF1 expression in SLE patient samples compared to healthy donor samples. However, we detected anti-SCARF1 autoantibodies in 26% of SLE patients, which was associated with dsDNA antibody positivity. Furthermore, our data shows a direct correlation of the levels of anti-SCARF1 in the serum and defects in the removal of ACs. Depletion of immunoglobulin restores efferocytosis in SLE serum, suggesting that defects in the removal of ACs is partially mediated by SCARF1 pathogenic autoantibodies. Our data demonstrate that human SCARF1 is an AC receptor in DCs and plays a role in maintaining tolerance and homeostasis.

immunology↗

bioRxiv2020

Phosphoglycerol-type wall- and lipoteichoic acids are enantiomeric polymers differentially cleaved by the stereospecific glycerophosphodiesterase GlpQ

The cell envelope of Gram-positive bacteria generally comprises two types of polyanionic polymers, either linked to peptidoglycan, wall teichoic acids (WTA), or to membrane glycolipids, lipoteichoic acids (LTA). In some bacteria, including Bacillus subtilis strain 168, WTA and LTA both are glycerolphosphate polymers, yet are synthesized by different pathways and have distinct, although not entirely understood morphogenetic functions during cell elongation and division. We show here that the exo-lytic sn-glycerol-3-phosphodiesterase GlpQ can discriminate between B. subtilis WTA and LTA polymers. GlpQ completely degrades WTA, lacking modifications at the glycerol residues, by sequentially removing glycerolphosphates from the free end of the polymer up to the peptidoglycan linker. In contrast, GlpQ is unable to cleave unmodified LTA. LTA can only be hydrolyzed by GlpQ when the polymer is partially pre-cleaved, thereby allowing GlpQ to get access to the end of the polymer that is usually protected by a connection to the lipid anchor. This indicates that WTA and LTA are enantiomeric polymers: WTA is made of sn-glycerol-3-phosphate and LTA is made of sn-glycerol-1-phosphate. Differences in stereochemistry between WTA and LTA were assumed based on differences in biosynthesis precursors and chemical degradation products, but so far had not been demonstrated directly by differential, enantioselective cleavage of isolated polymers. The discriminative stereochemistry impacts the dissimilar physiological and immunogenic properties of WTA and LTA and enables independent degradation of the polymers, while appearing in the same location; e.g. under phosphate limitation, B. subtilis 168 specifically hydrolyzes WTA and synthesizes phosphate-free teichuronic acids in exchange.

microbiology↗