Biology subjects

Kauffmann, B.

Publications and source records attributed to Kauffmann, B..

5 recordsLinked to original sources

bioRxiv2024

Amyloid signaling in antiphage defense

Immune regulated cell death (RCD) is a defense strategy common to different domains of life involving purposeful sacrifice of infected cells. In animals and fungi, functional amyloids play a role in the control of RCD as molecular switches activating key cell death effectors, rather than causing direct toxicity as seen with pathological amyloids. Here, we describe a novel amyloid-based signal transduction mechanism in an antiphage defense system in Escherichia coli. This antiphage abortive infection (Abi) system is mediated by two proteins, Bab and Agp which share a common amyloid motif and are encoded by adjacent genes. Upon phage infection, Agp activates Bab through amyloid signaling, leading to cell death. We determined the structure of the Bab cell death execution domain, which is distantly related to pore-forming domains present in fungi, animals and plants. We show that Bab and the fungal HET-S amyloid-controlled cell death execution protein are functionally interchangeable in their respective roles in antiphage defense and allorecognition. These findings add antiphage defense to the functional repertoire of amyloids.

microbiology↗

bioRxiv2024

CapP mediates the structural formation of biofilm-specific pili in the opportunistic human pathogen Bacillus cereus

Polymeric proteinaceous filaments are structural scaffolds that diversify the functionality of the bacterial extracellular matrix. Here, we report a previously uncharacterized bacterial factor called bc1280 that is exclusive to B. cereus group and indispensable for the establishment of a biofilm lifestyle. We propose that BC1280 is an essential chaperone for the assembly of the filamentous platform that tightly controls the polymerization of heteropili containing CalY and TasA as major subunits in a concentration-dependent manner. Additionally, BC1280 modulates the expression of EPS via an uncharacterized pathway that is activated by a protease and an ECF-type sigma factor. The pilus biogenesis system described in this work highlights the complexity of extracellular matrix assembly in B. cereus and introduces a singular three-part structuration mechanism during biofilm formation and maturation. Graphical abstractDuring the process of biofilm formation in B. cereus, TasA, CapP, and CalY serve as the main components, in addition to other factors, ensuring that the extracellular matrix correctly assembles. The three proteins are produced and processed by the signal peptidase SipW and subsequently secreted through the Sec pathway in an unfolded conformation. At early biofilm formation stages, CapP is initially present at low levels, associates with the cell wall and is secreted into the ECM where it interacts with unfolded subunits of CalY, facilitating CalY folding and initiating fibril growth. CalY serves as a nucleator for incorporating TasA subunits into the pilus, forming TasA-CalY heteropolymers. Once the ECM scaffold is established, CapP levels increase, forming stable complexes with CalY that prevent its folding and arrest filament growth. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC="FIGDIR/small/582368v2_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@df9d9dorg.highwire.dtl.DTLVardef@e4b712org.highwire.dtl.DTLVardef@1af2421org.highwire.dtl.DTLVardef@16d02c7_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2020

Structural and molecular basis of cross-seeding barriers in amyloids

Neurodegenerative disorders are frequently associated with β-sheet-rich amyloid deposits. Amyloid-forming proteins can aggregate under different structural conformations known as strains, which can exhibit a prion-like behaviour and distinct patho-phenotypes. Precise molecular determinants defining strain specificity and cross-strain interactions (cross-seeding) are currently unknown. The HET-s prion protein from the fungus Podospora anserina represents a model system to study the fundamental properties of prion amyloids. Here, we report the amyloid prion structure of HELLF, a distant homolog of the model prion HET-s. We find that these two amyloids, sharing only 17% sequence identity, have nearly identical β-solenoid folds but lack cross-seeding ability in vivo, indicating that prion specificity can differ in extremely similar amyloid folds. We engineer the HELLF sequence to explore the limits of the sequence-to-fold conservation and to pinpoint determinants of cross-seeding and prion specificity. We find that amyloid fold conservation occurs even at an exceedingly low level of identity to HET-s (5%). Next, we derive a HELLF-based sequence, termed HEC, able to breach the cross-seeding barrier in vivo between HELLF and HET-s, unveiling determinants controlling cross-seeding at residue level. These findings show that virtually identical amyloid backbone structures might not be sufficient for cross-seeding and that critical side-chain positions could determine the seeding specificity of an amyloid fold. Our work redefines the conceptual boundaries of prion strain and shed new light on key molecular features concerning an important class of pathogenic agents.Competing Interest StatementThe authors have declared no competing interest.View Full Text

biochemistry↗

bioRxiv2020

Identification of NLR-associated amyloid signaling motifs in filamentous bacteria

NLRs (Nod-like receptors) are intracellular receptors regulating immunity, symbiosis, non-self recognition and programmed cell death in animals, plants and fungi. Several fungal NLRs employ amyloid signaling motifs to activate downstream cell-death inducing proteins. Herein, we identify in Archaea and Bacteria, short sequence motifs that occur in the same genomic context as fungal amyloid signaling motifs. We identify 10 families of bacterial amyloid signaling sequences (we term BASS), one of which (BASS3) is related to mammalian RHIM and fungal PP amyloid motifs. We find that BASS motifs occur specifically in bacteria forming multicellular structures (mainly in Actinobacteria and Cyanobacteria). We analyze experimentally a subset of these motifs and find that they behave as prion forming domains when expressed in a fungal model. All tested bacterial motifs also formed fibrils in vitro. We analyze by solid-state NMR and X-ray diffraction, the amyloid state of a protein from Streptomyces coelicolor bearing the most common BASS1 motif and find that it forms highly ordered non-polymorphic amyloid fibrils. This work expands the paradigm of amyloid signaling to prokaryotes and underlies its relation to multicellularity.

microbiology↗

bioRxiv2019

Invasive in the North: New latitudinal record for Argentine ants in Europe

Environmental niche models predict the presence of the invasive Argentine ant in north-western Europe, especially along all the French Atlantic coast. Yet, the species has never been observed North from the 45th parallel in Europe, suggesting either that current models are wrong or that Argentine ants are already spreading north inconspicuously. Here, we report a three-hectare wide colony of Argentine ants, detected in 2016 in Nantes, France, which is 300 km north of the former northern-most outdoor population of this species in Europe. COI sequencing revealed that the haplotype of this new colony is the same as the one found in the so-called Catalonian supercolony, which is distinct from the haplotype found over most of the species range in Europe. Our discovery confirms models predictions that Argentine ants can colonize north-western Europe and suggests that they might have already reached several other locations along the French Atlantic coast. Detection surveys should be conducted in order to assess Argentine ants invasion patterns in Western France, particularly in high introduction risk areas such as major cities and maritime ports.

ecology↗