Biology subjects

Julien, J.-P.

Publications and source records attributed to Julien, J.-P..

22 records · Page 2Linked to original sources

bioRxiv2019

Identification of the C. sordellii lethal toxin receptor elucidates principles of receptor specificity in clostridial toxins

Clostridium sordellii lethal toxin (TcsL) is responsible for an almost invariably lethal toxic shock syndrome associated with gynecological C. sordellii infections. Here, using CRISPR/Cas9 screening, we identify semaphorins SEMA6A and SEMA6B as the cellular receptors for TcsL and demonstrate that soluble extracellular SEMA6A can protect mice from TcsL-induced edema. A 3.3 [A] cryo-EM structure shows that TcsL binds SEMA6A with the same region that the highly related C. difficile TcdB toxin uses to bind structurally unrelated Frizzled receptors. Remarkably, reciprocal mutations in this evolutionarily divergent surface are sufficient to switch receptor specificity between the toxins. Our findings establish semaphorins as physiologically relevant receptors for TcsL, and reveal the molecular basis for the difference in tissue targeting and disease pathogenesis between highly related toxins.

molecular biology↗

bioRxiv2019

Evolution of protective human antibodies against Plasmodium falciparum circumsporozoite protein repeat motifs

Circumsporozoite protein of the human malaria parasite Plasmodium falciparum (PfCSP) is the main target of antibodies that prevent the infection and disease. Protective antibodies recognize the central PfCSP domain, but our understanding of how parasite inhibition is associated with recognition of this domain and with the evolution of potent antibodies remains scattered. Here, we characterized the epitope specificity of 200 human monoclonal PfCSP antibodies. We show that the majority of PfCSP antibodies bind to NANP and NANP-like motifs with different preferences and define the molecular basis for recognition. Epitope cross-reactivity evolved with increasing antibody affinity around a conserved (N/D)P-NANP-N(V/A) core. High affinity to this motif, but not binding to NANP-like motifs, was associated with parasite inhibition and protection. Thus, NANP drives the development of potent PfCSP antibodies independently of their cross-reactivity profile, a finding with direct implications for the design of a second-generation PfCSP-based malaria vaccine.\n\nHIGHLIGHTSO_LIThe majority of human PfCSP antibodies recognize multiple epitopes\nC_LIO_LINANP affinity maturation drives the evolution of cross-reactive PfCSP antibodies\nC_LIO_LIPreferential PfCSP antibody binding to a conserved core motif\nC_LIO_LIHigh affinity not epitope specificity is associated with PfCSP antibody potency\nC_LI

immunology↗

bioRxiv2019

Trivalent cocktail of de novo designed immunogens enables the robust induction and focusing of functional antibodies in vivo

De novo protein design has been successful in expanding the natural protein repertoire. However, most de novo proteins lack biological function, presenting a major methodological challenge. In vaccinology, the induction of precise antibody responses remains a cornerstone for next-generation vaccines. Here, we present a novel protein design algorithm, termed TopoBuilder, with which we engineered epitope-focused immunogens displaying complex structural motifs. Both in mice and non-human primates, cocktails of three de novo designed immunogens induced robust neutralizing responses against the respiratory syncytial virus. Furthermore, the immunogens refocused pre-existing antibody responses towards defined neutralization epitopes. Overall, our de novo design approach opens the possibility of targeting specific epitopes for vaccine and therapeutic antibody development, and more generally will be applicable to design de novo proteins displaying complex functional motifs.

bioengineering↗

bioRxiv2018

Lipid interactions enhance activation and potentiation of cystic fibrosis transmembrane conductance regulator (CFTR)

The recent cryo-electron microscopy structures of phosphorylated, ATP-bound CFTR in detergent micelles failed to reveal an open anion conduction pathway as expected on the basis of previous functional studies in biological membranes. We tested the hypothesis that interaction of CFTR with lipids is important for opening of its channel. Interestingly, molecular dynamics studies revealed that phospholipids associate with regions of CFTR proposed to contribute to its channel activity. More directly, we found that CFTR purified together with associated lipids using the amphipol: A8-35, exhibited higher rates of catalytic activity, channel activation and potentiation using ivacaftor, than did CFTR purified in detergent. Catalytic activity in CFTR detergent micelles was partially rescued by addition of phospholipids plus cholesterol, arguing that these lipids contribute directly to its modulation. In summary, these studies highlight the importance of lipids in regulated CFTR channel activation and potentiation.

biophysics↗