Biology subjects

Kurniyati, K.

Publications and source records attributed to Kurniyati, K..

7 recordsLinked to original sources

bioRxiv2026

Bacterial internalins exploit E-cadherin to promote head-neck tumor metastasis and drug resistance

Head and neck squamous cell carcinoma (HNSCC) is an aggressive malignancy characterized by local invasion, lymph node metastasis, and therapeutic resistance. Chronic periodontal disease has been linked to HNSCC progression, yet the responsible pathogens and underlying molecular mechanisms remain unclear. Here, we show that the keystone periodontal pathogen Porphyromonas gingivalis promotes HNSCC metastasis and chemoresistance through two internalin proteins that are secreted via the type IX secretion system (T9SS). These internalin proteins specifically bind the EC1 domain of E-cadherin through their curved solenoid-like leucine-rich repeats (LRRs), facilitating bacterial invasion and inducing epithelial-to-mesenchymal transition (EMT). Mechanistically, internalin-E-cadherin engagement drives {beta}-catenin nuclear translocation and activates p38 and JNK1/2 MAP kinase signaling pathways, enhancing tumor cell migration, metastatic dissemination, and resistance to cisplatin-induced apoptosis. Tissue microarrays detect internalin antigens in HNSCC specimens, supporting their in vivo relevance. Together, these findings establish a direct mechanistic link between an oral pathogen and HNSCC progression and extend the paradigm of internalin-E-cadherin interactions from microbial pathogenesis to cancer biology.

microbiology↗

bioRxiv2026

Bacterial exo-α-sialidases subvert the complement system through desialylation

The complement system is a central pillar of innate immunity, yet how bacterial glycan-modifying enzymes subvert complement function remains poorly understood. Bacterial sialidases remove terminal sialic acids from host sialoglycans, but their direct impact on complement immunity is unclear. Here, we investigate the impact of six sialidases from five human pathogens on complement immunity using an integrated approach combining genetics, biochemistry, glycobiology, mass spectrometry, and structural biology. We demonstrate that major complement components (IgG, C1q, C4, and C5) and regulators (Factor I, Factor H, and C4bp) are sialylated, and that bacterial sialidase-mediated desialylation suppresses complement activation and surface deposition, thereby enabling complement evasion. Despite extensive sequence diversity, biochemical and structural analyses reveal that all examined sialidases share a conserved six-bladed {beta}-propeller catalytic domain and cleave both N-acetylneuraminic and N-glycolylneuraminic acids, the predominant mammalian sialic acids. Together, these findings uncover a conserved mechanism by which diverse bacterial pathogens disable complement immunity through desialylation.

microbiology↗

bioRxiv2026

Asymmetric architecture and adaptation of Treponema flagella

Spirochetes exhibit a distinctive corkscrew-like motility driven by periplasmic flagella that wrap around the cell body in a supercoiled configuration, yet the structural basis of this unique propulsion remains poorly understood. Here we combine cryo-electron microscopy, cryo-electron tomography, and genetic and biochemical analyses to determine the assembly and adaptation principles of the supercoiled flagellar filament in Treponema denticola, a major periodontal pathogen. Near-atomic structures reveal a glycosylated FlaB flagellin core encased by a previously unrecognized asymmetric sheath. The major sheath protein FlaA forms the bulk of the sheath and mechanically couples to the core through defined interfaces required for efficient motility, whereas four minor sheath proteins (FlaA1, FlaA2, FlaAP1, and FlaAP2) assemble along the concave side of the filament to accommodate intrinsic curvature. Disruption of this asymmetric core-sheath organization compromises force transmission and impairs motility, establishing coordinated asymmetric assembly as a fundamental mechanism underlying spirochetal motility.

molecular biology↗

bioRxiv2025

An ELISA for discovering protein-protein interaction inhibitors: blocking lysinoalanine crosslinking between subunits of the spirochete flagellar hook as a test case

The inhibition of a specific protein-protein interaction is often difficult to achieve in targeted drug design. We report the development and optimization of a general-purpose, readily implemented enzyme-linked immunosorbent assay (ELISA) for high-throughput screening to identify small- molecule inhibitors of protein interactions. This ELISA does not involve the use of any capture antibodies, probes, or compounds coated on the plate and represents a general strategy to identify inhibitors of a given protein-protein interaction. We demonstrate its utility in blocking lysinoalanine crosslinking between subunits of the spirochete flagellar hook by targeting the native form of the FlgE protein, which differs from the strategies used in previous assays. The flagellar hook protein FlgE self-catalyzes the formation of a lysinoalanine (Lal) inter-subunit crosslink that is essential for the motility, and thus, infectivity of spirochetes. Prevention of Lal crosslinking through inhibition with small molecules thus represents an avenue for therapeutic development against spirochete-related diseases, such as Lyme and syphilis. Screening a library of [~]700 compounds with the ELISA confirmed that hexachlorophene, currently the only known inhibitor of Lal crosslinking in FlgE, effectively inhibits the crosslinking reaction. In addition, the assay identified two new potential inhibitors, honokiol and zafirlukast, and several activators which belong to well-known classes of antibiotics.

biochemistry↗

bioRxiv2024

Inhibitors of lysinoalanine crosslinking in the flagella hook as antimicrobials against spirochetes

Spirochetes are especially invasive bacteria that are responsible for several human diseases, including Lyme disease, periodontal disease, syphilis and leptospirosis. Spirochetes rely on an unusual form of motility based on periplasmic flagella (PFs) to infect hosts and evade the immune system. The flexible hook of these PFs contains a post-translational modification in the form of a lysinoalanine (Lal) crosslink between adjacent subunits of FlgE, which primarily comprise the hook. Lal crosslinking has since been found in key species across phylum and involves residues that are highly conserved. The requirement of the Lal crosslink for motility of the pathogens Treponema denticola (Td) and Borreliella burgdorferi (Bb) establish Lal as a potential therapeutic target for the development of anti-microbials. Herein, we present the design, development and application of a NanoLuc-based high-throughput screen that was used to successfully identify two, structurally related Lal crosslink inhibitors (hexachlorophene and triclosan) from a library of clinically approved small molecules. A structure-activity relationship study further expanded the inhibitor set to a third compound (dichlorophene) and each inhibitor was demonstrated to biochemically block autocatalytic crosslinking of FlgE from several pathogenic spirochetes with varied mechanisms and degrees of specificity. The most potent inhibitor, hexachlorophene, alters Lal crosslinking in cultured cells of Td and reduces bacterial motility in swimming plate assays. Overall, these results provide a proof-of-concept for the discovery and development of Lal-crosslink inhibitors to combat spirochete-derived illnesses.

biochemistry↗

bioRxiv2022

A new class of protein sensor links spirochete pleomorphism, persistence, and chemotaxis

Pathogenic spirochetes can alter their morphologies and behaviors to infect and survive within their hosts. Previous reports demonstrate that the formation of so-called round bodies and biofilms, and chemotaxis are involved in spirochete pathogenesis. Here, in the spirochete Treponema denticola, we report a direct link between these cellular states that involves a new class of protein sensor (CheWS) with hitherto unclear function. Using cryo-EM methods, protein modeling, bioinformatics, genetics methods, and behavioral assays we demonstrate that spirochetes regulate these behaviors in response to the small molecule s-adenosylmethionine (SAM) via a SAM sensor that is anchored to chemotaxis arrays. CheWS influences chemotaxis, biofilm and round body formation under nonstressed conditions by a novel sporulation-like mechanism. Taken together, we establish an improved model for round body formation, we discovered a direct link between this SAM sensor and changes in cellular states, as well as characterized a new sensor class involved in chemotaxis.

microbiology↗

bioRxiv2020

Spirochetes produce ordered chemoreceptor arrays of unusual composition, arrangement, and symmetry to compensate for a highly curved membrane

Abstract/SummaryThe prokaryotic chemotaxis system is arguably the best-understood signaling pathway in biology, but most insights have been obtained from only a few model organisms and many studies have relied on artificial systems that alter membrane curvature1-3. In all previously described species, chemoreceptors organize with the histidine kinase (CheA) and coupling protein (CheW) into a hexagonal (P6 symmetry) extended array that is considered universal among archaea and bacteria4,5. Here, for the first time, we report an alternative symmetry (P2) of the chemotaxis apparatus that emerges from a strict linear organization of CheA in Treponema denticola cells, which possesses arrays with the highest native curvature investigated thus far. Using cryo-ET, we reveal that the Td chemoreceptor arrays assume a truly unusual arrangement of the supra-molecular protein assembly that has likely evolved to accommodate the high membrane curvature. The arrays have several additional atypical features, such as an extended dimerization domain of CheA and a variant CheW-CheR-like fusion protein that is critical for maintaining an ordered chemosensory apparatus in an extremely curved cell. Furthermore, the previously characterized Td oxygen sensor ODP influences array integrity and its loss substantially orders CheA. These results suggest a greater diversity of the chemotaxis signaling system than previously thought and demonstrate the importance of examining transmembrane systems in vivo to retain native membrane curvature.

microbiology↗