Biology subjects

Nelea, V.

Publications and source records attributed to Nelea, V..

4 recordsLinked to original sources

bioRxiv2026

Structural tuning of native type V fimbriae shapes mechanical specialization in Porphyromonas gingivalis

Fimbriae are proteinaceous filaments central to bacterial adhesion, colonization, and biofilm formation. Porphyromonas gingivalis, a keystone periodontal pathogen, utilizes two type V fimbriae systems, the major Fim and the minor Mfa fimbriae, that support distinct adhesive and biofilm-associated functions. Here, we determine the high-resolution cryo-electron microscopy structures of natively assembled FimA and Mfa1 stalks purified directly from P. gingivalis. Despite a shared donor-strand exchange mechanism, the two stalks exhibit distinct helical geometries and donor-strand environments. FimA has a larger helical pitch, whereas the Mfa1 donor strand is more extensively buried and further shielded by an ordered N-terminal latch. Comparison with monomeric stalk pilin structures reveals distinct assembly-associated remodeling around the donor-strand interface. Deletion of the Mfa1 latch reduces heat-resistant oligomer accumulation and produces species consistent with incomplete processing, yet recovered filaments retain the donor-strand-exchanged stalk architecture and exhibit initial force peaks comparable to native Mfa1 during simulated axial extension. Atomic force microscopy reveals greater apparent local stiffness of FimA under indentation, whereas steered molecular dynamics simulations show multiple lower-force axial transitions in FimA but a dominant higher-force transition in Mfa1. In both systems, the exchanged donor strands remain engaged during simulated extension while distinct surrounding contact networks rearrange. Together, these findings demonstrate how a conserved polymerization linkage can support structurally and mechanically distinct adhesive filaments, providing a molecular basis for mechanical diversification of type V fimbriae.

molecular biology↗

bioRxiv2026

Rewiring of EGFR oncogenic program by opposing actions of membrane versus soluble CD109 in HNSCC

The epidermal growth factor receptor (EGFR) expression is often dysregulated in head and neck squamous cell carcinoma (HNSCC), driving cancer cell proliferation, invasion, and metastasis through diverse pathways, thereby contributing to aggressive chemo- and radio-therapy resistance. A GPI-anchored protein, CD109 is upregulated in multiple cancers, including HNSCC. While membrane-anchored CD109 (mCD109) is pro-tumorigenic in SCC via EGFR/STAT3 activation, the role of protease-cleaved soluble CD109 (sCD109) is poorly understood. Our groundbreaking findings demonstrate that sCD109 antagonizes EGFR signaling by directly binding to the EGFR extracellular domain, preventing mCD109-EGFR stabilizing interactions on the cell surface, followed by inhibition of EGFR phosphorylation at Y1068 and downstream signaling cascades (AKT, MAPK, and STAT3) consequently suppressing cancer cell migration, invasion, 3D tumor spheroid formation and angiogenic tube formation. In addition, we found that sCD109 regulates EGFR fates by inhibiting nuclear localization of phosphorylated EGFR and promoting EGFR degradation. Additionally, sCD109 significantly reduces EGF-induced expression of cancer stem cell markers (CD44 and CD133) and embryonic stem cell markers (Nanog and Sox2), suggesting a suppressive role in cancer stemness. Taken together, these results underscore the opposing roles of mCD109 and sCD109: with sCD109 acting as an antagonist by inhibiting mCD109/EGFR-driven oncogenic signaling and phenotypes. Our current findings reveal a complex interplay among mCD109, sCD109, and EGFR, identifying a mechanism for targeting EGFRs degradation in HNSCC, and lay the groundwork for future research on investigating sCD109s modulatory role in preclinical models of HNSCC.

Cancer Biology↗

bioRxiv2023

Microfibril-associated glycoprotein 4 forms octamers that mediate interactions with elastogenic proteins and cells

Microfibrillar-associated protein 4 (MFAP4) is a 36-kDa extracellular glycoprotein with critical roles in human pathologies, including fibrosis in several organ systems, chronic obstructive pulmonary disease, and cardiovascular disorders. In elastic tissues such as arteries, lungs, and skin, MFAP4 associates with microfibrils and elastic fibres, which are the central extracellular fibres affected in thoracic aneurysms. MFAP4 directly interacts with elastogenic proteins, including fibrillin-1 and tropoelastin, and with cells via integrins. MFAP4 multimerisation represents a critical hallmark required for its physiological and pathological properties. However, molecular details and functional consequences of MFAP4 multimerisation are lacking. Here we present a cryo-electron microscopy structure of human MFAP4. In the presence of calcium, MFAP4 assembles as an octamer with D2 point group symmetry, where two sets of homodimers constitute the top and bottom halves of each octamer. Each of the homodimers is linked together by an inter-molecular disulfide bond. An engineered C34S missense mutation in MFAP4 prevented disulfide-bond formation between monomers, but the mutant formed octamers similar to wild type MFAP4. The atomic model, built into the 3.55 [A] cryo-EM map, suggests that several salt-bridges are important for interactions within and between homodimers, while non-polar interactions are important for octamer halves to assemble. In the absence of calcium, MFAP4 dissociates into tetramers, representing the top/bottom halves of the octamers. Binding studies with elastogenic proteins, including fibrillin-1, tropoelastin, LTBP4, and small fibulins showed that MFAP4 has multiple surfaces for protein-protein interactions, which depend upon the higher-order assembly of MFAP4. While the disulfide-bond mediated by C34S contributes little to those protein interactions, it modulated cell interaction. When MFAP4 forms assemblies with fibrillin-1, it abrogates MFAP4 interactions with cells. Overall, the study provides detailed molecular structure-function relationships of MFAP4 interactions with elastogenic proteins and cells.

cell biology↗

bioRxiv2019

Luminal Calcification of the Microvasculature in Fetuin-A Deficient Mice Leads to Premature Aging and Death

ObjectiveThe plasma protein fetuin-A mediates the formation of protein-mineral colloids known as calciprotein particles (CPP) - rapid clearance of these CPP by the reticuloendothelial system prevents errant mineral precipitation and therefore ectopic mineralization (calcification). The mutant mouse strain D2,Ahsg-/- combines fetuin-A deficiency with the mineralization-prone DBA/2 genetic background, having a particularly severe compound phenotype of microvascular and soft tissue mineralization. Here we studied mechanisms leading to soft tissue mineralization, organ damage and premature aging in these mice.\n\nApproach and ResultsWe analyzed mice longitudinally by echocardiography, X-ray-computed tomography, analytical electron microscopy, histology, mass spectrometry proteomics, and genome-wide microarray-based expression analyses of D2 wildtype and Ahsg-/- mice.\n\nFetuin-A deficient mice had calcified lesions in myocardium, lung, brown adipose tissue, reproductive organs, spleen, pancreas, kidney and the skin, associated with reduced growth, cardiac output and premature aging. Importantly, early stage calcified lesions presented in the lumen of the microvasculature suggesting precipitation of mineral containing complexes from the fluid phase of blood. Genome-wide expression analysis of calcified lesions and surrounding (not calcified) tissue, together with morphological observations, indicated that the ectopic mineralization was not associated with osteochondrogenic cell differentiation, but rather with thrombosis and fibrosis.\n\nConclusionsCollectively, these results demonstrate that pathological mineralization can start by intravascular mineral deposition causing microvasculopathy, which impacts on growth, organ function and survival. Our study underscores the importance of fetuin-A and related systemic regulators of mineralized matrix metabolism to prevent cardiovascular disease, especially in dysregulated mineral homeostasis.

physiology↗