Biology subjects

Almahayni, K.

Publications and source records attributed to Almahayni, K..

5 recordsLinked to original sources

bioRxiv2025

DNASE1L3 surveils mitochondrial DNA on the surface of distinct mammalian cells

The extracellular space is a critical environment for discriminating self versus non-self nucleic acids and initiating the appropriate immune responses through signaling cascades to relay information about extracellular nucleic acids. Here, we provide evidence that oxidized mitochondrial DNA is tethered to the surface of select mammalian cells through cell surface proteins and heparan sulfate proteoglycans. We demonstrate that cell surface DNA accumulates in large clusters that partially overlap with domains enriched in RNA binding proteins. Finally, we show that human and murine B cell surfaces contain DNA that can be cleared by the secreted nuclease DNASE1L3, and that patients with a DNASE1L3 missense variant associated with increased risk for autoimmune disease harbor increased levels of surface DNA on B and T cells. Taken together, this work expands the scope of cell surface nucleic acid biology and provides a mechanistic link between cell surface molecules and DNA targeting in autoimmune disease.

cell biology↗

bioRxiv2025

Bottom-up investigation of spatiotemporal glycocalyx dynamics with interferometric scattering microscopy

Over recent decades, the glycocalyx, an extracellular organelle comprised of a multitude of glycolipids, glycoproteins, proteoglycans and glycoRNA, has gained considerable interest in cellular biology. While research in this field has revealed its tremendous importance in evermore aspects of physiological and pathological cellular processes, many of the principles that govern the role of the glycocalyx in these processes on a molecular level are still unknown. In order to unravel the fundamental laws underlying glycocalyx function, new technologies are required that enable the distinction between individual subprocesses within the intricate environment of the glycocalyx. Here, we establish an experimental platform to investigate the dynamics of the glycocalyx at the nanometer and microsecond length and time scales in a bottom-up fashion. We synthesized defined model glycans and installed them on supported lipid bilayers, assembling glycocalyx model systems with tunable properties. By investigating these tunable model systems with interferometric scattering (iSCAT) microscopy, we gain access to the required spatiotemporal resolution. We found a strong correlation between the molecular structure of several investigated model glycans and global dynamics of the system. Our findings are corroborated by atomistic and coarsegrained molecular dynamics simulations. Our results provide the first direct experimental evidence on the relationship between glycan structure, organization, and dynamics, offering a robust and versatile basis for a quantitative understanding of glycocalyx biology and physics at the molecular level.

biophysics↗

bioRxiv2025

Glycan Atlassing: Nanoscale analysis of glycocalyx architecture enables functional tracing of cell state

The glycocalyx is a complex layer of glycosylated biomolecules surrounding all cells in the human body. It is involved in the regulation of critical cellular processes such as immune response modulation, cell adhesion, and host-pathogen interactions. Despite these insights, the functional relationship between glycocalyx architecture and cellular state has remained elusive so far, mainly attributable to the structural diversity of glycocalyx constituents and their nanoscale organization. Here, we show that DNA-tagged lectin labeling and metabolic oligosaccharide engineering enables multiplexed super-resolution microscopy of glycocalyx constituents, yielding an atlas of glycocalyx architecture with nanometer resolution. Quantitative analysis of the obtained nanoscale map of glycocalyx constituents facilitates the extraction of characteristic spatial relationships that accurately report on cellular state. We demonstrate the capacity of our approach, which we term Glycan Atlassing, across cell and tissue types, ranging from cultured cell lines to primary immune cells, neurons, and primary patient tissue. Glycan Atlassing establishes a powerful strategy for investigating glycocalyx remodeling in development and disease, potentially enabling the development of new glycocalyx-centered targets in diagnosis and therapy.

biophysics↗

bioRxiv2025

Angstrom-resolution imaging of cell-surface glycans

Glycobiology is rooted in the study of monosaccharides, [A]ngstrom-sized molecules that are the building blocks of intricate glycosylation patterns. Glycosylated biomolecules form the glycocalyx, a dense coat encasing every human cell with central relevance - among others - in immunology, oncology, and virology. In order to understand glycosylation function, visualizing its molecular structure is fundamental. However, the ability to visualize the molecular architecture of the glycocalyx has remained elusive. Techniques like mass spectrometry, electron microscopy, and fluorescence microscopy lack the necessary cellular context, specificity, and resolution. Here, we address these limitations by combining metabolic labeling with [A]ngstrom-resolution fluorescence microscopy, enabling the first-ever visualization of individual sugars within glycans on the cell surface. Our work provides unprecedented insights into the molecular architecture of the glycocalyx and constitutes the foundation for future explorations of its function in health and disease.

biophysics↗

bioRxiv2023

RNA binding proteins and glycoRNAs form domains on the cell surface for cell penetrating peptide entry

The composition and organization of the cell surface determine how cells interact with their environment. Traditionally, glycosylated transmembrane proteins were thought to be the major constituents of the external surface of the plasma membrane. Here, we provide evidence that a group of RNA binding proteins (RBPs) are present on the surface of living cells. These cell surface RBPs (csRBPs) precisely organize into well-defined nanoclusters that are enriched for multiple RBPs, glycoRNAs, and their clustering can be disrupted by extracellular RNase addition. These glycoRNA-csRBP clusters further serve as sites of cell surface interaction for the cell penetrating peptide TAT. Removal of RNA from the cell surface, or loss of RNA binding activity by TAT, causes defects in TAT cell internalization. Together, we provide evidence of an expanded view of the cell surface by positioning glycoRNA-csRBP clusters as a regulator of communication between cells and the extracellular environment.

cell biology↗