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Nephrin promotes cell-cell adhesion through homophilic interactions.

ABSTRACT: Nephrin is a type-1 transmembrane protein and a key component of the podocyte slit diaphragm, the ultimate glomerular plasma filter. Genetic and acquired diseases affecting expression or function of nephrin lead to severe proteinuria and distortion or absence of the slit diaphragm. Here, we showed by using a surface plasmon resonance biosensor that soluble recombinant variants of nephrin, containing the extracellular part of the protein, interact with each other in a specific and concentration-dependent manner. This molecular interaction was increased by twofold in the presence of physiological Ca(2+)concentration, indicating that the binding is not dependent on, but rather promoted by Ca(2+). Furthermore, transfected HEK293 cells and an immortalized mouse podocyte cell line overexpressing full-length human nephrin formed cellular aggregates, with cell-cell contacts staining strongly for nephrin. The distance between plasma membranes at the nephrin-containing contact sites was shown by electron microscopy to be 40 to 50 nm, similar to the width of glomerular slit diaphragm. The cell contacts could be dissociated with antibodies reacting with the first two extracellular Ig-like domains of nephrin. Wild-type HEK293 cells were shown to express slit diaphragm components CD2AP, P-cadherin, FAT, and NEPH1. The results show that nephrin molecules exhibit homophilic interactions that could promote cellular contacts through direct nephrin-nephrin interactions, and that the other slit diaphragm components expressed could contribute to that interaction.

SUBMITTER: Khoshnoodi J

PROVIDER: S-EPMC1892394 | biostudies-literature | 2003 Dec

REPOSITORIES: biostudies-literature

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Nephrin promotes cell-cell adhesion through homophilic interactions.

Khoshnoodi Jamshid J Sigmundsson Kristmundur K Ofverstedt Lars-Göran LG Skoglund Ulf U Obrink Björn B Wartiovaara Jorma J Tryggvason Karl K

The American journal of pathology 20031201 6

Nephrin is a type-1 transmembrane protein and a key component of the podocyte slit diaphragm, the ultimate glomerular plasma filter. Genetic and acquired diseases affecting expression or function of nephrin lead to severe proteinuria and distortion or absence of the slit diaphragm. Here, we showed by using a surface plasmon resonance biosensor that soluble recombinant variants of nephrin, containing the extracellular part of the protein, interact with each other in a specific and concentration-d ...[more]

PMID: 14633607

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Project description:UNLABELLED:Staphylococcus aureus is an important opportunistic pathogen which is a leading cause of biofilm-associated infections on indwelling medical devices. The cell surface-located fibronectin-binding protein A (FnBPA) plays an important role in the accumulation phase of biofilm formation by methicillin-resistant S. aureus (MRSA), but the underlying molecular interactions are not yet established. Here, we use single-cell and single-molecule atomic force microscopy to unravel the mechanism by which FnBPA mediates intercellular adhesion. We show that FnBPA is responsible for specific cell-cell interactions that involve the FnBPA A domain and cause microscale cell aggregation. We demonstrate that the strength of FnBPA-mediated adhesion originates from multiple low-affinity homophilic interactions between FnBPA A domains on neighboring cells. Low-affinity binding by means of FnBPA may be important for biofilm dynamics. These results provide a molecular basis for the ability of FnBPA to promote cell accumulation during S. aureus biofilm formation. We speculate that homophilic interactions may represent a generic strategy among staphylococcal cell surface proteins for guiding intercellular adhesion. As biofilm formation by MRSA strains depends on proteins rather than polysaccharides, our approach offers exciting prospects for the design of drugs or vaccines to inhibit protein-dependent intercellular interactions in MRSA biofilms. IMPORTANCE:Staphylococcus aureus is a human pathogen that forms biofilms on indwelling medical devices, such as central venous catheters and prosthetic joints. This leads to biofilm infections that are difficult to treat with antibiotics because many cells within the biofilm matrix are dormant. The fibronectin-binding proteins (FnBPs) FnBPA and FnBPB promote biofilm formation by clinically relevant methicillin-resistant S. aureus (MRSA) strains, but the molecular mechanisms involved remain poorly understood. We used atomic force microscopy techniques to demonstrate that FnBPA mediates cell-cell adhesion via multiple, low-affinity homophilic bonds between FnBPA A domains on adjacent cells. Therefore, FnBP-mediated homophilic interactions represent an interesting target to prevent MRSA biofilms. We propose that such homophilic mechanisms may be widespread among staphylococcal cell surface proteins, providing a means to guide intercellular adhesion and biofilm accumulation.

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Nephrin promotes cell-cell adhesion through homophilic interactions.

Publications

Nephrin promotes cell-cell adhesion through homophilic interactions.

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