The fibronectin synergy site re-enforces cell adhesion and mediates a crosstalk between integrin classes
- Universitat de València, Spain
- Ludwig-Maximilians-Universität München, Germany
- Klinikum der Universtaet Muenchen, Germany
- Eidgenössische Technische Hochschule Zürich, Switzerland
- ETH Zürich, Switzerland
Abstract
Fibronectin (FN), a major extracellular matrix component, enables integrin-mediated cell adhesion via binding of α5β1, αIIbβ3 and αv-class integrins to an RGD-motif. An additional linkage for α5 and αIIb is the synergy site located in close proximity to the RGD motif. We report that mice with a dysfunctional FN-synergy motif (FNsyn/syn) suffer from surprisingly mild platelet adhesion and bleeding defects due to delayed thrombus formation after vessel injury. Additional loss of β3 integrins dramatically aggravates the bleedings and severely compromises smooth muscle cell coverage of the vasculature leading to embryonic lethality. Cell-based studies revealed that the synergy site is dispensable for the initial contact of α5β1 with the RGD, but essential to re-enforce the binding of α5β1/αIIbβ3 to FN. Our findings demonstrate a critical role for the FN synergy site when external forces exceed a certain threshold or when αvβ3 integrin levels decrease below a critical level.
Article and author information
Author details
Maria Benito-Jardón
Funding
Ministerio de Economía y Competitividad (National grant)
- Maria Benito-Jardón
- Irene Gimeno-LLuch
- Mercedes Costell
Conselleria Valenciana d'Educació i Ciència (Graduate student fellowship)
- Maria Benito-Jardón
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Reinhard Fässler, Max Planck Institute of Biochemistry, Germany
Ethics
Animal experimentation: Mice were housed in special pathogen free animal facilities. All mouse work was performed in accordance with the Government of the Valencian Community (Spain) guidelines (permission reference A1327395471346). Mice containing the integrin β3 deletion were bred under the permission reference 55.2-1-54-2532-96-2015 (Government of Upper Bavaria). The tail-bleeding and cremaster muscle venules injury assays performed under the permission reference 55.2-1-54-2532-115-12 (Government of Upper Bavaria).
Version history
- Received: October 11, 2016
- Accepted: January 15, 2017
- Accepted Manuscript published: January 16, 2017 (version 1)
- Version of Record published: January 30, 2017 (version 2)
- Version of Record updated: March 20, 2018 (version 3)
Copyright
© 2017, Benito-Jardón et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 3,600
- views
-
- 652
- downloads
-
- 64
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
The fibronectin synergy site re-enforces cell adhesion and mediates a crosstalk between integrin classes
eLife 6:e22264.
https://doi.org/10.7554/eLife.22264
Further reading
-
- Cell Biology
- Neuroscience
The cytosolic proteins synucleins and synapsins are thought to play cooperative roles in regulating synaptic vesicle (SV) recycling, but mechanistic insight is lacking. Here, we identify the synapsin E-domain as an essential functional binding-partner of α-synuclein (α-syn). Synapsin E-domain allows α-syn functionality, binds to α-syn, and is necessary and sufficient for enabling effects of α-syn at synapses of cultured mouse hippocampal neurons. Together with previous studies implicating the E-domain in clustering SVs, our experiments advocate a cooperative role for these two proteins in maintaining physiologic SV clusters.
-
- Cell Biology
Here, we investigated the mechanisms by which aging-related reductions of the levels of Numb in skeletal muscle fibers contribute to loss of muscle strength and power, two critical features of sarcopenia. Numb is an adaptor protein best known for its critical roles in development, including asymmetric cell division, cell-type specification, and termination of intracellular signaling. Numb expression is reduced in old humans and mice. We previously showed that, in mouse skeletal muscle fibers, Numb is localized to sarcomeres where it is concentrated near triads; conditional inactivation of Numb and a closely related protein Numb-like (Numbl) in mouse myofibers caused weakness, disorganization of sarcomeres, and smaller mitochondria with impaired function. Here, we found that a single knockout of Numb in myofibers causes reduction in tetanic force comparable to a double Numb, Numbl knockout. We found by proteomics analysis of protein complexes isolated from C2C12 myotubes by immunoprecipitation using antibodies against Numb that Septin 7 is a potential Numb-binding partner. Septin 7 is a member of the family of GTP-binding proteins that organize into filaments, sheets, and rings, and is considered part of the cytoskeleton. Immunofluorescence evaluation revealed a partial overlap of staining for Numb and Septin 7 in myofibers. Conditional, inducible knockouts of Numb led to disorganization of Septin 7 staining in myofibers. These findings indicate that Septin 7 is a Numb-binding partner and suggest that interactions between Numb and Septin 7 are critical for structural organization of the sarcomere and muscle contractile function.
