Secretomics reveals gelatinase substrates at the blood-brain barrier that are implicated in astroglial barrier function
Miriam Burmeister, Annika Frauenstein, Martin Kahms, Laura Arends, Hanna Gerwien, Tushar Deshpande, Tanja Kuhlmann, Catharina C. Groß, Venu Narayanan Naik, Heinz Wiendl, Juergen Klingauf, Felix Meissner, Lydia Sorokin
Abstract
The gelatinases, matrix metalloproteinase 2 (MMP-2) and MMP-9, are key for leukocyte penetration of the brain parenchymal border in neuroinflammation and the functional integrity of this barrier; however, it is unclear which MMP substrates are involved. Using a tailored, sensitive, label-free mass spectrometry-based secretome approach, not previously applied to nonimmune cells, we identified 119 MMP-9 and 21 MMP-2 potential substrates at the cell surface of primary astrocytes, including known substrates (β-dystroglycan) and a broad spectrum of previously unknown MMP-dependent events involved in cell-cell and cell-matrix interactions. Using neuroinflammation as a model of assessing compromised astroglial barrier function, a selection of the potential MMP substrates were confirmed in vivo and verified in human samples, including vascular cell adhesion molecule-1 and neuronal cell adhesion molecule. We provide a unique resource of potential MMP-2/MMP-9 substrates specific for the astroglia barrier. Our data support a role for the gelatinases in the formation and maintenance of this barrier but also in astrocyte-neuron interactions.