Immunomodulatory role of the extracellular matrix protein tenascin-C in neuroinflammation.

The extracellular matrix (ECM) consists of a dynamic network of various macromolecules that are synthesized and released by surrounding cells into the intercellular space. Glycoproteins, proteoglycans and fibrillar proteins are main components of the ECM. In addition to general functions such as structure and stability, the ECM controls several cellular signaling pathways. In this context, ECM molecules have a profound influence on intracellular signaling as receptor-, adhesion- and adaptor-proteins. Due to its various functions, the ECM is essential in the healthy organism, but also under pathological conditions. ECM constituents are part of the glial scar, which is formed in several neurodegenerative diseases that are accompanied by the activation and infiltration of glia as well as immune cells. Remodeling of the ECM modulates the release of pro- and anti-inflammatory cytokines affecting the fate of immune, glial and neuronal cells. Tenascin-C is an ECM glycoprotein that is expressed during embryonic central nervous system (CNS) development. In adults it is present at lower levels but reappears under pathological conditions such as in brain tumors, following injury and in neurodegenerative disorders and is highly associated with glial reactivity as well as scar formation. As a key modulator of the immune response during neurodegeneration in the CNS, tenascin-C is highlighted in this mini-review.