Thy-1-mediated cell–cell contact induces astrocyte migration through the engagement of αVβ3 integrin and syndecan-4

Abstract

Cell adhesion to the extracellular matrix (ECM) proteins occurs through interactions with integrins that bind to Arg-Gly-Asp (RGD) tripeptides, and syndecan-4, which recognizes the heparin-binding domain (HBD) of other proteins. Both receptors trigger signaling pathways, including those that activate RhoGTPases such as RhoA and Rac1. This sequence of events modulates cell adhesion to the ECM and cell migration. Using a neuron-astrocyte model, we have reported that the neuronal protein Thy-1 engages αVβ3 integrin and syndecan-4 to induce RhoA activation and strong astrocyte adhesion to their underlying substrate. Thus, because cell-cell interactions and strong cell attachment to the matrix are considered antagonistic to cell migration, we hypothesized that Thy-1 stimulation of astrocytes should preclude cell migration. Here, we studied the effect of Thy-1 expressing neurons on astrocyte polarization and migration using a wound-healing assay and immunofluorescence analysis. Signaling molecules involved were studied by affinity precipitations, western blots and the usage of specific antibodies. Intriguingly, Thy-1 interaction with its two receptors was found to increase astrocyte polarization and migration. The latter events required interactions of these receptors with both the RGD-like sequence and the HBD of Thy-1. Additionally, prolonged Thy-1-receptor interactions inhibited RhoA activation while activating FAK, PI3K and Rac1. Therefore, sustained engagement of integrin and syndecan-4 with the neuronal surface protein Thy-1 induces astrocyte migration. Interestingly we identify here, a cell-cell interaction that although initially induces strong cell attachment, upon persistant stimulation favors cell migration by engaging the same signaling receptors and molecules as those utilized by ECM proteins to stimulate cell movement.

Integrin-mediated transactivation of P2X7R via hemichannel-dependent ATP release stimulates astrocyte migration

“…Additionally, our previous results implicate PLC in Thy-1-induced RhoA activation and astrocyte adhesion [20]. We have also reported that PI3K activation occurs downstream of V 3 integrin/FAK autophosphorylation [19]. By…”

“…2B). Importantly, neither of these mutated Thy-1 proteins individually stimulates cell adhesion or migration [11,19]; however, the addition of low amounts of BzATP (<10 M) with the Thy-1 mutant that binds Syndecan-4, suffices to…”

“…Integrin signaling also involves PKC , and possibly inositol trisphosphate (IP3) receptor (IP3R) activation because IP3R inhibitors reduce RhoA activity and astrocyte adhesion induced by Thy-1 [11]. Moreover, prolonged Thy-1 stimulation induces the polarization and migration of DITNC1 astrocytes via the activation of FAK, phosphatidylinositol-3-kinase (PI3K), and the small GTPase Rac1 [19].…”

“…Reorientation of the Golgi apparatus towards the leading edge was evaluated as previously described [19,45].…”

An electrically resistive sheet of glial cells for amplifying signals of neuronal extracellular recordings

“…Previous studies in the area of molecular biology revealed that neuron-glia adhesion is mediated by the binding of neuronal Thy-1 and glial integrin a v b 3 and that this binding occurs in less than 20 min after cell-cell contact. 20 The Thy-1/integrin interaction can be blocked by the RGD peptide, 21 and hence adding the peptide to the bath solution can decrease the extent of neuronal abduction by the glia sheet. Alternatively, pre-treating the glial cell membrane with an anti-fouling agent such as polyethylene glycol or polyvinyl alcohol could also have positive effects in reducing the extent of neuron-glia adhesion.…”