Fig 7. Model of optic nerve head astrocyte signaling downstream of integrin activation in response intraocular pressure fluctuation.

Physiologic and experimental intraocular pressure (IOP) fluctuation within the optic nerve head (ONH) results in tissue strain and extracellular matrix (ECM) stretch. Interaction between the ECM and integrin receptors on astrocyte cell membranes, leads to integrin activity, which phosphorylate focal adhesion kinase (p-FAK). Active p-FAK can target paxillin for phosphorylation, which is important for focal contact/adhesion formation. FAK phosphorylation also allows for cortactin phosphorylation through active FAK and Src kinase. Phosphorylated cortactin enhances actin polymerization. Increased focal contact formation and actin polymerization are required for dynamic astrocyte extension formation and maintenance within the ONH.