Integrins regulate centrosome integrity and astrocyte polarization following a wound

Abstract

In response to a wound, astrocytes in culture extend microtubule-rich processes and polarize, orienting their centrosomes and Golgi apparatus woundside. β1 Integrin null astrocytes fail to extend processes toward the wound, and are disoriented, and often migrate away orthogonal, to the wound. The centrosome is unusually fragmented in β1 integrin null astrocytes. Expression of a β1 integrin cDNA in the null background yields cells with intact centrosomes that polarize and extend processes normally. Fragmented centrosomes rapidly assemble following integrin ligation and cell attachment. However, several experiments indicated that cell adhesion is not necessary. For example, astrocytes in suspension expressing a chimeric β1 subunit that can be activated by an antibody assemble centrosomes suggesting that β1 activation is sufficient to cause centrosome assembly in the absence of cell adhesion. siRNA knockdown of PCM1, a major centrosomal protein, inhibits cell polarization, consistent with the notion that centrosomes are necessary for polarity and that integrins regulate polarity via centrosome integrity. Screening inhibitors of molecules downstream of integrins indicate that neither FAK nor ILK is involved in regulation of centrosome integrity. In contrast, blebbistatin, a specific inhibitor of non-muscle myosin II (NMII), mimics the response of β1 integrin null astrocytes by disrupting centrosome integrity and cell polarization. Blebbistatin also inhibits integrin-mediated centrosome assembly in astrocytes attaching to fibronectin, consistent with the hypothesis that NMII functions downstream of integrins in regulating centrosome integrity.

Depletion of kinesin-12, a myosin-IIB-interacting protein, promotes migration of cortical astrocytes

“…This makes sense because in neurons, myosin-IIB predominates in growth cones (Rochlin et al, 1995). In astrocytes, it has already been reported that inhibition of myosin-II increases migration (Peng et al, 2013) (which we found also in our experiments, data not shown), which supports the idea of an interaction between myosin-IIB and kinesin-12, the depletion of either of which increases migration. Moreover, we found in our present studies that it is within amino acids 743-1333 of kinesin-12 and amino acids 1345-1976 of myosin-IIB that the interaction occurs.…”

Control of Astrocyte Quiescence and Activation in a Synthetic Brain Hydrogel

“…To create a brain ECM‐mimicking hydrogel, we narrowed the ECM Matrisome quantification results to proteins with known interactions with integrin heterodimers . From the pool of proteins present in Figure d,f, integrin‐binding sequences were matched via literature mining to their integrin heterodimer pairs (Tables S2, S4, and S5, Supporting Information).…”

Macrophage-derived osteopontin induces reactive astrocyte polarization and promotes re-establishment of the blood brain barrier after ischemic stroke

“…Astrocytes upregulate integrin receptors which have been linked to the extension of glial processes in development (Hirsch et al, 1994) and to astrocyte polarization (Peng et al, 2013). Astrocytes upregulate integrin receptors which have been linked to the extension of glial processes in development (Hirsch et al, 1994) and to astrocyte polarization (Peng et al, 2013).…”

“…Osteopontin (OPN) is a multifunctional matricellular glycoprotein implicated in a variety of proinflammatory (Chabas et al, 2001) as well as neuroprotective (Meller et al, 2005;Schroeter et al, 2006) and repair-promoting (Suzuki et al, 2010;van Velthoven et al, 2011) effects in CNS injury. Interestingly, OPN is a ligand for integrins (Ellison et al, 1998;Ruoslahti and Pierschbacher, 1987), which are implicated in astrocyte polarization (Peng et al, 2013). Interestingly, OPN is a ligand for integrins (Ellison et al, 1998;Ruoslahti and Pierschbacher, 1987), which are implicated in astrocyte polarization (Peng et al, 2013).…”

“…The astrocyte reaction to tissue injury is characterized by an elongation of processes and polarization of astrocytes towards the injured tissue. Astrocytes upregulate integrin receptors which have been linked to the extension of glial processes in development (Hirsch et al, 1994) and to astrocyte polarization (Peng et al, 2013). Osteopontin (OPN) is a multifunctional matricellular glycoprotein implicated in a variety of proinflammatory (Chabas et al, 2001) as well as neuroprotective (Meller et al, 2005;Schroeter et al, 2006) and repair-promoting (Suzuki et al, 2010;van Velthoven et al, 2011) effects in CNS injury.…”