Application of Force to a Syndecan-4 Containing Complex With Thy-1–αVβ3 Integrin Accelerates Neurite Retraction

Abstract

Inflammation contributes to the genesis and progression of chronic diseases, such as cancer and neurodegeneration. Upregulation of integrins in astrocytes during inflammation induces neurite retraction by binding to the neuronal protein Thy-1, also known as CD90. Additionally, Thy-1 alters astrocyte contractility and movement by binding to the mechano-sensors α V β 3 integrin and Syndecan-4. However, the contribution of Syndecan-4 to neurite shortening following Thy-1–α V β 3 integrin interaction remains unknown. To further characterize the contribution of Syndecan-4 in Thy-1-dependent neurite outgrowth inhibition and neurite retraction, cell-based assays under pro-inflammatory conditions were performed. In addition, using Optical Tweezers, we studied single-molecule binding properties between these proteins, and their mechanical responses. Syndecan-4 increased the lifetime of Thy-1–α V β 3 integrin binding by interacting directly with Thy-1 and forming a ternary complex (Thy-1–α V β 3 integrin + Syndecan-4). Under in vitro -generated pro-inflammatory conditions, Syndecan-4 accelerated the effect of integrin–engaged Thy-1 by forming this ternary complex, leading to faster neurite retraction and the inhibition of neurite outgrowth. Thus, Syndecan-4 controls neurite cytoskeleton contractility by modulating α V β 3 integrin mechano-receptor function. These results suggest that mechano-transduction, cell-matrix and cell-cell interactions are likely critical events in inflammation-related disease development.

An Outside-In Switch in Integrin Signaling Caused by Chemical and Mechanical Signals in Reactive Astrocytes

“…Thus, it is possible that force applied to a tri-molecular complex—rather than to a bimolecular interaction—accounts for a faster response when a mechanical force is applied. However, our recently published data indicate that the slip-bond Thy-1-α V β 3 Integrin interaction remains as a slip-bond when Syndecan-4 is introduced into the Optical miniTweezers system ( Burgos-Bravo et al, 2020 ). In addition, under in vitro -generated pro-inflammatory conditions, Syndecan-4 accelerates the effect of integrin-engaged Thy-1 by forming a ternary complex, leading to a faster neuronal response, a phenomenon also related to cell contraction ( Burgos-Bravo et al, 2020 ).…”

“…However, our recently published data indicate that the slip-bond Thy-1-α V β 3 Integrin interaction remains as a slip-bond when Syndecan-4 is introduced into the Optical miniTweezers system ( Burgos-Bravo et al, 2020 ). In addition, under in vitro -generated pro-inflammatory conditions, Syndecan-4 accelerates the effect of integrin-engaged Thy-1 by forming a ternary complex, leading to a faster neuronal response, a phenomenon also related to cell contraction ( Burgos-Bravo et al, 2020 ). Similar contractile outcomes could also occur in astrocytes upon the formation of the trimolecular complex; however, this aspect requires further investigation.…”

“…Our laboratory has previously reported that endogenous Thy-1 (CD90) expressed by neurons directly binds to the α V β 3 integrin receptor in astrocytes, triggering downstream signaling events in these cells. The signaling pathways induce the formation of focal adhesions, increasing cell adhesion to the ECM ( Leyton et al, 2001 ; Avalos et al, 2004 ; Hermosilla et al, 2008 ; Burgos-Bravo et al, 2020 ). These focal points are linked to stress fibers, which generate cell contractile forces through bundles of microfilaments associated with cytoskeletal proteins, such as myosin II ( Stachowiak et al, 2012 ).…”

Thy-1 (CD90), Integrins and Syndecan 4 are Key Regulators of Skin Wound Healing

“…FA turnover is an important event during directional cell migration. Moreover, Thy-1 has been shown to directly interact with integrins and syndecan 4 to form a trimolecular complex that facilitates initial cell adhesion by enhancing FA formation and subsequently, promoting migration by regulating contractility and FA turnover (Avalos et al, 2004;Hermosilla et al, 2008;Avalos et al, 2009;Kong et al, 2013;Fiore et al, 2014;Fiore et al, 2015;Lagos-Cabre et al, 2017;Burgos-Bravo et al, 2020;Valdivia et al, 2020). Although the bidirectional signaling pathways triggered by Thy-1/integrin/ syndecan 4 clustering and activation remain unexplored during skin injury, the biological significance of each of these molecules by themselves has been proven important for an efficient wound healing process.…”

Integrin Signaling in the Central Nervous System in Animals and Human Brain Diseases

“…Furthermore, αvβ3 integrin in astrocytes limits the neurites growth and also induces retraction of already existing processes by Thy-1 clustering induction [56]; it also triggers neurite retraction via the RhoA/ROCK pathway [57]. Moreover, upregulation of integrins in the astrocytes by inflammation induces neurite retraction by binding Thy-1, and formation of a ternary complex, i.e., Thy-1-αvβ3 integrin and Syndecan-4, alters astrocyte contractility and inhibits neurite outgrowth [58]. Astrocytic migration requires a large increase in the intracellular Ca 2+ concentration and connexin 43 hemichannel opening, which are induced by Thy-1 via αvβ3 integrin in astrocytes [59,60].…”