Tensin1 positively regulates RhoA activity through its interaction with DLC1

Abstract

DLC1 is a RhoGAP-containing tumor suppressor and many of DLC1’s functions are absolutely dependent on its RhoGAP activity. Through its RhoGAP domain, DLC1 inhibits the activity of RhoA GTPase, which regulates actin cytoskeleton networks and dis/assembly of focal adhesions. Tensin1 (TNS1) is a focal adhesion molecule that links the actin cytoskeleton to integrins and forms signaling complexes through its multiple binding domains. Here, we report that TNS1 enhances RhoA activity in a DLC1-dependent manner. This is accomplished by binding to DLC1 through TNS1’s C2, SH2, and PTB domains. Point mutations at these three sites disrupt TNS1’s interaction with DLC1 as well as its effect on RhoA activity. The biological relevance of this TNS1-DLC1-RhoA signaling axis is investigated in TNS1 knockout (KO) cells and mice. Endothelial cells isolated from TNS1 KO mice or those silenced with TNS1 siRNA show significant reduction in proliferation, migration, and tube formation activities. Concomitantly, the RhoA activity is down-regulated in TNS1 KO cells and this reduction is restored by further silencing of DLC1. Furthermore, the angiogenic process is compromised in TNS1 KO mice. These studies demonstrate that TNS1 binds to DLC1 and fine-tunes its RhoGAP activity toward RhoA and that the TNS1-DLC1-RhoA signaling axis is critical in regulating cellular functions that lead to angiogenesis.

Regulating Rho GTPases and their regulators

“…Similarly, DLC1 localizes to focal adhesions through its interaction with tensin proteins, which link the actin cytoskeleton to integrins [108][109][110] . Tensins sequester DLC1 away from RhoA, thereby increasing RhoA activity.…”

Tensin 3 is a new partner of Dock5 that controls osteoclast podosome organization and activity

“…Nevertheless, only full-length tensin 3 could stimulate Dock5 activity, suggesting that, as in the case of Dlc1 (Shih et al, 2015), the functional interaction between tensin 3 and Dock5 is complicated. The activation of Dock5 by tensin 3 might involve conformational cues provided by full-length tensin 3 as well as other partners of the protein, which would need more extensive investigation.…”

“…At the molecular level, the function of tensins is also a matter of debate. The SH2-PTB domain of tensins can bind and inhibit Dlc-family RhoGAPs (Shih et al, 2015) whereas, the ABD of tensin 3 has been shown to stimulate the RhoGAP activity by relieving Dlc1 intramolecular inhibition mediated by its N-terminal SAM domain (Cao et al, 2012). Upon EGF or PDGF stimulation, tensin 3 can also associate with phosphoinositide 3-kinase (PI3K) and promote Rac activation at the leading edge of the cell (Cao et al, 2015).…”

“…S3C-E). Tensins were shown to exert a complex effect on RhoA GTPaseactivating protein (GAP) Dlc1: on one hand, binding of tensin ABD to Dlc1 has been shown to relieve the intramolecular inhibition of the GAP (Cao et al, 2012); however, on the other hand, tensins have been reported to inhibit Dlc1, in a manner that involves the C2, the SH2 and the PTB domains of tensin (Shih et al, 2015). Thus, we investigated a potential effect of tensin 3 on the exchange activity of Dock5.…”

Down-regulation of DLC1 in endothelial cells compromises the angiogenesis process

“…DLC1 negatively regulates RhoA GTPase activity through its RhoGAP domain, which is essential for DLC1's tumor suppression function [12, 14]. Its RhoGAP activity is tightly regulated through phosphorylation by CDK5 [20] or ERK [15] as well as binding partners such as tensins [3, 18], which also recruit DLC1 to focal adhesions. On the other hand, not all suppression roles rely on controlling RhoA function.…”