The RhoGEF TEM4 Regulates Endothelial Cell Migration by Suppressing Actomyosin Contractility

Abstract

Persistent cellular migration requires efficient protrusion of the front of the cell, the leading edge where the actin cytoskeleton and cell-substrate adhesions undergo constant rearrangement. Rho family GTPases are essential regulators of the actin cytoskeleton and cell adhesion dynamics. Here, we examined the role of the RhoGEF TEM4, an activator of Rho family GTPases, in regulating cellular migration of endothelial cells. We found that TEM4 promotes the persistence of cellular migration by regulating the architecture of actin stress fibers and cell-substrate adhesions in protruding membranes. Furthermore, we determined that TEM4 regulates cellular migration by signaling to RhoC as suppression of RhoC expression recapitulated the loss-of-TEM4 phenotypes, and RhoC activation was impaired in TEM4-depleted cells. Finally, we showed that TEM4 and RhoC antagonize myosin II-dependent cellular contractility and the suppression of myosin II activity rescued the persistence of cellular migration of TEM4-depleted cells. Our data implicate TEM4 as an essential regulator of the actin cytoskeleton that ensures proper membrane protrusion at the leading edge of migrating cells and efficient cellular migration via suppression of actomyosin contractility.

Biomarkers Discovery for Colorectal Cancer: A Review on Tumor Endothelial Markers as Perspective Candidates

“…TEM4 upregulation was identified in the endothelial cells during tumor angiogenesis of colorectal cancer patients [39]. Consistent with the TEM4 central role in controlling activation of RhoC in endothelial cells, the organization of actin cytoskeleton, cell-substrate adhesion, and cellular migration, it is suggested that TEM4 is critical for blood vessel formation during angiogenesis [105]. …”

“…TEM4 is localized in the subcellular compartment. The biological role of TEM4 is associated with regulating activation of Rho GTPases, various members of the cadherin-catenin complex, and several cytoskeleton proteins [105, 106]. TEM4 upregulation was identified in the endothelial cells during tumor angiogenesis of colorectal cancer patients [39].…”

Rho GAPs and GEFs

“…In endothelial cells, TEM4 appears critical for organization of the actin cytoskeleton and integrin-based adhesions at membrane protrusions of migrating cells 180 . This work was followed up by Ngok and co-workers, who showed that TEM4 associates with the cadherin complex at endothelial cell–cell junctions in confluent monolayers, independent of F-actin binding, whereas TEM4 remains associated with the F-actin cytoskeleton in cells cultured at low density 181 .…”

RhoC maintains vascular homeostasis by regulating VEGF-induced signaling in endothelial cells

“…For example, Wang and colleagues have observed that RhoC knockdown decreases migration and invasion of human mammary endothelial cells (Wang et al, 2008), whereas our results suggest that RhoC knockdown increases HUVEC migration. Previous HUVEC studies have demonstrated that RhoC deletion promotes vascular sprouting twofold (Del Galdo et al, 2013), and that RhoC knockdown results in a loss-of-directionality migration phenotype and inefficient migration from the point of origin in single-cell tracking experiments (Mitin et al, 2013). The discrepancy in HUVEC migration might stem from the different assays utilized and inherent differences in the migratory properties of a single cell versus numerous cells.…”