Inactivation of Ras by p120GAP via Focal Adhesion Kinase Dephosphorylation Mediates RGMa-Induced Growth Cone Collapse

Abstract

The repulsive guidance molecule RGMa performs several functions in the developing and adult CNSs. RGMa, through its receptor neogenin, induces growth cone collapse and neurite outgrowth inhibition. Here, we demonstrate that RGMa binding to neogenin leads to the inactivation of Ras, which is required for the RGMa-mediated repulsive function in cortical neurons. This signal transduction is mediated by the Ras-specific GTPase-activating protein (GAP) p120GAP. The SH2 domain of p120GAP interacts with focal adhesion kinase (FAK), which is phosphorylated at Tyr-397. When the cells are stimulated with RGMa, FAK undergoes dephosphorylation at Tyr-397 and is dissociated from p120GAP, and this dissociation is followed by an increase in the interaction between p120GAP and GTP-Ras. In addition, the knockdown of p120GAP prevents RGMa-induced growth cone collapse and neurite outgrowth inhibition. Furthermore, RGMa stimulation induces Akt inactivation through p120GAP, and the expression of the constitutively active Akt prevents RGMa-induced growth cone collapse. Thus, RGMa binding to neogenin regulates p120GAP activity through FAK Tyr-397 dephosphorylation, leading to the inactivation of Ras and its downstream effector Akt, and this signal transduction plays a role in the RGMa-mediated repulsive function.

In-depth Characterization of the Secretome of Colorectal Cancer Metastatic Cells Identifies Key Proteins in Cell Adhesion, Migration, and Invasion

“…NEO1 is a receptor of Netrin, which also binds ITGB1 (80), inducing a collaborative signaling that enhances cell adhesion (51). NEO1 also inhibits focal adhesion kinase (FAK) activation, which is an activator of Ras (81). SOSTDC1, also known as USAG1, is an inhibitor of several BMPs (82).…”

Differential Regulation of RasGAPs in Cancer

“…[92][93][94] Furthermore, the SH3 domain in p120GAP, which is unusual because of its inability to interact with proline-rich motifs, binds the calpain subunit Capns1 and has been implicated in Rho-mediated cytoskeletal rearrangements. 95,96 Altogether, this could indicate that SH2 and SH3 domains recruiting p120GAP to specific plasma membrane microdomains involved in actin remodeling, where coordination of Ras and Rho regulated signaling pathways, for example, for the formation of stress fibers, focal adhesions, establishment of cell polarity, and cell migration, are essential.…”

“…95,96 Altogether, this could indicate that SH2 and SH3 domains recruiting p120GAP to specific plasma membrane microdomains involved in actin remodeling, where coordination of Ras and Rho regulated signaling pathways, for example, for the formation of stress fibers, focal adhesions, establishment of cell polarity, and cell migration, are essential. [92][93][94][95][96] Little is known about the PH domain in p120GAP, which generally facilitates binding to phosphoinositides in membranes or in some cases proteins. 97 Some evidence suggests that the PH domain can interfere with Ras/GAP assembly.…”

p120RasGAP Protein Mediates Netrin-1 Protein-induced Cortical Axon Outgrowth and Guidance

“…ERK is activated downstream of netrin-1 and DCC and is required for netrin-1-dependent axon outgrowth and guidance (30 -32), but it remains unclear whether Ras mediates ERK activation downstream of netrin-1 and DCC. Until now, the Ras GTPaseactivating protein (GAP) p120RasGAP was considered only to be an inhibitor of axon outgrowth and guidance because of the activity of its C-terminal RasGAP domain (33)(34)(35). In addition to its C-terminal GAP domain, the N terminus of p120RasGAP, comprising one Src homology (SH) 3 and two SH2 domains, interacts with a wide variety of proteins to regulate cell survival, proliferation, and migration (36,37).…”