EPHB4-RASA1-Mediated Negative Regulation of Ras-MAPK Signaling in the Vasculature: Implications for the Treatment of EPHB4- and RASA1-Related Vascular Anomalies in Humans

Abstract

Ephrin receptors constitute a large family of receptor tyrosine kinases in mammals that through interaction with cell surface-anchored ephrin ligands regulate multiple different cellular responses in numerous cell types and tissues. In the cardiovascular system, studies performed in vitro and in vivo have pointed to a critical role for Ephrin receptor B4 (EPHB4) as a regulator of blood and lymphatic vascular development and function. However, in this role, EPHB4 appears to act not as a classical growth factor receptor but instead functions to dampen the activation of the Ras-mitogen activated protein signaling (MAPK) pathway induced by other growth factor receptors in endothelial cells (EC). To inhibit the Ras-MAPK pathway, EPHB4 interacts functionally with Ras p21 protein activator 1 (RASA1) also known as p120 Ras GTPase-activating protein. Here, we review the evidence for an inhibitory role for an EPHB4–RASA1 interface in EC. We further discuss the mechanisms by which loss of EPHB4–RASA1 signaling in EC leads to blood and lymphatic vascular abnormalities in mice and the implications of these findings for an understanding of the pathogenesis of vascular anomalies in humans caused by mutations in EPHB4 and RASA1 genes. Last, we provide insights into possible means of drug therapy for EPHB4- and RASA1-related vascular anomalies.

A temporally‐restricted pattern of endothelial cell collagen 4 alpha 1 expression during embryonic development determined with a novel knockin Col4a1‐P2A‐eGFP mouse line

“…The finding that EC synthesis of collagen IV alpha 1 is mostly confined to embryonic development is consistent with and provides at least part of an explanation for the temporally-restricted blood vascular phenotypes of mice induced to express mutant collagen IV alpha 1 or to lose expression of RASA1 or EPHB4 (Alavi et al, 2016;Chen et al, 2019Chen et al, , 2022Chen et al, , 2023Jeanne et al, 2015;Jeanne & Gould, 2017;Kuo et al, 2012;Lapinski et al, 2012Lapinski et al, , 2017van Agtmael et al, 2010). In addition, findings provide a basis for the occurrence of vascular lesions at birth or in early childhood in most patients with inherited mutations in COL4A1, COL4A2, RASA1 and EPHB4 genes (Amyere et al, 2017;Jeanne & Gould, 2017;Kuo et al, 2012;Revencu et al, 2013).…”

“…CM-AVM is an autosomal dominant disorder caused by inactivating mutations of RASA1 that encodes the RASA1 Ras GTPase-activating protein (CM-AVM1) or the Ephrin receptor B4 (EPHB4) growth factor receptor tyrosine kinase (CM-AVM2) (Amyere et al, 2017;Eerola et al, 2003;Revencu et al, 2013). Studies of conditional RASA1-and EPHB4-deficient mice have revealed that in EC, RASA1 and EPHB4 act together to limit activation of the Ras-mitogen active protein kinase (MAPK) signaling pathway (Chen et al, 2019(Chen et al, , 2022(Chen et al, , 2023.…”

“…In turn, this impairs collagen IV folding leading to EC apoptosis, again as a result of an unresolved unfolded protein response and/or EC detachment from an incompletely formed basement membrane (Chen et al, 2019(Chen et al, , 2022(Chen et al, , 2023. Like vascular defects in patients with COL4A1 and COL4A2 mutations, vascular lesions in CM-AVM are present at birth in the vast majority of cases (Amyere et al, 2017;Revencu et al, 2013).…”

“…Like vascular defects in patients with COL4A1 and COL4A2 mutations, vascular lesions in CM-AVM are present at birth in the vast majority of cases (Amyere et al, 2017;Revencu et al, 2013). Furthermore, from late gestation through adult life, disruption of Ephb4 or Rasa1 genes in mice does not result in spontaneous blood vascular defects (Chen et al, 2019(Chen et al, , 2022(Chen et al, , 2023Lapinski et al, 2012Lapinski et al, , 2017. Thus, the absence of functional EPHB4 or RASA1 in EC during development is necessary for the appearance of vascular lesions.…”

“…In addition, findings provide a basis for the occurrence of vascular lesions at birth or in early childhood in most patients with inherited mutations in COL4A1, COL4A2, RASA1 and EPHB4 genes (Amyere et al, 2017;Jeanne & Gould, 2017;Kuo et al, 2012;Revencu et al, 2013). In mice, although disruption of Rasa1 and Ephb4 genes after birth does not result in spontaneous blood vascular abnormalities, both retinal and pathological angiogenesis are impaired (Chen et al, 2019(Chen et al, , 2022(Chen et al, , 2023. However, in these situations, it is expected that EC would re-engage in synthesis of collagen IV as part of the angiogenic process that would necessitate de novo production of basement membrane.…”