Laminin regulates mouse embryonic stem cell migration: involvement of Epac1/Rap1 and Rac1/cdc42

Abstract

Suh HN, Han HJ. Laminin regulates mouse embryonic stem cell migration: involvement of Epac1/Rap1 and Rac1/cdc42. Am J Physiol Cell Physiol 298: C1159 -C1169, 2010. First published January 20, 2010 doi:10.1152/ajpcell.00496.2009Laminin is the first extracellular matrix (ECM) component to be expressed in the developing mammalian embryo. However, the roles of laminin or the related signal pathways are not well known in mouse embryonic stem cells (mESCs). Presently, we examined the effect of laminin on mESC migration. Laminin (10 g/ml) decreased cell aggregation, whereas migration was increased. Laminin bound ␣6␤1 integrin and laminin receptor 1 (LR1), decreasing their mRNA levels. Laminin increased focal adhesion kinase (FAK) and paxillin phosphorylation, cAMP intracellular concentration, and the protein levels of exchange factor directly activated by cAMP (Epac1) and Rap1. These increases were completely blocked by ␣6␤1 integrin and LR1 neutralizing antibody, indicating that laminin-bound LR1 assists laminin-induced ␣6␤1 integrin activity and initiates signal. As a downstream signal molecule, laminin activated small G protein such as Rac1/cdc42 and its effector protein p21-activated kinase (PAK). Subsequently, laminin stimulated E-cadherin complex disruption. Inhibition of each pathway such as those for ␣6␤1 integrin and LR1, FAK, Rap1, and PAK1 blocked laminin-induced migration. We conclude that laminin binds both ␣6␤1 integrin and LR1 and induces signaling FAK/paxillin and cAMP/Epac1/Rap1. These signaling merge at Rac1/cdc42 subsequently activate PAK1. Activated PAK1 enhances E-cadherin complex disruption and finally increases mESCs migration. cAMP/Epac1/Rap1; Rac1/cdc42/p21-activated kinase; E-cadherin

RAP1-mediated MEK/ERK pathway defects in Kabuki syndrome

“…RAP1A, and the highly related protein RAP1B (95% amino acid identity), belong to the Ras family of small GTPases, regulating various cellular processes such as cell adhesion and migration (14)(15)(16); studies in Xenopus and zebrafish have shown that rap1a and rap1b morphants exhibit similar gastrulation defects, highlighting the important role of both proteins in early development (17). RAP1 is known to exert opposing effects on the MAPK pathway (18), depending on tissue-and cell-specific context: an activating effect through BRAF (19,20) and a repressive effect through RAF1 (21).…”

Laminins containing the β2 and γ3 chains regulate astrocyte migration and angiogenesis in the retina

“…For example, in keratinocytes, laminin-integrin interactions result in keratinocyte polarization, lamellipodia extension and induction of migration (Choma et al, 2007). Similarly, laminin-integrin interactions regulate embryonic stem cell migration (Suh and Han, 2010).…”

“…Moreover, deletion of laminin genes disrupts the formation of the retinal inner limiting membrane (ILM) (Pinzón-Duarte et al, 2010;Edwards et al, 2010). As laminins and their receptors regulate cell migration (Suh and Han, 2010;Fujiwara et al, 2004;Desban et al, 2006;Echtermeyer et al, 1996), including brain astrocytes in vitro (Armstrong et al, 1990), we hypothesize that laminins regulate both astrocyte migration and spatial organization in the retina.…”

Exchange Protein Directly Activated by cAMP (epac): A Multidomain cAMP Mediator in the Regulation of Diverse Biological Functions

“…The Epac effector Rap2 is involved in Wnt/b-catenin signaling by stabilizing b-catenin (Choi and Han, 2005) and could in this contribute to fibrotic processes. Epac strengthens tethering of catenin to adherens junctions and tight junctions (Netherton et al, 2007;Raymond et al, 2007;Noda et al, 2010;Rampersad et al, 2010;Suh and Han, 2010). Intriguingly, the secreted lysophospholipase D autotaxin promotes cancer invasion through a cAMP-Epac-Rac1 pathway in response to lysophosphatidic acid receptor 4 stimulation, a process supported by blood vessel formation through autotaxin (van Meeteren et al, 2006;Harper et al, 2010).…”

“…Notably, Epac1 modulates the endothelial barrier independent from the Rho GTPases and Rap (see below). As Rap1 promotes cell-cell junction formation through signaling to E-cadherin-catenin and integrin-extracellular matrix complexes (Retta et al, 2006;Pannekoek et al, 2009;Noda et al, 2010;Suh and Han, 2010; Fig. 7), reduction of endothelial permeability through Rap1 activation by Epac1 most likely reflects its signaling property to the actin-microtubule network.…”