Rho Guanosine 5′-Triphosphatases Differentially Regulate Insulin-Like Growth Factor I (IGF-I) Receptor-Dependent and -Independent Actions of IGF-II on Human Trophoblast Migration

Abstract

Both IGF-I and IGF-II stimulate migration of human extravillous trophoblast (EVT) cells. Although IGF-I is known to signal through IGF type 1 receptor (IGF1R), IGF-II signals through IGF1R as well as in an IGF1R-independent manner. The purpose of this study was to investigate the roles of Rho GTPases in IGF1R-independent and -dependent actions of IGF-II on EVT cell migration. To distinguish IGF1R-dependent and -independent actions, we used picropodophyllin, a selective inhibitor of IGF1R tyrosine kinase, and IGF analogs with differential affinities for IGF1R, IGF-II/cation-independent mannose 6-phosphate receptor, and IGF-binding proteins. IGF1R-dependent actions of IGF-II were confirmed by showing the effects of IGF1R-selective agonist Des1-3 IGF-I. We used pharmacological inhibitors or selective small interfering RNAs to investigate the roles of RhoA, RhoC, Rac1, Cdc42, and Rho effector kinases called ROCK-I and -II in IGF-induced EVT cell migration. Although basal migration of EVT cells required each member of the Rho GTPase family studied, IGF1R-dependent and -independent EVT cell migration exhibited differential requirements for these enzymes. IGF1R-mediated EVT cell migration was found to depend on RhoA and RhoC but not on Rac1 or Cdc42. However, IGF1R-independent effect of IGF-II on EVT cell migration required ROCKs but not RhoA, RhoC, Rac1, or Cdc42. Most importantly, IGF1R-independent action of IGF-II was found to be exaggerated when RhoA or RhoC was down-regulated. Thus, different members of the Rho GTPase family regulate IGF-II-mediated EVT cell migration differentially, depending upon whether it signals through IGF1R or in an IGF1R-independent manner.

Prostaglandin E2-Mediated Migration of Human Trophoblast Requires RAC1 and CDC421

“…1B), but the addition of these compounds did not restore their migratory abilities, suggesting again that RAC1 is an important mediator of PGE 2 -induced migration. In our previous report, we have documented successful knockdown of RAC1 protein following the same siRNA transfection of HTR-8/SVneo cells following 48 h posttransfection [33]. In the present study, we show that knockdown of RAC1 protein remains even 96 h posttransfection (Fig.…”

Insulin-Like Growth Factor Type-I Receptor-Dependent Phosphorylation of Extracellular Signal-Regulated Kinase 1/2 but not Akt (Protein Kinase B) Can Be Induced by Picropodophyllin

“…PPP inhibits activity of IGF-1R Vasilcanu et al, 2004Vasilcanu et al, , 2006Ulfarsson et al, 2005;Strömberg et al, 2006;Colón et al, 2007;Conti et al, 2007;Guha et al, 2007;Razuvaev et al, 2007;Shields et al, 2007) but also down-regulates the receptor (Vasilcanu et al, 2008). Even though PPP may have other effects, we conclude that it does not cross-target the highly homologous insulin receptor .…”

“…We and others demonstrated that PPP is an inhibitor of the IGF-1R tyrosine phosphorylation Colón et al, 2007;Conti et al, 2007;Shields et al, 2007). In contrast, PPP did not inhibit the tyrosine kinase activity of insulin receptor or other major cancer-relevant growth factor receptors .…”

Effect of Leptin on Mouse Trophoblast Giant Cells1

“…In addition, extremely small (less than 1.5-fold) but statistically significant differences in Rhoa (higher in leptin) and Rock2 (higher in control) were seen at 1 h, suggesting dynamic regulation of this pathway by leptin, but not a specific direction of change. Both RHOA and RHOC are involved in control of focal adhesion and cell motility in many cell types, including human extravillous trophoblasts [41]. In addition, both MAP2K1 (MEK) and rho-dependent kinase activity have been implicated in leptin stimulation of invasion in cancer cells [42].…”