Tumor metastasis suppressor nm23H1 regulates Rac1 GTPase by interaction with Tiam1

Abstract

The putative tumor metastasis suppressor nm23H1 was originally identified in murine melanomas by subtraction cloning. It displays nucleoside diphosphate kinase activity and regulates cellular events, including growth and development. Recently nm23H1 has been reported to also act as a GTPase-activating protein of the Ras-related GTPase Rad. We attempted to determine whether nm23H1 also regulates Rho-family GTPases. Although we were unable to detect a direct association between nm23H1 and Rhofamily GTPases, nm23H1 was shown to be associated with a Rac1-specific nucleotide exchange factor, Tiam1, by interaction with its amino-terminal region in extracts from the cells expressing exogenous Tiam1 and from native tissue. Overexpression of nm23H1 inhibited the Tiam1-induced production of GTP-bound Rac1 and activation of c-Jun kinase. On the other hand, forced overexpression of the wild type, but not the kinase-inactivated mutant of nm23H1, converted the GDP-bound forms of Rac1, Cdc42, and RhoA to their GTP-bound forms in vitro by its nucleoside diphosphate kinase activity, but nm23H1 alone apparently did not produce the GTP-bound form of these GTPases in vivo. These results suggest that nm23H1 negatively regulates Tiam1 and inhibits Rac1 activation in vivo. Moreover, adhesion-stimulated membrane ruffles of Rat1 fibroblasts were reduced by overexpression of nm23H1. Based on these observations, we concluded that we had identified a function of nm23H1 as a regulator of Rac1 and that it may be related to the effect of nm23H1 as a tumor metastasis suppressor.

NM23 et les genès Suppresseurs de métastases

“…Paradoxalement, il s'agit d'une inhibition, en accord avec le rôle de suppresseur de métastases. L'interaction de NM23-H1 avec Tiam1, facteur d'échange nucléotidique de Rac1, Rho-GTPase impliquée dans la motilité cellulaire, inhibe l'activation de Rac1 [10]. NM23-H1, en interagissant avec la protéine d'échaffaudage KSR, inhibe l'activation de la voie ERK/MAPK [11].…”

Phosphorylation of nm23-H1 by CKI induces its complex formation with h-prune and promotes cell motility

“…The nm23 proteins have been reported to possess both a histidine protein kinase activity and a phosphotransferase activity; the latter potentially represents an additional mechanism by which the nm23s can influence the metastasis and differentiation processes (MacDonald et al, 1996;Wagner et al, 1997). To date, several nm23 interactors have been described in mammals, including Rad, Tiam1, Arf6, the nucleosome assembly protein SET, Cdc42, EBNA1 and KSR (Otsuki et al, 2001;Tseng et al, 2001;Palacios et al, 2002), although their roles are not fully understood. AMPKa1, a heterotrimeric kinase that is a sensor of cellular energy status, binds to and phosphorylates nm23-H1, which in turn channels the ATP produced by its enzymatic activity to AMP activated kinase (AMPK) (Crawford et al, 2005(Crawford et al, , 2006).…”

Inhibition of ovarian cancer metastasis by adeno-associated virus-mediated gene transfer of nm23H1 in an orthotopic implantation model

“…Recent studies have demonstrated that the nm23H1 gene plays a major role in metastasis and its mechanism of suppressing metastasis may involve downregulation of nm23H1 and inhibition of ovarian cancer metastasis J Li et al genes associated with cell adhesion and motility (integrins alpha2, -8, -9, -L, and -V, collagen type VIII alpha1, fibronectin 1, catenin, TGF-beta2, FGF7, MMP14 and 16, ErbB2), and possibly certain tumor/metastasis suppressors (two members of SWI/SNF-related matrix-associated proteins 2 and 5, and PTEN). 2,8,38 Moreover, nm23H1 may negatively regulate Tiam1 and inhibit Rac1 activation in vivo. Its regulation of Rac1 implicated nm23H1 in the suppression of tumor metastasis.…”