NM23-H1 Tumor Suppressor Physically Interacts with Serine-Threonine Kinase Receptor-associated Protein, a Transforming Growth Factor-β (TGF-β) Receptor-interacting Protein, and Negatively Regulates TGF-β Signaling

Abstract

NM23-H1 is a member of the NM23/NDP kinase gene family and a putative metastasis suppressor. Previously, a screen for NM23-H1-interacting proteins that could potentially modulate its activity identified serine-threonine kinase receptor-associated protein (STRAP), a transforming growth factor (TGF) . Ectopic expression of wild-type NM23-H1, but not NM23-H1(C145S), negatively regulated TGF-␤ signaling in a dose-dependent manner, enhanced stable association between the TGF-␤ receptor and Smad7, and prevented nuclear translocation of Smad3. Similarly, wild-type NM23-H1 inhibited TGF-␤-induced apoptosis and growth inhibition, whereas NM23-H1(C145S) had no effect. Knockdown of NM23-H1 by small interfering RNA stimulated TGF-␤ signaling. Coexpression of wild-type STRAP, but not STRAP(C152S/C270S), significantly stimulated NM23-H1-induced growth of HaCaT cells. These results suggest that the direct interaction of NM23-H1 and STRAP is important for the regulation of TGF-␤-dependent biological activity as well as NM23-H1 activity.-The NM23 family of genes is characterized by reduced expression in certain highly metastatic cell lines and tumors (1).In humans, the eight NM23 genes that have been identified to date, NM23-H1, , and NM23-H8, encode NDP kinases or homologous isoforms (2). However, although NM23-H1 was initially identified as a putative metastasis suppressor, its enzymatic activity does not appear to be responsible for its function as a metastasis suppressor during tumor progression (3). Studies of NM23 family proteins in other species have provided evidence for their role in proliferation, differentiation, apoptosis, development, and endocytosis (4). In Drosophila, for example, abnormal wing discs (awd) is an NDP kinase, and the killerof-prune mutation of awd (awd k-pn ) causes abnormalities in cell morphology and differentiation (5). Recently, both NM23-H1 and NM23-H2 have been reported to play a role in endocytosis (6). In addition, NM23 has been associated with the differentiation of human MDA-MB-435 breast carcinoma cells (7). The ability of NM23 family proteins to regulate such a diverse set of cellular processes has recently been linked to their ability to modulate signal transduction by a diverse set of growth factors, such as transforming growth factor-␤1 (TGF-␤1), 2 nerve growth factor, platelet-derived growth factor, and insulin-like growth factor-1 (8). However, the mechanism of regulation of these signaling pathways by NM23 family proteins is unknown. To date, NM23 family proteins have been shown to associate with several cellular proteins, including glyceraldehyde-3-phosphate dehydrogenase (9), Hsc70 (70-kDa heat shock cognate protein) (10), telomere (11), ROR␣ (retinoid acid receptor-related orphan receptor ␣)/RZR␤ (retinoid Z receptor ␤) (12), Rad, a Ras-related small GTPase (13), creatine kinase and antioxidant protein (14), and thromboxane A2 receptor, a G protein-coupled receptor (6). These results suggest that the identification of additional binding partners of NM23 proteins will provide gre...

Serine-Threonine Kinase Receptor-associated Protein Inhibits Apoptosis Signal-regulating Kinase 1 Function through Direct Interaction

“…Anti-phospho-PDK1(Ser 241 ) antibody was from Cell Signaling Technology (Danvers, MA). Wild-type and kinase-dead ASK1, ASK1-N, ASK1-K, ASK1-C, wild-type STRAP and its mutants (WD1-3, WD4 -6, WD4, C152S, WD5, WD6, C270S, C152S/ C270S, and CT), activator protein 1 (AP-1)-Luc reporter, pSuper vector, GST-tagged MKK6(K82A) and p38, and c-fos were also previously described (11,25).…”

Signaling Receptors for TGF-β Family Members

“…STRAP has also been reported to link the kinase phosphoinositide-dependent kinase 1 (PDK1), which activates Akt, to TbRI and to promote its activation (Seong et al 2005), and to bind and inhibit the nucleoside diphosphate (NDP) kinase NM23-H1 (Seong et al 2007). STRAP thus affects TGF-b signaling via several mechanisms.…”

Targeting Tumor Metastasis by Regulating Nm23 Gene Expression

“…There is much cross talk between the growth factors and the receptors in signaling. The ability of Nm23 to regulate a diverse set of cellular processes has been linked to their ability to modulate signal transduction by a diverse set of growth factors such as TGF-β 1, PDGF, ILGF and NGF (Otero, 2000;Seong et al, 2007).…”