title: The suppressor of metastasis Nm23-H1 interacts with the Cdc42 Rho family member and the pleckstrin homology domain of oncoprotein Dbl-1 to suppress cell migration.
abstract: Tumor invasion and metastasis is regulated by a number of cellular molecules known to be involved in signaling and cytoskeletal rearrangement. One of these molecules is the suppressor of tumor metastasis Nm23-H1 which linked to invasiveness and metastatic potential of human cancers. Nm23-H1 expression is down-regulated in human melanoma and invasive breast carcinoma. Recent studies have shown an association between the Nm23-H1 and oncoprotein Dbl-1 which is associated with guanine exchange and belongs to a family of Guanine Exchange Factors (GEF). In this report we show a direct interaction in vitro and in human B cells and specifically identified the pleckstrin homology domain of Dbl-1 as the domain which binds to Nm23-H1. Furthermore, Nm23-H1 and Dbl-1 colocalized in the cytoplasm of COS-7 cells when expressed exogenously and showed predominant signals at the periphery of the cells particularly at the plasma membrane. Interestingly, Dbl-1 and Cdc42 expression rescued the suppressive activities of Nm23-H1 in cell migration assays. We show that Cdc42 a regulatory protein involved in cytoskeletal reorganization, cell growth and development can bind to Nm23-H1 and the kinase deficient mutant H118F but only weakly to the mutant P96S which lacks the ability to suppress cell migration and metastasis. Cdc42 also colocalized with Nm23-H1 and the Dbl-1 proteins as specific punctate signals in the cytoplasm and at the cell membrane. Nm23-H1 also lead to the reduction in membrane ruffles and protuberances when expressed with Dbl-1 and Cdc42. Surprisingly, Nm23-H1 interacted with Cdc42 as well as Rac1 but somewhat weaker with RhoA. These studies suggests that Nm23-H1 can negatively regulate cell migration and tumor metastasis by modulating the activity of Cdc42 and possibly other Rho family members through interaction with Dbl-1.
authors: The Department of Microbiology and The Tumor Virology Program of the Abramson Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors: Masanao
authors: M
authors: Murakami
authors: Patricio I
authors: PI
authors: Meneses
authors: Ke
authors: K
authors: Lan
authors: Erle S
authors: ES
authors: Robertson
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000737:chemistry*; D019556:COS Cells; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D054778:NM23 Nucleoside Diphosphate Kinases / Q000378:metabolism*; D009362:Neoplasm Metastasis; D010750:Phosphoproteins / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D001798:Blood Proteins; D020662:Guanine Nucleotide Exchange Factors; C057811:MCF2 protein, human; D054778:NM23 Nucleoside Diphosphate Kinases; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; C039077:platelet protein P47; C517938:NME1 protein, human; D020764:cdc42 GTP-Binding Protein