FAM129B/MINERVA, a Novel Adherens Junction-associated Protein, Suppresses Apoptosis in HeLa Cells

Abstract

A recent proteomics study identified FAM129B or MINERVA as a target of the MAP kinase (Erk1/2) signaling cascade in human melanoma cells. Phosphorylation of the protein was found to promote cell invasion and the dissociation of the protein from the cell-cell junctions. Suppression of apoptosis during metastasis is a prerequisite for the survival and spread of cancer cells. During apoptosis, the adherens junctions are disassembled as the dying cell retracts, and new contacts are formed between normal neighboring cells. In this study, we show that FAM129B was cytosolic in exponentially growing HeLa cells but was translocated to the adherens junctions where it colocalized with ␤-catenin whenever contact between two or more cells was established. Silencing the FAM129B gene expression by specific siRNAs did not induce apoptosis or inhibit the growth of HeLa cells. However, when apoptosis was induced by exposure to TNF␣/cycloheximide or other apoptotic signaling molecules, the onset of apoptosis was accelerated 3-4-fold when FAM129B was depleted. Annexin V binding, the inactivation of the DNA repair enzyme, poly(ADP-ribose) polymerase, and the activation of the caspases occurred more rapidly in the cells lacking FAM129B. The rapid induction of apoptosis in FAM129B knockdown cells was reversed by co-transfection with recombinant FAM129B, indicating that its effect on apoptosis was specific. As apoptosis proceeded, FAM129B was degraded and disappeared from the plasma membrane. Thus, one crucial facet of the mechanism by which FAM129B promotes cancer cell invasion is likely to be the suppression of apoptosis.FAM129B or MINERVA is a member of a small family of proteins that include Niban (FAM129A) and Niban-like protein 2 (FAM129C). The function of these homologous proteins is not well understood. FAM129A is an endoplasmic reticulum stress-induced protein that is up-regulated in renal and thyroid cancer (1-3), whereas FAM129C is a B-cell membrane protein that is overexpressed in chronic lymphocytic leukemia (4). FAM129B has a predicted molecular mass of 83 kDa and includes two distinctive regions (Fig. 1). The PH or pleckstrin homology domain found near the amino end of the polypeptide of FAM129B is also present in FAM129C, whereas FAM129A has only a truncated PH domain. Near the carboxyl end of the FAM129B polypeptide chain is a region rich in proline shown in a recent proteomics study to be phosphorylated at six serine residues (5). The phosphorylation of four of these serines is catalyzed by the B-RAF/MAPKK/ERK (MAP kinase) signaling cascade. In melanoma cells, FAM129B was found dispersed throughout the cytoplasm when the MAPK cascade was active. However, exposure to the MAPKK inhibitor, UO126, which effectively shuts down the cascade, resulted in the migration of FAM129B to the cell membrane. A well established in vitro assay for invasion (6), in which cells are grown in a three-dimensional collagen matrix, was used to show that shRNA-mediated knockdown of FAM129B had no effect on growth. However, the invasion into th...

A phase 2 study of vorinostat in locally advanced, recurrent, or metastatic adenoid cystic carcinoma

“…The mutations in this tumor included 3 predicted high impact mutations in MTOR a regulator of stress response, OGT a glycosyltransferase that modifies a broad range of targets including H2B, AKT1, EZH2, PFKL, KMT2E/MLL5, MAPT/TAU and HCFC1, and FAM129B a negative regulator of apoptosis [19]. Additional mutations included the cell cycle regulator CDC25C , the chromatin regulators PHF2 and BRD1 , and the NOTCH1 ligand JAG1 .…”

Intra-Familial Tests of Association between Familial Idiopathic Scoliosis and Linked Regions on 9q31.3–q34.3 and 16p12.3–q22.2

“…[38]. Rs7259 lies within the CERCAM gene, which produces a cerebral endothelial cell adhesion molecule potentially involved in leukocyte transmigration across the blood-brain barrier [39].…”

Molecular Assembly and Biosynthesis of Acetylcholinesterase in Brain and Muscle: the Roles of t-peptide, FHB Domain, and N-linked Glycosylation

“…Elimination of N -glycosylation sites did not interfere with the ability of AChE T to form a soluble dimer (Velan et al, 1993), or to assembly with PRiMA to form a PRiMA-linked AChE tetramer (Chen et al, 2011). It appears therefore that the oligosaccharide side chains do not affect the structural elements that are responsible for the interaction of different subunits.…”

“…Moreover, the glycosylation of AChE T can greatly affects the protein folding and membrane trafficking. When the glycosylation is eliminated, the folding of AChE T fails, leading to a severe lost of the enzymatic activity (Chen et al, 2011). In the absence of glycosylation, the secreted G 1 and G 2 AChE are dramatically reduced in transfected cells, and the PRiMA-linked G 4 AChE is retained in ER and fails to be exported to plasma membrane (Chen et al, 2011).…”