The Rac1/Cdc42 effector, p21-activated kinase (PAK), is activated by various signaling cascades, including receptor-tyrosine kinases and integrins, and regulates a number of processes such as cell proliferation and motility. PAK activity has been shown to be required for maximal activation of the canonical RAF-MEK-MAPK signaling cascade, possibly because of PAK co-activation of RAF and MEK. Here we have shown that trihydrophobin 1 (TH1), originally identified as a negative regulator of A-RAF kinase, also interacted with PAK1 in cultured cells. Confocal microscopy assay indicated that TH1 colocalized with PAK1 in both the cytoplasm and nucleus, which is consistent with our previous results. GST pulldown and coimmunoprecipitation experiments demonstrated that TH1 interacted directly with PAK1 and bound selectively to the carboxyl-terminal kinase domain of PAK1, and the ability of the binding was enhanced along with activation of PAK1. The binding pattern of PAK1 implies that this interaction was mediated in part by PAK1 kinase activity. As indicated by in vitro kinase activity assays and Western blot detections, TH1 inhibited PAK1 kinase activity and negatively regulated MAPK signal transduction. Interestingly, TH1 bound with MEK1/ERK in cells and in vitro without directly suppressing their kinase activity. Furthermore, we observed that TH1 localized to focal adhesions and filopodia in the leading edge of cells, where TH1 reduced cell migration through affecting actin and adhesion dynamics. Based on these observations, we propose a model in which TH1 interacts with PAK1 and specifically restricts the activation of MAPK modules through the upstream region of the MAPK pathway, thereby influencing cell migration.

BCL2L12, a newly identified member of Bcl-2 family, contains a BH2 domain and a putative BH3 domain. It was found to be highly expressed in normal breast tissues, and was associated with favorable prognosis in breast cancer patients. Here, we reported that the mRNA levels of BCL2L12 and its transcript variant BCL2L12A could be upregulated upon cisplatin treatment in MDA-MB-231 breast cancer cells. Knockdown of BCL2L12 and BCL2L12A dramatically inhibited cisplatin-induced apoptosis. In contrast, ectopic expressions of each of the proteins promoted cisplatin-induced apoptosis. These results indicated that decreased expressions or loss of BCL2L12 and BCL2L12A may contribute to the cisplatin resistance in breast cancer patients. Furthermore, we found that cisplatin-induced downregulation of beta-catenin was partially suppressed in BCL2L12- and BCL2L12A-knocked down MDA-MB-231 cells, which indicated that knockdown of these two proteins may stabilize beta-catenin in cisplatin-induced apoptosis. In short, we proposed that BCL2L12 and BCL2L12A may play an important role in cisplatin-induced apoptosis in MDA-MB-231 breast cancer cells.

␤1,4-galactosyltransferase V (GalT V; EC 2.4.1.38) can effectively galactosylate the GlcNAc␤13 6Man arm of the highly branched N-glycans that are characteristic of glioma. Previously, we have reported that the expression of GalT V is increased in the process of glioma. However, currently little is known about the role of GalT V in this process. In this study, the ectopic expression of GalT V could promote the invasion and survival of glioma cells and transformed astrocytes. Furthermore, decreasing the expression of GalT V in glioma cells promoted apoptosis, inhibited the invasion and migration and the ability of tumor formation in vivo, and reduced the activation of AKT. In addition, the activity of GalT V promoter could be induced by epidermal growth factor, dominant active Ras, ERK1, JNK1, and constitutively active AKT. Taken together, our results suggest that GalT V functioned as a novel glioma growth activator and might represent a novel target in glioma therapy.The carbohydrate moieties of cell surface glycoconjugates play an important role in cell adhesion and metastasis (1). One of the most prominent transformation-associated changes in the sugar chains of glycoproteins is an increase in the large N-glycans of cell surface glycoprotein (2). ␤1,4-galactosyltransferase (GalT) 2 family are the enzymes responsible for the biosynthesis of N-acetyllactosamine on N-glycans by transferring UDP-galactose to the terminal N-acetylglusamine (N-GlcNAc) residues, and this family consist of seven members, from GalT I to GalT VII (3,4).GalT V, a member of ␤1,4-galactosyltransferase (GalT) family, could effectively galactosylate the GlcNAc␤136 branch (5), which is a marker of glioma (6). The expression change of GalT V has been investigated using NIH3T3 and the highly malignant transformed cell line MTAg. Northern blot analysis has revealed that the transcript of GalT V gene increases by 2-3-fold in the transformed cells (7). Similar results have been obtained in several human cancer cell lines (8). Consistently, our previous study has shown that the expression of GalT V is increased in the process of glioma development, with the highest level in grade IV glioma (9). Despite this knowledge, currently little is known about the role of GalT V in the process of glioma formation.The experiments reported here were undertaken to further study the role of GalT V in glioma malignancy, including cell migration, invasion, growth, and survival. Our results indicate that GalT V functioned as a novel glioma growth activator and could represent a novel target in glioma therapy. EXPERIMENTAL PROCEDURESMaterials-Restriction enzymes, bovine calf serum, fetal bovine serum (FBS), DMEM, RPMI 1640 medium, and TRIzol reagent were from Invitrogen. G418, phenylmethylsulfonyl fluoride, aprotinin, pepstatin, epidermal growth factor (EGF), etoposide (VP16), and toluidine blue O were from Sigma. [␥-32 P]dATP and the ECL assay kit were from Amersham Biosciences. Sialidase was from Roche Applied Science. The following antibodies were purchased from Sa...

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a b s t r a c t BCL2L12 has been found to be associated with favorable prognosis in breast cancer patients while correlated with tumorigenesis of glioblastoma and colon cancer. Here, we report that BCL2L12 and its transcript variant BCL2L12A are degraded through ubiquitin-proteasome system (UPS). Interestingly, the ubiquitinations and degradations of BCL2L12 and BCL2L12A are independent of the internal lysine residues but the first N-terminal residues. In addition, HSP70 was identified to interact with BCL2L12 and BCL2L12A and protected them from ubiquitinations and degradations in mammalian cells. In summary, HSP70 protects BCL2L12 and BCL2L12A from N-terminal ubiquitination-mediated proteasomal degradation. Structured summary:MINT-7026352, MINT-7026366: BCL2L12 (uniprotkb:Q9HB09-1) physically interacts (MI:0218) with Hsp70 (uniprotkb:P62988) by anti tag coimmunoprecipitation (MI:0007) MINT-7026290: BCL2L12 (uniprotkb:Q9HB09-1) physically interacts (MI:0218) with ubiquitin (uniprotkb:P62988) by pull down (MI:0096) MINT-7026326: Hsp70 (uniprotkb:P08107) physically interacts (MI:0218) with BCL2L12A (uniprotkb:Q9HB09-2) by anti bait coimmunoprecipitation (MI:0006) MINT-7026338: BCL2L12 (uniprotkb:Q9HB09-1) physically interacts (MI:0218) with Hsp70 (uniprotkb:P08107) by anti tag coimmunoprecipitation (MI:0007) MINT-7026304: BCL2L12A (uniprotkb:Q9HB09-2) physically interacts (MI:0218) with Hsp70 (uniprotkb:P08107) by anti tag coimmunoprecipitation (MI:0007)