Involvement of c-Abl and D40 (AF15Q14/CASC5) proteins in the regulation of cell proliferation and cancer

Although c-Abl and D40 proteins are located predominantly in the nucleus, they are involved in different cellular processes. c-Abl is a tyrosine-kinase that takes part in protein phosphorylation at tyrosine. Recently, D40 has been identified as a component of the outer kinetochore complex. Despite the functional differences between c-Abl and D40 proteins, they do have some similarities. First, high expression levels of c-Abl and D40 were observed not only in proliferating somatic cells, such as tumors, but also in healthy human testis. The increased expression levels of c-Abl and D40 protein in spermatocytes and acrosome of spermatids indicate their role in meiosis and spermatogenesis. Second, both proteins interact with specific regions of chromatin and are involved in the regulation of cell growth and division. Third, ABL and D40 (AF15q14) genes are involved in chromosomal translocations that subsequently form chimeric oncoproteins BCR-ABL, TEL-ABL, and MLL-AF15q14 in human leukemia. Lastly, both proteins interact with the tumor suppressor pRb protein and, consequently, can lead to the regulation of cell proliferation. The possible regulatory pathways that are controlled by c-Abl and D40 proteins are described in detail.     

Aph2, a protein with a zf-DHHC motif,interacts with c-Abl and has pro-apoptotic activity

c-Abl is a non-receptor tyrosine kinase implicated in DNA damage-induced cell death and in growth factor receptor signaling. To further understand the function and regulation of c-Abl, a yeast two-hybrid screen was performed to identify c-Abl-interacting proteins. Here we report the identification of Abl-philin 2 (Aph2), encoding a novel protein with a unique cysteine-rich motif (zf-DHHC) and a 53-amino acid stretch sharing homology with the creatine kinase family. The zf-DHHC domain is highly conserved from yeast to human. Two proteins containing this motif, Akr1p and Erf2p, have been characterized in Saccharomyces cerevisiae, both implicated in signaling pathways. Deletion analysis by two-hybrid assays revealed that the N-terminal portion of Aph2 interacts with the C terminus of c-Abl. Aph2 was demonstrated to interact with c-Abl by co-immunoprecipitation assays. Aph2 is expressed in most tissues tested and is localized in the cytoplasm, mainly in the endoplasmic reticulum (ER). The sequences required for ER location reside in the N terminus and the zf-DHHC motif of Aph2. It has been reported that a portion of c-Abl is localized in the ER. We demonstrate here that Aph2 and c-Abl are co-localized in the ER region. Overexpression of Aph2 leads to apoptosis as justified by TUNEL assays, and the induction of apoptosis requires the N terminus. Co-expression of c-Abl and Aph2 had a synergistic effect on apoptosis induction and led to a decreased expression of both proteins, suggesting either that these two proteins are mutually down-regulated or that cells expressing both c-Abl and Aph2 rapidly disappeared from the culture. These results suggest that Aph2 may be involved in ER stress-induced apoptosis in which c-Abl plays an important role.     

14-3-3 proteins are involved in the regulation of mammalian cell proliferation

Summary. The 14-3-3 proteins are a family of abundant, widely expressed acidic polypeptides. The seven isoforms interact with over 70 different proteins. 14-3-3 isoforms have been demonstrated to be involved in the control of positive as well as negative regulators of mammalian cell proliferation. Here we used the approach of inactivating 14-3-3 protein functions via overexpression of dominant negative mutants to analyse the role of 14-3-3 proteins in mammalian cell proliferation. We found 14-3-3 dominant negative mutants to downregulate the proliferation rates of HeLa cells. Overexpression of these dominant negative mutants triggers upregulation of the protein levels of the cyclin-dependent kinase inhibitor p27, a major negative cell cycle regulator. In addition, they downregulate the protein levels of the important cell cycle promoter cyclin D1. These data provide new insights into mammalian cell proliferation control and allow a better understanding of the functions of 14-3-3 proteins.     

酪氨酸激酶c-Abl与信号转导

c-Abl是一种非受体型酪氨酸激酶,在细胞核和细胞质中都有分布,通过调控多种信号通路的信号转导参与多种细胞活动。细胞核中的c-Abl在DNA损伤应激中被激活并参与调控细胞凋亡,细胞质中的c-Abl参与调控细胞增殖、细胞周期、黏附迁移和细胞凋亡等细胞活动。我们简要综述了c-Abl参与调控的信号通路。     

Determination of c-Abl tyrosine kinase and mTERT catalytic subunit of telomerase expression level during prenatal-postnatal mouse ovary-testis development

Expression levels of genes involved in the development of germ cells vary throughout the process from bipotential gonadal period to adult gonadal formation. In mice, developments of female and male reproductive system are regulated by germ cell-specific factors and hormones, and determinative days in this regulation are very important. c-Abl is a non-receptor tyrosine kinase with cellular functions including cell proliferation, growth and development. mTERT is involved in maintaining telomerase activity and proliferation of surviving cells. We suggested that c-Abl and mTERT might be important for the healthy development of prenatal and postnatal mouse ovary and testis. We aim to demonstrate localization and expressions of c-Abl and mTERT in crucial days of ovary and testis development in prenatal and postnatal period in mouse by immunofluorescence staining and qRT-PCR, respectively. The importance of c-Abl and mTERT expressions during the healthy gonadal development is indicated in the prenatal and postnatal gonadal development. Also, protein expression levels were detected by Western Blot in only postnatal ovary and testis. Determining the functions of the c-Abl and mTERT throughout the process will be important in terms of understanding the infertility cases in the female and male with future studies.     

The TspanC8 Subgroup of Tetraspanins Interacts with A Disintegrin and Metalloprotease 10 (ADAM10) and Regulates Its Maturation and Cell Surface Expression

A disintegrin and metalloprotease 10 (ADAM10) is a ubiquitous transmembrane metalloprotease that cleaves the extracellular regions from over 40 different transmembrane target proteins, including Notch and amyloid precursor protein. ADAM10 is essential for embryonic development and is also important in inflammation, cancer, and Alzheimer disease. However, ADAM10 regulation remains poorly understood. ADAM10 is compartmentalized into membrane microdomains formed by tetraspanins, which are a superfamily of 33 transmembrane proteins in humans that regulate clustering and trafficking of certain other transmembrane “partner” proteins. This is achieved by specific tetraspanin-partner interactions, but it is not clear which tetraspanins specifically interact with ADAM10. The aims of this study were to identify which tetraspanins interact with ADAM10 and how they regulate this metalloprotease. Co-immunoprecipitation identified specific ADAM10 interactions with Tspan5, Tspan10, Tspan14, Tspan15, Tspan17, and Tspan33/Penumbra. These are members of the largely unstudied TspanC8 subgroup of tetraspanins, all six of which promoted ADAM10 maturation. Different cell types express distinct repertoires of TspanC8 tetraspanins. Human umbilical vein endothelial cells express relatively high levels of Tspan14, the knockdown of which reduced ADAM10 surface expression and activity. Mouse erythrocytes express predominantly Tspan33, and ADAM10 expression was substantially reduced in the absence of this tetraspanin. In contrast, ADAM10 expression was normal on Tspan33-deficient mouse platelets in which Tspan14 is the major TspanC8 tetraspanin. These results define TspanC8 tetraspanins as essential regulators of ADAM10 maturation and trafficking to the cell surface. This finding has therapeutic implications because focusing on specific TspanC8-ADAM10 complexes may allow cell type- and/or substrate-specific ADAM10 targeting.     

c-Abl is involved in high glucose-induced apoptosis in embryonic E12.5 cortical neural progenitor cells from the mouse brain

Hyperglycemia causes direct apoptosis of neural progenitor cells (NPCs) in diabetic-induced neural tube defects in embryos. However, the underlying mechanisms are poorly understood. The present study is aimed to investigate the specific cellular proteins that may be involved in NPCs apoptosis as well as mechanisms by which the proteins regulate the oxidative stress-induced NPCs apoptosis. Our present results have shown that the expression of c-Abl was up-regulated in NPCs exposed to high glucose in vitro . The increased c-Abl was localized mainly in the nucleus. High glucose also induced an increase in nuclear p53 protein levels and the p53-c-Abl complex in NPCs. Administration of reactive oxygen species scavengers decreased the protein level of c-Abl, p53 and NPCs apoptosis. Inhibition of c-Abl reduced NPCs apoptosis and the nuclear protein level of p53 in response to high glucose. These results demonstrate that c-Abl is involved in the reactive oxygen species-activated apoptotic pathways in NPCs apoptosis. Inhibition of c-Abl may protect NPCs against insults induced by high glucose via the modulation of NPCs apoptotic machinery.     

c-Abl proto-oncoprotein is expressed and tyrosine phosphorylated in human sperm cell

The presence and possible role of c-Abl proto-oncoprotein was investigated in human sperm cell. The c-Abl monoclonal antibody (mAb), against the protein tyrosine kinase domain of v-Abl protein, reacted specifically with the acrosomal region of methanol-fixed capacitated and non-capacitated human sperm cell in the indirect immunofluorescence technique. The c-Abl mAb predominantly recognized two protein bands of 145 kD and 95 kD in detergent-solubilized (Triton X-100 and NP-40) sperm and testes preparations in the Western blot procedure. The 95 kD protein band reacted stronger than the 145 kD band and was the only band detected in the lithium diiodosalicylate (LIS)–solubilized sperm preparation, and even in the Triton X-100/NP-40 extracts of sperm of some men. In the in vitro kinase assay using the Triton X-100–solubilized capacitated sperm preparation, the 95 kD protein was autophosphorylated at the tyrosine residues, which was inhibited in the presence of c-Abl mAb. The tyrosine phosphorylation of sperm proteins, especially of the 95 kD protein, has been shown to have a vital role in human sperm function, namely, the sperm capacitation/acrosomal exocytosis and binding to zona pellucida of oocyte. These findings suggest that the c-Abl or c-Abl-like proteins are present in mature sperm cells that are tyrosine autophosphorylated and may have a role in human sperm cell function. Mol. Reprod. Dev. 51:210–217, 1998. © 1998 Wiley-Liss, Inc.     

Proteome analysis of chick embryonic cerebrospinal fluid

During early stages of embryo development, the brain cavity is filled with embryonic cerebrospinal fluid (E-CSF), a complex fluid containing different protein fractions that contributes to the regulation of the survival, proliferation and neurogenesis of the neuroectodermal stem cells. Using 2-DE, protein sequencing and database searches, we identified and analyzed the proteome of the E-CSF from chick embryos (Gallus gallus). We identified 26 different gene products, including proteins related to the extracellular matrix, proteins associated with the regulation of osmotic pressure and metal transport, proteins related to cell survival, MAP kinase activators, proteins involved in the transport of retinol and vitamin D, antioxidant and antimicrobial proteins, intracellular proteins and some unknown proteins. Most of these gene products are involved in the regulation of developmental processes during embryogenesis in systems other than E-CSF. Interestingly, 14 of them are also present in adult human CSF proteome, and it has been reported that they are altered in the CSF of patients suffering neurodegenerative diseases and/or neurological disorders. Understanding these molecules and the mechanisms they control during embryonic neurogenesis is a key contribution to the general understanding of CNS development, and may also contribute to greater knowledge of these human diseases.     

The adaptor protein 3BP2 in leukocyte signaling

Adaptor proteins that do not contain intrinsic enzymatic activity play a critical role in cell biology by regulating the assembly of large multimolecular signaling complexes involved in extracellular signal transduction. The increasing number of diseases associated with aberrant function or expression of adaptor proteins further illustrate their key role in cellular regulation. The adaptor 3BP2 (or SH3BP2) was originally identified more than 10 years ago as an c-Abl binding protein, and next as a partner of Syk family kinases in 1998. 3BP2 displays the typical modular organization of an adapter protein with an amino-terminal PH domain, a central proline rich region and a carboxyl-terminal SH2 domain. Although its physiological function remains unknown, studies have implicated a role for 3BP2 in immunoreceptor signaling through its interaction with a number of signaling molecules including Src and Syk families of protein tyrosine kinases, the membrane adaptor LAT, Vav exchange factors, PLC-gamma, and 14-3-3 proteins. Recently, the 3bp2/sh3bp2 locus was shown to be mutated in a rare human disease involved in cranial-facial development called cherubism, suggesting a role for 3BP2 in regulating osteoclast and hematopoietic cell function.     

A Novel Human Gene (WDR25) Encoding a 7-WD40-Containing Protein Maps on 14q32

Members of the large family of WD-repeat proteins are involved in diverse functions such as RNA-procession, signal transduction, vesicular trafficking, cytoskeletal assembly, and cell cycle control. By large-scale-sequencing analysis of a human fetal brain cDNA library, we isolated a novel human cDNA encoding a 7-WD40-repeat protein. This cDNA is 2004 bp in length and it codes for a 544-amino-acid protein. We term it human WD40-repeat-containing gene 25 (WDR25) and this gene shows significant similarity with human pre-mRNA splicing factor 17. The WDR25 gene is mapped to chromosome 14q32 and contains seven exons. RT-PCR analysis shows that the WDR25 gene is widely expressed in human tissues and the expression levers in heart, muscle, testis, ovary, uterus, and prostate are relatively high.