ABSTRACT
[This corrects the article DOI: 10.1371/journal.pone.0004080.].
ABSTRACT
The recent application of mass spectrometry to the study of the sperm cell has led to an unprecedented capacity for identification of sperm proteins in a variety of species. Knowledge of the proteins that make up the sperm cell represents the first step towards understanding its normal function and the molecular anomalies associated with male infertility. The present review starts with an introduction of the sperm cell biology and is followed by the consideration of the methodological key aspects to be aware of during sample sourcing and preparation, including data interpretation. It then overviews the initiatives developed so far towards the completion of the sperm proteome, with a particular focus in human but with the inclusion of some comments on different model species. Finally, all studies performing differential proteomics in infertile patients are reviewed, pointing to future potential applications.
Subject(s)
Clinical Medicine , Proteomics , Spermatozoa/metabolism , Animals , Humans , Infertility, Male/metabolism , Male , Mass Spectrometry , Proteome/metabolism , Spermatozoa/cytologyABSTRACT
A role for Rac1 GTPase in canonical Wnt signaling has recently been demonstrated, showing that it is required for ß-catenin translocation to the nucleus. In this study, we investigated the mechanism of Rac1 stimulation by Wnt. Upregulation of Rac1 activity by Wnt3a temporally correlated with enhanced p120-catenin binding to Rac1 and Vav2. Vav2 and Rac1 association with p120-catenin was modulated by phosphorylation of this protein, which was stimulated upon serine/threonine phosphorylation by CK1 and inhibited by tyrosine phosphorylation by Src or Fyn. Acting on these two post-translational modifications, Wnt3a induced the release of p120-catenin from E-cadherin, enabled the interaction of p120-catenin with Vav2 and Rac1, and facilitated Rac1 activation by Vav2. Given that p120-catenin depletion disrupts gastrulation in Xenopus, we analyzed p120-catenin mutants for their ability to rescue this phenotype. In contrast to the wild-type protein or other controls, p120-catenin point mutants that were deficient in the release from E-cadherin or in Vav2 or Rac1 binding failed to rescue p120-catenin depletion. Collectively, these results indicate that binding of p120-catenin to Vav2 and Rac1 is required for the activation of this GTPase upon Wnt signaling.
Subject(s)
Catenins/metabolism , Proto-Oncogene Proteins c-vav/metabolism , Wnt3A Protein/pharmacology , rac1 GTP-Binding Protein/metabolism , Animals , Cadherins/metabolism , Cell Line , Cell Nucleus/drug effects , Cell Nucleus/metabolism , Cytosol/drug effects , Cytosol/metabolism , Embryo, Nonmammalian/drug effects , Embryo, Nonmammalian/metabolism , Enzyme Activation/drug effects , Gastrulation/drug effects , Humans , Models, Biological , Mutant Proteins/metabolism , Phosphorylation/drug effects , Phosphoserine/metabolism , Phosphotyrosine/metabolism , Protein Binding/drug effects , Protein Transport/drug effects , Signal Transduction/drug effects , Xenopus/embryology , Xenopus/metabolism , beta Catenin/metabolism , Delta CateninABSTRACT
p120-catenin is an E-cadherin-associated protein that modulates E-cadherin function and stability. In response to Wnt3a, p120-catenin is phosphorylated at Ser268 and Ser269, disrupting its interaction with E-cadherin. Here, we describe that Wnt-induced p120-catenin phosphorylation at Ser268 and Ser269 also enhances its binding to the transcriptional factor Kaiso, preventing Kaiso-mediated inhibition of the ß-catenin-Tcf-4 transcriptional complex. Kaiso-mediated repression of this complex is due to its association not only with Tcf-4 but also with ß-catenin. Disruption of Tcf-4-Kaiso and ß-catenin-Kaiso interactions by p120-catenin not only releases Tcf-4 and ß-catenin enabling its mutual association and the formation of the transcriptional complex but also permits Kaiso binding to methylated CpG islands, an interaction that is weakly inhibited by p120-catenin. Consequently, Wnt stimulates Kaiso association to the CDKN2A promoter, which contains CpG sequences, in cells where these sequences are extensively methylated, such as HT-29 M6, an effect accompanied by decreased expression of its gene product. These results indicate that, when released from E-cadherin by Wnt3a-stimulated phosphorylation, p120-catenin controls the activity of the Kaiso transcriptional factor, enhancing its binding to repressed promoters and relieving its inhibition of the ß-catenin-Tcf-4 transcriptional complex.
Subject(s)
Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/metabolism , Catenins/metabolism , Transcription Factors/metabolism , Transcriptional Activation , Wnt3A Protein/metabolism , Cadherins/metabolism , Catenins/genetics , CpG Islands , Genes, p16 , Humans , Methylation , Phosphorylation , Promoter Regions, Genetic , Protein Binding , Signal Transduction/genetics , Transcription Factor 4 , beta Catenin/metabolism , Delta CateninABSTRACT
Presenilin1 (PS1) is a component of the gamma-secretase complex mutated in cases of Familial Alzheimer's disease (FAD). PS1 is synthesized as a 50 kDa peptide subsequently processed to two 29 and 20 kDa subunits that remain associated. Processing of PS1 is inhibited by several mutations detected in FAD patients. PS1 acts as negative modulator of beta-catenin.Tcf-4 transcriptional activity. In this article we show that in murine embryonic fibroblasts (MEFs) the mechanisms of action of the processed and non-processed forms of PS1 on beta-catenin.Tcf-4 transcription are different. Whereas non-processed PS1 inhibits beta-catenin.Tcf-4 activity through a mechanism independent of gamma-secretase and associated with the interaction of this protein with plakoglobin and Tcf-4, the effect of processed PS1 is prevented by gamma-secretase inhibitors, and requires its interaction with E- or N-cadherin and the generation of cytosolic terminal fragments of these two cadherins, which in turn destabilize the beta-catenin transcriptional cofactor CBP. Accordingly, the two forms of PS1 interact differently with E-cadherin or beta-catenin and plakoglobin: whereas processed PS1 binds E-cadherin with high affinity and beta-catenin or plakoglobin weakly, the non-processed form behaves inversely. Moreover, contrarily to processed PS1, that decreases the levels of c-fos RNA, non-processed PS1 inhibits the expression c-myc, a known target of beta-catenin.Tcf-4, and does not block the activity of other transcriptional factors requiring CBP. These results indicate that prevention of PS1 processing in FAD affects the mechanism of repression of the transcriptional activity dependent on beta-catenin.
Subject(s)
Amyloid Precursor Protein Secretases/metabolism , Presenilin-1/metabolism , TCF Transcription Factors/genetics , Transcription, Genetic , beta Catenin/metabolism , Alzheimer Disease/genetics , Alzheimer Disease/metabolism , Animals , Cell Proliferation , Cells, Cultured , Humans , Mice , TCF Transcription Factors/metabolism , Transfection , beta Catenin/geneticsABSTRACT
INTRODUCTION: Comorbidity between epilepsy and cancer is elevated. As a life-time condition, it is not impossible for a patient with epilepsy to have a cancer at some point. Besides, at least 30% of patients with primary brain tumors have epileptic seizures, but also in patients with metastatic infiltrating lesions of the central nervous system and with extracerebral tumors, epilepsy can be related. Seizures may also appear associated with paraneoplastic syndromes, such as limbic encephalitis and metabolic and infectious complications of chemotherapy and radiotherapy. RESULTS: The precise mechanisms by which brain tumors and the other conditions mentioned above produce seizures are not fully understood, but are reviewed in this article, as well as the many different therapeutic options that may be used in the treatment of epileptic seizures. Pharmacological treatment poses various controversies, such as the utility of prophylactic treatment, interactions between antiepileptic drugs (AEDs) and chemotherapeutic drugs and the complications derived from the adverse effects of AEDs in this population. Finally, other treatments are proposed such as chemotherapy, radiotherapy and surgery, the rational application of which allows for an improvement in the patients' quality of life. CONCLUSION: In order to arrive at a diagnosis, the different causes that could condition the appearance of epileptic seizures in cancer patients must be known. After this, the most adequate treatment should be chosen, thus ensuring the comprehensive treatment of cancer and epilepsy.
