Differential interactions between transforming growth factor-β3/ TβR1, TAB1, and CD2AP disrupt blood-testis barrier and sertoli-germ cell adhesion

The biochemical basis that regulates the timely and selective opening of the blood-testis barrier (BTB) to migrating preleptotene/leptotene spermatocytes at stage VIII of the epithelial cycle in adult rat testes is virtually unknown. Recent studies have shown that cytokines (e.g. transforming growth factor (TGF)-β3) may play a crucial role in this event. However, much of this information relies on the use of toxicants (e.g. CdCl 2), making it difficult to relay these findings to normal testicular physiology. Here we report that overexpression of TGF-β3 in primary Sertoli cells cultured in vitro indeed perturbed the tight junction (TJ) barrier with a concomitant decline in the production of BTB constituent proteins as follows: occludin, N-cadherin, and ZO-1. Additionally, local administration of TGF-β3 to testes in vivo was shown to reversibly perturb the BTB integrity and Sertoli-germ cell adhesion via the p38 MAPK and ERK signaling pathways. Most importantly, the simultaneous activation of p38 and ERK signaling pathways is dependent on the association of the TGF-β3-TβR1 complex with adaptors TAB1 and CD2AP because if TβR1 was associated preferentially with CD2AP, only Sertoli-germ cell adhesion was perturbed without compromising the BTB. Collectively, these data illustrate that local production of TGF-β3, and perhaps other TGF-βs and cytokines, by Sertoli and germ cells into the microenvironment at the BTB during spermatogenesis transiently perturbs the BTB and Sertoli-germ cell adhesion to facilitate germ cell migration when the activated TβRI interacts with adaptors TAB1 and CD2AP. However, TGF-β3 selectively disrupts Sertoli-germ cell adhesion in the seminiferous epithelium to facilitate germ cell migration without compromising BTB when TβRI interacts only with adaptor CD2AP. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc.postprin

Unraveling the molecular targets pertinent to junction restructuring events during spermatogenesis using the Adjudin-induced germ cell depletion model

During spermatogenesis, extensive restructuring takes place at the Sertoli-Sertoli and Sertoli-germ cell interface, which is regulated via intriguing interactions among cytokines, proteases, protease inhibitors, kinases, phosphatases, and transcription factors. This in turn determines the steady-state levels of integral membrane proteins at the cell junctions. We sought to further expand these observations using the Adjudin model. Adjudin is a potential male contraceptive that targets Sertoli-germ cell adhesion, causing exfoliation of spermatids and spermatocytes, but not spermatogonia, from the seminiferous epithelium. This model thus provides the means to identify crucial regulatory molecules and signaling pathways pertinent to junction restructuring events during spermatogenesis. In this study, genome-wide expression profiling of rat testes after treatment with Adjudin at the time of extensive junction restructuring was performed. Differentially regulated genes, such as cytokines, proteases, protease inhibitors, cell junction-associated proteins, and transcription factors pertinent to junction restructuring were identified. These data were consistent with earlier findings; however, much new information was obtained which has been deposited at the Gene Expression Omnibus data repository website: http://www.ncbi.nih.gov/geo/ with Accession number: GSE5131. The primary signaling events pertinent to junction restructuring in the testis induced by Adjudin were also delineated using bioinformatics. These findings were also consistent with recently published reports. The identified molecular signatures or targets pertinent to junction dynamics in the testis as reported herein, many of which have not been investigated, thus offer a framework upon which the regulation of junction restructuring events at the Sertoli-Sertoli and Sertoli-germ cell interface pertinent to spermatogenesis can be further studied.postprin

Cytokines and junction restructuring during spermatogenesis - A lesson to learn from the testis

In the mammalian testis, preleptotene and leptotene spermatocytes residing in the basal compartment of the seminiferous epithelium must traverse the blood-testis barrier (BTB) at late stage VIII through early stage IX of the epithelial cycle during spermatogenesis, entering the adluminal compartment for further development. However, until recently the regulatory mechanisms that regulate BTB dynamics remained largely unknown. We provide a critical review regarding the significance of cytokines in regulating the 'opening' and 'closing' of the BTB. We also discuss how cytokines may be working in concert with adaptors that selectively govern the downstream signaling pathways. This process, in turn, regulates the dynamics of either Sertoli-Sertoli tight junction (TJ), Sertoli-germ cell adherens junction (AJ), or both junction types in the epithelium, thereby permitting TJ opening without compromising AJs, and vice versa. We also discuss how adaptors alter their protein-protein association with the integral membrane proteins at the cell-cell interface via changes in their phosphorylation status, thereby altering adhesion function at AJ. These findings illustrate that the testis is a novel in vivo model to study the biology of junction restructuring. Furthermore, a molecular model is presented regarding how cytokines selectively regulate TJ/AJ restructuring in the epithelium during spermatogenesis. © 2005 Elsevier Ltd. All rights reserved.postprin

Decision support for personalized cloud service selection through multi-attribute trustworthiness evaluation

Facing a customer market with rising demands for cloud service dependability and security, trustworthiness evaluation techniques are becoming essential to cloud service selection. But these methods are out of the reach to most customers as they require considerable expertise. Additionally, since the cloud service evaluation is often a costly and time-consuming process, it is not practical to measure trustworthy attributes of all candidates for each customer. Many existing models cannot easily deal with cloud services which have very few historical records. In this paper, we propose a novel service selection approach in which the missing value prediction and the multi-attribute trustworthiness evaluation are commonly taken into account. By simply collecting limited historical records, the current approach is able to support the personalized trustworthy service selection. The experimental results also show that our approach performs much better than other competing ones with respect to the customer preference and expectation in trustworthiness assessment. © 2014 Ding et al

Disruption of Sertoli-germ cell adhesion function in the seminiferous epithelium of the rat testis can be limited to adherens junctions without affecting the blood-testis barrier integrity: An in vivo study using an androgen suppression model

During spermatogenesis, both adherens junctions (AJ) (such as ectoplasmic specialization (ES), a testis-specific AJ type at the Sertoli cell-spermatid interface (apical ES) or Sertoli-Sertoli cell interface (basal ES) in the apical compartment and BTB, respectively) and tight junctions (TJ) undergo extensive restructuring to permit germ cells to move across the blood-testis barrier (BTB) as well as the seminiferous epithelium from the basal compartment to the luminal edge to permit fully developed spermatids (spermatozoa) to be sloughed at spermiation. However, the integrity of the BTB cannot be compromised throughout spermatogenesis so that postmeiotic germ cell-specific antigens can be sequestered from the systemic circulation at all times. We thus hypothesize that AJ disruption in the seminiferous epithelium unlike other epithelia, can occur without compromising the BTB-barrier, even though these junctions, namely TJ and basal ES, co-exist side-by-side in the BTB. Using an intratesticular androgen suppression-induced germ cell loss model, we have shown that the disruption of AJs indeed was limited to the Sertoli-germ cell interface without perturbing the BTB. The testis apparently is using a unique physiological mechanism to induce the production of both TJ- and AJ-integral membrane proteins and their associated adaptors to maintain BTB integrity yet permitting a transient loss of cell adhesion function by dissociating N-cadherin from β-catenin at the apical and basal ES. The enhanced production of TJ proteins, such as occludin and ZO-1, at the BTB site can supersede the transient loss of cadherin-catenin function at the basal ES. This thus allows germ cell depletion from the epithelium without compromising BTB integrity. It is plausible that the testis is using this novel mechanism to facilitate the movement of preleptotene and leptotene spermatocytes across the BTB at late stage VIII through early stage IX of the epithelial cycle in the rat while maintaining the BTB immunological barrier function. © 2005 Wiley-Liss, Inc.postprin

Regulation of ectoplasmic specialization dynamics in the seminiferous epithelium by focal adhesion-associated proteins in testosterone-suppressed rat testes

Apical ectoplasmic specialization (ES) is a unique testis-specific cell-cell actin-based adherens junction type restricted to the Sertoli-round/elongating/elongate spermatid interface in the seminiferous epithelium. An endogenous testosterone (T) suppression model was used to study the regulation of apical ES dynamics in the testis. By providing sustained releases of T and estradiol using subdermal implants in rats, this treatment reduced endogenous testicular T level. This in turn led to sloughing of spermatids (step 8 and beyond) from the seminiferous epithelium, which can be reversed by removing the implants, or replacing them with a higher dose of T implants. This model thus allows us to study the restructuring events at the apical ES. It was shown that apical ES restructuring involved proteins that were usually restricted to the cell-matrix focal adhesion site in other epithelia. For instance, the protein levels of β1-integrin, Tyr-phosphorylated focal adhesion kinase (p-FAK), and c-Src were induced during the T suppression-induced germ cell loss and recovery, implicating that these proteins are putative regulators of ES dynamics. Indeed, the formation of p-FAK/c-Src protein complex, but not their association with β1-integrin, was stimulated during T suppression-induced germ cell loss. ERK, a MAPK known to regulate focal adhesion turnover, was also activated during the androgen suppression-induced spermatid loss and the early phase of the recovery when germ cells began to repopulate the epithelium. Collectively, these data suggest that the apical ES is a cell-cell adherens junction type with the characteristics of cell-matrix focal contacts. In addition to its role in conferring cell adhesion formation, the p-FAK/c-Src protein complex apparently also regulates apical ES disruption via the ERK signaling pathway.postprin

Dictionary Learning and Sparse Coding-based Denoising for High-Resolution Task Functional Connectivity MRI Analysis

We propose a novel denoising framework for task functional Magnetic Resonance Imaging (tfMRI) data to delineate the high-resolution spatial pattern of the brain functional connectivity via dictionary learning and sparse coding (DLSC). In order to address the limitations of the unsupervised DLSC-based fMRI studies, we utilize the prior knowledge of task paradigm in the learning step to train a data-driven dictionary and to model the sparse representation. We apply the proposed DLSC-based method to Human Connectome Project (HCP) motor tfMRI dataset. Studies on the functional connectivity of cerebrocerebellar circuits in somatomotor networks show that the DLSC-based denoising framework can significantly improve the prominent connectivity patterns, in comparison to the temporal non-local means (tNLM)-based denoising method as well as the case without denoising, which is consistent and neuroscientifically meaningful within motor area. The promising results show that the proposed method can provide an important foundation for the high-resolution functional connectivity analysis, and provide a better approach for fMRI preprocessing.Comment: 8 pages, 3 figures, MLMI201

Regulation of sertoli-germ cell adherens junction dynamics via changes in protein-protein interactions of the N-cadherin-β-catenin protein complex which are possibly mediated by c-Src and myotubularin-related protein 2: An in vivo study using an androgen suppression model

Using a well characterized model of cell-cell actin-based adherens junction (AJ) disruption by suppressing the intratesticular testosterone level in adult rats with testosterone-estradiol implants, we have confirmed earlier findings that Sertoli-germ cell AJ dynamics are regulated by the activation of kinases via putative signaling pathways but with some unexpected findings as follows. First, the loss of germ cells from the seminiferous epithelium during androgen suppression was associated with a surge in myotubularin-related protein 2 (MTMR2, a lipid phosphatase, in which adult MTMH2-/- mice were recently shown to be azoospermic because of the loss of cell adhesion function between germ and Sertoli cells); kinases: phosphatidylinositol 3-kinase, c-Src, and C-terminal Src kinase; adaptors: α-actinin, vinculin, afadin, and p130 Crk-associated protein; and AJ-integral membrane proteins at the ectoplasmic specialization (ES, a testis-specific cell-cell actin-based AJ type) site: N-cadherin, β-catenin, integrin β1, and nectin 3. Second, MTMR2, instead of structurally interacting with phosphatidylinositol 3-kinase, a protein and lipid kinase, was shown to associate only with c-Src, a nonreceptor protein tyrosine kinase, as demonstrated by both coimmunoprecipitation and fluorescent microscopy at the site of apical ES, but none of the kinases, adaptors, and AJ-infegral proteins that were examined. Collectively, these results suggest that the MTMR2/c-Src is an important phosphatase/kinase protein pair in AJ dynamics in the testis. Because c-Src is known to associate with the cadherin/catenin protein complex at the ES in the testis, we next sought to investigate any changes in the protein-protein interactions of this protein complex during androgen suppression-induced germ cell loss. Indeed, there was a loss of N-cadherin and β-catenin association, accompanied by a surge in Tyr phosphorylation of β-catenin, during germ cell loss from the epithelium. Third, and perhaps the most important of all, during natural recovery of the epithelium after removal of testosterene-estradiol implants when spermatids were reattaching to Sertoli cells, an increase in N-cadherin and β-catenin association was detected with a concomitant loss in the increased Tyr phosphorylation in β-catenin. In summary, these results illustrate that the cadherin/catenin is a crucial cell adhesion complex that regulates AJ dynamics in the testis, and its functionality is likely modulated by the MTMR2/c-Src protein complex.postprin

Simulation of an Optional Strategy in the Prisoner's Dilemma in Spatial and Non-spatial Environments

This paper presents research comparing the effects of different environments on the outcome of an extended Prisoner's Dilemma, in which agents have the option to abstain from playing the game. We consider three different pure strategies: cooperation, defection and abstinence. We adopt an evolutionary game theoretic approach and consider two different environments: the first which imposes no spatial constraints and the second in which agents are placed on a lattice grid. We analyse the performance of the three strategies as we vary the loner's payoff in both structured and unstructured environments. Furthermore we also present the results of simulations which identify scenarios in which cooperative clusters of agents emerge and persist in both environments.Comment: 12 pages, 8 figures. International Conference on the Simulation of Adaptive Behavio

A transient homotypic interaction model for the influenza A virus NS1 protein effector domain

Influenza A virus NS1 protein is a multifunctional virulence factor consisting of an RNA binding domain (RBD), a short linker, an effector domain (ED), and a C-terminal 'tail'. Although poorly understood, NS1 multimerization may autoregulate its actions. While RBD dimerization seems functionally conserved, two possible apo ED dimers have been proposed (helix-helix and strand-strand). Here, we analyze all available RBD, ED, and full-length NS1 structures, including four novel crystal structures obtained using EDs from divergent human and avian viruses, as well as two forms of a monomeric ED mutant. The data reveal the helix-helix interface as the only strictly conserved ED homodimeric contact. Furthermore, a mutant NS1 unable to form the helix-helix dimer is compromised in its ability to bind dsRNA efficiently, implying that ED multimerization influences RBD activity. Our bioinformatical work also suggests that the helix-helix interface is variable and transient, thereby allowing two ED monomers to twist relative to one another and possibly separate. In this regard, we found a mAb that recognizes NS1 via a residue completely buried within the ED helix-helix interface, and which may help highlight potential different conformational populations of NS1 (putatively termed 'helix-closed' and 'helix-open') in virus-infected cells. 'Helix-closed' conformations appear to enhance dsRNA binding, and 'helix-open' conformations allow otherwise inaccessible interactions with host factors. Our data support a new model of NS1 regulation in which the RBD remains dimeric throughout infection, while the ED switches between several quaternary states in order to expand its functional space. Such a concept may be applicable to other small multifunctional proteins