The RalB Small GTPase Mediates Formation of Invadopodia through a GTPase-Activating Protein-Independent Function of the RalBP1/RLIP76 Effector

Our recent studies implicated key and distinct roles for the highly related RalA and RalB small GTPases (82% sequence identity) in pancreatic ductal adenocarcinoma (PDAC) tumorigenesis and invasive and metastatic growth, respectively. How RalB may promote PDAC invasion and metastasis has not been determined. In light of known Ral effector functions in regulation of actin organization and secretion, we addressed a possible role for RalB in formation of invadopodia, actin-rich membrane protrusions that contribute to tissue invasion and matrix remodeling. We determined that a majority of KRAS mutant PDAC cell lines exhibited invadopodia and that expression of activated K-Ras is both necessary and sufficient for invadopodium formation. Invadopodium formation was not dependent on the canonical Raf-MEK-ERK effector pathway and was instead dependent on the Ral effector pathway. However, this process was more dependent on RalB than on RalA. Surprisingly, RalB-mediated invadopodium formation was dependent on RalBP1/RLIP76 but not Sec5 and Exo84 exocyst effector function. Unexpectedly, the requirement for RalBP1 was independent of its best known function as a GTPase-activating protein for Rho small GTPases. Instead, disruption of the ATPase function of RalBP1 impaired invadopodium formation. Our results identify a novel RalB-mediated biochemical and signaling mechanism for invadopodium formation

Reduced T-cell receptor CD3ζ-chain protein and sustained CD3ε expression at the site of mycobacterial infection

Control of mycobacterial infection by the cellular immune system relies both on antigen-presenting cells and on T lymphocytes. The quality of an effective cellular immune response is dependent on functional signal transduction residing in the cytoplasmic tails of the T-cell receptor CD3 components. In order to investigate potential effects of mycobacteria on T-cell receptor signalling, we examined the protein expression of T-cell signal transduction molecules (CD3ζ, ZAP-70, p59(fyn), p56(l ck)). In Western blots of peripheral blood mononuclear cells of Mycobacterium tuberculosis infected patients, only the CD3ζ-chain showed a marked reduction in protein expression. To investigate the situation in situ, immunoenzymatic and immunofluorescence stainings for CD3ε and CD3ζ expression were performed on sections of normal lymphoid tissue, M. leprae infected and sarcoid tissue. CD3ε and CD3ζ expression were similar with respect to intensity, localization and the number of cells stained in normal lymphoid tissue and in sarcoid granulomas. In contrast, the granulomas of M. leprae infected tissues showed a significantly reduced expression of CD3ζ compared to CD3ε. Using double immunofluorescence analysis, virtually no CD3ζ expression could be detected in comparison to the CD3ε expression in the lesions. Apparently, mycobacteria are capable of significantly reducing CD3ζ-chain expression, which may be restored by cytokines. IL-2-enhanced ζ-chain expression and T-cell effector functions, defined by interferon-γ release, in M. tuberculosis-specific and human leucocyte antigen-DR restricted CD4(+) T cells isolated from granuloma lesions from patients with pulmonary tuberculosis. Because CD3ζ is essential for CD3 signalling and for eliciting T-cell effector functions, reduced CD3ζ protein expression could result in altered signal transduction and inefficient T-cell effector functions. Alternatively, reduced CD3ζ-chain expression may protect T cells from repetitive TCR stimulation associated with anergy or apoptosis

Parental support and enjoyment of learning in mathematics: Does change in parental support predict change in enjoyment of learning?

Positive and negative emotions are ubiquitous in everyday school life, and can foster or impair processes of learning and achievement. However, learning- and achievement-related emotions are not based solely on experiences from respective situations in the school context. Rather, experiences outside of school, e.g. learning at home, are also important. The present study focused on the importance of perceived parental support for children’s enjoyment of learning in the subject of mathematics. We were interested in the following two characteristics of perceived parental support: perceived parental control, in the sense of intrusive parental support, and perceived parental structure, in the sense of clarity of parents’ learning-related expectations. The central question concerned the predictive effects of intraindividual changes in perceived parental control and perceived parental structure with respect to intraindividual changes in enjoyment of learning. This issue was tested by means of a latent change model. Data were analyzed of 396 children (six measurement time points from the sixth to the eighth school year). The results showed the expected indirect positive effects of intraindividual changes in perceived parental structure, and indirect negative effects of intraindividual changes in perceived parental control, with regard to intraindividual changes in enjoyment of learning. In both cases, intraindividual changes in control beliefs and value beliefs acted as mediating variables