Rap1a deficiency modifies cytokine responses and MAPK-signaling in vitro and impairs the in vivo inflammatory response.

Rap1, which is closely related to ras, plays a key role in T-cell receptor (TCR)-signaling. TCR-stimulation without costimulation leads to constitutively activated rap1, which may mediate T-cell anergy via inhibition of ras-dependent induction of extracellular signal-regulated kinases (ERK). This activation is mediated by a second protein kinase b-Raf. Rap1-GTP is thought to activate ERK in a ras-independent manner by binding b-raf. Generally, T cells do not express b-raf while they express the adaptor protein raf-1, which is usually sequestered by rap1 leading to inhibition of ras-mediated ERK activation. In this study, we demonstrate that in rap1-deficient T cells, signaling by the ERK and p38 kinases is increased following activation by different stimuli leading to increased intracellular accumulation and secretion of cytokines. In addition, in a hypersensitivity model rap1-deficient mice demonstrated reduced contact dermatitis compared to wildtype mice, demonstrating the impact of rap1-deficiency on the inflammatory response in vivo.

Retrotransposition and mutation events yield Rap1 GTPases with differential signalling capacity.

BACKGROUND: Retrotransposition of mRNA transcripts gives occasionally rise to functional retrogenes. Through acquiring tempero-spatial expression patterns distinct from their parental genes and/or functional mutations in their coding sequences, such retrogenes may in principle reshape signalling networks. RESULTS: Here we present evidence for such a scenario, involving retrogenes of Rap1 belonging to the Ras family of small GTPases. We identified two murine and one human-specific retrogene of Rap1A and Rap1B, which encode proteins that differ by only a few amino acids from their parental Rap1 proteins. Markedly, human hRap1B-retro and mouse mRap1A-retro1 acquired mutations in the 12th and 59th amino acids, respectively, corresponding to residues mutated in constitutively active oncogenic Ras proteins. Statistical and structural analyses support a functional evolution scenario, where Rap1 isoforms of retrogenic origin are functionally distinct from their parental proteins. Indeed, all retrogene-encoded GTPases have an increased GTP/GDP binding ratio in vivo, indicating that their conformations resemble that of active GTP-bound Rap1. We furthermore demonstrate that these three Rap1 isoforms exhibit distinct affinities for the Ras-binding domain of RalGDS. Finally, when tested for their capacity to induce key cellular processes like integrin-mediated cell adhesion or cell spreading, marked differences are seen. CONCLUSIONS: Together, these data lend strong support for an evolution scenario, where retrotransposition and subsequent mutation events generated species-specific Rap1 isoforms with differential signaling potential. Expression of the constitutively active human Rap1B-retro in cells like those derived from Ramos Burkitt's lymphoma and bone marrow from a patient with myelodysplastic syndrome (MDS) warrants further investigation into its role in disease development.

Rap1A-deficient T and B cells show impaired integrin-mediated cell adhesion.

Studies in tissue culture cells have demonstrated a role for the Ras-like GTPase Rap1 in the regulation of integrin-mediated cell-matrix and cadherin-mediated cell-cell contacts. To analyze the function of Rap1 in vivo, we have disrupted the Rap1A gene by homologous recombination. Mice homozygous for the deletion allele are viable and fertile. However, primary hematopoietic cells isolated from spleen or thymus have a diminished adhesive capacity on ICAM and fibronectin substrates. In addition, polarization of T cells from Rap1-/- cells after CD3 stimulation was impaired compared to that of wild-type cells. Despite this, these defects did not result in hematopoietic or cell homing abnormalities. Although it is possible that the relatively mild phenotype is a consequence of functional complementation by the Rap1B gene, our genetic studies confirm a role for Rap1A in the regulation of integrins.

Pre-B-cell transcription factor 1 and steroidogenic factor 1 synergistically regulate adrenocortical growth and steroidogenesis.

A variety of transcription factors including Wilms tumor gene (Wt-1), steroidogenic factor 1 (Sf-1), dosage-sensitive sex reversal, adrenal hypoplasia congenita on the X-chromosome, Gene 1 (Dax-1), and pre-B-cell transcription factor 1 (Pbx1) have been defined as necessary for regular adrenocortical development. However, the role of Pbx1 for adrenal growth and function in the adult organism together with the molecular relationship between Pbx1 and these other transcription factors have not been characterized. We demonstrate that Pbx haploinsufficiency (Pbx1(+/-)) in mice is accompanied by a significant lower adrenal weight in adult animals compared with wild-type controls. Accordingly, baseline proliferating cell nuclear antigen levels are lower in Pbx1(+/-) mice, and unilateral adrenalectomy results in impaired contralateral compensatory adrenal growth, indicating a lower proliferative potential in the context of Pbx1 haploinsufficiency. In accordance with the key role of IGFs in adrenocortical proliferation and development, real-time RT-PCR demonstrates significant lower expression levels of the IGF-I receptor, and up-regulation of IGF binding protein-2. Functionally, Pbx1(+/-) mice display a blunted corticosterone response after ACTH stimulation coincident with lower adrenal expression of the ACTH receptor (melanocortin 2 receptor, Mc2-r). Mechanistically, in vitro studies reveal that Pbx1 and Sf-1 synergistically stimulates Mc2-r promoter activity. Moreover, Sf-1 directly activates the Pbx1 promoter activity in vitro and in vivo. Taken together, these studies provide evidence for a role of Pbx1 in the maintenance of a functional adrenal cortex mediated by synergistic actions of Pbx1 and Sf-1 in the transcriptional regulation of the critical effector of adrenocortical differentiation, the ACTH receptor.

Clinical response to Auron Misheil Therapy in a man with advanced multifocal hepatocellular carcinoma: A case report.

INTRODUCTION: Auron Misheil Therapy was developed based on similarities between carcinogenesis and inflammation. Auron Misheil Therapy is a combination of natural and synthetic compounds, including anti-inflammatory drugs and insulin, expected to exhibit synergistic effects. CASE PRESENTATION: Here, we report the case of a 78-year-old Caucasian male patient who presented with multifocal hepatocellular carcinoma and chronic hepatitis C virus infection. Over a four-year period our patient was treated with radiofrequency ablation and transarterial chemoembolization. After these treatments there was tumor progression, with new hyperperfused lesions without evidence of extrahepatic tumor involvement. Our patient refused sorafenib therapy. Therefore, he received twice daily intramuscular injections of Auron Misheil Therapy on an outpatient basis for two months. Partial remission of the hepatic lesions was observed eight weeks after the start of treatment, and confirmed four weeks later. Unfortunately, at that time our patient refused therapy due to dizziness. During follow-up two target lesions remained stable, but one lesion increased in size. At the latest follow-up, one year later, there was still tumor control. CONCLUSION: While the mechanisms underlying the antitumor effects of Auron Misheil Therapy are not fully understood, stable disease and remissions have been observed in different types of tumors, including hepatocellular carcinoma.

Novel integrin-dependent platelet malfunction in siblings with leukocyte adhesion deficiency-III (LAD-III) caused by a point mutation in FERMT3.

Leukocyte adhesion deficiency-III (LAD-III) also called leukocyte adhesion deficiency-1/variant (LAD1v) is a rare congenital disease caused by defective integrin activation of leukocytes and platelets. Patients with LAD-III present with non-purulent infections and increased bleeding symptoms. We report on a novel integrin-dependent platelet dysfunction in two brothers with LAD-III syndrome caused by a homozygous mutation 1717C>T in the FERMT3 gene leading to a premature stop codon R573X in the focal adhesion protein kindlin-3. Stimulation of patients platelets with all used agonists resulted in a severely decreased binding of soluble fibrinogen indicating a defect in inside-out activation of the integrin alpha(IIb) beta(3) (GPIIb/IIIa). Patients platelets did not respond to the alpha(2)beta(1)-integrin agonist aggretin-A at all. Our data on granula secretion indicate for the first time that the thrombin receptor PAR-4 but not PAR-1 may be important in integrin-triggered granule secretion in response to thrombin. In contrast, collagen mediated platelet granule secretion was not affected in LAD-III-patients. Thus, integrin-signalling may be not essential in collagen-induced granule secretion. The patients' peripheral blood mononuclear cells showed a severe loss of adhesion capacity to VCAM-1 and to endothelial cells compared to cells from healthy donors. Rap-1 activation after PMA stimulation could be observed in controls but not in patients cells. After haematogenesis stem cell transplantation (HSCT) the brothers showed no symptoms of bleeding or immunodeficiency and the integrin-dependent platelet and leukocyte functions normalised.

The Spt-Ada-Gcn5-acetyltransferase complex interaction motif of E2a is essential for a subset of transcriptional and oncogenic properties of E2a-Pbx1.

The oncogene E2a-Pbx1 is formed by the t(1;19) translocation, which joins the N-terminal transactivation domain of E2a with the C-terminal homeodomain of PBX1. The goal of this work was to elucidate the mechanisms by which E2a-Pbx1 can lead to deregulated target gene expression. For reporter constructs it was shown that E2a-Pbx1 can activate transcription through homodimer elements (TGATTGAT) or through heterodimer elements with Hox proteins (e.g. TGATTAAT). We show a novel mechanism by which E2a-Pbx1 activates transcription of EF-9 using a promoter in intron 1 of the EF-9 gene, resulting in an aminoterminal truncated transcript. Our results indicate that the LDFS motif of E2a is essential for the transactivation of EF-9, but dispensable for transactivation of fibroblast growth factor 15. The E2a LDFS motif was also essential for proliferation of NIH3T3 fibroblasts but was dispensable for the E2a-Pbx1-induced differentiation arrest of myeloid progenitors.

PBX1 is dispensable for neural commitment of RA-treated murine ES cells.

Experimentation with PBX1 knockout mice has shown that PBX1 is necessary for early embryogenesis. Despite broad insight into PBX1 function, little is known about the underlying target gene regulation. Utilizing the Cre-loxP system, we targeted a functionally important part of the homeodomain of PBX1 through homozygous deletion of exon-6 and flanking intronic regions leading to exon 7 skipping in embryonic stem (ES) cells. We induced in vitro differentiation of wild-type and PBX1 mutant ES cells by aggregation and retinoic acid (RA) treatment and compared their profiles of gene expression at the ninth day post-reattachment to adhesive media. Our results indicate that PBX1 interactions with HOX proteins and DNA are dispensable for RA-induced ability of ES to express neural genes and point to a possible involvement of PBX1 in the regulation of imprinted genes.

Role of the interdomain linker probed by kinetics of CO ligation to an endothelial nitric oxide synthase mutant lacking the calmodulin binding peptide (residues 503-517 in bovine).

Oxygenase and reductase domains in nitric oxide synthase are linked by a peptide region that binds calmodulin. Here we study the effects of modifying the length of the interdomain linker in a deletion mutant lacking 15 amino acids (residues 503-517) in bovine eNOS. The kinetics of CO ligation with the mutant were determined in the presence and absence of tetrahydrobiopterin and arginine and compared with the CO binding kinetics of wild-type eNOS and the eNOS oxygenase domain. In the mutant, electron flow is interrupted. The association kinetics of CO with both mutant and wild-type eNOS can be approximated with two kinetic phases, but the relative proportions change in the mutant. Both the abrogation of electron flow in the mutant and the differences in CO binding may be explained by an alteration in the docking of the FMN domain to the heme domain. We propose that the calmodulin binding residues form a helix that is critical for the proper alignment of the adjacent reductase and oxygenase domains within the active eNOS dimer in achieving proper electron transfer between them.