EBF1-JAK2 inhibits the PAX5 function through physical interaction with PAX5 and kinase activity

Gene aberrations of B-cell regulators and growth signal components such as the JAK-STAT pathway are frequently found in B-cell acute lymphoblastic leukemia (B-ALL). EBF1 is a B-cell regulator that regulates the expression of PAX5 and co-operates with PAX5 to regulate B-cell differentiation. Here, we analyzed the function of the fusion protein of EBF1 and JAK2, EBF1-JAK2 (E-J). E-J caused constitutive activation of JAK-STAT and MAPK pathways and induced autonomous cell growth in a cytokine-dependent cell line. E-J did not affect the transcriptional activity of EBF1 but inhibited that of PAX5. Both the physical interaction of E-J with PAX5 and kinase activity of E-J were required for E-J to inhibit PAX5 function, although the detailed mechanism of inhibition remains unclear. Importantly, gene set enrichment analysis using the results of our previous RNA-seq data of 323 primary BCR-ABL1-negative ALL samples demonstrated repression of the transcriptional target genes of PAX5 in E-J-positive ALL cells, which suggests that E-J also inhibited PAX5 function in ALL cells. Our results shed new light on the mechanisms of differentiation block by kinase fusion proteins.

Essential role of a carboxyl-terminal α-helix motif in the secretion of coagulation factor XI

BACKGROUND

Coagulation factor XI (FXI) is a plasma serine protease zymogen that contributes to hemostasis. However, the mechanism of its secretion remains unclear.

OBJECTIVE

To determine the molecular mechanism of FXI secretion by characterizing a novel FXI mutant identified in a FXI-deficient Japanese patient.

PATIENT/METHODS

The FXI gene (F11) was analyzed by direct sequencing. Mutant recombinant FXI (rFXI) was overexpressed in HEK293 or COS-7 cells. Western blotting and enzyme-linked immunosorbent assay were performed to examine the FXI extracellular secretion profile. Immunofluorescence microscopy was used to investigate the subcellular localization of the rFXI mutant.

RESULTS

We identified a novel homozygous frameshift mutation in F11 [c.1788dupC (p.E597Rfs*65)], resulting in a unique and extended carboxyl-terminal (C-terminal) structure in FXI. Although rFXI-E597Rfs*65 was intracellularly synthesized, its extracellular secretion was markedly reduced. Subcellular localization analysis revealed that rFXI-E597Rfs*65 was abnormally retained in the endoplasmic reticulum (ER). We generated a series of C-terminal-truncated rFXI mutants to further investigate the role of the C-terminal region in FXI secretion. Serial rFXI experiments revealed that a threonine at position 622, the fourth residue from the C-terminus, was essential for secretion. Notably, Thr622 engages in the formation of an α-helix motif, indicating the importance of the C-terminal α-helix in FXI intracellular behavior and secretion.

CONCLUSION

FXI E597Rfs*65 results in the pathogenesis of a severe secretory defect resulting from aberrant ER-to-Golgi trafficking caused by the lack of a C-terminal α-helix motif. This study demonstrates the impact of the C-terminal structure, especially the α-helix motif, on FXI secretion.

Direct and indirect stimulation of megakaryocytopoiesis by TAN-1511 A, a microbial lipopeptide

TAN-1511 A, a microbial lipopeptide, stimulates granulocytopoiesis through the induction of various hematopoietic cytokines. The ability of synthetic TAN-1511 A to affect megakaryocytopoiesis was examined. TAN-1511. A augmented the activity of acetylcholine esterase (AChE), which is a cell-lineage marker enzyme of megakaryocytes in cultured murine bone marrow cells and enhanced megakaryocyte colony formation in fibrin clot culture. These effects were observed not only in the presence, but also in the absence of IL-3, which is a megakaryocyte colony-stimulating factor. The increase in AChE activity mediated by TAN-1511 A was blocked by anti-IL-6 but not anti-IL-3 or anti-GM-CSF neutralizing antibodies. RT-PCR analysis also showed that the remarkable induction of IL-6 was triggered by treatment with TAN-1511 A, while each message level of c-mpl ligand and c-mpl remained unchanged, suggesting that the IL-6 induced by the lipopeptide plays a role in enhanced megakaryocytopoiesis. TAN-1511 A also stimulated the proliferation of CMK86, a human megakaryoblastic cell line. This promoted growth was partially and additively affected by anti-IL-3, anti-IL-6, and anti-GM-CSF antibodies. TAN-1511 A slightly reduced the expression of GpIb and GpIIb/IL1a in CMK86 cells. The enhanced platelet recovery mediated by TAN-1511 A was also demonstrated in a model of myelosuppressive mice. These results suggest that TAN-1511 A directly affects megakaryocytopoiesis, and indirectly modulates megakaryocytopoiesis through the induction of cytokines such as IL-6.

Hepatocyte growth factor is a potent promoter of mitogenesis in cultured rat visceral glomerular epithelial cells

Hepatocyte growth factor (HGF) was originally identified as an hepatotrophic factor inducing liver regeneration, and was also recently found to stimulate mitogenesis of various epithelial cells. In the present study, we examined the mitogenic effects of native and recombinant HGF on cells of rat visceral glomerular epithelial cell line (SGE1). Native and recombinant HGF each stimulated DNA synthesis in and growth of SGE1 cells to a remarkable degree. These mitogenic activities were dose-dependent, being detectable at 2.5 ng/ml and maximal at 20 ng/ml. Over 30% of SGE1 cells tested were shifted to S-phase by HGF alone, as judging by labeling index values. DNA synthesis stimulated by native or recombinant HGF was high at low SGE1 cell density and was strongly suppressed at high cell density. DNA synthesis in and growth of SGE1 cells were stimulated more strongly by recombinant HGF than by native HGF. In addition, the effects of recombinant HGF and epidermal growth factor were additive, while transforming growth factor-beta 1 strongly inhibited the stimulation of DNA synthesis by recombinant HGF. These findings suggest that HGF may play a role in controlling visceral glomerular epithelial cell growth.

Immunocytochemical characterization and identification of SGE1, a rat glomerular epithelial cell line

Glomerular epithelial cells (GEC) in culture facilitate the study of glomerular physiology and pathology. However, characterization and identification of GECs in culture have been difficult due to the absence of markers specific to them. We compared the immunocytochemical characteristics of a rat normal GEC line (SGE1) and glomerular cells from rat kidney sections using a lectin and commercially available and newly raised monoclonal and polyclonal antibodies. Antivimentin, anti-dipeptidyl-peptidase-IV (gp 108) and monoclonal antibody 5-1-6 antibodies and Limax flavus lectin bound to visceral GECs, anticytokeratin antibody and antibody against common acute lymphocytic leukemia antigen bound to parietal GECs, and anti-SGE1 cell membrane and monoclonal antibody PHM 5 antibodies bound to both visceral GECs and parietal GECs in normal rat kidney sections, and all of these antibodies and L. flavus lectin consistently bound to SGE1 cells in culture. The pattern of antigenic expression on SGE1 cells indicates that SGE1 cells possess phenotypic characteristics of visceral GECs and parietal GECs, and it further suggests that SGE1 cells may be stem cells or cells undergoing differentiation.

Retinoic acid enhances the number of epidermal growth factor receptors in rat glomerular epithelial cells in vitro

The renal epithelium appears to be an important target tissue for retinoic acid and epidermal growth factor (EGF). We report here that retinoic acid enhances the proliferative effect of EGF on glomerular epithelial cells (GEC) in vitro and also increases EGF binding to GEC. When GEC were exposed to EGF (> or = 1 ng/ml), cellular DNA synthesis was markedly increased. Moreover, the stimulating effect of EGF was synergistically increased by retinoic acid at 5 micrograms/ml. 125I-EGF binding to cultured GEC was increased approximately 3-fold after addition of retinoic acid to cultures for 48 h. Analysis of 125I-EGF binding revealed 8.1 x 10(4) receptors per control (untreated) cell, while retinoic acid-treated cells demonstrated an increase to 14.3 x 10(4) receptors per cell with no detectable change in receptor affinity. These findings suggest that interactions between retinoic acid and EGF may play an important role in the regulation of GEC growth.

[Circadian rhythm of urinary somatostatin-like immunoreactivity (SLI) and its contents in several organs after oral TRH administration in rats]

Urinary SLI was measured every six hours for twenty four hours in rats fed a regular diet. Previously, we found that the urinary SLI increased after the administration of TRH intravenously. In the present study, in order to reveal the localization of increased SLI, we measured the contents in the hypothalamus, pituitary, thyroid, stomach and pancreas after the oral TRH administration. (1) The rat urinary SLI levels showed a circadian rhythm. The maximum level of SLI was collected from 0.00--6.00 a.m. (89.4 +/- 8.6 pg/6 hrs) (mean +/- SEM). This level was reduced during the daytime 6.00 a.m.--6.00 p.m. The minimum level was obtained from 6.00 p.m.--0.00 a.m. (49.3 +/- 7.2 pg/6 hrs). (2) The rats were decapitated at three and six hours after the oral TRH (500 micrograms/ml) administration. The SLI content was measured by RIA after extraction from each organ with 2.5 ml of 2 M acetic acid. The pituitary SLI content was reduced three hours after the oral TRH administration. The thyroid SLI content was reduced six hours after the oral TRH administration. The hypothalamic, gastric and pancreatic SLI contents didn't change at three and six hours after the oral TRH administration. As the result, the data suggest that augmentation by the oral TRH administration of urinary SLI was caused by its effect on the both the pituitary and the thyroid.

C-19393 S2 and H2, new carbapenem antibiotics. III. Mode of action

Biochemical activities of new carbapenem antibiotics, C-19393 H2(H2) and C-19393 S2(S2), were examined in comparison with those of mecillinam using Escherichia coli. H2 showed remarkably high affinity for penicillin-binding protein (PBP) 2, and high affinity for PBPs 1 and 3. S2 showed high affinity for PBP 2, moderate affinity for PBP 1 and low affinity for PBP 3. They induced ovoid cells at lower concentrations and cell lysis at higher concentrations. The inhibitory potency of H2 for peptidoglycan synthesis was similar to that of mecillinam at lower concentrations up to 0.1 micrograms/ml. At concentrations higher than 0.1 micrograms/ml, the inhibition rate by H2 gradually increased up to 100%, whereas that by mecillinam remained at 60% level. The MICs of H2, S2 and mecillinam corresponded to the lowest concentrations giving 60% of inhibition of peptidoglycan synthesis at which concentrations the function of PBP 2 seemed to be prevented completely. These findings indicate that the primary targets of H2 and S2 are PBP 2 involved in cell shape determination in E. coli.

[Epidemiological studies on the symptoms due to strawberry culture in the vinyl-house. 2. An analysis of clinical examinations with emphasis on allergic response (author's transl)]

Clinical mass surveys were carried out on the residents to whom questionnaires on symptoms with reference to strawberry culture in the vinyl-house had been delivered. Two hundred and eleven persons attended at the first survey in September, 1976 (off the season of strawberry culture) and the 58 attended at the second survey in March, 1977 (within the season). The participants of the first survey consisted of three groups, i.e. farmers with and without strawberry culture and people without farming. The participants of the second survey consisted only of farmers with strawberry culture. Results are summarized as follows. 1) There were no difference of incidence of various clinical findings detected by an ophthalmologist and otolaryngologists among the three groups. 2) There were also no difference of incidence of abnormal findings in urine tests, liver functions, respiratory test, blood examinations and blood pressure test among the three groups. However, the comparison of persons in charge of strawberry culture and attended at both tof the first and the second surveys, such changes were detected as increases in the value of GOT (within normal limits), of stab neutrophiles, lymphocytes and of monocytes within the season of strawberry culture. 3) Increases of positive rates in skintest by extracts of house dust and Candida sp. were observed in the farmers with and without strawberry culture. Positive rates of skintest by strawberry pollen and honey bee extracts among the farmers with strawberry culture were markedly higher than the allergic patients in Dokkyo Hospital having no relation to this culture. This positive rate was markedly elevated among the persons who complained the symptom of rhinorrea within the season.

Regulation of glucosamine utilization in Staphylococcus aureus and Escherichia coli

Glucosamine- or N-acetylglucosamine-requiring mutants of Staphylococcus aureus 209P and Escherichia coli K12, which lack glucosamine-6-phosphate synthetase [2-amino-2-deoxy-D-glucose-6-phosphate ketol-isomerase (amino-transferring); EC 5.3.1.19], were isolated. Growth of these mutants on glucosamine was inhibited by glucose, but growth on N-acetylglucosamine was not. Addition of glucose to mutant cultures growing exponentially on glucosamine inhibited growth and caused death of bacteria, though chloramphenicol prevented death. Uptake of glucosamine by S. aureus and E. coli mutants was severely inhibited by glucose whereas uptake of N-acetylglucosamine was only slightly inhibited. Uptake of glucose was not inhibited by either glucosamine or N-acetylglucosamine. In glucosamine auxotrophs, glucose causes glucosamine deficiency which interrupts cell wall synthesis and results in some loss of viability in the presence of continued protein synthesis.