Tyrosine phosphorylation of 3BP2 is indispensable for the interaction with VAV3 in chicken DT40 cells

Adaptor protein c-Abl SH3 domain-binding protein-2 (3BP2) is known to play regulatory roles in immunoreceptor-mediated signal transduction. We have previously demonstrated that Tyr¹⁷⁴, Tyr¹⁸³ and Tyr⁴⁴⁶ in mouse 3BP2 are predominantly phosphorylated by Syk, and the phosphorylation of Tyr¹⁸³ and the Src homology 2 (SH2) domain of mouse 3BP2 are critical for B cell receptor (BCR)-induced activation of nuclear factor of activated T cells (NFAT) in human B cells. In this report, we have shown that Syk, but not Abl family protein-tyrosine kinases, is critical for BCR-mediated tyrosine phosphorylation of 3BP2 in chicken DT40 cells. Mutational analysis showed that Tyr¹⁷⁴, Tyr¹⁸³ and Tyr⁴²⁶ of chicken 3BP2 are the major phosphorylation sites by Syk and the SH2 domain of 3BP2 is critical for tyrosine phosphorylation. In addition, phosphorylation of Tyr⁴²⁶ is required for the inducible interaction with the SH2 domain of Vav3. Moreover, the expression of the mutant form of 3BP2 in which Tyr⁴²⁶ was substituted to Phe resulted in the reduction in BCR-mediated Rac1 activation, when compared with the case of wild-type. Altogether, these data suggest that 3BP2 is involved in the activation of Rac1 through the regulation of Vav3 by Syk-dependent phosphorylation of Tyr⁴²⁶ following BCR stimulation.     

Down-regulation of miR-199b associated with imatinib drug resistance in 9q34.1 deleted BCR/ABL positive CML patients

Chronic myeloid leukemia (CML) occurs due to t(9,22) (q34;q11) and molecularly BCR/ABL gene fusion. About 15–18% Philadelphia positive CML patients have gene deletions around the translocation breakpoints on 9q34.1. The microRNAs (miRNAs), namely miR-219-2 and miR-199b, centromeric to the ABL1 gene are frequently lost in CML patients. We have designed a study to determine miR-219-2 and miR-199b expression levels which would help to understand the prognosis of imatinib therapy. A total of 150 CML patients were analyzed to identify 9q deletion. Fluorescent in-situ hybridization (FISH) was performed using BCR/ABL dual color, dual fusion probe to study the signal pattern and BAC probes for miR-199b and miR-219-2 (RP11-339B21 and RP11-395P17) to study the miRNA deletions. The expression level of miRNA was analyzed by real-time polymerase chain reaction (RT-PCR). FISH analysis revealed 9q34.1 deletion in 34 (23%) CML patients. The deletions were not detected using BAC probes for miRNAs in 9q deleted patients. The expression analysis showed down-regulation of miR-199b and miR-219-2 in the 9q deleted patients (34 CML) as compared to a pool of patients without deletion. However, miR-199b (9q34.11) was significantly (p = 0.001) down-regulated compared to miR-219-2. The follow-up study showed that the miR-199b was found to be strongly associated with imatinib resistance, as 44.11% patients showed resistance to imatinib therapy. Hence, the deletion in 9q34.1 region (ABL) plays an important role in disease pathogenesis. Eventually, miRNAs can provide new therapeutic strategies and can be used as a prognostic indicator.     

B淋巴细胞活化分子事件及相关病理机制

B细胞是体液免疫的重要执行细胞,其活化是机体产生保护性抗体的关键步骤.目前人们对B细胞早期活化的动态分子事件和信号起始机制等仍然未知.本文将重点总结超高清成像技术和高速高分辨率活体成像技术在B细胞领域的应用,这些研究将帮助人们理解B细胞早期活化的机制.本文系列总结了静息态下维持B细胞存活的B细胞受体(B cell receptor,BCR)滋养信号的研究进展,并提出了滋养信号来源的几种可能的模型.描述了抗原刺激导致的BCR活化的信号通路,并重点探讨了成像技术进步带来的关于BCR信号通路起始的机制探索这一免疫学领域的重大问题.结合高速高分辨率活细胞成像技术在免疫学领域的应用,抗原刺激后BCR活化过程中一系列动态变化过程和高级结构的形成能够被实时捕获.此外,还探讨了B细胞记忆性免疫发生的机制,重点阐述了亲和力成熟和BCR亚型转换,尤其是IgG(Immunoglobulin G)型BCR胞内尾巴对快速强烈的记忆性免疫反应的帮助.B细胞活化机制的调节过程发生异常会破坏正常的B细胞稳态平衡和免疫疾病的发生,本文总结抑制性调节受体FcγRIIB(Fcγreceptor IIB)突变与自身免疫病的关系,以及BCR信号通路信号分子突变与B细胞肿瘤的关系,这些研究将加深人们对B细胞免疫疾病的认识和相应医疗手段的改进.     

Characterization of Heavy Metal Fractions in Agricultural Soils by Sequential Extraction Procedure: The Relationship Between Soil Properties and Heavy Metal Fractions

The present research was conducted to determine heavy metals in agricultural soils from Çanakkale, Turkey, using a sequential extraction procedure (acid soluble, reducible, oxidizable, and residual) as proposed by the Community Bureau of Reference (BCR) of the European Commission. Soil samples were taken from 12 different cultivated sites and analyzed for Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn concentrations. The results revealed an order of Mn > Cd > Pb > Co > Ni > Cu > Zn > Cr for the heavy metals based on the sum of the first three fractions (acid soluble + reducible + oxidizable). The relationships between soil properties and each metal fraction were identified through Pearsons's correlation analysis. Hierarchical cluster analysis was performed to determine the behaviors and similarities of metals in each fraction. While Mn, Pb, and Zn exhibited subjective behaviors in the acid-soluble fraction, Cd, Co, Cu, Cr, and Ni exhibited similar behaviors with each other.     

Salarin C inhibits the maintenance of chronic myeloid leukemia progenitor cells

We previously showed that incubation of chronic myeloid leukemia (CML) cells in very low oxygen selects a cell subset where the oncogenetic BCR/Abl protein is suppressed and which is thereby refractory to tyrosine kinase inhibitors used for CML therapy. In this study, salarin C, an anticancer macrolide extracted from the Fascaplysinopsis sponge, was tested as for its activity on CML cells, especially after their incubation in atmosphere at 0.1% oxygen. Salarin C induced mitotic cycle arrest, apoptosis and DNA damage. Salarin C also concentration-dependently inhibited the maintenance of stem cell potential in cultures in low oxygen of either CML cell lines or primary cells. Surprisingly, the drug also concentration-dependently enforced the maintenance of BCR/Abl signaling in low oxygen, an effect which was paralleled by the rescue of sensitivity of stem cell potential to IM. These results suggest a potential use of salarin C for the suppression of CML cells refractory to tyrosine kinase inhibitors     

A new mutation that predicted a drastic alteration of the BTK protein function

X-linked agammaglobulinemia (XLA) or Bruton disease is a relatively rare constitutionally immune disorder due to a genetic mutation of BTK (Bruton tyrosine kinase) gene which encodes for BTK protein. BTK is a signal-transducing protein expressed in hematopoietic lineages. The genetic disorder is responsible for B cell lymphocytes' maturation arrest. The humoral immunodeficiency caused by BTK mutation is linked with recurrent bacterial and viral infections. Genetic investigations of the prepositus as well as the other members of the family are necessary to characterize a mutation in BTK gene to confirm the diagnosis and reveal a hereditary transmission or de novo mutation.