Nck,a missing adaptor between the B-cell receptor complex and the BCAP/PI3K/Akt pathway

The signaling pathways activated by the B-cell antigen receptor （BCR）play a crucial role in the development, activation, and differentiation of B cells. Among them, the activation ofphospha- tidylinositol 3-kinase （PI3K）/Akt is par- ticularly important.1-5 The recruitment of PI3K to the plasma membrane is necessary for the generation ofphospha- tidyl-inositol-3,4,5-triphosphate, which activates PDK1 （Akt/PKB kinase）; in turn, PDK1 activates Akt （Figure 1）.     

Src蛋白研究进展

Src is a non - receptor protein tyrosine kinase activated by a number of extracellular signal moleculars. It is recruited to peripheral sites through myristoylation and the SH3 domain. Src initiates intracel-lular signal trandsduction pathways that influence cell adhesion, migration, growth, differentiation and survival though catalytic domain. Src is normally maintained in an inactive conformation because of carboxy terminal Src kinase, but can be activated transiently during cellular events such as mitosis or constitutively by abnormal events such as mutation and some cancers. In additions, c - Sre protein is found to be highly activated and the Src gene is frequently over- expressed in many cancers. These findings suggest that the relationship between c- Src activation/over - expression and cancer progression appears to be significant.     

Expression of the Apoptosis Inhibitor Survivin and its correlation with Thymidine Kinase and Axillary Lymph Node Metastasis in Breast Cancer

1 Introduction Many molecular factors have been demonstrated to interfere with cellular proliferation and programmed cell death. One of these factors is a recently discovered member of the "inhibitor of apoptosis protein(IAP)" called survivin. Survivin is abundantly expressed in most solid and hematologic malignancies, but undetectable in normal adult tissues. Interference with survivin function induces pleiotropic cell-division defects and apoptosis. Cytosolic thymidine kinase (TK) is a marker for proliferating cells and TK is one of several key enzymes involved in DNAmetabolism that phosphorylates thymidine to thymidine mono-phosphate. This study was aimed to detect the expression of suvivin and TK in breast cancer, and to explore a possible relationship between survivin expression and axillary lymph node metastasis.     

Intracellular signals of T cell costimulation

Ligation of T cell receptor （TCR） alone is insufficient to induce full activation of T lymphocytes. Additional ligand-receptor interactions （costimulation） on antigen presenting cells （APCs） and T cells are required. T cell costimulation has been shown to be essential for eliciting efficient T cell responses, involving all phases during T cell development. However, the mechanisms by which costimulation affects the function of T cells still need to be elucidated. In recent years, advances have been made in studies of costimulation as potential therapies in cancer, infectious disease as well as autoimmune disease. In this review, we discussed intracellular costimulation signals that regulate T cell proliferation, cell cycle progression, cytokine production, survival, and memory development. In general, the pathway of phosphoinositide-3 kinase （PI3K）/protein kinase B （PKB, also known as Akt）/nuclear factor κB （NF-κB） might be central to many costimulatory effects. Through these pathways, costimulation controls T-cell expansion and proliferation by maintenance of survivin and aurora B expression, and sustains long-term T-cell survival and memory development by regulating the expression of bcl-2 family members. Cellular ＆ Molecular Immunology. 2008;5（4）：239-247.     

Expression of the Apoptosis Inhibitor Survivin and its correlation with Thymidine Kinase and Axillary Lymph Node Metastasis in Breast Cancer

1 Introduction Many molecular factors have been demonstrated to interfere with cellular proliferation and programmed cell death.One of these factors is a recently discovered member of the “inhibitor of apoptosis protein(IAP)” called survivin. Survivin is abundantly expressed in most solid and hematologic malignancies, but undetectable in normal adult tissues. Interference with survivin function induces pleiotropic cell-division defects and apoptosis. Cytosolic thymidine kinase (TK) is a m…     

Diverse functions of VDUP1 in cell proliferation, differentiation, and diseases

Vitamin D3 up-regulated protein 1 （VDUP1） is a multifunctional protein involved in maintaining cellular homeostasis. VDUP1 is induced by a variety of stresses. Inversely, VDUP1 is often reduced in various tumor tissues and cell lines. Over-expression of VDUP1 inhibits cell proliferation through cell cycle arrest. VDUP1 interacts with thioredoxin （Trx） and negatively regulates the expression and antioxidant function of Trx which is involved in redox regulation. VDUP1/ mice are more susceptible to carcinogenesis than wild-type mice and are defective in establishing immune system induding the development and function of natural killer cells. Furthermore, VDUP1^-/- mice show impaired Kreb cycle-mediated fatty acid utilization. In this review, we have discussed the multifunctional roles of VDUP1 in diverse cellular responses, in particular its relation to proliferation, apoptosis, differentiation, and diseases such as cancer and stress-related diseases.     

糖原合酶激酶-3β信号分子在心肌肥厚中的作用

Glycogen synthase kinase-3β (GSK-3β) is a serine/threonine protein kinase, which takes part not only in glycogen metabolism, but also in cell proliferation, differentiation and apoptosis. GSK-3β is inhibited by growth factors and hypertrophic stimuli through phosphorylation of its N-terminal end serine (Ser9) residue. It is also activated by phosphorylation of its tyrosine (Tyr216) residue. GSK-3β is profoundly inactivated in mice with hypertrophic cardiomyopathy (HCM) and plays a secondary role in myosin heavy chain mutation. However, the role of GSK-3β in HCM was controversial. Recent studies have demonstrated that the activation of GSK-3β inhibits the myocardial hypertrophy, and is regulated by Wnt/Frizzld and PI3-K/Akt signaling pathways. This article introduces the molecular role of glycogen synthase kinase-3β signaling in myocardial hypertrophy and the different pathways on the activity of glycogen synthase kinase-3β (GSK-3β)     

Galectin-3 induces pulmonary artery endothelial cell morphogenesis and angiogenesis

AIM: Increasing evidence suggests that carbohydrate-binding proteins play an essential role in tumor growth and metastasis. Galectin-3,a multifunctional protein of an expanding family of β-galactoside-binding animal lectins,is the major nonintegrin cellular laminin-binding protein,and is implicated in a variety of biologic events,such as inflammation and angiogenesis. Because galectin-3expression was shown to participate in mediating tumor angiogenesis and initiate signaling cascades in several diseases. We hypothesized that galectin-3 may promote pulmonary vascular endothelial neovascularization. METHODS: Hypoxic and MCT rat model of pulmonary artery remodeling was used. The m RNA and protein levels of galectin-3 in rats were measured by in situ hybrization and Western blot analysis. Endothelial cell( EC) proliferation,migration and tube formation were measured using MTT,cell scratch and Matrigel assays,respectively. Protein expression was quantitated by Western blot analysis. LC 3A / B staining was detected with cellular immunofluorescence staining. RESULTS: We found that galectin-3 was localized on the intima and adventitial wall. Galectin-3 was increased after rat hypoxia and MCT administration. Galectin-3 promoted EC proliferation,migration and tube formation,while its roles were reversed by RNA interference. Galectin-3 induced Atg 5,Beclin-1,LAMP-2,and LC 3A / B expression increases. Galectin-3 also increased LC 3A / B staining in ECs. Akt / m TOR and GSK-3β signaling pathways were activated after galectin-3 treated ECs using its specific phosphorylation antibodies,while blocked it with LY294002 inhibited cell autophagy and EC dynamic alterations induced by galectin-3. CONCLUSION: These findings demonstrate that galectin-3 can induce an Akt signaling cascade leading to cell autophagy,and then the differentiation and angiogenesis of pulmonary artery endothelial cells.     

The role of the p38 pathway in adaptive immunity

Since its discovery in 1993, the mitogen-activated protein （MAP） kinase p38 has attracted much attention for its role in a wide range of cellular processes, many of which involve the immune system. Although p38 has been heavily implicated in the function of all type immune cells, research has tended focus on its role in innate immunity. In this review we attempt to highlight some of the major discoveries that have been made regarding p38＇s role in adaptive immunity, and also to discuss the possible future implications of these discoveries.     

The ubiquitin-proteasome system and its role in inflammatory and autoimmune diseases

Protein degradation through the ubiquitin-proteasome system is the major pathway of non-lysosomal proteolysis of intracellular proteins. It plays important roles in a variety of fundamental cellular processes such as regulation of cell cycle progression, division, development and differentiation, apoptosis, cell trafficking, and modulation of the immune and inflammatory responses. The central element of this system is the covalent linkage of ubiquitin to targeted proteins, which are then recognized by the 26S proteasome, an adenosine triphosphate-dependent, multi-catalytic protease. Damaged, oxidized, or misfolded proteins as well as regulatory proteins that control many critical cellular functions are among the targets of this degradation process. Aberration of this system leads to the dysregulation of cellular homeostasis and the development of multiple diseases. In this review, we described the basic biochemistry and molecular biology of the ubiquitin-proteasome system, and its complex role in the development of inflammatory and autoimmune diseases. In addition, therapies and potential therapeutic targets related to the ubiquitin-proteasome system are discussed as well.     

Activation of protein kinase B/Akt in the periphery contributes to pain behavior induced by capsaicin in rats

Protein kinase B (PKB/Akt) is a member of the second-messenger regulated subfamily of protein kinases. It is implicated in signaling downstream of growth factors, insulin receptor tyrosine kinases and phosphoinositide 3-kinase (PI3K). Current studies indicate that nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and PI3K help mediate inflammatory hyperalgesia. However, little is known about the role of PKB/Akt in the nociceptive system. In this study, we investigated whether PKB/Akt in primary sensory neurons is activated after noxious stimulation and contributes to pain behavior induced in rats by capsaicin. We demonstrated that phospho-PKB/Akt (p-PKB/Akt) is increased in dorsal root ganglia (DRG) at 5 min after intradermal injection of capsaicin. p-PKB/Akt is distributed predominantly in small- and medium-sized DRG cells. After capsaicin injection, p-PKB/Akt (473) is colocalized with isotectin-B4 (IB4), tyrosine kinase A (TrkA), and calcitonin gene-related peptide (CGRP). Furthermore, most transient receptor potential vanilloid type 1 (TRPV1) positive DRG neurons double label for p-PKB/Akt. Behavioral experiments show that intradermal injection of a PI3K (upstream of PKB/Akt) inhibitor, wortmannin, dose-dependently inhibits the changes in exploratory behavior evoked by capsaicin injection. The PKB/Akt inhibitor, Akt inhibitor IV, has the same effect. The results suggest that the PKB/Akt signaling pathway in the periphery is activated by noxious stimulation and contributes to pain behavior.     

机械张应变诱导蛋白激酶B活化对血管平滑肌细胞迁移的影响

目的研究机械张应变诱导蛋白激酶B活化对大鼠血管平滑肌细胞迁移能力的影响。方法应用FX-4000T细胞应变加载系统,对大鼠血管平滑肌细胞施加牵拉幅度为15%、频率为1Hz的张应变。以Transwell和Westernblot等方法观察张应变作用下蛋白激酶B磷酸化和血管平滑肌细胞迁移能力的变化,以未加载张应变的血管平滑肌细胞为对照组。结果与对照组相比,机械张应变增加细胞中蛋白激酶B磷酸化水平,促进血管平滑肌细胞的迁移;PI3K的特异性抑制剂Wortmannin抑制张应变诱导的蛋白激酶B的磷酸化,降低了血管平滑肌细胞迁移能力。结论机械张应变通过上调蛋白激酶B磷酸化水平促进了血管平滑肌细胞迁移,提示蛋白激酶B信号通路参与机械张应变条件下血管平滑肌细胞迁移过程的信号传导。     

Akt2/PKBβ-sensitive regulation of renal phosphate transport

Aim: The protein kinase B (PKB)/Akt is known to stimulate the cellular uptake of glucose and amino acids. The kinase is expressed in proximal renal tubules. The present study explored the influence of Akt/PKB on renal tubular phosphate transport. Methods: The renal phosphate transporter NaPi-IIa was expressed in Xenopus oocytes with or without PKB/Akt and Na⁺ phosphate cotransport determined using dual electrode voltage clamp. Renal phosphate excretion was determined in Akt2/PKBβ knockout mice (akt2^−/−) and corresponding wild-type mice (akt2^+/+). Transporter protein abundance was determined using Western blotting and phosphate transport by ³²P uptake into brush border membrane vesicles. Results: The phosphate-induced current in NaPi-IIa-expressing Xenopus oocytes was significantly increased by the coexpression of Akt/PKB. Phosphate excretion [μmol per 24 h per g BW] was higher by 91% in akt2^−/− than in akt2^+/+ mice. The phosphaturia of akt2^−/− mice occurred despite normal transport activity and expression of the renal phosphate transporters NaPi-IIa, NaPi-IIc and Pit2 in the brush border membrane, a significantly decreased plasma PTH concentration (by 46%) and a significantly enhanced plasma 1,25-dihydroxyvitamin D₃ concentration (by 46%). Moreover, fractional renal Ca²⁺ excretion was significantly enhanced (by 53%) and bone density significantly reduced (by 11%) in akt2^−/− mice. Conclusions: Akt2/PKBβ plays a role in the acute regulation of renal phosphate transport and thus contributes to the maintenance of phosphate balance and adequate mineralization of bone.     

Nitric oxide prevents phosphorylation of neuronal nitric oxide synthase at serine1412 by inhibiting the Akt/PKB and CaM-K II signaling pathways

Neuronal nitric oxide synthase (nNOS) is an important regulatory enzyme in the central nervous system catalyzing the production of NO, which regulates multiple biological processes in the central nervous system. However, the mechanisms by which nNOS activity is regulated are not completely understood. In the present study, the effects of protein kinases on the phosphorylation of nNOS in GH3 rat pituitary tumor cells were evaluated. We show that phosphorylation of nNOS at Ser1412 could be induced by the phosphatidylinositol 3-kinase/protein kinase B (Akt/PKB) agonist insulin, the calcium/calmodulin-dependent protein kinase II (CaM-K II) agonist A23187 or the cAMP-dependent protein kinase A (PKA) agonist IBMX, respectively. The phosphorylation levels of nNOS at Ser1412, induced by activation of Akt/PKB or CaM-K II, but not by PKA signaling, were reduced by pre-treatment with the NO donor diethylamine-NONOate. This inhibitory effect could be reversed by addition of a reducing reagent, dithiothreitol. Furthermore, the levels of phosphorylation of nNOS at Ser1412, induced by Akt/PKB or CaM-K II but not by PKA signaling, were enhanced by inhibition of nNOS activity with 7-nitroindazole. These findings suggest that the activation of nNOS can be catalyzed by at least three protein kinases, Akt/PKB, CaM-K II or PKA. NO generated from nNOS feedback prevents the activation of nNOS by inhibiting either Akt/PKB or CaM-K II but not PKA signaling.     

NGF-TrkA-SH2-Bβ-Akt/PKB信号通路与哮喘

NGF-TrkA-SH2-Bβ-Akt/PKB这一信号通路参与神经细胞分化和增殖,也参与哮喘炎症反应和气道高反应。AKT/PKB是一种分子量约60kD的丝/苏氨酸激酶,有3种亚型,在许多组织中表达的量不同。AKT/PKB通过直接或间接影响3个转录因子家族(Forkhead、CREB、NF-κB),促使Bad,caspase-3和caspase-9磷酸化,抑制糖原合成酶激酶-3(GSK3)活性等作用。NGF与TrkA结合,通过调节SH2-Bβ及其下游蛋白Akt/PKB参与哮喘发病。     

激酶调控PKB/Akt活性的机制

PKB/Akt是胞内信号转导通路网络的中心分子。活化的PKB参与多种生物学效应的调控过程,调控PKB活性作用机制的研究一直是信号转导通路领域的难点。新近的研究结果确定了若干新的调控PKB活性的激酶,从多方面解释了PKB活化和作用的分子机制。其中mTORC2、ATM和DNA-PK均通过磷酸化PKB的Ser473位点以依赖于PI3K的方式全面活化PKB;此外,其它以不依赖PI3K的方式调控PKB活性的激酶包括,RET/PTC通过磷酸化PKB的Tyr315位点、JNK通过磷酸化PKB的Thr450位点以及CK2通过磷酸化PKB的Ser129位点活化PKB,Brk通过磷酸化PKB的Tyr474位点以及GRK2均可通过磷酸化PKB抑制其活性。     

Modulation of prosurvival signaling in fibroblasts by a protein kinase inhibitor protects against fibrotic tissue injury

Progressive fibrotic diseases involving diverse organ systems are associated with the persistence of fibroblasts/myofibroblasts in injured tissues. Activation of focal adhesion kinase (FAK) and protein kinase B (PKB/Akt) by transforming growth factor-beta1 mediate stable induction of myofibroblast differentiation and survival. In this report, we demonstrate that transforming growth factor-beta1-induced activation of both PKB/Akt and FAK are dose dependently inhibited by the protein kinase inhibitor, AG1879, in cultured human lung fibroblasts. In a murine model of intratracheal bleomycin-induced lung fibrosis, regions of active fibrogenesis demonstrate elevated expression of PKB/Akt and FAK phosphorylation in vivo, effects that are attenuated in mice receiving daily intraperitoneal injections of AG1879 (bleomycin-AG1879) versus a chemically inactive analog (bleomycin-control). PKB/Akt and FAK phosphorylation are elevated in fibroblasts isolated from lungs of bleomycin-injured mice, effects that are inhibited in bleomycin-AG1879 mice. Accumulation of alpha-smooth muscle actin-expressing myofibroblasts is markedly reduced in lungs of bleomycin-AG1879 mice. The numbers of recruited inflammatory cells were not significantly different between these groups. Bleomycin-AG1879 mice are protected from lung fibrosis as evidenced by histopathology, trichrome staining, and biochemical analysis for collagen. Thus, targeting of prosurvival signaling pathways in fibroblasts/myofibroblasts may provide a novel and effective strategy for anti-fibrotic therapy of treatment-unresponsive fibrotic disorders.     

Adenosine-mediated activation of Akt/protein kinase B in the rat hippocampus in vitro and in vivo

Adenosine is considered an endogenous neuroprotective metabolite that through activation of the A(1) receptor results in reduction of neuronal damage following cerebral ischemia. Protein kinase B, also known as Akt/PKB, is part of an endogenous pathway that exerts effective neuroprotection from both necrotic and apoptotic cell death. Using a rat model of unilateral common carotid artery occlusion coupled with hypoxia, and using in vitro rat hippocampal slices, we examined the ability of adenosine to directly activate Akt/PKB. Western blot analysis revealed that levels of phosphorylated Akt/PKB were elevated in vivo under ischemic conditions in an adenosine A(1)-dependent manner and elevated in hippocampal slices treated with an adenosine A(1) agonist. We conclude from these studies that the activation of an adenosine A(1) receptor-mediated signal transduction pathway, either by endogenous adenosine (in vivo) or by an adenosine A(1) agonist (in vitro), results in the activation of the neurotrophic kinase Akt/PKB.     

Uncoupling protein 3 expression levels influence insulin sensitivity, fatty acid oxidation, and related signaling pathways

Controversy exists on whether uncoupling protein 3 (UCP3) positively or negatively influences insulin sensitivity in vivo, and the underlying signaling pathways have been scarcely studied. We studied how a progressive reduction in UCP3 expression (using UCP3 +/+, UCP3 +/-, and UCP3 -/- mice) modulates insulin sensitivity and related metabolic parameters. In order to further validate our observations, we also studied animals in which insulin resistance was induced by administration of a high-fat diet (HFD). In UCP3 +/- and UCP3 -/- mice, gastrocnemius muscle Akt/protein kinase B (Akt/PKB) (serine 473) and AMP-activated protein kinase (AMPK) (threonine 171) phosphorylation, and glucose transporter 4 (GLUT4) membrane levels were reduced compared to UCP3 +/+ mice. The HOMA-IR index (insulin resistance parameter) was increased both in the UCP3 +/- and UCP3 -/- mice. In these mice, insulin administration normalized Akt/PKB phosphorylation between genotypes while AMPK phosphorylation was further reduced, and sarcolemmal GLUT4 levels were induced but did not reach control levels. Furthermore, non-insulin-stimulated muscle fatty acid oxidation and the expression of several involved genes both in muscle and in liver were reduced. HFD administration induced insulin resistance in UCP3 +/+ mice and the aforementioned parameters resulted similar to those of chow-fed UCP3 +/- and UCP3 -/- mice. In conclusion, high-fat-diet-induced insulin resistance in wild-type mice mimics that of chow-fed UCP3 +/- and UCP3 -/- mice showing that progressive reduction of UCP3 levels results in insulin resistance. This is accompanied by decreased fatty acid oxidation and a less intense Akt/PKB and AMPK signaling.