神经纤毛蛋白在血管生成中的作用

神经纤毛蛋白(neuropilin,NRP)作为轴突导向分子col-lapsin/semaphorin的受体,在神经细胞导向、轴突生长方面发挥着调控作用。近年来,关于NRP的研究已从最早的神经轴突导向扩展至血管生成、肿瘤的增殖与转移等多个方面,尤其是其在血管生成方面的研究逐渐成为热点[1]。现就NRP的结构和功能特性及其在血管生成中的作用作一综述。1神经纤毛蛋白的结构和功能Neuropilin-1(NRP-1)是最早被发现的NRP家族成员,这是一种相对分子质量为120000~130000的跨膜糖蛋白,最初在非洲蟾蜍属视顶盖的神经纤维轴突上发现。1995年,Fujisawa等[2]将之命名为neuropilin-1(NRP-1)。进一步的研究显示,NRP-1作为轴突导向因子collapsin/semaphorin家族的受体,可与轴突生长导向因子SEMA-3A结合,从而参与神经发育时,轴突导向、神经纤维成束、细胞迁移以及成人神经细胞的损伤修复等重要过程[3]。而近年来,越来越多的研究显示,除了作为SEMA-3型的受体,NRP-1还作为血管内皮生长因子(vascular endothelial growth fac...     

Troponin I phosphorylation plays an important role in the relaxant effect of beta-adrenergic stimulation in mouse hearts

OBJECTIVE: The present study was designed to address the question of the contribution of cardiac troponin I (cTnI) phosphorylation to the enhanced rate of relaxation during beta-adrenergic stimulation in hearts in situ. METHODS: In situ hemodynamic measurements were performed in mouse hearts that (1) express normal level of phospholamban (PLB) and either express cTnI (PLB/cTnI) or the slow skeletal isoform of TnI (PLB/ssTnI) that cannot be phosphorylated by protein kinase A (PKA) or (2) do not express PLB and either express cTnI (PLBKO/cTnI) or ssTnI (PLBKO/ssTnI). RESULTS: In the basal state, there was no difference in heart rate (HR), developed pressure (DP), left ventricular end-diastolic pressure (LVEDP) or rate of contraction (+dP/dt) between PLB/cTnI and PLB/ssTnI groups. However, hearts expressing ssTnI (PLB/ssTnI) showed a significantly decreased rate of relaxation (-dP/dt) when compared with hearts expressing cTnI (PLB/cTnI). In response to beta-adrenergic agonist, isoproterenol (ISO), HR increased similarly in both groups. At the two highest doses of ISO, the rate of relaxation (-dP/dt) was significantly smaller in PLB/ssTnI than in PLB/cTnI hearts. In the basal state, there was no difference in HR, DP, LVEDP,+dP/dt and -dP/dt between PLBKO/cTnI and PLBKO/ssTnI hearts. In response to ISO, HR increased similarly in both groups and was only slightly smaller in PLBKO/ssTnI group at the lowest dose of ISO. However, during ISO perfusion, when cTnI was phosphorylated, the rate of relaxation was significantly slower in PLBKO/ssTnI compared to PLBKO/cTnI hearts. CONCLUSION: Our data support the hypothesis that phosphorylation of cTnI significantly contributes to the enhanced rate of relaxation during beta-adrenergic stimulation.     

Puromycin-insensitive leucyl-specific aminopeptidase (PILSAP) binds and catalyzes PDK1, allowing VEGF-stimulated activation of S6K for endothelial cell proliferation and angiogenesis

Puromycin-insensitive leucyl-specific aminopeptidase (PILSAP) plays an important role in angiogenesis by regulating the proliferation and migration of endothelial cells (ECs). Here we characterize the mechanism by which PILSAP regulates the vascular endothelial growth factor (VEGF)-stimulated proliferation of ECs. The specific elimination of PILSAP expression or its enzymatic activity inhibited VEGF-stimulated G1/S transition in ECs. This G1 arrest correlated with reduced cyclin dependent kinase 4/6 (CDK4/6) activity and retinoblastoma (Rb) protein phosphorylation. Analyses of signaling molecules upstream of CDK4/6 revealed that S6 kinase (S6K) activation was affected by PILSAP, whereas that of phosphatidylinositol-3 kinase (PI3K), Akt, and extracellular signal-related kinase 1/2 (ERK1/2) was not. We further demonstrated that PILSAP bound phosphatidylinositol-dependent kinase 1 (PDK1) and removed 9 amino acids from its N-terminus, which allowed S6K to associate with PDK1 and PILSAP upon VEGF stimulation. We constructed mutant PILSAP, which lacked the aminopeptidase activity but bound PDK1. Mutant PILSAP abrogated S6K activation upon VEGF stimulation in a dominant-negative manner. An N-terminal truncated form of PDK1 abolished the dominant-negative effect of mutant PILSAP. Finally, the introduction of a mutated PILSAP gene in ECs inhibited angiogenesis and retarded tumor growth in vivo. These results indicate that PILSAP plays a crucial role in the cell cycle progression of ECs and angiogenesis via the binding and modification of PDK1.     

Endoplasmic reticulum aminopeptidase 1 (ERAP1) trims MHC class I-presented peptides in vivo and plays an important role in immunodominance

CD8(+) T cells respond to short peptides bound to MHC class I molecules. Although most antigenic proteins contain many sequences that could bind to MHC class I, few of these peptides actually stimulate CD8(+) T cell responses. Moreover, the T cell responses that are generated often follow a very reproducible hierarchy to different peptides for reasons that are poorly understood. We find that the loss of a single enzyme, endoplasmic reticulum aminopeptidase 1 (ERAP1), in the antigen-processing pathway results in a marked shift in the hierarchy of immunodominance in viral infections, even when the responding T cells have the same T cell receptor repertoire. In mice, ERAP1 is the major enzyme that trims precursor peptides in the endoplasmic reticulum and, in this process, can generate or destroy antigenic peptides. Consequently, when ERAP1 is lost, the immune response to some viral peptides is reduced, to others increased, and to yet others unchanged. Therefore, many epitopes must be initially generated as precursors that are normally trimmed by ERAP1 before binding to MHC class I, whereas others are normally degraded by ERAP1 to lengths that are too short to bind to MHC class I. Moreover, peptide trimming and the resulting abundance of peptide-MHC complexes are dominant factors in establishing immunodominance.     

The second STE12 homologue of Cryptococcus neoformans is MATa-specific and plays an important role in virulence

Cryptococcus neoformans STE12alpha, a homologue of Saccharomyces cerevisiae STE12, exists only in MATalpha strains. We identified another STE12 homologue, STE12a, which is MATa specific. As in the case with Deltaste12alpha, the mating efficiency for Deltaste12a was reduced significantly. The Deltaste12a strains surprisingly still mated with Deltaste12alpha strains. In MATalpha strains, STE12a functionally complemented STE12alpha for mating efficacy, haploid fruiting, and regulation of capsule size in the mouse brain. Furthermore, when STE12a was replaced with two copies of STE12alpha, the resulting MATa strain produced hyphae on filament agar. STE12a regulates mRNA levels of several genes that are important for virulence including CNLAC1 and CAP genes. STE12a also modulates enzyme activities of phospholipase and superoxide dismutase. Importantly, deletion of STE12a markedly reduced the virulence in mice, as is the case with STE12alpha. Brain smears of mice infected with the Deltaste12a strain showed yeast cells with a considerable reduction in capsule size compared with those infected with STE12a strains. When the disrupted locus of ste12a was replaced with a wild-type STE12a gene, both in vivo and in vitro mutant phenotypes were reversed. These results suggest that STE12a and STE12alpha have similar functions, and that the mating type of the cells influences the alleles to exert their biological effects. C. neoformans, thus, is the first fungal species that contains a mating-type-specific STE12 homologue in each mating type. Our results demonstrate that mating-type-specific genes are not only important for saprobic reproduction but also play an important role for survival of the organism in host tissue.     

循环内皮祖细胞在原发性高血压与动脉粥样硬化中的作用

内皮祖细胞(endothelial progenitor cells,EPCs)是来源于骨髓而存在于外周血的单核干细胞,具有分化为成熟内皮细胞功能,参与了内皮损伤修复、血管新生和血管形成等过程,有学者提议用循环内皮祖细胞数量代替C反应蛋白作为新一代预测冠心病的工具.本文主要讨论内皮祖细胞的特性及其在原发性高血压与动脉粥样硬化中的作用.     

Calcium store sensor stromal-interaction molecule 1-dependent signaling plays an important role in cervical cancer growth, migration, and angiogenesis

Store-operated Ca(2+) entry (SOCE) is the principal Ca(2+) entry mechanism in nonexcitable cells. Stromal-interaction molecule 1 (STIM1) is an endoplasmic reticulum Ca(2+) sensor that triggers SOCE activation. However, the role of STIM1 in regulating cancer progression remains controversial and its clinical relevance is unclear. Here we show that STIM1-dependent signaling is important for cervical cancer cell proliferation, migration, and angiogenesis. STIM1 overexpression in tumor tissue is noted in 71% cases of early-stage cervical cancer. In tumor tissues, the level of STIM1 expression is significantly associated with the risk of metastasis and survival. EGF-stimulated cancer cell migration requires STIM1 expression and EGF increases the interaction between STIM1 and Orai1 in juxta-membrane areas, and thus induces Ca(2+) influx. STIM1 involves the activation of Ca(2+)-regulated protease calpain, as well as Ca(2+)-regulated cytoplasmic kinase Pyk2, which regulate the focal-adhesion dynamics of migratory cervical cancer cells. Because of an increase of p21 protein levels and a decrease of Cdc25C protein levels, STIM1-silencing in cervical cancer cells significantly inhibits cell proliferation by arresting the cell cycle at the S and G2/M phases. STIM1 also regulates the production of VEGF in cervical cancer cells. Interference with STIM1 expression or blockade of SOCE activity inhibits tumor angiogenesis and growth in animal models, confirming the crucial role of STIM1-mediated Ca(2+) influx in aggravating tumor development in vivo. These results make STIM1-dependent signaling an attractive target for therapeutic intervention.     

IL-17A plays an important role in induction of type 2 diabetes and its complications

Type 2 diabetes (T2D) is the most prevalent metabolic disease worldwide. Previous studies revealed that immune responses, genetic factors, and inflammatory processes played important roles in the pathogenesis and complications of T2D. It has been documented that some people who have T2D are suffering from serious organ-specific pathophysiological conditions including nephropathy and retinopathy. The mechanisms responsible for progression of the disease and its long-term complications are yet to be clarified. IL-17A as a pro-inflammatory cytokine has a dual function, inducing early immune responses against infections and participating in autoimmunity and destructive inflammatory conditions. Therefore, the aim of this review was to address the recent information regarding the status and association of IL-17A with T2D and its related disorders.     

Relaxin plays an important role in the regulation of airway structure and function

Relaxin is a reproductive hormone with pleiotropic actions. In addition to airway fibrosis, relaxin deficiency results in airway structural changes (epithelial thickening) and increased lung recoil, suggesting that relaxin may impact other aspects of airway/lung structure and function beyond its ability to regulate collagen turnover. Furthermore, these structural changes associated with relaxin deficiency show marked similarity to the structural changes seen in asthma. The current study investigated the broader role of relaxin in regulating airway structure and function and examined the relationship between airway inflammation, structural changes, and airway hyperresponsiveness (AHR) using an ovalbumin (OVA)-induced model of allergic airways disease (AAD). The model of AAD was applied to 12-month-old relaxin-deficient (Rln(-/-)) mice with established airway fibrosis and age-matched wild-type (Rln(+/+)) controls. OVA-treated Rln(+/+) mice (induced inflammation) developed increased epithelial thickening (P < 0.05) and AHR (P < 0.05) but not airway fibrosis, compared with saline-treated Rln(+/+) controls. Saline-treated Rln(-/-) mice had significantly increased lung collagen deposition (existing fibrosis) and epithelial thickening and remarkably were found to have increased AHR that was equivalent to that in OVA-treated Rln(+/+) mice (all P < 0.05 vs. saline-treated Rln(+/+) controls). OVA-treated Rln(-/-) mice (existing fibrosis and induced inflammation) had increased airway/lung fibrosis (P < 0.05) but equivalent airway inflammation and AHR compared with OVA-treated Rln(+/+) animals. These findings demonstrate for the first time a role for relaxin in the regulation of airway responses using Rln(-/-) mice and suggest that airway fibrosis and/or epithelial thickening can result in increased AHR equivalent to that induced by airway inflammation in AAD.     

巨噬细胞程序性坏死在肝脏免疫应答中的作用

肝脏巨噬细胞持续接受抗原的刺激,处于免疫耐受及免疫应答的动态平衡状态。肝脏巨噬细胞对肝外抗原的免疫应答与肝脏的免疫稳态密切相关,程序性坏死通路是调控其功能和存亡的关键通路。回顾了程序性坏死通路与凋亡通路的关系,具体阐述了IKK复合物的活性在程序性坏死和凋亡通路交互调控中的重要作用。程序性坏死在肝脏巨噬细胞对肝外抗原的应答中的作用仍然有待阐明。     

Maternal ghrelin plays an important role in rat fetal development during pregnancy

Ghrelin, an acylated peptide serving as an endogenous ligand for GH secretagogue receptor (GHS-R), was originally isolated from rat and human stomach. In this study, we report the critical role of maternal ghrelin in fetal development. High levels of ghrelin receptor (GHS-R) mRNA were detected in various peripheral fetal tissues beginning at embryonic d 14 and lasting until birth. Fetal GHS-R expression was also confirmed in fetal tissues by immunohistochemistry. Autoradiography revealed that both des-acyl ghrelin and acyl ghrelin bind to fetal tissues. Chronic treatment of mothers with ghrelin resulted in a significant increase in birth weight in comparison to newborns from saline-treated mothers. Even when maternal food intake after ghrelin treatment was restricted through paired feeding, significant stimulation of fetal development still occurred. Conversely, active immunization of mothers against ghrelin decreased fetal body weight during pregnancy. A single ghrelin injection into the mother increased circulating ghrelin levels in the fetus within 5 min of injection, suggesting that maternal ghrelin transits easily to the fetal circulation. High levels of des-acyl ghrelin were detected in fetal blood and amniotic fluid. Both acylated and des-acyl ghrelin increased [3H]thymidine and 5-bromo-2'-deoxyuridine incorporation of cultured fetal skin cells in a dose-dependent manner, and calcium-imaging analysis revealed that acyl and des-acyl ghrelin increased the Ca2+ influx in discrete cultured fetal skin cells, respectively. These results indicate that maternal ghrelin regulates fetal development during the late stages of pregnancy.     

Novel role of lactosylceramide in vascular endothelial growth factor-mediated angiogenesis in human endothelial cells

Vascular endothelial growth factor (VEGF) has been implicated in angiogenesis associated with coronary heart disease, vascular complications in diabetes, inflammatory vascular diseases, and tumor metastasis. The mechanism of VEGF-driven angiogenesis involving glycosphingolipids such as lactosylceramide (LacCer), however, is not known. To demonstrate the involvement of LacCer in VEGF-induced angiogenesis, we used small interfering RNA (siRNA)-mediated silencing of LacCer synthase expression (GalT-V) in human umbilical vein endothelial cells. This gene silencing markedly inhibited VEGF-induced platelet endothelial cell adhesion molecule-1 (PECAM-1) expression and angiogenesis. Second, we used D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP), an inhibitor of LacCer synthase and glucosylceramide synthase, that significantly mitigated VEGF-induced PECAM-1 expression and angiogenesis. Interestingly, these phenotypic changes were reversed by LacCer but not by structurally related compounds such as glucosylceramide, digalactosylceramide, and ceramide. In a human mesothelioma cell line (REN) that lacks the endogenous expression of PECAM-1, VEGF/LacCer failed to stimulate PECAM-1 expression and tube formation/angiogenesis. In REN cells expressing human PECAM-1 gene/protein, however, both VEGF and LacCer-induced PECAM-1 protein expression and tube formation/angiogenesis. In fact, VEGF-induced but not LacCer-induced angiogenesis was mitigated by SU-1498, a VEGF receptor tyrosine kinase inhibitor. Also, VEGF/LacCer-induced PECAM-1 expression and angiogenesis was mitigated by protein kinase C and phospholipase A2 inhibitors. These results indicate that LacCer generated in VEGF-treated endothelial cells may serve as an important signaling molecule for PECAM-1 expression and in angiogenesis. This finding and the reagents developed in our report may be useful as anti-angiogenic drugs for further studies in vitro and in vivo.     

Myosin-actin interaction plays an important role in human immunodeficiency virus type 1 release from host cells.

We examined the potential role of myosin and actin in the release of human immunodeficiency virus type 1 (HIV-1) from infected cells. Wortmannin (100 nM to 5 microM), an effective inhibitor of myosin light chain kinase, blocked the release of HIV-1 from infected T-lymphoblastoid and monocytoid cells in a concentration-dependent manner. Cytochalasin D, a reagent that disrupts the equilibrium between monomeric and polymeric actin, also partially inhibited the release of HIV-1 from the infected cells. At the budding stage, myosin and HIV-1 protein were detected in the same areas on the plasma membrane by using dual-label immunofluorescence microscopy and immunoelectron microscopy. In the presence of 5 microM wortmannin, viral components were observed on the plasma membrane by using immunofluorescence microscopy and electron microscopy, implying that wortmannin did not disturb the transport of viral proteins to the plasma membrane but rather inhibited budding.