Growth factors modify the epidermal growth factor receptor through multiple pathways

Previous results have shown that tumor promoters modify the properties of the epidermal growth factor (EGF) receptor through the activation of protein kinase C. Diacylglycerol-generating factors such as platelet-derived growth factor (PDGF) and p28sis should activate protein kinase C and alter EGF receptor properties in a similar manner. To test directly the involvement of protein kinase C in the action of media from v-sis-transformed cells on the EGF receptor, Swiss 3T3 cells were first extensively treated with various concentrations of the tumor-promoter phorbol dibutyrate (PDBu) This treatment reduced levels of active protein kinase C in the cells, making them less responsive to subsequent rechallenge with the tumor promoter. The results demonstrate that there are at least two components to the action of media from v-sis transformed cells on EGF binding: a labile factor that confers protein kinase C independence and a stable factor that appears to be dependent on protein kinase C. The action of the first factor cannot be mimicked by transforming growth factor-beta or EGF in either the presence or absence of PDGF. The action of the second factor is similar to that of PDGF. These findings indicate that heterologous regulation of the EGF receptor can occur through both protein kinase C-dependent and -independent pathways.     

细胞因子与膜受体蛋白相互作用的研究方法

细胞因子与膜受体的相互作用是生命活动中的重要环节。癌症、自身免疫疾病、代谢紊乱等疾病的发生都和细胞因子失调有着密切的关系,研究细胞因子和受体的相互作用成为治疗上述疾病的基石。本文综述了现今常用的研究方法,包括从最经典的同位素标记直接检测受体与配体的结合,到生化通路下游信号检测,再到生物物理高通量检测方法。     

Biology of platelet-derived growth factors in development

Platelet-derived growth factor (PDGF) was one of the first growth factors to be characterized, and the PDGF family of ligand and receptors has remained an archetype system for studies of the mechanisms of action of growth factors and receptor tyrosine kinases for more than two decades. The small size of the family has also facilitated genetic studies and, in particular, manipulations of the mouse PDGF and PDGF receptor genes have given important insights into the role of this family during mammalian development. These studies have shown that discrete populations of mesenchymal and neuroectodermal progenitor cells depend on PDGF signaling for their growth and distribution within developing organs. Other studies suggest that the same, or similar, cells may be targeted by exaggerated PDGF signaling in a number of pathological processes, including different types of cancer. The present review summarizes current views on the roles of PDGFs in developmental processes, and discusses the critical importance of the amount, spatial distribution, and bioavailability of the PDGF proteins for acquisition of the correct number and location of target cells.     

Cross-talk at the crossroads of sphingosine-1-phosphate, growth factors, and cytokine signaling

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid that mediates a wide array of biologic effects through its interaction with a family of five G protein-coupled receptors. Cytokines and growth factors interact with this signaling pathway in a variety of ways, including both activation and regulation of the expression of the enzymes that regulate synthesis and degradation of S1P. Not only do many growth factors and cytokines stimulate S1P production, leading to transactivation of S1P receptors, ligation of S1P receptors by S1P can also transactivate growth factor tyrosine kinase receptors and stimulate growth factor and cytokine signaling cascades. This review discusses the mechanisms involved in cross-talk between S1P, cytokines, and growth factors and the impact of that cross-talk on cell signaling and cell biology.     

RasGRP Ras guanine nucleotide exchange factors in cancer

RasGRP proteins are activators of Ras and other related small GTPases by the virtue of functioning as guanine nucleotide exchange factors （GEFs）. In vertebrates, four RasGRP family members have been described. RasGRP-1 through -4 share many structural domains but there are also subtle differences between each of the different family members. Whereas SOS RasGEFs are ubiquitously expressed, RasGRP proteins are expressed in distinct patterns, such as in different cells of the hematopoietic system and in the brain. Most studies have concentrated on the role of RasGRP proteins in the development and function of immune cell types because of the predominant RasGRP expression profiles in these cells and the immune phenotypes of mice deficient for Rasgrp genes. However, more recent studies demonstrate that RasGRPs also play an important role in tumorigenesis. Examples are skin- and hematological- cancers but also solid malignancies such as melanoma or prostate cancer. These novel studies bring up many new and unanswered questions related to the molecular mechanism of RasGRP-driven oncogenesis, such as new receptor systems that RasGRP appears to respond to as well as regulatory mechanisms for RasGRP expression that appear to be perturbed in these cancers. Here we will review some of the known aspects of RasGRP biology in lymphocytes and will discuss the exciting new notion that RasGRP Ras exchange factors play a role in oncogenesis downstream of various growth factor receptors.     

肠易激综合症患者结肠组织中促肾上腺皮质激素释放因子受体表达的研究

目的 检测肠易激综合症（IBS）患者结肠组织中促肾上腺皮质激素释放因子受体（CRFR）1及CRFR2的表达,探讨其与IBS发病的关系,从而为靶向治疗IBS提供依据.方法 分别采集15例腹泻型IBS（D-IBS）患者、15例便秘型IBS（C-IBS）患者和10例正常健康人结肠组织标本,采用Elivision（TM）PLUS/HRP免疫组化染色方法和Western blot测定CRFR1、CRFR2在各组结肠组织中的蛋白表达.结果 实验结果显示,正常对照组CRFR1和CRFR2免疫组化染色以浅黄色为主,分布范围局限,平均光密度值分别为（0.254±0.099）和（0.201±0.030）;D-IBS组中CRFR1以深或棕黄色为主,分布范围较为广泛,平均光密度值为（0.384±0.048）,显著高于C-IBS组（0.144±0.077）及正常对照组（P〈0.01）;C-IBS组中CRFR2染色以深或棕黄色为主,分布范围较为广泛,平均光密度值为（0.322±0.022）,显著高于D-IBS组（0.162±0.023）（P〈0.01）及正常对照组（P〈0.05）.Western blot结果显示,D-IBS组CRFR1蛋白表达明显高于C-IBS组和正常对照组;C-IBS组CRFR2表达高于D-IBS组和正常对照组.结论 不同亚型IBS患者其CRFR表达的亚型亦不同,提示不同亚型IBS的发生可能与患者结肠组织中CRFR1、CRFR2的表达水平有关.     

Neuron-derived factors negatively modulate ryanodine receptor-mediated calcium release in cultured mouse astrocytes

Changes in intracellular Ca²⁺ concentration ([Ca²⁺]_i) produced by ryanodine receptor (RyR) agonist, caffeine (caf), and ionotropic agonists: N-methyl-d-aspartate (NMDA) receptor (NMDAR) agonist, NMDA and P2X7 receptor (P2X7R) agonist, 3′-O-(4-benzoyl)benzoyl adenosine 5′-triphosphate (BzATP) were measured in cultured mouse cortical astrocytes loaded with the fluorescent calcium indicator Fluo3-AM in a confocal laser scanning microscope. In mouse astrocytes cultured in standard medium (SM), treatment with caf increased [Ca²⁺]_i, with a peak response occurring about 10 min after stimulus application. Peak responses to NMDA or BzATP were observed about <1 min and 4.5 min post stimulus, respectively. Co-treatment with NMDA or BzATP did not alter the peak response to caf in astrocytes cultured in SM, the absence of the effects being most likely due to asynchrony between the response to caf, NMDA and BzATP. Incubation of astrocytes with neuron-condition medium (NCM) for 24 h totally abolished the caf-evoked [Ca²⁺]_i increase. In NCM-treated astrocytes, peak of [Ca²⁺]_i rise evoked by NMDA was delayed to about 3.5 min, and that induced by BzATP occurred about three minutes earlier than in SM. The results show that neurons secrete factors that negatively modulate RyR-mediated Ca²⁺-induced Ca²⁺ release (CICR) in astrocytes and alter the time course of Ca²⁺ responses to ionotropic stimuli.     

IgG receptor polymorphisms: risk factors for disease

 Two groups of receptors for immunoglobulin G (FcγR) can be distinguished. Endothelial cells and placental syncytiotrophoblasts express an MHC class I-like FcγR important for regulation of IgG half-life and IgG transport, respectively. FcγR expressed on leukocytes constitute a heterogeneous family of membrane bound and soluble proteins. The various FcγR (sub) classes of this family differ in ligand affinity and specificity, which is determined by primary structure, glycosylation, association with signaling subunits, and environmental factors (such as serine proteases). The finding that polymorphisms of FcγRIIa, FcγRIIIa, and FcγRIIIb critically affect interaction with antibodies has prompted analysis in patients which provided tantalizing evidence for the relevance of FcγR polymorphisms as risk factors for a number of infectious and autoimmune diseases. Received: 15 January 1998     

钵水母水螅体横裂诱发条件及调控机制研究进展

横裂是水螅体世代向水母体世代转变的重要阶段.对水螅体横裂诱发条件及调控分子机制的研究不仅对水母爆发生态学和水母人工繁育具有重要意义,而且对比较研究两栖类、昆虫以及刺胞动物等具有复杂生活史生物的变态分子机制起源也具有很好的理论价值.现有研究表明,诱发水螅体横裂的自然环境因素有温度、光照、盐度和共生虫黄藻等,不同门类水母的横裂方式以及环境诱导因素各不相同.能够诱导水螅体横裂的化学因素有吲哚类化合物、9-顺式维甲酸、碘元素和过氧化氢等,其中吲哚类化合物对绝大多数水母水螅体都有诱导作用.尽管水螅体横裂的分子机制尚未明晰,但对海月水母的研究表明,RxR信号通路以及一种横裂诱导激素前体假定蛋白CL390在水母横裂过程中起着重要的作用,提示水母变态分子机制与两栖类和昆虫在分子水平上存在一定程度的共性.     

Physiological roles of the angiogenic factors during posthatching development period and adults in the quail lung

The bronchus and vasculature form an intrinsic functional component of the avian lung, and its growth must be tightly regulated and coordinated by lung epithelial and endothelial development. Vascular endothelial growth inhibitor (VEGI), vascular endothelial growth factor (VEGF) and its receptors (flk1/KDR, flt1/fms, flt4) are required for epithelial and endothelial cell survival and apoptosis. Especially, VEGF and its receptors are critical for the development of the lung and serve as a maintenance factor during adult life. To determine the function of VEGI, VEGF and its receptors in the posthatching lung development, we revealed its expression and localization using by immunohistochemical procedure. VEGI, VEGF and its receptors were observed in the structural components of the bronchi, atria and air capillaries, as well as in the pulmonary blood vessels throughout the posthatching development period. On the other hand, immunostaining for VEGI, VEGF and its receptors was faintly detected in the glands of the secondary bronchi. Furthermore, it was determined that the secondary bronchial and atrial muscles did not display VEGF immunoreactions. Our results showed that VEGF and its receptors (flt1/fms, flk1/KDR and flt4) and VEGI were expressed at varying intensity by different cell groups. Therefore, they are also required for the development of the lung component during posthatching period.     

Soluble factors released by activated cytotoxic T lymphocytes interfere with death receptor pathways in neuroblastoma

Neuroblastoma (NB) is often described as an unfavorable target for both HLA-restricted and death receptor-mediated elimination by cytotoxic T lymphocytes (CTLs) due to low or absent HLA class I and caspase-8 expression. We investigated the effects of soluble factors released by CTLs activated by TCR triggering (named as activated supernatant; AS) on the levels and composition of cell surface molecules involved in HLA-restricted and HLA-independent NB cell recognition (surface immune phenotype). Using a panel of long-term propagated NB cell lines and freshly isolated primary human NB cells, we analyzed surface expression of the (1) cognate receptors for TNFα, Fas and TRAIL; (2) HLA class I and II heterodimers; (3) adhesion molecules; (4) the intracellular expression and activation of caspase-8, as well as (5) the susceptibility of NB cells to death receptor-mediated killing prior to and after exposure to AS. The exposure of NB cells to soluble factors released by activated CTLs skewed the surface immune phenotype of both long term cultured and primary NB cells, induced the expression and activation of caspase-8 and increased the susceptibility of tumor cells to lysis by TRAIL and Fas-agonistic antibody. Blocking experiments identified IFNγ and TNFα as main factors responsible for modulating the surface antigens of NB cells by AS. Our data suggest that recruitment of CTLs activated on third party targets into the vicinity of the NB tumor mass, may override the “silent” immune phenotype of NB cells via the action of soluble factors. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. This work was supported by grants from the Swedish Children’s Cancer Foundation, the Swedish Cancer Society, the Cancer Society of Stockholm, the King Gustav the Vth Jubilee Fund, Karolinska Institutet and the Swedish Research Council.     

Effect of E-cadherin on activation of MAP-kinase by growth factors in human carcinoma cells

Met and EGF receptors can induce a decrease in intercellular adhesion and an increase in cell motility, which is a cause of metastatic progressions. Therefore, mechanisms of interaction in receptor tyrosine kinase and proteins of intercellular contacts attract the attention of researchers. The main protein that provides cellular adhesion is E-cadherin. Earlier, we have shown that the intracellular Met localization was dependent on function of E-cadherin. In the present work, we have found that localization of the EGF receptor also was determined by adhesion stability. Loss of intercellular contacts in HBL-100 cells leads to the EGF receptor being not stabilized at the cell membrane. A comparative study of MAP kinase activation by growth factors was carried out in cells differing by their intercellular adhesion states. It has been established that E-cadherin is able to modulate level and duration of activation of ERK kinase. The presented results allow for the suggestion to be made that not only intracellular localization, but also the intracellular signal pathway activated by Met and EGF receptors, depend on the E-cadherin function, which in turn can determine the specificity of cellular response.     

Genetic host factors in Helicobacter pylori-induced carcinogenesis: Emerging new paradigms

Helicobacter Pylori is a gram negative rod shaped microaerophilic bacterium that colonizes the stomach of approximately half the world's population. Infection with c may cause chronic gastritis which via a quite well described process known as Correas cascade can progress through sequential development of atrophic gastritis, intestinal metaplasia and dysplasia to gastric cancer. H. pylori is currently the only bacterium that is classified as a class 1 carcinogen by the WHO, although the exact mechanisms by which this bacterium contributes to gastric carcinogenesis are still poorly understood. Only a minority of H. pylori-infected patients will eventually develop gastric cancer, suggesting that host factors may be important in determining the outcome of H. pylori infection. This is supported by a growing body of evidence suggesting that the host genetic background contributes to risk of H. pylori infection and gastric carcinogenesis. In particular single nucleotide polymorphisms in genes that influence bacterial handling via pattern recognition receptors appear to be involved, further strengthening the link between host risk factors, H. pylori incidence and cancer. Many of these genes influence cellular pathways leading to inflammatory signaling, inflammasome formation and autophagy. In this review we summarize known carcinogenic effects of H. pylori, and discuss recent findings that implicate host genetic pattern recognition pathways in the development of gastric cancer and their relation with H. pylori.     

Endothelium-derived relaxing and contracting factors

Key discoveries in the past decade revealed that the endothelium can modulate the tone of underlying vascular smooth muscle by the synthesis/release of potent vasorelaxant (endothelium-derived relaxing factors; EDRF) and vasoconstrictor substances (endothelium-derived contracting factors; EDCF). It has become evident that the synthesis and release of these substances contribute to the multitude of physiological functions the vascular endothelium performs. Accumulating evidence suggests that at least one of the EDRFs is identical with nitric oxide (NO) or a labile nitroso compound, which is produced from L-arginine by an NADPH- and Ca(2+)-dependent enzyme, arginine oxidase. The existence of more than one chemically distinct EDRF has been proposed, including an endothelium-derived hyperpolarizing factor (EDHF). The target of EDRF (NO) is soluble guanylate cyclase (increase in cyclic GMP) while EDHF appears to activate a K(+)-channel in vascular smooth muscle. Recent data suggest that muscarinic receptor subtypes selectively mediate the release of EDRF(NO) (M2) and EDHF (M1). EDRF(NO) affects not only the underlying vascular smooth muscle, but also platelets, inhibiting their aggregation and adhesion to the endothelium. The antiaggregatory effect of EDRF is synergistic with prostacyclin, so their combined release may represent a physiological mechanism aimed at preventing thrombus formation. An additional proposed biological function of EDRF(NO) is cytoprotection by virtue of scavenging superoxide radicals. The endothelium can also mediate vasoconstriction by the release of a variety of endothelium-derived contracting factors (EDCF). Other than the unique peptide endothelin, the nature of EDCFs has not yet been firmly established. Autoregulation of cerebral and renal blood flow and hypoxic pulmonary vasoconstriction may represent the physiological role of endothelium-dependent vasoconstriction. Growing evidence indicates that the endothelium can serve as a unique mechanoreceptor, sensing and transducing physical stimuli (e.g., shear forces, pressure) into changes in vascular tone by the release of EDRFs or EDCFs. In physiological states, a delicate balance exists between endothelium-derived vasodilators and vasoconstrictors. Alterations in this balance can result in local (vasospasm) and generalized (hypertension) increase in vascular tone and also in facilitated thrombus formation. Endothelial dysfunction may also contribute to the pathophysiology of angiopathies associated with hypercholesterolemia and atherosclerosis.