细胞穿透肽穿膜机制的研究进展

细胞穿透肽是一类少于30个氨基酸的短肽,它们能穿过细胞膜并携带各种“货物”包括小分子、蛋白、肽、核酸等进入细胞,而发挥“货物”的生物学作用。其转导机制一直是研究的热点,至今仍不明确。本文讨论直接入胞、转导、内吞3种可能的穿膜机制及其特点。     

生物活性肽调节胰岛素分泌的信号转导机制

Mastoparan(MAS) and α-latrotoxin(α-LTX) are two kinds of insulinotropic peptides obtained from insect toxins which can interact with islet β-cells and induce insulin secretion. The signal mechanism of these insulinotropic peptides regulating insulin-releasing attracts notable attention and has been elucidated more and more details. MAS mainly acts on the molecular components of exocytosis at a late stage. Insulin secretion induced by MAS is obviously dependent on GTP, which subsequently activates G-protein located on insulin secretion granules(ISG), or activates the Rho subfamily of small G proteins to evoke exocytosis and sensitize fusion machinery. The MAS stimulated insulin-releasing activity can be augmented by nutrients. However, its effect is not Ca2+ dependent. There are two regulatory pathway triggered by α-LTX: one way is pore formation caused through plasma membrane, another way is the transmembrane signal transduction evoked by cytosolic second messengers. Tetrameri complexs assembled at high concentration of α-LTX toxin or in the presence of extracellular Ca2+, can insert α-LTX into plasma membrane to form Ca2+ permeable channels and trigger Ca2+-dependent secretion. By binding to transmembrane receptors and activating phospholipase C, α-LTX induces the generation of second messenger DAG and IP3. IP3 triggers Ca2+ influx and subsequently activates CaMK pathway, however, DAG also activates PKC pathway to increase insulin release.     

甲状腺滤泡旁细胞的研究进展

甲状腺滤泡旁细胞是甲状腺中产生降钙素的细胞。但作为ＡＰＵＤ系的甲状腺滤泡旁细胞也有分泌多种调节肽的功能。本文对甲状腺滤泡旁细胞分泌调节肽的种类，分泌调节肽的基因机制以及调节肽的作用机制的研究进行综述     

SM蛋白家族在分泌过程中的作用机制研究进展

Secl/Munc-18(SM)蛋白是一类与分泌相关的亲水性蛋白质,能以多种结合方式与可溶性N-乙基马莱酰胺敏感因子(NSF)附着蛋白受体(SNARE)的Syntaxin蛋白家族结合,进而参与细胞的分泌调控。虽然SM蛋白对于细胞分泌至关重要,但是SM蛋白调节细胞分泌的分子机制尚不清楚。SM蛋白可能主要在囊泡的锚定(docking)过程中起作用,但是也有文献表明SM蛋白可能也参与锚定以后的启动(priming)、融合(fusion)等分泌步骤中的调控。     

甲亢和甲减患者血清胃泌素变化的初步探讨

胃泌素 (gastrin ,Gs)系由胃窦部十二指肠上部、胰腺等组织的G细胞分泌的一种脑肠肽类激素。其主要生理功能是短期的强烈刺激胃酸分泌作用和长期的胃粘膜营养作用 ,是临床判断消化道是否正常的一个重要指标。Gs水平不但可以反映消化系统疾病 ,而且在甲状腺疾病时也可以引起改变。为探讨两者之间的内在关系 ,我们对 4 5例甲亢和 74例甲减患者进行了血清Gs含量检测 ,现将结果报道如下。1　材料和方法1 1　对象1 1 1　正常人　 4 0人 (男 2 5 ,女 15 ) ,年龄 (18～ 35 )岁 ,平均2 6 5岁。均为我院部队合格的健康人 ,无心、肝、肺、肾等重要…     

细胞穿透肽转运机制、分子改造及相关免疫治疗

细胞穿透肽(cell penetrating peptides,CPPs)也称为蛋白转导结构域(protein transduction domain,PTD)是一类具有较强的穿膜活性的多肽,可以携带各种生物分子转运到细胞内,这一特点使其在药物转运系统及疾病治疗等领域有着广泛的研究,但是其穿膜转运机制尚不清楚。CPPs的穿膜过程可以分为3步,首先CPPs特殊的生化性质使其与细胞表面相互作用,形成空间优势,然后通过不同的方式进行跨膜转运,之后在CPPs在细胞内有不同的转运路径与定位。这种特性使其在免疫治疗方面有广阔的应用前景。本文就其运转过程的研究做一概括总结。随着研究不断深入,需要对传统的PTD进行改建、开发或者构建新的仿CPPs分子达到提高其运转效率、细胞内特异性定位及靶向不同种类细胞的目的,优化CPPs运转系统,为疫苗设计提供新的思路,并满足基础研究的需要。     

肝纤维化发病机制的研究进展

肝纤维化是对慢性肝损伤的一种修复反应,肝纤维化的特征改变是肝脏内细胞外基质（extracellular matrix,ECM）的过度沉积。肝星状细胞（hepatic stellate cells, HSCs）的活化被认为是这一过程中的关键事件。在纤维形成过程中,促纤维形成细胞、细胞因子、生长因子、酶及其抑制因子发挥了十分重要的作用。     

一种新的来源于人的穿膜肽通过细胞膜屏障和血脑屏障的研究

目的 :观察一种新的人体蛋白结构域 (Circadianlocomoteroutputcycleskaput protein’sDNA bindingpeptide ,hCLOCK’sDNA_BIND)通过细胞膜屏障和血脑屏障的现象。方法 :化学合成hCLOCK’sDNA_BIND ,N端标记FITC荧光素 ,与培养的血管内皮细胞株 (ECV 3 0 4)和原代培养的神经胶质细胞孵化后 ,荧光显微镜下观察并做荧光强度分析。大鼠颈动脉注射hCLOCK’sDNA_BIND ,做脑冰冻切片 ,荧光显微镜下观察。结果 :hCLOCK’sDNA_BIND能够有效通过细胞膜屏障和血脑屏障 ,内化的量随时间和肽段浓度的增加而增加。结论 :hCLOCK…     

NK细胞识别和杀伤机制研究进展

NK细胞（Natural killer cell）是一类大颗粒淋巴细胞,存在于淋巴器官和外周组织中,行使多种重要功能：分泌细胞因子如IFN-γ,调节获得性免疫反应,防御感染以及溶解破坏肿瘤细胞等.NK细胞的主要特征是不需预先刺激就可直接溶解破坏肿瘤细胞和病毒感染细胞，通过分泌穿孔素、丝氨酸蛋白酶如颗粒酶A和B、硫酸软骨素蛋白聚糖等分子降解细胞膜、破坏靶细胞完整性而发挥溶细胞效应。本文旨在对NK细胞识别和杀伤机制作一综述，为深入研究NK细胞作用提供参考。     

营养物质调节胰岛素分泌机制的研究进展

胰岛素是人体内唯一起到降低血糖功能的重要激素.它调节机体血糖维持稳定,促进代谢,调节细胞的分裂分化和生长发育.胰岛素分泌不足或分泌功能障碍都将引起机体的糖代谢紊乱,从而引起糖尿病.该文简述营养物质,即糖、脂肪酸和多肽对胰岛素分泌的调节机制,并对可能影响胰岛素分泌的研究进行进一步展望.     

Gonadotropin-Releasing Hormone Stimulates Biliary Proliferation by Paracrine/Autocrine Mechanisms

During cholestatic liver disease, there is dysregulation in the balance between biliary growth and loss in bile duct–ligated (BDL) rats modulated by neuroendocrine peptides via autocrine/paracrine pathways. Gonadotropin-releasing hormone (GnRH) is a trophic peptide hormone that modulates reproductive function and proliferation in many cell types. We evaluated the autocrine role of GnRH in the regulation of cholangiocyte proliferation. The expression of GnRH receptors was assessed in a normal mouse cholangiocyte cell line (NMC), sham, and BDL rats. The effect of GnRH administration was evaluated in normal rats and in NMC. GnRH-induced biliary proliferation was evaluated by changes in intrahepatic bile duct mass and the expression of proliferation and function markers. The expression and secretion of GnRH in NMC and isolated cholangiocytes was assessed. GnRH receptor subtypes GnRHR₁ and GnRHR₂ were expressed in cholangiocytes. Treatment with GnRH increased intrahepatic bile duct mass as well as proliferation and function markers in cholangiocytes. Transient knockdown and pharmacologic inhibition of GnRHR₁ in NMC decreased proliferation. BDL cholangiocytes had increased expression of GnRH compared with normal rats, accompanied by increased GnRH secretion. In vivo and in vitro knockdown of GnRH decreased intrahepatic bile duct mass/cholangiocyte proliferation and fibrosis. GnRH secreted by cholangiocytes promotes biliary proliferation via an autocrine pathway. Disruption of GnRH/GnRHR signaling may be important for the management of cholestatic liver diseases.Cholangiocytes, which line the intrahepatic biliary epithelium, play key roles in the modification of canalicular bile and are the target of chronic cholestatic liver diseases (ie, cholangiopathies). Cholangiopathies are characterized by dysregulation of the balance between biliary proliferation and loss, leading to chronic liver injury, liver failure, and, ultimately, liver transplantation.¹ Among several gastrointestinal hormones/peptides regulating biliary functions, secretin is a key stimulatory factor that promotes ductal secretion and cholangiocyte proliferation.^2,3 Secretin stimulates bicarbonate secretion by interaction with its receptor (SR), which causes phosphorylation of the cAMP-dependent cystic fibrosis transmembrane conductance regulator (CFTR) with subsequent activation of the Cl⁻/HCO₃^- anion exchanger 2 (AE2).^4–6 Secretin-stimulated ductal secretion increases in parallel to enhanced biliary hyperplasia but decreases during biliary damage, suggesting that the secretin–SR–CFTR–AE2 axis may be an important functional index/regulator of changes in biliary proliferation/loss.^2,5,7,8Several animal models including bile duct ligation (BDL) mimic human cholangiopathies.^2,7,8 For example, in rodents with BDL, there is enhanced proliferation of large cAMP-dependent cholangiocytes that leads to increased intrahepatic bile duct mass (IBDM).^3,9 The proliferative response of the biliary epithelium to liver injury is characterized by cholangiocytes acquiring neuroendocrine phenotypes, which allows these cells to secrete a number of peptides and hormones [such as follicle-stimulating hormone (FSH), secretin, melatonin, and vascular endothelial factor] that are key for maintaining the homeostasis of the biliary epithelium by both autocrine/paracrine mechanisms.^3,8,10 In addition, these factors modulate the liver fibrosis that accompanies the onset of cholestatic liver diseases.¹¹ The BDL model of cholestatic injury also is characterized by marked hepatic fibrosis, which starts primarily around the biliary epithelium.¹² Activation of hepatic stellate cells and myofibroblasts contribute to the progression of fibrosis, although some studies have highlighted the contribution of cholangiocytes in this process.¹³The peptide gonadotropin-releasing hormone (GnRH), which is synthesized and released from neurons within the hypothalamus,¹⁴ mediates the release of FSH and luteinizing hormone from the anterior pituitary gland. GnRH exerts its effects by interacting with two GnRH receptor (GnRHR) subtypes, GnRHR₁ and GnRHR₂, which are expressed in mammals.¹⁵ There is evidence of an extrahypothalamic origin for GnRH as well as an extrapituitary presence of GnRHR in numerous peripheral tissues including reproductive organs such as testis, ovary, oviduct, and mammary glands.¹⁶ The mRNA for GnRHRs has been shown to be expressed in various nonreproductive human tissues such as liver, pancreas, colon, kidney, heart, and pituitary.^17,18 Several studies have shown that GnRH exerts its cellular functions both in vivo and in vitro by activation of cAMP levels.^19,20 With regard to inositol triphosphate (IP₃)-dependent signaling (an important pathway modulating biliary function),^21,22 some studies have shown that GnRH exerts its effects by increasing IP₃ levels,^23,24 although other studies have shown that GnRH has no effects on IP₃ levels.²⁵ GnRH has been shown to promote or inhibit cell proliferation (depending on the cell type) in various carcinomas of the breast, ovary, endometrium, pancreas, and liver.²⁶ A study has shown higher expression of both GnRH and GnRHRs in grade I and grade II human hepatocellular carcinoma, suggesting modulation of hepatocellular growth by this neuroendocrine hormone.²⁷ However, limited information exists regarding the cellular localization of GnRH and its receptors in the liver and particularly in the biliary epithelium, and the effect of GnRH on liver pathophysiology.^26,28 Thus, we performed studies to show the paracrine/autocrine role of GnRH in the regulation of biliary mass in normal and cholestatic BDL rats.     

Bi-directional Signaling between Gastrointestinal Peptide Hormone Receptors and Epidermal Growth Factor Receptor

The mechanisms mediating the proliferative effects of gastrointestinal (GI) peptide hormones and their cognate G protein-coupled receptors are associated intimately with epidermal growth factor (EGF) receptor-regulated signaling pathways. Although transactivation of the EGF receptor is now recognized as a critical component in GI peptide hormone regulation of mitogenic signaling and cell migration, their interactions are far more complex and include potentiation of intracellular signaling pathways, regulation of ligand expression and release, and modulation of cell surface receptor expression. Mitogen-activated protein kinases play a central role integrating the signals from these receptor systems. This review summarizes the mechanisms that intertwine GI peptide hormone receptor- and EGF receptor-activation and functions.     

Mechanisms of the Effects of Adrenocorticotropic Hormone on Pain Sensitivity in Rats

Experiments on anaesthetized male Sprague-Dawley rats were performed to study the effects of adrenocorticotropic hormone (ACTH) on pain sensitivity. Systemic administration of ACTH to animals with normal hormone production induced rapidly developing (starting at 3 min) and prolonged (30 min) increases in pain response thresholds. Blockade of opiate receptors led to suppression of the initial stage of the analgesic effect of ACTH: the response was seen only from 15 to 30 min. In animals with deficient glucocorticoid production, the duration of the analgesic action of ACTH decreased to 15 min. Analgesia was completely eliminated by the combination of suppression of glucocorticoid production and blockade of opiate receptors. The analgesic effect of ACTH was mediated by two mechanisms: 1) a rapidly-acting (from 3 to 15 min) mechanism associated with opiate receptors and not related to glucocorticoids, and 2) a delayed (from 15 to 30 min) mechanism associated with glucocorticoids but not opiate receptors.     

Expression of CART Peptide in the Paleoamygdala Neurons and Its Relationship with Sex Hormone Levels

The location of CART peptide in the paleoamygdala neurons was studied by immunocytochemical reaction. Significant differences in the number of immunoreactive cells and optical density of CART-positive neurons detected over the course of the estrous cycle indicate modulating effects of sex steroids on the expression of CART peptide.     

Steroid Hormone Action in Musculoskeletal Cells Involves Membrane Receptor and Nuclear Receptor Mechanisms

Steroid hormones regulate target cells through traditional nuclear mechanisms as well as by membrane mechanisms. 1 &#102 ,25(OH) 2 D 3 and 24R,25(OH) 2 D 3 bind membrane receptors (mVDR) and mediate their effects on the physiological responses of musculoskeletal cells via protein kinase C (PKC). In cultures of costochondral growth plate chondrocytes, 1 &#102 ,25(OH) 2 D 3 binds the 1,25-mVDR in growth zone cells, activating phospholipase C (PLC), leading to diacylglycerol (DAG) production and PKC translocation to the plasma membrane. It also activates PLA 2 , increasing arachidonic acid release and prostaglandin synthesis. 24R,25(OH) 2 D 3 binds its membrane receptor in resting zone chondrocytes, activating phospholipase D (PLD), and increasing DAG and PKC activity, but translocation does not occur. PLA 2 activity is decreased, reducing arachidonic acid and prostaglandin production. 17 &#103 -Estradiol (E 2 ) activates PKC in both cartilage cells, but DAG is not involved. 1 &#102 ,25(OH) 2 D 3 and 24R,25(OH) 2 D 3 also increase PKC in osteoblasts in a cell-specific manner. Antibodies to the 1,25-mVDR block PKC activation. Membrane-mediated events influence gene expression via signaling cascades, including the ERK1/2 MAP kinases. The ability of steroid hormones to initiate events nongenomically is important for regulation of matrix vesicle (MV) function in the extracellular matrix. MVs have mVDRs, but ligand binding inhibits PKC-zeta (PKC &#145 ) via a mechanism that differs from PKC &#102 activation in the plasma membranes. Treatment of MVs from growth zone chondrocyte cultures with 1 &#102 ,25(OH) 2 D 3 releases stromelysin-1 (MMP-3) and increases TGF- &#103 activation. MMP-3 is also involved in proteoglycan degradation, facilitating calcification. 24R,25(OH) 2 D 3 inhibits PKC &#145 in MV from resting zone cell cultures and inhibits MMP-3 release. Chondrocytes and osteoblasts produce 1,25(OH) 2 D 3 , 24,25(OH) 2 D 3 , and E 2 ; thus, locally produced steroids may function as autocrine regulators of matrix events, including matrix vesicle enzyme activity and matrix protein remodelling during longitudinal growth, calcification, and growth factor activation.     

透析方式不影响慢性肾衰患者血浆内皮素、心钠素和甲状旁腺素水平的变化

对１２例持续非卧床腹膜透析（ＣＡＰＤ）维持一年以上和１６例维持一年以上血液透析的慢性肾衰透析患者（其中９例合并高血压），用放射免疫分析测定血浆内皮素（ＥＴ）、心钠素（ＡＮＰ）和甲状旁腺素（ＰＴＨ）的水平，以观察经ＨＤ和ＣＡＰＤ的慢性肾衰患者血浆ＥＴ、ＡＮＰ和ＰＴＨ的变化。慢性肾衰患者血浆ＥＴ、ＡＮＰ和ＰＴＨ浓度均较对照组显著升高，而透析８周前、后差异不显著，合并高血压的透析患者ＥＴ、ＡＮＰ和ＰＴＨ较对照组显著升高，但与无高血压的透析组比，差异也不显著。结果表明ＥＴ、ＡＮＰ和ＰＴＨ在慢性肾衰的发病机制中起重要作用，但ＣＡＰＤ与ＨＤ对ＥＴ、ＡＮＰ和ＰＴＨ水平的影响无明显差异。