新的天然免疫保护分子SPLUNC1的结构与功能研究进展

腭、肺及鼻咽上皮克隆(palate,lung,and nasal epithelium clone,PLUNC) 家族为一新近发现的具有宿主防御功能的蛋白质家族,它们大多存在于呼吸道上皮与消化道上皮的表面,在上皮组织与外界各种信号之间起着信号传递中介与信号执行分子的作用．在迄今为止发现的人类10个PLUNC家族成员中,我们所克隆的NASG基因即为这一免疫保护分子家族的成员,对其结构与功能分析表明,它属于SPLUNC1 (short palate,lung,and nasal epithelium clone 1) 的全新转录本,具有杀菌/ 渗透增强蛋白质结构域,能对外来物理及化学刺激做出反应,并具有抗微生物、清除有害化学物质、抗肿瘤等多重功效．SPLUNC1 作为上呼吸道的一种新的天然免疫保护分子,在维持上呼吸道的正常生理活动以及抗炎杀菌抑瘤中起着重要作用．     

PLUNC蛋白家族在抑制鼻咽上皮“炎-癌”演进中的作用和机制

人类鼻咽黏膜表面的分泌物中富含天然免疫蛋白,腭、肺及鼻咽上皮克隆(palate,lung and nasal epithelium clone,PLUNC)蛋白家族成员SPLUNC1和LPLUNC1就是其中的重要组成部分,这两个蛋白在鼻咽上皮相对特异高表达,它们都具有杀菌/渗透增强蛋白(bactericidal/permeability-increasing protein,BPI)结构域,可通过BPI结构域与细菌脂多糖(lipopolysaccharides,LPS)结合从而直接杀灭或抑制细菌生长,也可以有效抑制EB病毒(Epstein-Barr virus,EBV)等致癌微生物对鼻咽上皮的侵袭从而发挥其免疫防御功能.它们还可以通过抑制IL-6等炎症因子的分泌和NF-κB、STAT3等炎症相关通路的激活,阻止鼻咽部的慢性炎症反应及鼻咽上皮的恶性转化.在鼻咽癌细胞中重新表达PLUNC蛋白,可以通过促分裂素原活化蛋白激酶(Mitogen-activated protein kinase,MAPK)或miR-141-PTEN-AKT等信号通路抑制鼻咽癌细胞的增殖,促进鼻咽癌细胞的凋亡.进一步深入研究PLUNC蛋白家族在鼻咽癌发病中的作用机制,对指导鼻咽癌的防治具有重要的意义.     

综述:PLUNC蛋白家族在抑制鼻咽上皮“炎-癌”演进中的作用和机制

人类鼻咽黏膜表面的分泌物中富含天然免疫蛋白,腭、肺及鼻咽上皮克隆(palate,lung and nasal epithelium clone,PLUNC)蛋白家族成员SPLUNC1和LPLUNC1就是其中的重要组成部分,这两个蛋白在鼻咽上皮相对特异高表达,它们都具有杀菌/渗透增强蛋白(bactericidal/permeability-increasing protein,BPI)结构域,可通过BPI结构域与细菌脂多糖(lipopolysaccharides,LPS)结合从而直接杀灭或抑制细菌生长,也可以有效抑制EB病毒(Epstein-Barr virus,EBV)等致癌微生物对鼻咽上皮的侵袭从而发挥其免疫防御功能．它们还可以通过抑制IL-6等炎症因子的分泌和NF-κB、STAT3等炎症相关通路的激活,阻止鼻咽部的慢性炎症反应及鼻咽上皮的恶性转化．在鼻咽癌细胞中重新表达PLUNC蛋白,可以通过促分裂素原活化蛋白激酶(Mitogen-activated protein kinase,MAPK)或miR-141-PTEN-AKT等信号通路抑制鼻咽癌细胞的增殖,促进鼻咽癌细胞的凋亡．进一步深入研究PLUNC蛋白家族在鼻咽癌发病中的作用机制,对指导鼻咽癌的防治具有重要的意义．     

人PYHIN家族在固有免疫信号转导的研究进展

PYHIN家族亦称为HIN-200蛋白家族/干扰素诱导P200蛋白家族(IFI-P200家族),目前已经鉴定出人的PYHIN家族成员有AIM2、IFI16、IFIX和MNDA四种。近几年来研究发现,PYHIN家族在转导固有免疫信号时扮演重要角色,一些成员如AIM2、IFI16、IFIX等已被证实作为DNA传感器识别外源DNA分子进而启动机体自我保护机制。就人类PYHIN家族成员在DNA传感器研究和固有免疫信号转导等的研究进展作一综述。     

SFRP分子对心脏发育的影响

Wnt信号通路对心脏发育起着重要的作用.分泌型卷曲相关蛋白（SFRP）家族作为调控 Wnt信号的重要分子,对心脏发育和心肌分化的作用也越来越被人们所重视.最近,研究人员们对SFRP家族蛋白有了新的认识,认为它们不仅具有拮抗Wnt的作用,还对Wnt信号的转导有着复杂的调节作用.本文就SFRP分子与Wnt信号转导对心脏发育的影响进行综述.     

癌蛋白D52家族

癌蛋白D52家族近年来引起人们的研究兴趣.D52最早是从人乳腺癌中发现的.该家族成员分子中都含有一个叫做Coil-coil基序的高度保守结构域,这个结构域在从低等生物到哺乳动物或者同种生物的不同成员间是高度保守的.已有研究表明,该家族成员可以通过选择性剪接的方式产生功能不同的拼接体.D52家族基因在多种癌症中广泛扩增,蛋白表达水平升高.目前认为,他们的基因功能可能与包括癌症在内的人类疾病相关,然而,关于该家族成员发挥作用的分子机制还有待深入研究.     

PAQR 膜蛋白家族研究进展

孕激素和脂联素分子受体家族(PAQRs)是一类不同于G蛋白耦联受体家族的7次跨膜蛋白家族,目前发现该家族在人类具有11个成员。这类蛋白的结构类似于细菌的溶血素蛋白III,跨膜区域完全由一个高度保守的PFAM-UPF0073结构域构成。对该家族成员的生理功能研究发现,PAQR1,PAQR2具有维持代谢稳态和参与炎症反应的作用。PAQR5,PAQR7,PAQR8对于精子顶体反应,卵细胞的成熟和细胞凋亡有着重要的调节作用。随着对该家族成员分子的深入研究,一方面将更新对其现有生理病理过程的认识,另一方面将更加明确该类蛋白介导的信号转导通路,为相关疾病的治疗提供新的靶点和新的策略。     

富亮氨酸α2糖蛋白1(LRG1)在肿瘤中的研究进展

富亮氨酸α2糖蛋白1(Leucine-rich-alpha-2-glycoprotein1,LRG1)是富亮氨酸重复序列(leucine-rich repeat,LRR)家族蛋白成员之一。LRG1在人类多种肿瘤中表达异常,可以作为部分肿瘤早期诊断的潜在生物标记,而且这种异常表达可能提示患者预后不良。LRG1在肿瘤的发生、侵袭转移、上皮间质转化和血管生成中发挥重要作用。这些环节中,协同参与调控的辅助因子众多且有差异,因而经历的信号途径有所不同。本文综合目前的研究进展,旨在阐述LRG1与肿瘤的关系以及其调控肿瘤发生发展的分子机制。LRG1有望成为一种新的肿瘤分子标志物,将为恶性肿瘤的分子诊断及靶向治疗提供新的方向和手段。     

转录调控因子Fox的功能及分子机制研究进展

Fox (Forkhead box)蛋白家族有19个亚族, 它们通过结合DNA, 激活或抑制目的基因的转录活性, 同时还能参与细胞信号转导、 细胞周期调控和新陈代谢的调节, 在生物体发育及其成熟的组织器官中均能发挥重要作用, 目前, 有关Fox蛋白家族的功能及分子机制已逐步成为免疫学、 遗传学、 医学以及肿瘤学领域的研究热点。本文综述了Fox家族成员的命名及分类、 蛋白结构及其DNA识别机制以及该家族成员如何参与Hh, TGF-β/SMAD, MAPK, Wnt/β-catenin和IGF信号通路的调控。Fox家族可调控线虫的咽、 果蝇的唾液腺以及哺乳动物的肝脏和眼睛等器官的发育, 能够影响细胞周期, 其家族成员FoxA可以和CREB、 GR结合调控新陈代谢。不同物种的Fox家族成员个数存在差异, 并且受到严格的进化选择。对其功能和分子进化机制进一步研究可为阐明生物的发育机理和人类疾病的防治提供新的思路。     

支架蛋白Gab2信号调控与乳腺癌

Gab2是支架蛋白Gabs家族中的重要成员.该家族蛋白通过介导膜受体与信号转运蛋白间的偶联及各信号分子间的整合参与信号传导.作为支架蛋白,Gab2可被酪氨酸激酶磷酸化激活,接受胞外多种因子刺激,招募富含SH2结构域的信号转运分子,活化下游SHP2/Ras/ERK和PI3K/AKT等一系列信号传导途径,在细胞增殖、分化、...     

Paneth cells of the human small intestine express an antimicrobial peptide gene.

Mucosal surfaces of several organ systems are important interfaces for host defense against microbes. Recent evidence suggests that antimicrobial peptides contribute to the defense of these surfaces. Defensins are one family of antimicrobial peptide, but their known distribution in humans has been limited to four members found in cells of myeloid origin. We sought to determine if the human defensin family was more complex. We found that the family of human defensins is diverse and is not restricted to expression in leukocytes. Southern blot and genomic clone analyses reveal that numerous defensin-related sequences are present in the human genome. A gene for a new human defensin family member was characterized. This gene, designated human defensin-5, is highly expressed in Paneth cells of the small intestine. This is the first example of an antimicrobial peptide gene expressed in an epithelial cell in humans. The data support the hypotheses that epithelial defensins equip the human small bowel with a previously unrecognized defensive capability which would augment other antimicrobial defenses.     

Mucins: structure, function, and associations with malignancy.

Mucins are a family of high molecular weight, highly glycosylated glycoproteins found in the apical cell membrane of human epithelial cells from the mammary gland, salivary gland, digestive tract, respiratory tract, kidney, bladder, prostate, uterus and rete testis. Increased synthesis of the core protein and alterations in the carbohydrates attached to these glycoproteins are believed to play important roles in the function and proliferation of tumour cells. Aberrant glycosylation leads not only to the production of novel carbohydrate structures, but also to the exposure of the core peptide. These novel epitopes may be candidates for diagnosis or therapy, by using either synthetic mucin fragments as vaccines, or monoclonal antibody-based reagents which detect these structures.     

Human LPLUNC1 is a secreted product of goblet cells and minor glands of the respiratory and upper aerodigestive tracts

Long PLUNC1 (LPLUNC1, C20orf114) is a member of a family of poorly described proteins (PLUNCS) expressed in the upper respiratory tract and oral cavity, which may function in host defence. Although it is one of the most highly expressed genes in the upper airways and has been identified in sputum and nasal secretions by proteomic studies, localisation of LPLUNC1 protein has not yet been described. We developed affinity purified antibodies and localised the protein in tissues of the human respiratory tract, oro- and nasopharynx. We have complemented these studies with analysis of LPLUNC1 expression in primary human lung cell cultures and used Western blotting to study the protein in cell culture secretions and in BAL. LPLUNC1 is a product of a population of goblet cells in the airway epithelium and nasal passages and is also present in airway submucosal glands and minor glands of the oral and nasal cavities. The protein is not expressed in peripheral lung epithelial cells. LPLUNC1 is present in bronchoalveolar lavage fluid as two glycosylated isoforms and primary airway epithelial cells produce identical proteins as they undergo mucociliary differentiation. Our results suggest that LPLUNC1 is an abundant, secreted product of goblet cells and minor mucosal glands of the respiratory tract and oral cavity and suggest that the protein functions in the complex milieu that protects the mucosal surfaces in these locations.     

Water channel protein AQP3 is present in epithelia exposed to the environment of possible water loss.

Aquaporins (AQPs) are membrane water channel proteins expressed in various tissues in the body. We surveyed the immunolocalization of AQP3, an isoform of the AQP family, in rat epithelial tissues. AQP3 was localized to many epithelial cells in the urinary, digestive, and respiratory tracts and in the skin. In the urinary tract, AQP3 was present at transitional epithelia. In the digestive tract, abundant AQP3 was found in the stratified epithelia in the upper part, from the oral cavity to the forestomach, and in the simple and stratified epithelia in the lower part, from the distal colon to the anal canal. In the respiratory tract, AQP3 was present in the pseudostratified ciliated epithelia from the nasal cavity to the intrapulmonary bronchi. In the skin, AQP3 was present in the epidermis. Interestingly, AQP3 was present at the basal aspects of the epithelia: in the basolateral membranes in the simple epithelia and in the multilayered epithelia at plasma membranes of the basal to intermediate cells. During development of the skin, AQP3 expression commenced late in fetal life. Because these AQP3-positive epithelia have a common feature, i.e., they are exposed to an environment of possible water loss, we propose that AQP3 could serve as a water channel to provide these epithelial cells with water from the subepithelial side to protect them against dehydration. (J Histochem Cytochem 47:1275-1286, 1999)     

Human beta-defensin-2.

Human beta-defensin-2 (HBD-2) is a cysteine-rich cationic low molecular weight antimicrobial peptide recently discovered in psoriatic lesional skin. It is produced by a number of epithelial cells and exhibits potent antimicrobial activity against Gram-negative bacteria and Candida, but not Gram-positive Staphylococcus aureus. HBD-2 represents the first human defensin that is produced following stimulation of epithelial cells by contact with microorganisms such as Pseudomonas aeruginosa or cytokines such as TNF-alpha and IL-1 beta. The HBD-2 gene and protein are locally expressed in keratinocytes associated with inflammatory skin lesions such as psoriasis as well as in the infected lung epithelia of patients with cystic fibrosis. It is intriguing to speculate that HBD-2 is a dynamic component of the local epithelial defense system of the skin and respiratory tract having a role to protect surfaces from infection, and providing a possible reason why skin and lung infections with Gram-negative bacteria are rather rare.     

Predicted expansion of the claudin multigene family

Claudins (Cldn) are essential membrane proteins of tight junctions (TJs), which form the paracellular permselective barrier. They are produced by a multi-gene family of 24 reported members in mouse and human. Based on a comprehensive search combined with phylogenetic analyses, we identified three novel claudins (claudin-25, -26, and -27). Quantitative RT-PCR revealed that the three novel claudins were expressed in a tissue- and/or developmental stage-dependent manner. Claudins-25 and -26, but not claudin-27, were immunofluorescently localized to TJs when exogenously expressed in cultured MDCK and Eph epithelial cell lines. These findings expand the claudin family to include at least 27 members.     

Differential expression of claudin 1, 3, and 4 during normal mammary gland development in the mouse

The claudins are a family of tight junction proteins that display varied tissue distribution and preferential specificity. We recently identified by microarray analysis, members of this family, particularly claudin 1 (cldn1), as highly upregulated genes in the mouse mammary gland during early involution. Gene expression was confirmed by immunohistochemistry and real-time PCR. We then examined gene and protein expression throughout normal mammary gland development. The cldn3 gene showed a steady increase in expression from pregnancy to involution, while cldn1 and cldn4 gene expression increased during pregnancy, but decreased sharply by D10 of lactation, and once again was significantly increased by D1 of involution (P < 0.001 for both genes). The different patterns of gene expression observed between cldn3, and cldn1, and 4 suggest that different family members may be functionally important at different times during mouse mammary gland development. All three genes exhibited a high level of expression at day 1 (D1) of involution, followed by a dramatic decrease in gene expression to day 10 of involution. Immunostaining with the cldn3 antibody showed intense staining of epithelial cells; however, a lesser degree of staining was evident with the cldn1 antibody. In addition to the lateral staining of epithelial cells, basal staining was evident at D1 and D2 of involution and cytoplasmic staining was evident during lactation. Since claudins are known to play a role as tight junction proteins, lateral and basal staining may suggest a role in other functions such as vesicle trafficking or remodeling of tight junctions at different stages of mammary gland development. Cldn1 and 3 antibodies also stained epithelial cells in mouse mammary tumors. In summary, cldn1, 3, and 4 are differentially expressed in the mammary gland during pregnancy, lactation, and involution, suggesting different roles for these proteins at different stages of mammary gland function. In addition, cldn1 and cldn3 are detected in mammary tumors and the wide distribution of cldn3 in particular, suggest specific roles for these proteins in mammary tumorigenesis.