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1.
Molecular sorting in the secretory pathway 总被引：13，自引：0，他引：13
Proteins can be secreted from animal cells by either a constitutive or a regulated pathway; those destined for regulated secretion are actively sorted into dense-core secretory granules. Although sorting is generally assumed to be accomplished by specific carriers, the nature of these carriers remains elusive. In this study, peptide hormones were used as affinity ligands to purify a set of 25-kilodalton proteins from canine pancreatic tissue. Their ligand specificities and patterns of expression have the characteristics of sorting carriers. 相似文献
2.
Directionality in intracellular trafficking is essential to ensure the correct localization of proteins along the secretory pathway. Here, we found evidence for an active mechanism that prohibited back-fusion of de novo-generated vesicles with their donor compartment. Tip20p is a peripheral membrane protein implicated in consumption of COPI vesicles at the endoplasmic reticulum. However, a specific mutant of TIP20 did not interfere with COPII vesicle generation but allowed these vesicles to fuse back to the endoplasmic reticulum, a process that does not occur normally in the cell. 相似文献
3.
Lysosomes are membrane-bound organelles that are found in all mammalian cells and contain hydrolases and lipases required for protein and membrane degradation. In many cells of the immune system, lysosomes also contain secretory proteins that can be released by regulated exocytosis in response to an external stimulus, providing different cell types with a wide range of effector functions. Melanosomes also use a lysosome-related organelle to secrete melanin for pigmentation. Links between albinism and immunity in patients have uncovered a number of key proteins required for lysosomal secretion and have revealed a versatile secretory mechanism that can be fine-tuned by distinct interactions in different cell types. 相似文献
4.
Bacterial type III protein secretion systems deliver effector proteins into eukaryotic cells in order to modulate cellular processes. Central to the function of these protein-delivery machines is their ability to recognize and secrete substrates in a defined order. Here, we describe a mechanism by which a type III secretion system from the bacterial enteropathogen Salmonella enterica serovar Typhimurium can sort its substrates before secretion. This mechanism involves a cytoplasmic sorting platform that is sequentially loaded with the appropriate secreted proteins. The sequential loading of this platform, facilitated by customized chaperones, ensures the hierarchy in type III protein secretion. Given the presence of these machines in many important pathogens, these findings can serve as the bases for the development of novel antimicrobial strategies. 相似文献
5.
Helical structures of ESCRT-III are disassembled by VPS4 总被引：1，自引：0，他引：1
Lata S Schoehn G Jain A Pires R Piehler J Gottlinger HG Weissenhorn W 《Science (New York, N.Y.)》2008,321(5894):1354-1357
During intracellular membrane trafficking and remodeling, protein complexes known as the ESCRTs (endosomal sorting complexes required for transport) interact with membranes and are required for budding processes directed away from the cytosol, including the budding of intralumenal vesicles to form multivesicular bodies; for the budding of some enveloped viruses; and for daughter cell scission in cytokinesis. We found that the ESCRT-III proteins CHMP2A and CHMP3 (charged multivesicular body proteins 2A and 3) could assemble in vitro into helical tubular structures that expose their membrane interaction sites on the outside of the tubule, whereas the AAA-type adenosine triphosphatase VPS4 could bind on the inside of the tubule and disassemble the tubes upon adenosine triphosphate hydrolysis. CHMP2A and CHMP3 copolymerized in solution, and their membrane targeting was cooperatively enhanced on planar lipid bilayers. Such helical CHMP structures could thus assemble within the neck of an inwardly budding vesicle, catalyzing late steps in budding under the control of VPS4. 相似文献
6.
The relation of cellular sex genotype to phenotype was examined in seminal vesicles of adult allophenic mice with cellular sex chromosome mosaicism. Each animal originated from conjoined blastomeres of an embryo of female (XX) and one of male (XY) constitution, from different inbred strains. Cells of both sexes were detected in bone marrow and certain other somatic tissues; cellular sex of seminal vesicles was deduced from strain-associated electrophoretic variants of proteins coded for at autosomal loci. Seminal vesicles composed partly or entirely of female cells were found in male and pseudohermaphrodite individuals. In a pseudohermaphrodite, both allelic variants of the tissue-specific normal male seminal vesicle protein (Svp-locus) were present, signifying that female as well as male cells were synthesizing the protein. Male-determining factors on the Y chromosome are thus not required in cells that differentiate into functional seminal vesicles. 相似文献
7.
A test of clathrin function in protein secretion and cell growth 总被引：37，自引：0，他引：37
Clathrin-coated membranes are intimately associated with a variety of protein transport processes in eukaryotic cells, yet no direct test of clathrin function has been possible. The data presented demonstrate that Saccharomyces cerevisiae does not require clathrin for either cell growth or protein secretion. Antiserum to the yeast clathrin heavy chain has been used to isolate a molecular clone of the heavy chain gene (CHC1) from a library of yeast DNA in lambda gt11. Clathrin-deficient mutant yeast have been obtained by replacing the single chromosomal CHC1 gene with a disrupted version of the cloned DNA. Cells harboring a nonfunctional chc1 allele produce no immunoreactive heavy chain polypeptide, and vesicles prepared from mutant cells are devoid of clathrin heavy and light chains. Although clathrin-deficient cells grow two to three times more slowly than normal, secretion of invertase occurs at a nearly normal rate. Therefore protein transport through the secretory pathway is not obligately coupled to the formation of clathrin-coated vesicles. 相似文献
8.
Living with clathrin: its role in intracellular membrane traffic 总被引：53，自引：0，他引：53
F M Brodsky 《Science (New York, N.Y.)》1988,242(4884):1396-1402
Clathrin polymerization at the cytoplasmic side of the plasma membrane forms coated pits and vesicles that mediate uptake of cell surface receptors. Clathrin-coated vesicles have also been implicated in protein export but definition of their precise role has been controversial. Recent advances in characterization of the clathrin subunits and additional coated vesicle components have identified molecular interactions involved in clathrin polymerization and coated vesicle formation, and have provided new approaches to investigating its function. These studies suggest that clathrin's role, in both inward and outward membrane traffic, is to facilitate receptor transport by a concentration and sorting process that initiates targeting to specific intracellular compartments. 相似文献
9.
Regulatory role for GTP-binding proteins in endocytosis 总被引：25，自引：0，他引：25
Guanosine 5'-triphosphate (GTP)-binding proteins have been implicated in the transport of newly synthesized proteins along the secretory pathway of yeast and mammalian cells. Early vesicle fusion events that follow receptor-mediated endocytosis as measured by three in vitro assays were blocked by guanosine 5'-O-(3-thiotriphosphate) and aluminum fluoride. The effect was specific for guanosine nucleotides and depended on the presence of cytosolic factors. Thus, GTP-binding proteins may also have a role in the transport of molecules along the endocytic pathway. 相似文献
10.
The Golgi-localized, gamma-ear-containing, adenosine diphosphate ribosylation factor-binding proteins (GGAs) are multidomain proteins that bind mannose 6-phosphate receptors (MPRs) in the Golgi and have an essential role in lysosomal enzyme sorting. Here the GGAs and the coat protein adaptor protein-1 (AP-1) were shown to colocalize in clathrin-coated buds of the trans-Golgi networks of mouse L cells and human HeLa cells. Binding studies revealed a direct interaction between the hinge domains of the GGAs and the gamma-ear domain of AP-1. Further, AP-1 contained bound casein kinase-2 that phosphorylated GGA1 and GGA3, thereby causing autoinhibition. This could induce the directed transfer of the MPRs from GGAs to AP-1. MPRs that are defective in binding to GGAs are poorly incorporated into AP-1-containing clathrin-coated vesicles. Thus, the GGAs and AP-1 interact to package MPRs into AP-1-containing coated vesicles. 相似文献
11.
WU Wei-cheng GAOQi-kang CHEN Jin-e YE Jian QIAN Yang-wen LI Jian-ying LU Hua-yun MENG Zhi-qi NI Chun-xiao ZHONG Bo-xiong 《中国农业科学(英文版)》2007,6(2):249-254
The posterior silk gland （PSG） of silkworm is an important organ where fibroin is synthesized and secreted exclusively. Because fibroin constitutes 75-80% of the silk filament, the mechanism governing fibroin secretion, quality and yield of cocoon can be elucidated by the study on the PSG. Using two-dimensional gel electrophoresis （2-DE） and image analysis system, the changes in the protein composition in the PSG cell were investigated on the day 1 （D1） and day 4 （D4） in the 5th instar stage from five different strains of silkworm （Bombyx mori）. While differences at protein level between days and strains were far less than those observed at the gene level using EST analysis. The change trends in protein composition from D1 to D4 were diverse among the different strains. The results suggest that the secretion of fibroin is regulated by multiple proteins. The site of regulation and the proteins responsible for the regulation vary with the strain, which leads to differences between strains in the capacity of fibroin secretion in the PSG cell. 相似文献
12.
Peptide processing and targeting in the neuronal secretory pathway 总被引：14，自引：0，他引：14
The abdominal ganglion of the marine mollusk Aplysia contains a pair of identified neuronal clusters, the bag cells, which control egg laying by means of a number of unique regulatory mechanisms. Each neuron in the bag cell clusters synthesizes several peptides derived from a single prohormone and packages them into separate vesicles. These vesicles are then differentially localized in specific neuronal processes, thus segregating peptides destined for autocrine and hormonal release sites. Therefore in this system, protein trafficking through the secretory pathway organizes multiple peptide neurochemical messengers to efficiently regulate simple behaviors. 相似文献
13.
Gaietta G Deerinck TJ Adams SR Bouwer J Tour O Laird DW Sosinsky GE Tsien RY Ellisman MH 《Science (New York, N.Y.)》2002,296(5567):503-507
Recombinant proteins containing tetracysteine tags can be successively labeled in living cells with different colors of biarsenical fluorophores so that older and younger protein molecules can be sharply distinguished by both fluorescence and electron microscopy. Here we used this approach to show that newly synthesized connexin43 was transported predominantly in 100- to 150-nanometer vesicles to the plasma membrane and incorporated at the periphery of existing gap junctions, whereas older connexins were removed from the center of the plaques into pleiomorphic vesicles of widely varying sizes. Selective imaging by correlated optical and electron microscopy of protein molecules of known ages will clarify fundamental processes of protein trafficking in situ. 相似文献
14.
Mediation of the attachment or fusion step in vesicular transport by the GTP-binding Ypt1 protein 总被引：32，自引：0，他引：32
N Segev 《Science (New York, N.Y.)》1991,252(5012):1553-1556
The function of the guanosine triphosphate (GTP)-binding protein Ypt1 in regulating vesicular traffic was studied in a cell-free system that reconstitutes transport from the endoplasmic reticulum to the Golgi. Blocking the Ypt1 protein activity resulted in accumulation of vesicles that act as an intermediate passing between the two compartments. The Ypt1 protein was found on the outer side of these vesicles. The transport process is completed by fusion of these vesicles with the acceptor compartment, and Ypt1 protein activity was needed for this step. Thus, a specific GTP-binding protein is required for either attachment or fusion (or both) of secretory vesicles with the acceptor compartment during protein secretion. 相似文献
15.
Gram-positive bacteria face unique challenges in generating biologically active conformations for their exported proteins because they lack a dedicated compartment for folding secreted polypeptides. We have discovered that protein secretion by way of the general secretory (Sec) pathway in the important human pathogen Streptococcus pyogenes proceeds through a single microdomain. Unlike other mechanisms for asymmetry involving the Sec pathway, proteins destined for secretion are targeted to a single locus distal to either cell pole that has specialized to contain the Sec translocons. This subcellular organization may represent a paradigm for secretion common to other Gram-positive pathogens with profound implications for pathogenesis. 相似文献
16.
以长双歧杆菌NCC2705基因组序列为研究对象,使用Signal P 4.0、Lipo P、TMHMM 2.0软件分析该基因组中的分泌蛋白及其信号肽的类型,同时采用COG(Cluster of Orthologous Groups of proteins)功能数据库对预测的分泌蛋白进行功能注释和聚类分析。结果表明,长双岐杆菌NCC2705中共有37个Sec途径分泌蛋白,其中Sec途径分泌蛋白包括27个被I型(SPaseⅠ)信号肽酶和10个Ⅱ型信号肽酶(Spase II)识别的蛋白,Sec途径分泌蛋白信号肽长度最多的有52个氨基酸,最少的有10个氨基酸。分泌蛋白的功能分析表明,该菌株分泌蛋白中含有大部分的假定蛋白,主要参与氨基酸代谢与转运、碳水化合物代谢转运,无机盐离子代谢转运,细胞壁和细胞膜生物合成的功能有关。 相似文献
17.
The molecular control of blood cell development 总被引：24，自引：0，他引：24
L Sachs 《Science (New York, N.Y.)》1987,238(4832):1374-1379
The establishment of a cell culture system for the clonal development of blood cells has made it possible to identify the proteins that regulate the growth and differentiation of different blood cell lineages and to discover the molecular basis of normal and abnormal cell development in blood forming tissues. A model system with myeloid blood cells has shown that (i) normal blood cells require different proteins to induce cell multiplication (growth inducers) and cell differentiation (differentiation inducers), (ii) there is a hierarchy of growth inducers as cells become more restricted in their developmental program, and (iii) a cascade of interactions between proteins determines the correct balance between immature and mature cells in normal blood cell development. Gene cloning has shown that there is a family of different genes for these proteins. Normal protein regulators of blood cell development can control the abnormal growth of certain types of leukemic cells and suppress malignancy by inducing differentiation to mature nondividing cells. Chromosome abnormalities that give rise to malignancy in these leukemic cells can be bypassed and their effects nullified by inducing differentiation, which stops cells from multiplying. These blood cell regulatory proteins are active in culture and in the body, and they can be used clinically to correct defects in blood cell development. 相似文献
18.
Implantation of genetically engineered fibroblasts into mice: implications for gene therapy 总被引：7，自引：0，他引：7
R F Selden M J Skoskiewicz K B Howie P S Russell H M Goodman 《Science (New York, N.Y.)》1987,236(4802):714-718
In a variety of human genetic diseases, replacement of the absent or defective protein provides significant therapeutic benefits. As a model for a somatic cell gene therapy system, cultured murine fibroblasts were transfected with a human growth hormone (hGH) fusion gene and cells from one of the resulting clonal lines were subsequently implanted into various locations in mice. Such implants synthesized and secreted hGH, which was detectable in the serum. The function of the implants depended on their location and size, and on the histocompatibility of the donor cells with their recipients. The expression of hGH could be modified by addition of regulatory effectors, and, with appropriate immunosuppression, the implants survived for more than 3 months. This approach to gene therapy, here termed "transkaryotic implantation," is potentially applicable to many genetic diseases in that the transfected cell line can be extensively characterized prior to implantation, several anatomical sites are suitable for implantation, and regulated expression of the gene of therapeutic interest can be obtained. 相似文献
19.
Salmonella enterica causes a variety of diseases, including gastroenteritis and typhoid fever. The success of this pathogen depends on its capacity to proliferate within host cells in a membrane-bound compartment. We found that the Salmonella-containing vacuole recruited the plus-end-directed motor kinesin. Bacterial effector proteins translocated into the host cell by a type III secretion system antagonistically regulated this event. Among these effectors, SifA targeted SKIP, a host protein that down-regulated the recruitment of kinesin on the bacterial vacuole and, in turn, controlled vacuolar membrane dynamics. 相似文献
20.
Guanosine 5'-triphosphate (GTP)-binding proteins (G proteins) are involved in exocytosis, endocytosis, and recycling of vesicles in yeast and mammalian secretory cells. However, little is known about their contribution to fast synaptic transmission. We loaded guanine nucleotide analogs directly into a giant nerve terminal in rat brainstem slices. Inhibition of G-protein activity had no effect on basal synaptic transmission, but augmented synaptic depression and significantly slowed recovery from depression. A nonhydrolyzable GTP analog blocked recovery of transmission from activity-dependent depression. Neither effect was accompanied by a change in presynaptic calcium currents. Thus, G proteins contribute to fast synaptic transmission by refilling synaptic vesicles depleted after massive exocytosis. 相似文献