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At least 217 records · Page 12Linked to original sources
PubMed1988

Impaired chloride secretion, as well as bicarbonate secretion, underlies the fluid secretory defect in the cystic fibrosis pancreas.

Pancreatic fluid and electrolyte secretion was assessed in 56 patients with cystic fibrosis (CF) and 56 non-CF control subjects undergoing pancreatic function testing while stimulated with cholecystokinin and secretin. Both CF patients and control subjects exhibited a wide range of pancreatic function. Fluid and trypsin outputs were positively correlated in both groups. Fluid output in CF subjects was significantly lower, however, than that of control subjects at any given level of trypsin output. Sodium, bicarbonate, and chloride secretions were all significantly decreased in CF subjects. Bicarbonate and chloride were important determinants of fluid secretion, but at any given bicarbonate or chloride output CF subjects secreted significantly less fluid than control subjects. When bicarbonate and chloride were analyzed as simultaneous predictor variables, adjusted fluid secretion was not significantly different in CF and control subjects. Diminished fluid secretion in CF subjects is therefore caused by impaired chloride, as well as bicarbonate, secretion.

Bicarbonates↗
PubMed1982

Metabolic energy and cytoskeletal requirements for synthesis and secretion by acini from rat mammary gland-II. Intracellular transport and secretion of protein and lactose.

1. Iodoacetate, 2,4-dinitrophenol, cyanide and cycloheximide inhibited protein secretion as well as synthesis by acini (alveoli) from rat mammary gland. Cytochalasin B and vinblastine inhibited protein secretion and marginally reduced protein synthesis. Colchicine was without effect on protein synthesis but inhibited secretion. 2. Intracellular protein transport was altered during incubation with metabolic and cytoskeletal inhibitors. Cycloheximide, iodoacetate. 2,4-dinitrophenol and cytochalasin B appeared to block protein synthesis on polysomes of rough endoplasmic reticulum. Vinblastine inhibited protein transport from rough endoplasmic reticulum to Golgi apparatus and colchicine appeared to cause accumulation of protein in several endomembrane fractions. 3. Iodoacetate reduced acinar lactose content but was without effect on lactose synthetase activity. Cyanide, cycloheximide and vinblastine reduced reduced lactose synthetase activity but not tissue lactose concentration. Cytochalasin B reduced glucose incorporation but was without effect on lactose content and lactose synthetase activity. Colchicine and 2,4-dinitrophenol did not alter glucose incorporation, lactose content or lactose synthetase activity. Lactose secretion was inhibited by all metabolic and cytoskeletal inhibitors examined. 4. Results indicated that sustained protein secretion depended on continued protein synthesis and that lactose secretion was coupled to protein secretion.

Animals↗
PubMed1988

Prostaglandin secretion by perifused porcine endometrium: further evidence for an endocrine versus exocrine secretion of prostaglandins.

Bilateral perifusion devices were utilized for measurement of prostaglandin secretion by luminal and myometrial surfaces of porcine endometrium. Tissues were collected from Days 10, 12 and 14 pregnant, Day 14 cyclic and Day 14 estrogen-induced pseudopregnant gilts. Each tissue was placed into duplicate perifusion devices and perifused with Krebs-Ringer Bicarbonate solution at 3 ml/10 min for 2 h, fractions collected every 10 min and oxytocin (1 IU/ml) perifused during fractions 6-10 to the luminal side of one chamber and to the myometrial side of the other chamber. Secretion rates of PGF were higher (P less than 0.05) than PGE2 for each status. Secretion rates of PGF and PGE2 were higher (P less than 0.01) from the luminal side for Day 12 pregnant, Day 14 pregnant and Day 14 pseudo-pregnant gilts, whereas secretion was higher from the myometrial side for Day 10 pregnant and Day 14 cyclic gilts. Oxytocin increased (P less than 0.01) prostaglandin secretion from the luminal side regardless of reproductive status. Pregnancy at Day 12 and Day 14, as well as estrogen treatment, were associated with prostaglandin secretion in a luminal (exocrine) orientation versus a myometrial (endocrine) orientation for Day 14 cyclic and Day 10 pregnant gilts. These data indicate an estrogen associated switch between Days 10 and 12 of pregnancy from an endocrine to an exocrine secretion of prostaglandins.

Animals↗
PubMed1988

Prostaglandin secretion by perifused bovine endometrium: secretion towards the myometrial and luminal sides at day 17 post-estrus as altered by pregnancy.

Bilateral perifusion devices were utilized to measure prostaglandin secretion towards luminal and myometrial sides of bovine endometria. Tissues were collected at Day 17 post-estrus from cyclic (n = 4), pregnant (n = 5) and bred but subsequently non-pregnant (n = 6) cows. Tissue from each cow was placed into two perifusion devices, perifused with Krebs-Ringer Bicarbonate solution (3 ml/10 min) for 2.5 h and fractions collected every 10 min. Oxytocin (1 IU/ml) was perifused during fractions 7-12 to the luminal side of one device and to the myometrial side of the other device. Regardless of status, prostaglandin secretion rates (PGF and PGE2) were higher (P less than 0.01) from the luminal side than the myometrial side. Secretion rates of PGF were lower (P less than 0.01) for endometria from pregnant cows than for endometria from cyclic or bred/non-pregnant cows, whereas secretion rates of PGE2 were not affected by pregnancy status. Regardless of the side of perifusion, secretion rates of PGF and PGE2 from endometria of cyclic and bred/non-pregnant cows were elevated (P less than 0.01) throughout the period of oxytocin treatment, whereas prostaglandin secretion by endometria from pregnant cows was not stimulated by oxytocin. Decreased secretion of PGF from endometria of pregnant cows suggests that the corpus luteum and pregnancy are maintained because of an inhibition of endometrial prostaglandin synthesis or an inability to respond to stimulators of prostaglandin synthesis (i.e. oxytocin).

Animals↗
PubMed2000

Primary response of naive CD4(+) T cells to amino acid-substituted analogs of an antigenic peptide can show distinct activation patterns: Th1- and Th2-type cytokine secretion, and helper activity for antibody production without apparent cytokine secretion.

Naive CD4(+) T cells differentiate into two types of helper T cells showing an interferon-gamma-predominant (Th1) or an interleukin-4-predominant (Th2) cytokine secretion profile after repeated antigenic stimulation. Their differentiation can be influenced by slight differences in the interaction between the T cell receptor (TCR) and its ligand at the time of primary activation. However, the primary response of freshly isolated naive CD4(+) T cells to altered TCR ligands is still unclear. Here, we investigated the primary response of splenic naive CD4(+) T cells derived from transgenic mice expressing TCR specific for residues 323-339 of ovalbumin (OVA323-339) bound to I-A(d) molecules. Naive CD4(+) T cells secreted either Th1- or Th2-type cytokines immediately after stimulation with OVA323-339 or its single amino acid-substituted analogs. Helper activity for antibody secretion by co-cultured resting B cells was also found in the primary response, accompanied by either low-level Th2-type cytokine secretion or no apparent cytokine secretion. Our results clearly indicate that dichotomy of the Th1/Th2 cytokine secretion profile can be elicited upon primary activation of naive CD4(+) T cells. We also demonstrate that the helper activity of naive CD4(+) T cells for antibody production does not correspond to the amounts of the relevant cytokines secreted.

Amino Acid Sequence↗
PubMed1997

Dietary carrot results in diminished ovarian progesterone secretion, whereas a metabolite, retinoic acid, stimulates progesterone secretion in the in vitro perfused rabbit ovary.

OBJECTIVE: To determine the effects of dietary carrots and retinoic acid on P secretion in the in vitro perfused rabbit ovary. DESIGN: Controlled experiment. SETTING: Laboratory. SUBJECTS: Sexually mature New Zealand white rabbits. INTERVENTION(S): Experiments were done in vitro using an isolated rabbit ovarian perfusion system after acute feeding of carrots or with in vitro exposure to retinoic acid. MAIN OUTCOME MEASURE(S): Progesterone and E2 were measured in aliquots taken from arterial and venous cannulas. RESULT(S): Progesterone secretion during the in vitro perfusion of six ovaries is significantly diminished after the acute feeding of carrots. Human chorionic gonadotropin-induced P secretion also is significantly reduced. Progesterone secretion during in vitro perfusion on day 1 of pseudopregnancy was significantly increased in the perfusate samples from ovaries taken from rabbits not acutely fed carrots but that were exposed to retinoic acid. Progesterone secretion was increased but only marginally significant on day 11 of pseudopregnancy in perfusate samples from ovaries exposed to retinoic acid. CONCLUSION(S): Rabbit ovarian P secretion may be modified by carrots and carotene metabolites. This effect on steroid secretion may contribute to the relationship between hypercarotenemia and alterations in menstrual function.

Animals↗
PubMedDate not supplied

Novel secretion system of recombinant Saccharomyces cerevisiae using an N-terminus residue of human IL-1 beta as secretion enhancer.

An N-terminus sequence of human interleukin 1beta (hIL-1beta) was used as a fusion expression partner for the production of two recombinant therapeutic proteins, human granulocyte-colony stimulating factor (hG-CSF) and human growth hormone (hGH), using Saccharomyces cerevisiae as a host. The expression cassette comprised the leader sequence of killer toxin of Kluyveromyces lactis, the N-terminus 24 amino acids (Ser5-Ala28) of mature hIL-1beta, the KEX2 dibasic endopeptidase cleavage site, and the target protein (hG-CSF or hGH). The gene expression was controlled by the inducible UAS(gal)/MF-alpha1 promoter. With the expression vector above, both recombinant proteins were well secreted into culture medium with high secretion efficiencies, and especially, the recombinant hGH was accumulated up to around 1.3 g/L in the culture broth. This is due presumably to the significant role of fused hIL-1beta as secretion enhancer in the yeast secretory pathway. In our recent report, various immunoblotting analyses have shown that the presence of a core N-glycosylation resident in the hIL-1beta fragment is likely to be of crucial importance in the high-level secretion of hG-CSF from the recombinant S. cerevisiae. When the N-glycosylation was completely blocked with the addition of tunicamycin to the culture, the secretion of hG-CSF and hGH was decreased to a negligible level although the other host-derived proteins were well secreted to the culture broth regardless of the presence of tunicamycin. The N-terminal sequencing of the purified hG-CSF verified that the hIL-1beta fusion peptide was correctly removed by in vivo KEX2 protease upon the exit of fusion protein from Golgi complex. From the results presented in this article, it is strongly suggested that the N-terminus fusion of the hIL-1beta peptide could be utilized as a potent secretion enhancer in the expression systems designed for the secretory production of other heterologous proteins from S. cerevisiae.

Enteropeptidase↗
PubMed1999

Evidence of mucin secretion in human lung adenocarcinoma cell lines NCIH650 and NCIH2077 and effect of select secretagogues on mucin secretion.

Mucins comprise an important class of tumor-associated antigens. The objectives of the present study were (a) to establish an in vitro model system using human non-small cell lung adenocarcinoma cell lines NCIH650 and NCIH2077 (b) provide evidence that these cell lines secrete mucin in culture conditions and (c) investigate the effects of select secretagogues on mucin secretion. The cell lines were established in ACL-4 medium containing several growth factors and retinoic acid and 5% fetal calf serum. The high molecular weight glycoconjugates secreted in the culture medium were purified by ammonium sulfate precipitation and Superose 6 and Superose 12 FPLC chromatography. The purified high molecular weight glycoconjugate fraction and the carcinoma cells were shown to have mucin by dot blot, Western blot and immunohistochemical analysis, respectively, using specific antibodies to purified major mucin, HTM-1. Also, incorporation experiments with mucin precursor 3H-glucosamine demonstrated that the cells indeed synthesize high molecular weight mucins. The effects of secretagogues such as, 8-bromocyclic AMP, ionomycin, phorbol-12-myristate-13-acetate and neutrophil elastase on mucin secretion were also investigated. Only 8-bromocyclic AMP and neutrophil elastase influenced mucin secretion. These studies provided strong evidence that the lung adenocarcinoma cell lines secrete high molecular weight mucins in culture conditions and only two of the four tested secretagogues significantly increased mucin secretion. Thus, this in vitro model system may be useful in determining alterations in mucin structure, if any, in lung adenocarcinomas as well as in studying the regulation of mucin gene expression.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2005

Extracellular secretion of polypeptides using a modified Escherichia coli flagellar secretion apparatus.

We developed a modified flagellar type III secretion apparatus to secrete heterologous polypeptides into the growth medium of Escherichia coli. The secretion was facilitated by fusing the 173-bp untranslated DNA fragment upstream of the gene fliC (encoding flagellin) as well as a transcriptional terminator from fliC, into the gene encoding the polypeptide of interest. The polypeptides secreted into the growth medium at concentrations ranging from 1 to 15 mg/l were from Campylobacter jejuni (262 residues in length), Streptococcus pneumoniae (434 residues), Staphylococcus aureus (115 residues), and N-terminal FliC hybrid proteins, for example, the eukaryotic green fluorescent protein (238 residues). The expressed proteins represented >50% of total secreted protein. Previously reported protein yields from extracellular secretion of foreign proteins in E. coli have been low, approximately 100 microg/l. The strengths of our method are the concentration and purity of the secreted proteins and its versatility with regard to the proteins' length and origin.

Bacterial Proteins↗
PubMed1997

Interactions of the components of the general secretion pathway: role of Pseudomonas aeruginosa type IV pilin subunits in complex formation and extracellular protein secretion.

The general secretion pathway (GSP), found in a wide range of bacteria, is responsible for extracellular targeting of a subset of proteins from the periplasm. In Pseudomonas aeruginosa, the GSP requires the participation of 12 proteins, of which XcpT, XcpU, XcpV, XcpW are homologues of PilA, the major subunit of type IV pili. The interaction between the pilin-like Xcp proteins was investigated using bifunctional crosslinking reagents. Cross-linking analysis of whole cells of wild-type P. aeruginosa, followed by immunoblot analysis, revealed a 34-kDa XcpT-containing complex. This complex was shown to consist of XcpT/PilA heterodimers. The role of PilA in the GSP was examined, using P. aeruginosa mutants in the pilA gene, or in rpoN, a gene regulating pilA expression. Each mutant showed a significant reduction in the efficiency of extracellular protein secretion, and this defect could be restored by expression of the cloned pilA gene in the mutant cells. The formation of the PilA/XcpT complex did not require XcpR or XcpQ, two other components of the secretion machinery, nor did it require the pilus biogenesis factors PilB and PIlC. The dimeric XcpT/PilA complex was also formed in a pilD mutant, which lacks the leader peptidase enzyme, demonstrating that the leader peptide at the N-terminus or PilA or XcpT did not have to be removed for the dimerization to occur. XcpW and XcpU can also be crosslinked to form dimeric complexes with PilA. When expression of XcpT is increased, its homodimers, as well as XcpT/XcpW heterodimers, can be detected. Finally, an oligohistidine-tagged XcpT was shown to form stoichiometric complexes with PilA, and with XcpT, U, V and W. These dimers were co-purified by nickel-affinity chromatography. The results of this study suggest that XcpT can form heterodimers with PilA, and Xcp U, V and W, which may be assembly intermediates of the secretion apparatus. Alternatively, these may represent dynamic intermediates that facilitate protein secretion by continuous association and dissociation. The requirement for PilA for efficient protein secretion argues for a critical role played by PilA in two related processes during P. aeruginosa infections: formation of an adhesive pilus organelle and secretion of exoenzymes.

Bacterial Outer Membrane Proteins↗
PubMed1999

Yersinia enterocolitica type III secretion: an mRNA signal that couples translation and secretion of YopQ.

Pathogenic Yersinia species export Yop proteins via a type III machinery to escape their phagocytic killing during animal infections. Here, we reveal the type III export mechanism of YopQ. In the presence of calcium, when type III secretion was blocked, yopQ mRNA was not translated. The signal of YopQ sufficient for the secretion of translationally fused reporter proteins was contained within the first 10 codons of its open reading frame. Some frameshift mutations that completely altered the peptide sequence specified by this signal did not impair secretion of the reporter protein. Exchanging the upstream untranslated mRNA leader of yopQ for that of E. coli lacZ also did not affect secretion. However, removal of the first 15 codons abolished YopQ export. Pulse-labelled YopE, but not YopQ, could be secreted after the polypeptide had been synthesized within the cytoplasm of Yersinia (post-translational secretion). Thus, YopQ appears to be exported by a mechanism that couples yopQ mRNA translation with the type III secretion of the encoded polypeptide.

5' Untranslated Regions↗
PubMed2002

The ShcA protein is a molecular chaperone that assists in the secretion of the HopPsyA effector from the type III (Hrp) protein secretion system of Pseudomonas syringae.

Pseudomonas syringae uses a type III protein secretion system encoded by the Hrp pathogenicity island (Pai) to translocate effector proteins into plant cells. One of these effector proteins is HopPsyA. A small open reading frame (ORF), named shcA, precedes the hopPsyA gene in the Hrp Pai of P. s. syringae 61. The predicted amino acid sequence of shcA shares general characteristics with chaperones used in type III protein secretion systems of animal pathogens. A functionally non-polar deletion of shcA in P. s. syringae 61 resulted in the loss of detectable HopPsyA in supernatant fractions, consistent with ShcA acting as a chaperone for HopPsyA. Cosmid pHIR11 carries a functional set of type III genes from P. s. syringae 61 and confers upon saprophytes the ability to secrete HopPsyA in culture and to elicit a HopPsyA-dependent hypersensitive response (HR) on tobacco. P. fluorescens carrying a pHIR11 derivative lacking shcA failed to secrete HopPsyA in culture, but maintained the ability to secrete another type III-secreted protein, HrpZ. This pHIR11 derivative was also greatly reduced in its ability to elicit an HR, indicating that the ability to translocate HopPsyA into plant cells was compromised. Using affinity chromatography, we showed that ShcA binds directly to HopPsyA and that the ShcA binding site must reside within the first 166 amino acids of HopPsyA. Thus, ShcA represents the first demonstrated chaperone used in a type III secretion system of a bacterial plant pathogen. We searched known P. syringae type III-related genes for neighbouring ORFs that shared the general characteristics of type III chaperones and identified five additional candidate type III chaperones. Therefore, it is likely that chaperones are as prevalent in bacterial plant pathogen type III systems as they are in their animal pathogenic counterparts.

Bacterial Proteins↗
PubMed1999

Immunogenicity and protective efficacy of DNA vaccines encoding secreted and non-secreted forms of Mycobacterium tuberculosis Ag85A.

OBJECTIVE: To determine the efficacy of Ag85A-DNA against challenge with a highly virulent human clinical isolate of Mycobacterium tuberculosis (CSU37) and to compare the potencies of two types of Ag85A-DNA vaccines; those expressing secreted and non-secreted forms of the protein. DESIGN: Ag85A-DNA vaccinated mice were challenged with a highly virulent clinical isolate of M. tuberculosis (CSU37) in order to compare the efficacy of these vaccines. In vitro studies were also performed. RESULTS: Enhanced humoral and cellular responses were induced in mice vaccinated with the secreted Ag85A-DNA compared to the non-secreted Ag85A-DNA. In addition, secreted Ag85A-DNA conferred protective immunity against infection with M. tuberculosis (CSU37). CONCLUSIONS: DNA vaccines encoding M. tuberculosis Ag85A have been shown to induce potent humoral and cellular immune responses leading to protection from M. tuberculosis (Erdman) challenge in mouse models. In this study we demonstrate that Ag85A can confer protection in a rigorous challenge model using a highly virulent human clinical isolate of M. tuberculosis (CSU37). This challenge model appears able to discriminate between DNA vaccines of differing potencies, as the more immunogenic DNA construct encoding a secreted form of Ag85A was protective, whereas the less immunogenic DNA construct encoding a non-secreted form of Ag85A was not.

Acyltransferases↗
PubMed2006

Secretion signal recognition by YscN, the Yersinia type III secretion ATPase.

Yersinia type III machines secrete protein substrates across the bacterial envelope. Secretion signals of some substrates have been identified; however, the mechanisms whereby these signals interact with type III machines are not known. Here we show that fusion of YopR, an early secretion substrate, to the N terminus of dihydrofolate reductase (DHFR) or other tightly folded proteins generates impassable hybrids that cannot travel the type III pathway. YopR hybrids capture YscN, the ATPase that provides energy for type III transport reactions, in the bacterial cytoplasm. Eleven N-terminal residues function as the YopR secretion signal, which is required for both binding to YscN and blocking the type III pathway. When expressed during type III machine assembly, YopR-DHFR blocks all secretion. Delayed expression of YopR-DHFR, when yersiniae have already engaged the type III pathway, blocks secretion of early (YscP) but not of late (effector Yops) substrates. These observations support a model whereby type III machines are programmed to secrete a sequence of proteins that can be disrupted when an impassable early substrate interacts with the YscN ATPase and blocks the transport of late substrates.

Adenosine Triphosphatases↗
PubMed1974

Antigen-secreting cells: enumeration of immunoglobulin-allotype-secreting cells in nonimmunized rabbits by means of hybrid-antibody-coated erythrocytes in a reverse hemolytic plaque assay.

A reverse hemolytic plaque-forming cell (PFC) assay for the enumeration of immunoglobulin-(Ig)secreting cells in nonimmunized rabbits was developed by using erythrocytes coated with anti-Ig antibody. These indicator cells lysed after reacting with the secreted Ig antigen and complement. The anti-Ig antibodies used were specific for the b4 or b5 allotypic specificities, which are antigenic determinants on the kappa chain of rabbit Ig and controlled by alleles at the b locus. We coated erythrocytes with anti-b4 or anti-b5 antibody, using hybrid antibody with dual specificity to sheep red blood cells and to the b4 or b5 kappa chain. The coated erythrocytes were plated with cells from various lymphoid organs of nonimmunized rabbits. These lymphoid cells formed allotype-specific plaques, i.e., the cells of b4 homozygous rabbits formed hemolytic plaques with anti-b4 but not with anti-b5-coated erythrocytes and vice versa. In eight nonimmunized rabbits, 0.06-0.3% of the spleen cells (590-2900 PFC per 10(6) cells) secreted the b locus Ig allotypes. In three nonimmunized rabbits, 320-590 PFC per 10(6) cells were counted in the lymph node or bone marrow; 26-40 PFC per 10(6) cells were detected in the thymus. Since the b4 and b5 specificities are present on approximately 90% of the serum Ig, our results indicate that less than 1% of the lymphoid cells in nonimmunized rabbits secrete Ig at any one time. By this reverse PFC assay, Ig-secreting cells were for the first time detected as antigen-secreting cells. This assay can be applied to the detection of cells secreting other antigens.

Animals↗
PubMedDate not supplied

Protein secretion in the absence of ATP: the autotransporter, two-partner secretion and chaperone/usher pathways of gram-negative bacteria (review).

Bacteria secrete a wide variety of proteins, many of which play important roles in virulence. In gram-negative bacteria, these proteins must cross the cytoplasmic or inner membrane, periplasm, and outer membrane to reach the cell surface. Gram-negative bacteria have evolved multiple pathways to allow protein secretion across their complex envelope. ATP is not available in the periplasm and many of these secretion pathways encode components that harness energy available at the inner membrane to drive secretion across the outer membrane. In contrast, the autotransporter, two-partner secretion and chaperone/usher pathways are comparatively simple systems that allow secretion across the outer membrane without the need for input of energy from the inner membrane. This review will present overviews of these 'self-sufficient' pathways, focusing on recent advances and secretion mechanisms. Similarities among the pathways and with other protein translocation mechanisms will be highlighted.

Adenosine Triphosphate↗
PubMed1993

Overexpression of uteroferrin, a lysosomal acid phosphatase found in porcine uterine secretions, results in its high rate of secretion from transfected fibroblasts.

Lysosomal enzymes can, under certain circumstances, be secreted in large amounts. One example is uteroferrin (Uf), an iron-containing, purple-colored acid phosphatase secreted by the uterus of the pig during pregnancy. Uf is identical to the intracellular tartrate-resistant acid phosphatase of pig spleen, yet is the major protein component of uterine secretions. To investigate possible regulatory mechanisms that might direct Uf along a secretory pathway, we expressed Uf in Chinese hamster ovary (CHO) cells under the control of the SV40 early promoter using an expression construct, pX/Uf. The proportion of Uf secreted into the medium relative to the amount retained intracellularly increased as total Uf expression was increased. At transfection doses of 15 micrograms pX/Uf per 10(6) cells, over 80% of the Uf produced in 48 h was secreted. A parallel situation was observed when human cathepsin D was overexpressed in CHO cells. Thus, high production of Uf, as occurs in the uterus in response to progesterone, may overwhelm the intracellular enzymatic and receptor systems that are normally employed to target acid hydrolases to lysosomes, resulting in secretion. Both Uf and cathepsin D secreted by CHO cells possess N-linked, phosphorylated high-mannose oligosaccharide chains. However, the phosphate groups on the oligosaccharide chains of Uf, unlike those on cathepsin D, cannot be readily removed by alkaline phosphatase treatment. These results suggest that the phosphate groups on Uf are masked at least partially by covering N-acetylglucosamine residues and that two mechanisms may contribute to hypersecretion of Uf in the uterus: 1) very high rates of synthesis and 2) partial masking of the mannose 6-phosphate recognition signal.

Acid Phosphatase↗
PubMed2003

Secretion trap tagging of secreted and membrane-spanning proteins using Arabidopsis gene traps.

Secreted and membrane-spanning proteins play fundamental roles in plant development but pose challenges for genetic identification and characterization. We describe a "secretion trap" screen for gene trap insertions in genes encoding proteins routed through the secretory pathway. The gene trap transposon encodes a beta-glucuronidase reporter enzyme that is inhibited by N-linked glycosylation specific to the secretory pathway. Treatment of seedlings with tunicamycin inhibits glycosylation, resulting in increased activity of secreted beta-glucuronidase fusions that result from gene trap integration downstream of exons encoding signal peptides. In the 2,059 gene trap lines that we screened, 32 secretion trap expression patterns were identified in a wide variety of tissues including embryos, meristems, and the developing vasculature. Genes disrupted by the secretion traps encode putative extracellular signaling proteins, membrane transport proteins, and novel secreted proteins of unknown function missed by conventional mutagenesis and gene prediction. Secretion traps provide a unique reagent for gene expression studies and can guide the genetic combination of loss of function alleles in related genes.

Arabidopsis↗