NK-lysin from skin-secreted mucus of Atlantic salmon and its potential role in bacteriostatic activity

NK-lysin, despite being a direct effector of cytotoxic T and natural killer cells, is an antimicrobial peptide (AMP) with known antibacterial function in vertebrates and so in fish. Its presence has been described in different tissues of teleost fish. One of the strongest antimicrobial barriers in fish is skin-secreted mucus; however, this mucus has been found to contain only a small number of AMPs. The present study describes for the first time the constitutive expression of NK-lysin in Atlantic salmon (Salmo salar) mucus produced by the skin, recording the AMP at a higher concentration than in serum with greater bacteriostatic activity. Hepcidin may be involved to a greater extent in systemic responses since it was expressed to a higher degree in serum which was more potent for alternative complement and peroxidase activities.

Haploid genetic screens identify an essential role for PLP2 in the downregulation of novel plasma membrane targets by viral E3 ubiquitin ligases

The Kaposi's sarcoma-associated herpesvirus gene products K3 and K5 are viral ubiquitin E3 ligases which downregulate MHC-I and additional cell surface immunoreceptors. To identify novel cellular genes required for K5 function we performed a forward genetic screen in near-haploid human KBM7 cells. The screen identified proteolipid protein 2 (PLP2), a MARVEL domain protein of unknown function, as essential for K5 activity. Genetic loss of PLP2 traps the viral ligase in the endoplasmic reticulum, where it is unable to ubiquitinate and degrade its substrates. Subsequent analysis of the plasma membrane proteome of K5-expressing KBM7 cells in the presence and absence of PLP2 revealed a wide range of novel K5 targets, all of which required PLP2 for their K5-mediated downregulation. This work ascribes a critical function to PLP2 for viral ligase activity and underlines the power of non-lethal haploid genetic screens in human cells to identify the genes involved in pathogen manipulation of the host immune system.

Mammaglobin and lipophilin B expression in breast tumors and their lack of effect on breast cancer cell proliferation

BACKGROUND

Mammaglobin (SCGB2A2) and lipophilin B (SCGB1D2) are members of the secretoglobin polypeptide family. Mammaglobin has been shown to be overexpressed in breast tumor tissue, indicating that mammaglobin might confer a growth advantage to mammaglobin-expressing tumor cells.

MATERIALS AND METHODS

The mammaglobin and lipophilin B mRNA expression levels were investigated in seven breast tumors and matched nonneoplastic tissues from the same patients using quantitative real-time RT-PCR. The effect of mammaglobin and lipophilin B expression on breast cancer cell proliferation rates was investigated by analyzing retrovirally transduced Hs578T cell clones. Cell proliferation rates were determined during the exponential growth phase by analyzing the change in lactate dehydrogenase activity over time.

RESULTS

All analyzed breast cancer tumors had lower expression levels of mammaglobin and lipophilin B than the respective mean level of the nonneoplastic breast tissues; no prominent overexpression was evident. There was high variability in the expression of mammaglobin and lipophilin B among the non-neoplastic samples, showing that caution should be taken when evaluating their over- and underexpression in tumors. The expression levels of mammaglobin and lipophilin B correlated with each other in the analyzed samples (p = 0.001). Ectopic overexpression of mammaglobin and lipophilin B did not affect the cell proliferation rate of Hs578T breast carcinoma cells in vitro.

CONCLUSION

Our findings suggest that the overexpression of mammaglobin observed in certain breast tumors is an epiphenomenon not causally involved in breast carcinogenesis.

Characterization of Japanese flounder (Paralichthys olivaceus) NK-lysin, an antimicrobial peptide

The NK-lysin cDNA of Japanese flounder, Paralichthys olivaceus, consists of 657bp, containing an open reading frame (ORF) of 444bp, which encodes 147 amino acid residues. The amino acid sequence of Japanese flounder NK-lysin has 21% identity to porcine NK-lysin and bovine NK-lysin, 23% to equine NK-lysin, and 46% to zebrafish NK-lysin-like protein. Multiple alignments of Japanese flounder NK-lysin and other known saposin-like proteins revealed that the six cysteine residues important for structural folding are completely conserved. The Japanese flounder NK-lysin gene is approximately 2kb and consists of five exons and four introns. Japanese flounder NK-lysin mRNA constitutive expression was mainly detected in gills, heart, head kidney, intestines, peripheral blood leukocytes (PBLs), spleen and trunk kidney, and was detected at low levels in liver, muscle and ovary. However, expression was not detected in brain, skin and stomach of apparently healthy Japanese flounder. Gene expression of Japanese flounder NK-lysin was not inducible by lipopolysaccharide (LPS) treatment. A synthesized NK-lysin peptide, consisting of 27 amino acid residues, showed antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Photobacterium damselae subsp. piscicida.

Production in Escherichia coli of a recombinant C-terminal truncated precursor of surfactant protein B (rproSP-BΔc). Structure and interaction with lipid interfaces

SP-B, a protein absolutely required to maintain the lungs open after birth, is synthesized in the pneumocytes as a precursor containing C-terminal and N-terminal domains flanking the mature sequence. These flanking-domains are cleaved to produce mature SP-B, coupled with its assembly into pulmonary surfactant lipid-protein complexes. In the present work we have optimized over-expression in Escherichia coli and purification of rproSP-B(DeltaC), a recombinant form of human proSP-B lacking the C-terminal flanking peptide, which is still competent to restore SP-B function in vivo. rProSP-B(DeltaC) has been solubilized, purified and refolded from bacterial inclusion bodies in amounts of about 4 mg per L of culture. Electrophoretic mobility, immunoreactivity, N-terminal sequencing and peptide fingerprinting all confirmed that the purified protein had the expected mass and sequence. Once refolded, the protein was soluble in aqueous buffers. Circular dichroism and fluorescence emission spectra of bacterial rproSP-B(DeltaC) indicated that the protein is properly folded, showing around 32% alpha-helix and a mainly hydrophobic environment of its tryptophan residues. Presence of zwitterionic or anionic phospholipids vesicles caused changes in the fluorescence emission properties of rproSP-B(DeltaC) that were indicative of lipid-protein interaction. The association of this SP-B precursor with membranes suggests an intrinsic amphipathic character of the protein, which spontaneously adsorbs at air-liquid interfaces either in the absence or in the presence of phospholipids. The analysis of the structure and properties of recombinant proSP-B(DeltaC) in surfactant-relevant environments will open new perspectives on the investigation of the mechanisms of lipid and protein assembly in surfactant complexes.

Effects of antioxidant vitamins on molecular regulators involved in lung hypoplasia induced by nitrofen

INTRODUCTION

Oxidant herbicide nitrofen (2,4-dichloro-4'-nitrodiphenyl ether) induces in rat embryos congenital diaphragmatic hernia (CDH) with lung hypoplasia. The present study aims at examining whether antioxidant vitamins A, E, and C reverse the effects of the teratogen in the lungs of exposed rats and how they modify the expression of molecular regulators known to be involved in their pathogenesis.

MATERIALS AND METHODS

Wet lung weight-body weight ratio, total DNA, and total protein were determined. Thyroid transcription factor 1 (TTF-1), hepatocyte nuclear factor 3beta (HNF-3beta), and surfactant protein B (SP-B) proteins were measured by immunoblot assay in lung homogenates from rat fetuses exposed in utero to either nitrofen 100 mg intragastrically or vehicle. The coexpression of these factors in the alveolar epithelium was demonstrated by immunohistochemistry. The effects of the addition of vitamins A, C, and E were assessed by comparison with analysis of variance.

RESULTS

Nitrofen decreased lung weight, total DNA, and total protein. The addition of antioxidant vitamins had no effect on lung weight, but increased DNA and protein contents. TTF-1, HNF-3beta, and SP-B proteins were decreased in lung homogenates of exposed rats with CDH. The addition of antioxidant vitamins nearly normalized these values.

CONCLUSIONS

The effects of nitrofen in fetal rat lungs are reversed in part by antioxidant vitamins by upregulating the expression of TTF-1, HNF-3beta, and SP-B. This approach could help to develop transplacental prenatal interventions for CDH.

Expression of tumor protein D52-like genes in childhood leukemia at diagnosis: clinical and sample considerations

The tumor protein D52 gene or protein is frequently overexpressed in several carcinomas, and has been identified as a B cell differentiation marker. D52-like genes are also differentially expressed in particular haematological malignancies, where transcript or protein levels may reflect cellular proliferative or differentiative status. We used RT-PCR to analyse the expression of three D52-like genes in bone marrow at the time of ALL or AML diagnosis in children. Whereas D53 transcripts were undetectable in all samples, D52 and D54 transcripts were frequently detected in ALL and AML, where they were frequently co-expressed. While D52 and D54 transcripts were detected in T-ALL and pre-B ALL at comparable frequencies, D52 was less frequently detected in ALL bone marrow with hyperdiploid karyotypes, compared with samples with normal karyotypes. We also found that total RNA yields significantly differed according to D52 and D54 expression status, and that bone marrow freezer storage time (up to 945 days) differed significantly according to D52 expression status. These results indicate that D52-like genes are not ubiquitously expressed in leukemic bone marrow in children, and that RNA sample parameters may influence measures of gene expression more than commonly appreciated.

Post-transcriptional downregulation of sarcolipin mRNA by triiodothyronine in the atrial myocardium

Thyroid hormone-mediated positive cardiotropic effects are differently regulated between the atria and ventricles. This regulation is, at least in part, dependent on sarcoplasmic reticulum (SR) proteins. Sarcolipin, a homologue of phospholamban, has been recently identified as an atrium-specific SR protein. The expression of sarcolipin mRNA was significantly decreased in the atria of mice with hyperthyroidism and in 3,5,3'-triiodo-l-thyronine-treated neonatal rat atrial myocytes. Promoter activity and mRNA stability analyses revealed that thyroid hormone post-transcriptionally down regulated the expression of sarcolipin mRNA. The atrium-specific effect of thyroid hormone may occur in part through the regulation of atrial sarcolipin gene expression.

Immunohistochemical analysis of secretoglobin SCGB 2A1 expression in human ocular glands and tissues

Human secretoglobin (SCGB) 2A1 (or lipophilin C, lacryglobin, mammaglobin B) is a small protein of unknown function that forms heterodimers with secretoglobin 1D1 (lipophilin A) in tears. SCGB 2A1 is homologous to mammaglobin (mammaglobin A) and the C3 component of prostatein, the major secretory protein of the rat ventral prostate. Androgen-dependent expression of SCGB 2A1 has been observed in the prostate. Besides identification of SCGB 2A1 in the tear proteome only its mRNA had been detected in the lacrimal gland. Here, we report expression of SCGB 2A1 in all ocular glands and in the keratinized stratified squamous epithelium of the eyelid as well as in the stratified epithelium of the conjunctiva and in the orbicularis oculi muscle. Almost all of these tissues are also known to express the androgen receptor. Therefore, we conclude that presence of the androgen signalling machinery could be the main general determinant of SCGB 2A1 expression. Implications of the presence in tear fluid of an androgen-regulated secretoglobin, which most likely binds hydrophobic ligands, for tear film lipid layer formation and function is discussed.

Sarcolipin and phospholamban mRNA and protein expression in cardiac and skeletal muscle of different species

The widely held view that SLN (sarcolipin) would be the natural inhibitor of SERCA1 (sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase 1), and PLB (phospholamban) its counterpart for SERCA2 inhibition is oversimplified and partially wrong. The expression of SLN and PLB mRNA and protein relative to SERCA1 or SERCA2 was assessed in ventricle, atrium, soleus and EDL (extensor digitorum longus) of mouse, rat, rabbit and pig. SLN protein levels were quantified by means of Western blotting using what appears to be the first successfully generated antibody directed against SLN. Our data confirm the co-expression of PLB and SERCA2a in cardiac muscle and the very low levels (in pig and rabbit) or the absence (in rat and mouse) of PLB protein in the slow skeletal muscle. In larger animals, the SLN mRNA and protein expression in the soleus and EDL correlates with SERCA1a expression, but, in rodents, SLN mRNA and protein show the highest abundance in the atria, which are devoid of SERCA1. In the rodent atria, SLN could therefore potentially interact with PLB and SERCA2a. No SLN was found in the ventricles of the different species studied, and there was no compensatory SLN up-regulation for the loss of PLB in PLB(-/-) mouse. In addition, we found that SLN expression was down-regulated at the mRNA and protein level in the atria of hypertrophic hearts of SERCA2(b/b) mice. These data suggest that superinhibition of SERCA by PLB-SLN complexes could occur in the atria of the smaller rodents, but not in those of larger animals.

Myelinogenesis in the Brachial and Lumbosacral Enlargements of the Spinal Cord of the Opossum Monodelphis domestica

Using immunohistochemistry in light microscopy, the myelin basic protein and proteolipid protein were localized on sections of the spinal cord enlargements of opossums, Monodelphis domestica, to determine the timecourse of myelinogenesis therein and compare it with other events of motor systems development. Additional tissue not processed for immunohistochemistry was prepared for transmission electron microscopy. No immunolabeling for either protein occurred on spinal sections from the newborn opossum, but in electron microscopy occasional fibers surrounded by loose, irregular membranous rings were seen on the outskirts of the ventral horn. Immunolabeling was detected first in the brachial enlargement during the second week, presumably on motoneuronal, vestibular and reticular axons. The areas of the dorsal columns, other spino-encephalic, reticulospinal and propriospinal projections became labeled in the third week, and the area of rubrospinal axons at 4 weeks. In the brachial gray matter, immunolabeling appeared along ventrodorsal and lateromedial gradients from the fourth to seventh weeks. Labeling developed similarly in the white and gray matter of the lumbosacral enlargement, but 3-5 days later than at brachial levels. Labeling intensity in the white and gray matter increased until at least 4 months, but remained light in laminae I-III. Thus, myelinogenesis in the spinal cord enlargements of the opossum is protracted and follows general rostrocaudal, ventrodorsal and lateromedial sequences. It occurs later than synaptogenesis at comparable levels of the cord, but earlier than myelinogenesis in the corresponding ventral and dorsal roots. Spinal myelinogenesis correlates with the development of sensorimotor reflexes, weight support and quadrupedal locomotion.

Caveolin-1 and MAL are located on prostasomes secreted by the prostate cancer PC-3 cell line

MAL, BENE and MAL2 are raft-associated integral membrane proteins of the MAL family of proteins involved in membrane trafficking processes. We show here that the human prostate carcinoma PC-3 cell line expresses the transcripts for the three proteins simultaneously. MAL, BENE and MAL2 co-fractionated with caveolin-1 in the raft fraction of PC-3 cells, and immunofluorescence analysis showed colocalization of these proteins with caveolin-1 in a multivesicular intracellular compartment. Markers of the Golgi apparatus, early and recycling endosomes and lipid droplets were excluded from this compartment. Prostate epithelial cells contain vesicular organelles enriched in raft components named prostasomes that are secreted in the prostate fluid. Interestingly, the prostasome fraction isolated from the culture supernatant of PC-3 cells consisted mainly of 30-130 nm cup-shaped vesicles that were positive for MAL, caveolin-1 and CD59, a glycosylphosphatidylinositol-anchored protein previously found in prostasomes. CD63, an integral membrane protein found in multivesicular bodies/lysosomes and secretory granules was also found in PC-3 cell-derived prostasomes. Prostasome secretion was not inhibited by brefeldin A, a compound that blocks the conventional secretory pathway. However, wortmannin, an inhibitor of phosphatidylinositol-3 kinase, reduced the secretion of prostasomes in PC-3 cells. Our results suggest that MAL family proteins are associated with caveolin-1 in a multivesicular compartment that may be involved in prostasomal secretion in PC-3 cells.

Genes transcriptionally modulated by interferon alpha2a correlate with the cytokine activity

BACKGROUND AND OBJECTIVES

Interferon alpha2a (IFNalpha2a) mediates important antiviral, antiproliferative and immunomodulatory responses and is employed in the treatment of human diseases, including chronic myelogenous leukemia. Here, we report the IFNalpha2a-dependent expression profiles of three malignant cell lines derived from liver, lymphocytes and muscle.

DESIGN AND METHODS

The experiments were performed in the presence of cycloheximide, thus our results exclusively reflect direct transcriptional modulation. The short exposure time i.e. 5 hours evidences only the early events, excluding the effects of complex phenotypic changes on the expression.

RESULTS

Our findings indicate that IFNalpha2a rapidly up-regulates the expression of STAT1, STAT2 and ISGF3G genes. This activity should result in the amplification of the cellular response to the cytokine. Moreover, IFNalpha2a directly modulates the expression of: (i) important transcriptional factors, e.g. IRF1 and IRF7 which control pivotal cellular events, and (ii) enzymes involved in the IFNalpha2a-dependent antiviral and apoptotic response. Interestingly, we showed that the cytokine induces transcriptional expression of Sjögren's syndrome antigen A1, a protein involved in several autoimmune diseases.

INTERPRETATION AND CONCLUSIONS

The observed changes induced by IFNalpha2a could be related to the development of autoimmune syndromes observed during IFNalpha2a treatment. A number of genes transcriptionally regulated by the cytokine have been identified for the first time; these might represent additional effectors of IFNalpha2a activity.

IFN-gamma stimulates the expression of a novel secretoglobin that regulates chemotactic cell migration and invasion

IFNs are a family of cytokines that alert the immune system against viral infections of host cells. The IFNs (IFN-alpha, IFN-beta, and IFN-gamma) interact with specific cellular receptors and stimulate the production of second messengers, leading to the expression of antiviral and immunomodulatory proteins. We report in this study that IFN-gamma stimulates the expression of a novel gene that encodes a protein with 30% amino acid sequence identity with uteroglobin, the founding member of the newly formed Secretoglobin (SCGB) superfamily. We named this protein IFN-gamma-inducible SCGB (IIS), because its expression in lymphoblast cells is augmented by IFN-gamma treatment. IIS is expressed in virtually all tissues, and the highest level of expression is detectable in lymph nodes, tonsil, cultured lymphoblasts, and the ovary. Interestingly, although the expression of IIS mRNA is not significantly different in resting lymphoid cells, it is markedly elevated in activated CD8(+) and CD19(+) cells. Furthermore, treatment of lymphoblast cells with IIS antisense phosphorothioate (S)-oligonucleotides prevents chemotactic migration and invasion. Taken together, these results raise the possibility that this novel SCGB has immunological functions.

Expression of MAL2, an integral protein component of the machinery for basolateral-to-apical transcytosis, in human epithelia

MAL2, an integral membrane protein of the MAL family, is an essential component of the machinery necessary for the indirect transcytotic route of apical transport in human hepatoma HepG2 cells. To characterize the range of human epithelia that use MAL2-mediated pathways of transport, we carried out an immunohistochemical survey of normal tissues using a monoclonal antibody specific to the MAL2 protein. MAL2 expression was detected in specific types of normal epithelial cells throughout the respiratory system, the gastrointestinal and genitourinary tracts, in exocrine and endocrine glands, and in hepatocytes. Many different types of specialized secretory cells, either organized in discrete clusters (e.g., endocrine cells in the pancreas) or in endocrine glands (e.g., prostate), were also positive for MAL2. In addition to epithelial cells, peripheral neurons, mast cells, and dendritic cells were found to express MAL2. For comparison with normal epithelial tissue, different types of renal carcinoma were also analyzed, revealing alterations in MAL2 expression/distribution dependent on the particular histological type of the tumor. Our results allow the prediction of the existence of MAL2-based trafficking pathways in specific cell types and suggest applications of the anti-MAL2 antibody for the characterization of neoplastic tissue.

Overexpression, purification, and characterization of recombinant Ca-ATPase regulators for high-resolution solution and solid-state NMR studies

Phospholamban (PLB) and Sarcolipin (SLN) are integral membrane proteins that regulate muscle contractility via direct interaction with the Ca-ATPase in cardiac and skeletal muscle, respectively. The molecular details of these protein-protein interactions are as yet undetermined. Solution and solid-state NMR spectroscopies have proven to be effective tools for deciphering such regulatory mechanisms to a high degree of resolution; however, large quantities of pure recombinant protein are required for these studies. Thus, recombinant PLB and SLN production in Escherichia coli was optimized for use in NMR experiments. Fusions of PLB and SLN to maltose binding protein (MBP) were constructed and optimal conditions for protein expression and purification were screened. This facilitated the large-scale production of highly pure protein. To confirm their functionality, the biological activities of recombinant PLB and SLN were compared to those of their synthetic counterparts. The regulation of Ca-ATPase activity by recombinant PLB and SLN was indistinguishable from the regulation by synthetic proteins, demonstrating the functional integrity of the recombinant constructs and ensuring the biological relevance of our future structural studies. Finally, NMR spectroscopic conditions were established and optimized for use in investigations of the mechanism of Ca-ATPase regulation by PLB and SLN.

Dysregulated secretoglobin expression in human lung cancers

Lipophilins A, B, C, mammaglobin, and uteroglobin are members of the secretoglobin family of small, secreted, proteins. The functions of these proteins are not well understood but uteroglobin has been implicated in the development of cancers. Uteroglobin is known to be highly expressed in normal lung and down-regulated in lung cancers but expression of the other secretoglobins in normal lung and lung neoplasms have not been investigated. Therefore, we developed quantitative real-time reverse transcription (RT-) PCR assays for the different secretoglobins and evaluated their expression in normal and neoplastic lung tissues. The secretoglobin transcript levels were quantitated by real-time RT-PCR in samples from three normal lungs, 24 lung tumors including six small cell lung carcinomas, seven adenocarcinomas, and five squamous cell carcinomas, and in cell lines from three small cell lung carcinomas and one mesothelioma. Uteroglobin was confirmed to be abundantly expressed in normal lung and the different lung tumors showed down-regulated uteroglobin expression. Of the other secretoglobins, only lipophilin C was detected in normal lung, albeit at low levels. The lung tumors, however, frequently showed neo- or up-regulation of lipophilins A, B, C, and mammaglobin. The results constitute the first quantitative evaluation of secretoglobin expression in normal and neoplastic human lung tissues and demonstrate dysregulation in various human lung cancers. These findings could have important biological and diagnostic implications.

Proteolipid plasmolipin: localization in polarized cells, regulated expression and lipid raft association in CNS and PNS myelin

The proteolipid plasmolipin is member of the expanding group of tetraspan (4TM) myelin proteins. Initially, plasmolipin was isolated from kidney plasma membranes, but subsequent northern blot analysis revealed highest expression in the nervous system. To gain more insight into the functional roles of plasmolipin, we have generated a plasmolipin-specific polyclonal antibody. Immunohistochemical staining confirms our previous observation of glial plasmolipin expression and proves plasmolipin localization in the compact myelin of rat peripheral nerve and myelinated tracts of the CNS. Western blot analysis indicates a strong temporal correlation of plasmolipin expression and (re-) myelination in the PNS and CNS. However, following axotomy plasmolipin expression is also recovered in non-regenerating distal nerve stumps. In addition, we detected plasmolipin expression in distinct neuronal subpopulations of the CNS. The observed asymmetric distribution of plasmolipin in compact myelin, as well as in epithelial cells of kidney and stomach, indicates a polarized cellular localization. Therefore, we purified myelin from the CNS and PNS and demonstrated an enrichement of phosphorylated plasmolipin protein in detergent-insoluble lipid raft fractions, suggesting selective targeting of plasmolipin to the myelin membranes. The present data indicate that the proteolipid plasmolipin is a structural component of apical membranes of polarized cells and provides the basis for further functional analysis.

MAL gene expression in esophageal cancer suppresses motility, invasion and tumorigenicity and enhances apoptosis through the Fas pathway

We isolated the MAL (T-lymphocyte maturation associated protein) gene from differentially expressed products of esophageal epithelium relative to esophageal carcinoma tissues. The Mal protein has been demonstrated as being a component of the protein machinery for apical transport in epithelial polarized cells. In this study, we describe the reduced expression of MAL in all 39 cases of esophageal carcinoma tested and 60 other human carcinomas. MAL gene transcription was induced in three out of 13 esophageal carcinoma cell lines by treatment with the demethylating agent 5-aza-2'-deoxycytidine (DAC), and in nine additional cell lines by simultaneous treatment with trichostatin A, an inhibitor of deacetylation, and DAC. We established a stable MAL gene transfectant whose expression was regulated by subcutaneous doxycycline injection in nude mice. Tumor growth was suppressed in cells expressing TE3-MAL compared with TE3 parent cells or cells not expressing TE3-MAL with doxycycline injection (20 microg/body) (P<0.01). Additionally, the TE3-MAL transfectant cells exhibited decreased cellular motility, a G1/S transition block and increased levels of apoptosis, concomitant with increased expression of Fas receptor in vitro. The apoptotic staining in MAL-expressing tumors was confirmed by TUNEL assay. Therefore, we conclude that expression of MAL was frequently decreased or diminished in gastrointestinal tract cancers, and that Mal expression confers reduced tumorigenicity in vivo to tumor TE3 cells through the induction of apoptosis via the Fas signaling pathway.

Atrial chamber-specific expression of sarcolipin is regulated during development and hypertrophic remodeling

Intracellular Ca2+ regulation is critical in the normal cardiac function and development of pathologic hearts. Phospholamban, an endogenous inhibitor of sarcoplasmic reticulum Ca2+ ATPase in the sarcoplasmic reticulum, plays an important role in Ca2+ cycling in heart. Recently, sarcolipin has been identified as having a similar function as phospholamban in skeletal muscle. Because phospholamban is differentially expressed in atrial and ventricular myocardia and its expression is often altered in diseased hearts, we investigated the cardiac chamber specificity of sarcolipin expression and its regulation during development and hypertrophic remodeling. Northern blot analysis revealed that the expression of mouse sarcolipin mRNA was most abundant in the atria and was undetectable in the ventricles, indicating an atrial chamber-specific expression pattern. Atrial chamber-specific expression of sarcolipin mRNA was increased during development. These findings were confirmed by in situ hybridization studies. In addition, sarcolipin expression was down-regulated in the atria of hypertrophic heart when induced by ventricular specific overexpression of the activated H-ras gene. In humans, sarcolipin mRNA was also expressed in the atria but not detected in the ventricles, although sarcolipin expression was most abundant in skeletal muscle. Taken together, sarcolipin is likely to be an atrial chamber-specific regulator of Ca2+ cycling in heart.

A mitochondrial dysfunction induces the expression of nuclear-encoded complex I genes in engineered male sterile Arabidopsis thaliana

To study the effect of a mitochondrial dysfunction induced by the expression of the unedited form of the subunit 9 of ATP synthase gene (u-atp9) in Arabidopsis, we constructed transgenic plants expressing u-atp9 under the control of three different promoters: CaMV 35S, apetala 3 and A9. The size and shape of transgenic plants bearing the apetala3::u-atp9 and A9::u-atp9 genes looked normal while the 35S::u-atp9 transformed plants showed a dwarf morphology. All u-atp9 expressing plants, independent of the promoter used, exhibited a male sterile phenotype. Molecular analysis of male sterile plants revealed the induction of the mitochondrial nuclear complex I (nCI) genes, psst, tyky and nadh binding protein (nadhbp), associated with a mitochondrial dysfunction. These results support the hypothesis that the expression of u-atp9 can induce male sterility and reveal that the apetala3::u-atp9 and A9::u-atp9 plants induced the sterile phenotype without affecting the vegetative development of Arabidopsis plants. Moreover, male sterile plants produced by this procedure are an interesting model to study the global changes generated by an engineered mitochondrial dysfunction at the transcriptome and proteome levels in Arabidopsis plants.

MAL expression in lymphoid cells: further evidence for MAL as a distinct molecular marker of primary mediastinal large B-cell lymphomas

The MAL mRNA was initially identified during T-cell development and was later found in myelin-forming cells and certain polarized epithelial cell lines. It encodes a proteolipid believed to participate in membrane microdomains stabilization, transport machinery and signal transduction. Using a differential display reverse-transcription approach, we identified MAL as a distinct molecular marker of primary mediastinal large B-cell lymphoma compared with nonmediastinal diffuse large B-cell lymphomas. In the present study, we used immunohistochemistry to extend MAL expression analysis to normal lymphoid tissues; to 185 lymphomas representing most B, T, and Hodgkin lymphoma entities; and to the primary mediastinal large B-cell lymphoma derived B-cell line MedB-1. In addition, B and T cells from peripheral blood, tonsil, and spleen were analyzed by flow cytometry. Our results show that MAL is highly expressed in thymocytes, in a large percentage of peripheral CD4 T cells, and in a lower proportion of CD8 peripheral T cells. In the normal B-cell compartment, MAL expression appears to be restricted to a minor subpopulation of thymic medullary B cells and to occasional mature plasma cells located in the interfollicular areas of tonsil and lymph nodes. Among B-cell lymphomas (n = 110), MAL expression in tumor cells was observed in 21/33 primary mediastinal large B-cell lymphomas (70%) and in 3/5 plasmacytoma/myeloma, but not in all other B-cell lymphomas with the exception of 1/33 nonmediastinal diffuse large B-cell lymphomas. The MedB-1 B-cell line was also MAL positive. Among T-cell neoplasms, MAL was highly expressed in lymphoblastic tumors (5/6), whereas mature T-cell lymphomas were essentially MAL negative (27/28). Among 41 Hodgkin lymphomas, 3 nodular-sclerosing cases with mediastinal involvement showed MAL-positive Reed Sternberg cells. In conclusion, this study further supports thymic B cells as the putative normal counterpart of primary mediastinal large B-cell lymphomas and supports MAL as a distinct molecular marker of this lymphoma subtype among diffuse large B-cell lymphomas.

Rafts in adult peripheral nerve myelin contain major structural myelin proteins and myelin and lymphocyte protein (MAL) and CD59 as specific markers

The myelin and lymphocyte protein (MAL) proteolipid is localized in central and peripheral compact myelin membranes, as well as in apical membranes of particular polarized cells. In this study, we addressed the question whether MAL and other peripheral myelin proteins are sorted and targeted to myelin membranes using mechanisms similar to those observed in polarized epithelial cells. To investigate the presence of raft-mediated sorting pathways in Schwann cells, we have isolated and analysed their composition in myelin membranes. Here, we show that rafts are present in adult human and rat peripheral compact myelin membranes and contain MAL, the GPI-anchored protein CD59, and substantial amounts of the PMP22 and P0. Colocalization studies show that CD59, and MAL have an almost identical expression pattern within compact myelin. Moreover, immuno-electron microscopy revealed that MAL, besides its localization in compact myelin, is also localized to Schmidt-Lanterman incisures. Taken together, our results demonstrate the presence of detergent-insoluble glycolipid-enriched complexes (DIGs) in different compartments of myelin membranes and indicate an important role for DIG-mediated transport mechanisms in the maintenance of the adult myelin sheath.

Biosynthesis of surfactant protein C (SP-C). Sorting of SP-C proprotein involves homomeric association via a signal anchor domain

Rat surfactant protein C (SP-C) is synthesized as a 194-amino acid propeptide (SP-C-(1-194)) that is directed to the distal secretory pathway and proteolytically processed as an integral membrane protein to yield its mature form. We had shown previously that trafficking of proSP-C is mediated both by a signal anchor domain contained within the mature SP-C sequence and by a targeting domain in the NH(2)-flanking propeptide. Based on evidence from other integral membrane proteins, we hypothesized that proSP-C targeting is effected by oligomerization of proSP-C monomers. To evaluate this in vitro, cDNA constructs encoding for either wild type proSP-C (pcDNA3/SP-C-(1-194)) or heterologous fusion proteins containing green fluorescent protein (EGFP) linked to SP-C-(1-194) (EGFP/SP-C-(1-194)), to mutant proSP-C lacking the NH(2) targeting domain (EGFP/SP-C-(24-194)), or to mature SP-C alone (EGFP/SP-C-(24-58)) were produced. In transfected A549 cells, fluorescence microscopy revealed that pcDNA3/SP-C-(1-194) and EGFP/SP-C-(1-194) were each expressed in CD63 (+), EEA1 (-) cytoplasmic vesicles. Expression of EGFP/SP-C-(24-194) or EGFP/SP-C-(24-58) resulted in translocation but retention in early compartments. When co-transfected with pcDNA3/SP-C-(1-194), both EGFP/SP-C-(24-194) and EGFP/SP-C-(24-58) were directed to CD63 (+) vesicles that also contained SP-C-(1-194). In contrast, trafficking of a folding mutant that forms juxtanuclear aggregates, EGFP/SP-C(C122/186G), was not corrected by cotransfection with pcDNA3/SP-C-(1-194). Chemical cross-linking studies of transfected cell lysates with bismaleimidohexane produced multimeric forms of both EGFP/SP-C-(1-194) and EGFP/SP-C-(24-58). These results indicate that sorting involves oligomeric association of proSP-C monomers mediated by the mature SP-C domain. Heteromeric assembly allows wild type proSP-C to facilitate trafficking of SP-C mutants with intact transmembrane domains but lacking targeting signals. We speculate that heterotypic oligomerization of wild type with SP-C folding mutants produces a dominant negative thus contributing to the pathology of chronic lung disease associated with patients heterozygous for mutant SP-C alleles.

Members of the C/EBP transcription factor family stimulate expression of the human and rat surfactant protein A (SP-A) genes

Members of the CCAAT enhancer binding protein (C/EBP) transcription factor family were detected in fetal lung of both human and rat. In rat lung, the level of C/EBPs increased with time of gestation, peaking around birth. In adult rat lung, C/EBPs were localized to the alveolar type II cells. The effect of C/EBPs on pulmonary surfactant protein A (SP-A), which is also expressed late in gestation, was investigated. In contrast to control plasmids, C/EBP delta expressing plasmids reversed the action of a transcriptional silencer just upstream of the rat SP-A promoter. In order to test the effect of C/EBPs on endogenous SP-A gene expression, cells that express SP-A were exposed to a phosphorothioate-substituted, double-stranded oligonucleotide matching the consensus C/EBP binding site (decoy oligonucleotide) at concentrations from 0.5 to 10 microM for 72 h. A mutant oligonucleotide with an 8-base pair (bp) substitution served as a control. The decoy oligonucleotide reduced SP-A mRNA as much as 75% compared to a mutant oligonucleotide both in the human lung cell line, NCI-H441, and in primary human fetal alveolar type II cells. The data indicate that C/EBPs facilitate SP-A gene expression, possibly by overcoming transcriptional silencing.

Solid-phase proteoliposomes containing human immunodeficiency virus envelope glycoproteins

The human immunodeficiency virus type 1 (HIV-1) exterior envelope glycoprotein gp120 mediates receptor binding and is the major target for neutralizing antibodies. A broadly neutralizing antibody response is likely to be a critical component of the immune response against HIV-1. Although antibodies against monomeric gp120 are readily elicited in immunized individuals, these antibodies are inefficient in neutralizing primary HIV-1 isolates. As a chronic pathogen, HIV-1 has evolved to avoid an optimal host response by a number of immune escape mechanisms. Monomeric gp120 that has dissociated from the functional trimer presents irrelevant epitopes that are not accessible on functional trimeric envelope glycoproteins. The resulting low level of antigenic cross-reactivity between monomeric gp120 and the functional spike may contribute to the inability of monomeric gp120 to elicit broadly neutralizing antibodies. Attempts to generate native, trimeric envelope glycoproteins as immunogens have been frustrated by both the lability of the gp120-gp41 interaction and the weak association between gp120 subunits. Here, we present solid-phase HIV-1 gp160DeltaCT (cytoplasmic tail-deleted) proteoliposomes (PLs) containing native, trimeric envelope glycoproteins in a physiologic membrane setting. We present data that indicate that the gp160DeltaCT glycoproteins on PLs are trimers and are recognized by several relevant conformational ligands in a manner similar to that for gp160DeltaCT oligomers expressed on the cell surface. The PLs represent a significant advance over present envelope glycoprotein formulations as candidate immunogens for HIV vaccine design and development.

Intracellular and intraalveolar localization of surfactant protein A (SP-A) in the parenchymal region of the human lung

Although it is clearly established that surfactant protein A (SP-A) is secreted by type II pneumocytes as a component of pulmonary surfactant, its secretion pathway as well as its subcellular localization in the human lung are uncertain. We therefore studied the intracellular and intra-alveolar localization of SP-A in eight adult human lungs by immunohistochemistry and immunoelectron microscopy. Only type II pneumocytes could be identified as SP-A positive cells within the parenchymal region. SP-A was localized mainly in small vesicles and multivesicular bodies close to the apical plasma membrane. Only few lamellar bodies were weakly labeled at their outer membranes. Stereologic analysis showed this weak signal to be due to specific labeling. In the alveolar space, lamellar body-like surfactant forms in close proximity to tubular myelin were labeled for SP-A at their periphery. The strongest SP-A labeling was found over tubular myelin figures. Labeling for SP-A was also found in close association with the surface film and unilamellar vesicles. Our results support the hypothesis that, in the human lung, SP-A is mainly secreted into the alveolar space via an alternative pathway that largely bypasses the lamellar bodies. After secretion, the outer membranes of unwinding lamellar bodies become enriched with SP-A when tubular myelin formation is initiated. SP-A may also be involved in the transition of tubular myelin into the surface film.

Overexpression of surfactant protein-C mature peptide causes neonatal lethality in transgenic mice

Surfactant replacement preparations containing either surfactant protein (SP)-B or SP-C significantly improve lung function in surfactant-deficient infants, suggesting that these peptides may be functionally redundant. SP-B is absent and SP-C is greatly diminished in the airspaces of SP-B (-/-) mice, which die of respiratory distress syndrome (RDS) shortly after birth. The goal of this study was to determine if elevated expression of SP-C mature peptide could reverse the neonatal lethality in SP-B (-/-) mice. SP-C peptide (residues 24-57 of mouse SP-C proprotein) with a hemagglutinin epitope (SP-C(24-57)HA) was expressed in type II cells of transgenic mice, with the goal of crossing these animals into the SP-B (-/-) background. Unexpectedly, expression of the SP-C(24-57)HA transgene resulted in delayed/arrested lung development and lethal, neonatal RDS of all transgenic progeny in two independent transgenic lines. In transgenic mice, SP-C(24-57)HA was localized predominantly to the endoplasmic reticulum and Golgi; in contrast, SP-B and SP-C were very difficult to detect in the endoplasmic reticulum of wild-type mice. These results suggest that elevated expression of SP-C(24-57)HA in type II cells resulted in aggregation of SP-C in the early secretory pathway, leading to cytotoxicity and, ultimately, altered lung development.

Identification of pulmonary surfactant that bears intestinal-type and tissue-nonspecific-type alkaline phosphatase in endotoxin-induced rat bronchoalveolar fluid

The characteristics of lipopolysaccharide (LPS)-induced alkaline phosphatase (AP) isozymes on the various pulmonary surfactant subtypes were investigated. We used continuous sucrose-gradient centrifugation to separate surfactant into subtypes. The density of each surfactant subtype isolated from LPS-instilled rats was greater than that of the subtypes from the control rats; and the proportion of light surfactant was lower, thereby decreasing the ratio of light to heavy surfactant. The results of an inhibition study revealed the main AP isozyme in bronchoalveolar fluid (BAF) to be tissue-nonspecific AP (TNAP), but some of the activity was characteristic of intestinal-type AP (IAP). IAP, in addition to TNAP and surfactant-associated protein A (SP-A), was detected on heavy surfactant, and LPS induced both APs. To examine the expression of IAP in the lungs, we prepared primers to detect the cDNAs of two types of rat IAP mRNA, IAP-I and -II, and amplified their cDNAs. LPS instillation induced IAP-I mRNA, but not IAP-II mRNA or TNAP mRNA. Immunohistochemical localization of IAP and TNAP revealed reaction products for both in type II cells. The present study thus demonstrated that, in rats, type II cells produce both IAP and TNAP and that these surfactants bearing AP isozymes are secreted into the alveolar space following induction by intratracheal instillation of LPS.

Could a combined administration of dexamethasone and 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) be a more effective alternative to dexamethasone alone in the prevention of RDS?

OBJECTIVE

To test whether the combined application of dexamethasone (DEXA) and 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) induces the synthesis of surfactant protein A (SP-A) mRNA at a higher rate than both substances given alone?

STUDY DESIGN

Organoid culture of fetal rat lungs (Wistar rats; day 19 of gestation) was prepared. After 48h of incubation we added DEXA (10(-5), 10(-7), 10(-8) and 10(-9)mol/l), DIMIT (10(-5), 10(-7) and 10(-9)mol/l) and the combination of DEXA in 10(-8)mol/l with various concentrations of DIMIT. After another 48h of incubation, northern blot and hybridization with a 32P-labeled SP-A cDNA probe was performed. One-way-variance-analysis with a Scheffé-test, Levene-test and one-sample-t-test were used for statistical analysis.

RESULTS

DEXA alone above 10(-8)mol/l resulted in a significant increase, DIMIT resulted in a decrease of SP-A mRNA induction. Combined application of DIMIT and DEXA resulted in a significant increase compared to the controls. Compared to DEXA alone in 10(-8)mol/l, we found an increased induction, but the data were not significant.

CONCLUSIONS

The combined application of DEXA and DIMIT shows a higher induction of SP-A mRNA than both drugs given alone.

Plasmolipin: genomic structure, chromosomal localization, protein expression pattern, and putative association with Bardet-Biedl syndrome

Plasmolipin is a membrane protein and belongs to the tetraspan molecule (4TM) family, an expanding group of myelin proteins many of which could be linked to human hereditary demyelinating neuropathies. We have cloned and sequenced the mouse plasmolipin gene, revealing the common organization of the 4TM gene group with four exons and a large first intron. Western blot analysis with an antibody raised against the C-terminal intracellular part of the protein showed that plasmolipin is expressed not only in the nervous system and kidney, but also in a number of other tissues such as thymus, testis, lung, and thyroid gland. By means of radiation hybrid mapping and FISH analysis, we could localize the human plasmolipin gene to Chromosome 16q13 within the putative region of the Bardet-Biedl syndrome type 2 (BBS2) gene locus. BBS2 is a clinically and genetically heterogeneous group of disorders resulting in rod-cone dystrophy, obesity, postaxial polydactyly, renal dysfunction, and mental retardation, which were very recently associated with a novel gene designated BBS2. With respect to intrafamiliar variations in the manifestation of BBS, we suggest that plasmolipin might be either another candidate gene or a modifier of the BBS2 phenotype.

Surfactant protein A expression in human normal and neoplastic breast epithelium

We studied the presence of surfactant protein A (Sp-A) immunoreactivity and messenger RNA in 62 normal and abnormal breast samples. Sections were immunostained with polyclonal anti-Sp-A antibody. The association between Sp-A immunoreactivity and histologic grade of 32 invasive ductal carcinomas was assessed by 3 pathologists who scored the intensity of Sp-A immunoreactivity times the percentage of tumor immunostained; individual scores were averaged, and the final scores were correlated with tumor grade, proliferative index, and expression of estrogen and progesterone receptors. Strong Sp-A immunoreactivity was present at the luminal surface of ductal epithelial cells in normal breast samples and in benign lesions; carcinomas displayed variable immunoreactivity, inversely proportional to the degree of differentiation. Sp-A messenger RNA was detected by reverse transcriptase-polymerase chain reaction in 3 of 3 normal breast samples and 9 of 9 carcinomas. The significance of Sp-A expression in breast epithelium requires further study; possibly it has a role in native host defense or epithelial differentiation.

Synthesis and post-translational processing of surfactant protein C

Traditional thinking about surfactant proteins has centered around their effects on the biophysical properties of surfactant phospholipids. Accumulated data now suggests that the four major surfactant proteins (SPs) are a biochemically and functionally diverse group of mammalian peptides that have function beyond modification of alveolar surface tension. Alveolar SP-C (SP-C3.7, Mr 21,000) is 35 amino acid peptide isolated from lung surfactant that is synthesized and processed from a 191-197 amino acid precursor (proSP-C21). Although its solubility in organic solvents and avidity for lipid membranes impart properties important for its biophysical activity, SP-C represents a structurally and functionally challenging protein for the alveolar type II cell that must synthesize and traffic the peptide through the regulated secretory pathway. Despite technical and analytical difficulties imposed by its unique structure, our current understanding of SP-C biosynthesis has evolved over the past 10 years. Recent data now require us to consider proSP-C21 as a hybrid molecule incorporating structural and functional features both of bitopic integral membrane proteins as well us more classically recognized propeptide hormones. Our article highlights major developments related to characterization of molecular and cellular mechanisms underlying expression, post-translational processing, and targeting of proSP-C21 that result in production of secreted SP-C3.7.

In situ hybridization of SP-A mRNA in adult human conducting airways

In our study, surfactant protein (SP)-A was characterized in adult human trachea and bronchi. SP-A mRNA and protein were localized to serous cells in submucosal gland by in situ hybridization and immunohistochemistry, respectively. A 2.2 kb SP-A mRNA transcript was detected in tracheal tissues by Northern blot analysis. Primer extension analysis and gene-specific reverse transcriptase polymerase chain reaction (RT-PCR) revealed the predominance of SP-A2 mRNA. However, using nested PCR, we also detected low amounts of SP-A1 mRNA in the tracheal tissues. A approximately 35 kDa SP-A immunoreactive protein was detected in the tracheal tissues by immunoblot analysis and was shown to be modified by the addition of N-linked oligosaccharides. We conclude that submucosal glands in the conducting airways produce a novel SP-A protein with a molecular weight and post-translational modification similar to the SP-A produced in the distal lung. We speculate that this SP-A2 protein, like other serous secretions from airway submucosal glands, functions in local antimicrobial host defense mechanisms in the conducting airways.

Fetal monkey surfactants after intra-amniotic or maternal administration of betamethasone and thyroid hormone

OBJECTIVE

To compare direct intra-amniotic injection of betamethasone and thyroxine (T4) with maternal treatment and controls for accelerating pulmonary surfactant production.

METHODS

Twelve pregnant monkeys (Macaca mulatta) on gestational day 125 (term 165 +/- 10 days) had surfactant protein A and B concentrations measured in amniotic fluid. In four controls, normal saline was injected into the amniotic fluid; four others (intra-amniotic) received intra-amniotic betamethasone (1 mg) and T4 (60 microg); and in four others (maternal), the dam was given betamethasone (12 mg) intramuscularly, repeated in 24 hours, plus TRH (400 microg) intravenously, repeated every 6 hours for 24 hours. Seventy-two hours after the initial amniocentesis, a hysterotomy was performed and fetal tissue and amniotic fluid harvested for determination of surfactant protein A and B concentrations and immunohistochemical staining for surfactant protein A.

RESULTS

Amniotic fluid surfactant protein A was higher with intra-amniotic injection than with maternal treatment (P <.04) or controls (P =.07). Amniotic fluid surfactant protein B was higher in the intra-amniotic group than in controls (P =.06). Immunohistochemical staining for surfactant protein A in the lung tissue was increased in the intra-amniotic group compared with controls (0.145 +/- 0.01 versus 0.097 +/- 0.001, percent positive staining for surfactant protein A cells per lung tissue cells; P <.03). Birth weight was greater in the intra-amniotic group compared with the maternal group (P <.03) although not different from the controls. Finally, gut motility and the presence of formed meconium were increased in the intra-amniotic group compared with the other groups (P <.05).

CONCLUSION

Intra-amniotic injection of betamethasone and T4 enhanced lung (and possibly intestinal) maturation of the preterm rhesus fetal monkey compared with maternal injections.

Both human SP-A1 and Sp-A2 genes are expressed in small and large intestine

The human SP-A locus consists of two functional genes and one pseudogene, and SP-A is shown to play a role in local host defense and the regulation of inflammation in lung. Because the intestine, like the lung, is constantly exposed to foreign and potentially harmful substances, we investigated the hypothesis that both human SP-A genes are expressed in intestine. We demonstrate that both SP-A genes are expressed in human small and large intestine. The presence of SP-A mRNA in human intestine was detected by reverse transcription polymerase chain reaction (RT-PCR), Northern blot analysis, and immunohistochemistry. The size of intestinal SP-A mRNA is the same as that in human lung, but the level of expression, compared with that in the lung, is very low in both the small and large intestine. Immunohistochemical analysis revealed positive reactivity for SP-A in a subgroup of epithelial cells in the intestine. Expression of both SP-A1 and SP-A2 genes was established by gene-specific PCR amplification, PCR-based converted RFLP discrimination, and direct sequencing of RT-PCR products. We speculate that SP-A in the intestine plays a role in local host defense and inflammation.

Maintenance of differentiated function of the surfactant system in human fetal lung type II epithelial cells cultured on plastic

We report a simplified culture system for human fetal lung type II cells that maintains surfactant expression. Type II cells isolated from explant cultures of hormone-treated lungs (18-22 wk gestation) by collagenase + trypsin digestion were cultured on plastic for 4 days in serum-free medium containing dexamethasone (Dex, 10 nM) + 8-bromo-cAMP (0.1 mM + isobutylmethylxanthine (0.1 mM) or were untreated (control). Surfactant protein (SP) mRNAs decreased markedly in control cells between days 1 and 4 of culture, but mRNA levels were high in treated cells on day) 4 (SP-A, SP-B, SP-C, SP-D; 600%, 100%, 85%, 130% of day 0 content, respectively). Dex or cAMP alone increased SP-B, SP-C, and SP-D mRNAs and together had additive effects. The greatest increase in SP-A mRNA occurred with cAMP alone. Treated cells processed pro-SP-B and pro-SP-C proteins to mature forms and had a higher rate of phosphatidylcholine (PC) synthesis (2-fold) and higher saturation of PC (approximately 34% versus 27%) than controls. Only treated cells maintained secretagogue-responsive phospholipid synthesis. By electron microscopy, the treated cells retained lamellar bodies and extensive microvilli. We conclude that Dex and cAMP additively stimulate expression of surfactant components in isolated fetal type II cells, providing a simplified culture system for investigation of surfactant-related, and perhaps other, type II cell functions.

Sarcolipin, the shorter homologue of phospholamban, forms oligomeric structures in detergent micelles and in liposomes

The human 31-amino acid integral membrane protein sarcolipin (SLN), which regulates the sarcoplasmic reticulum Ca-ATPase in fast-twitch skeletal muscle, was chemically synthesized. Appropriate synthesis and purification strategies were used to achieve high purity and satisfactory yields of this hydrophobic and poorly soluble protein. Structural and functional properties of SLN were analyzed and compared with the homologous region of human phospholamban (PLB) comprising residues Ala(24)-Leu(52) (PLB-(24-52)), the regulatory protein of the cardiac sarcoplasmic reticulum Ca-ATPase. Circular dichroism spectroscopy showed that SLN is a predominantly alpha-helical protein and that the secondary structure is highly resistant to SDS and thermal denaturation. In this respect SLN is remarkably similar to PLB-(24-52). However, SLN is monomeric in SDS gels, whereas PLB-(24-52) shows a monomer-pentamer equilibrium typical for native PLB. Analytical ultracentrifugation experiments revealed that SLN oligomerizes in the presence of the nonionic detergents octylpolyoxyethylene and octyl glucoside in a concentration-dependent manner. No plateau was observed, and a pentameric state was only reached at much higher protein concentrations compared with PLB-(24-52). Chemical cross-linking showed that also in liposomes SLN has the ability to self-associate to oligomers. PLB-(24-52) specifically oligomerized to pentamers in the presence of octylpolyoxyethylene as well as in liposomes at low protein concentrations. In the presence of octylpolyoxyethylene pentamers were the main oligomeric species, whereas in liposomes monomers and dimers were predominant. Increasing the protein concentration led to self-association of PLB-(24-52) pentamers in the presence of octylpolyoxyethylene. Functional reconstitution of Ca-ATPase with PLB-(24-52) and SLN in liposomes showed that both proteins regulate the Ca-ATPase in a similar manner.

Protein-protein interaction of retinoic acid receptor alpha and thyroid transcription factor-1 in respiratory epithelial cells

Surfactant protein B (SP-B) is a 79-amino acid peptide critical to postnatal respiratory adaptation and is developmentally regulated. Previous studies demonstrated that retinoic acid receptors (RARs) and thyroid transcription factor 1 (TTF-1) stimulated SP-B gene expression in respiratory epithelial cells. Clustered retinoic acid-responsive element and TTF-1 binding sites were identified in the enhancer region of the SP-B gene and were required for retinoic acid stimulation of the human SP-B (hSP-B) promoter. In addition, RAR and TTF-1 were colocalized in mouse bronchiolar and alveolar type II epithelial cells, the cellular site of SP-B synthesis. In the present studies, RAR and TTF-1 were colocalized in the nucleus of H441 cells. RAR and TTF-1 synergistically stimulated the hSP-B promoter in H441 cells. Direct protein-protein interactions between RAR and TTF-1 were demonstrated by the glutathione S-transferase pull-down assay and the mammalian cell two hybrid assay. Truncation/deletion studies showed that the RAR-TTF-1 interaction was mediated through the RAR DNA binding domain (DBD) and the TTF-1 homeodomain. RAR DBD greatly enhanced TTF-1 homeodomain DNA binding activity to a hSP-B enhancer oligonucleotide, in which retinoic acid-responsive element and TTF-1 DNA binding sites overlap. Chromatin immunoprecipitation assay demonstrated that retinoic acid treatment of H441 cells greatly stimulated both RAR and TTF-1 DNA binding to the hSP-B enhancer region in H441 cells. These findings support a model in which RAR/retinoid X receptor, TTF-1, and coactivators (p160 members and CBP) form an enhanceosome in the enhancer region of the hSP-B gene.

Induced repatterning of type XVIII collagen expression in ureter bud from kidney to lung type: association with sonic hedgehog and ectopic surfactant protein C

Epithelial-mesenchymal tissue interactions regulate the formation of signaling centers that play a role in the coordination of organogenesis, but it is not clear how their activity leads to differences in organogenesis. We report that type XVIII collagen, which contains both a frizzled and an endostatin domain, is expressed throughout the respective epithelial bud at the initiation of lung and kidney organogenesis. It becomes localized to the epithelial tips in the lung during the early stages of epithelial branching, while its expression in the kidney is confined to the epithelial stalk region and is lost from the nearly formed ureter tips, thus displaying the reverse pattern to that in the lung. In recombinants, between ureter bud and lung mesenchyme, type XVIII collagen expression pattern in the ureter bud shifts from the kidney to the lung type, accompanied by a shift in sonic hedgehog expression in the epithelium. The lung mesenchyme is also sufficient to induce ectopic lung surfactant protein C expression in the ureter bud. Moreover, the shift in type XVIII collagen expression is associated with changes in ureter development, thus resembling aspects of early lung type epigenesis in the recombinants. Respecification of collagen is necessary for the repatterning process, as type XVIII collagen antibody blocking had no effect on ureter development in the intact kidney, whereas it reduced the number of epithelial tips in the lung and completely blocked ureter development with lung mesenchyme. Type XVIII collagen antibody blocking also led to a notable reduction in the expression of Wnt2, which is expressed in the lung mesenchyme but not in that of the kidney, suggesting a regulatory interaction between this collagen and Wnt2. Respecification also occurred in a chimeric organ containing the ureter bud and both kidney and lung mesenchymes, indicating that the epithelial tips can integrate the morphogenetic signals independently. A glial cell line-derived neurotrophic factor signal induces loss of type XVIII collagen from the ureter tips and renders the ureter bud competent for repatterning by lung mesenchyme-derived signals. Our data suggest that differential organ morphogenesis is regulated by an intra-organ patterning process that involves coordination between inductive signals and matrix molecules, such as type XVIII collagen.

Expression and localization of lung surfactant protein B in Eustachian tube epithelium

Surfactant protein (SP) B is an essential component of the pulmonary surfactant complex, which participates in reducing the surface tension across the alveolar air-liquid interface. The Eustachian tube (ET) connects the upper respiratory tract to the middle ear, serving as an intermittent airway between the pharynx and the middle ear. Recently, we described the expression of SP-A and SP-D in the ET, suggesting their role in middle ear host defense. Our present aim was to detect whether the expression of SP-B is evident in the porcine ET. With Northern blot analysis, RT-PCR, and in situ hybridizations, SP-B mRNA was identified and localized in the ET epithelium. The cellular localization of SP-B was revealed with immunohistochemistry, electron microscopy, and immunoelectron microscopy. The protein was found in the secretory granules of epithelial cells and also attached to the microvilli at the luminal side of these cells. The SP-B immunoreactivity of aggregates isolated from ET lavage fluid was similar to that isolated from bronchoalveolar lavage fluid. We conclude that there are specialized cells in the ET epithelium expressing and secreting SP-B and propose that SP-B may facilitate normal opening of the tube and mucociliary transport.

Biosynthesis of surfactant protein C: characterization of aggresome formation by EGFP chimeras containing propeptide mutants lacking conserved cysteine residues

Surfactant protein C (SP-C) is a lung-specific secreted protein, which is synthesized as a 21-kDa propeptide (SP-C(21)) and then proteolytically processed as a bitopic transmembrane protein in subcellular compartments distal to the medial Golgi to produce a 3.7 kDa mature form. We have shown that initial processing of SP-C(21) involves two endoproteolytic cleavages of the C terminus and that truncation of nine amino acids from the C-flanking peptide resulted in retention of mutant protein in proximal compartments. Because these truncations involved removal of a conserved cysteine residue (Cys(186)), we hypothesized that intralumenal disulfide-mediated folding of the C terminus of SP-C(21) is required for intracellular trafficking. To test this, cDNA constructs encoding heterologous fusion proteins consisting of enhanced green fluorescent protein (EGFP) attached to the N terminus of wild-type rat proSP-C (EGFP/SP-C(1–194)), C-terminally deleted proSP-C (EGFP/SP-C(1–185); EGFP/SP-C(1–191)) or point mutations of conserved cysteine residues (EGFP/SP-C(C122G); EGFP/SP-C(C186G); or EGFP/SP-C(C122/186G)) were transfected into A549 cells. Fluorescence microscopy revealed that transfected EGFP/SP-C(1–194) and EGFP/SP-C(1–191)were expressed in a punctate pattern within CD-63 positive, EEA-1 negative cytoplasmic vesicles. In contrast, EGFP/SP-C(1–185), EGFP/SP-C(C122G), EGFP/SP-C(C186G) and EGFP/SP-C(C122/186G) were expressed but retained in a juxtanuclear compartment that stained for ubiquitin and that contained (γ)-tubulin and vimentin, consistent with expression in aggresomes. Treatment of cells transfected with mutant proSP-C with the proteasome inhibitor lactacysteine enhanced aggresome formation, which could be blocked by coincubation with nocodazole. Western blots using a GFP antibody detected a single form in lysates of cells transfected with EGFP/SP-C cysteine mutants, without evidence of smaller degradation fragments. We conclude that residues Cys(122) and Cys(186) of proSP-C are required for proper post-translational trafficking. Mutation or deletion of one or both of these residues results in misfolding with mistargeting of unprocessed mutant protein, leading to formation of stable aggregates within aggresomes.

Tissue-specific distribution and variation of the channel-forming protein ductin during development of Drosophila melanogaster

Ductins represent membrane channel proteins which are supposed to form both proton channels in V-ATPases and connexon channels in gap junctions. In order to localize and characterize these proteins in different tissues of Drosophila, we applied indirect immunofluorescence microscopy and immunoblots, using antisera prepared against Drosophila ductin and against Nephrops ductin. Previously, these antisera have been shown to recognize, in ovarian follicles and young embryos of Drosophila, the ductin monomer of 16 kDa and a putative dimer of 29 kDa. Moreover, both anti-ductin sera label antigens in plasma membranes and in the cytoplasm and block, when microinjected, cell-cell communication via gap junctions. In the present study, comparing several embryonic, larval and adult tissues, the anti-ductin sera were found to recognize antigens with various locations in cells of the midgut, the salivary gland, the nervous system, the muscles and the epidermis. For example, in midgut cells, antigens were labeled mainly in apical plasma membranes and in the apical part of the cytoplasm, while in salivary-gland cells, labeling was found throughout the plasma membranes and the cytoplasm. We conclude that putative gap junctions were revealed in the salivary gland, the nervous system and the epidermis, while plasma membrane-associated putative V-ATPases were detected in the midgut, the salivary gland and the muscles. Moreover, V-ATPases associated with cytoplasmic vesicles were found in almost every tissue. On immunoblots of homogenates from various tissues, the anti-ductin sera specifically labeled bands of 16, 21 and 29 kDa. When comparing these bands using peptide mapping with V8 protease, we found that they represent closely related proteins. Therefore, either different ductins or modifications of a single ductin appear to be present in different cellular regions, cell types and developmental stages of Drosophila.

Vacuolar H(+)-ATPase plays a crucial role in growth and phenotypic modulation of myofibroblasts in cultured human saphenous vein

BACKGROUND

The molecular mechanism of neointimal hyperplasia after vein graft surgery remains elusive. Vacuolar H(+)-ATPase (V-ATPase) is involved in intracellular trafficking and may play a crucial role in neointimal cell growth.

METHODS AND RESULTS

Cultured human saphenous vein segments developed neointimal formation within 10 days. Neointimal cells were positive for vimentin and alpha-smooth muscle actin but negative for desmin, which is indicative of myofibroblasts. Those myofibroblasts were found to have originated from periadventitial fibroblasts, which upregulated the expression of 16-kDa proteolipid of V-ATPase before proliferation and phenotypic modulation. Neointimal myofibroblast growth and survival were highly sensitive to inhibition of V-ATPase by bafilomycin A(1) (BA(1)), because the incorporation of [(3)H]thymidine into the myofibroblasts was significantly inhibited by nanomolar concentrations of BA(1) and apoptotic cell death was induced by a similar concentration range of BA(1). In contrast, endothelial cells and differentiated smooth muscle cells were resistant to apoptosis by BA(1).

CONCLUSIONS

These results suggest that V-ATPase plays a crucial role in growth and phenotypic modulation of myofibroblasts that contributes to neointimal formation in cultured human saphenous vein.

Identification of genes associated with the progression of adult T cell leukemia (ATL)

Patients with adult T-cell leukemia/lymphoma (ATL) exhibit a variety of clinical features, and this disease is therefore clinically subclassified into acute, lymphomatous, chronic, and smoldering types. Acute ATL is a typical leukemic form of ATL with rapid progression, and chronic ATL is a less aggressive clinical form allowing long-term survival even without chemotherapy. In the present study, we used fresh peripheral blood mononuclear cells (PBMC) from both types of ATL patients to identify molecules that may contribute to the difference between acute and chronic ATL. Isolated mRNAs expressed differentially between the two types of ATL include a T-cell differentiation antigen (MAL), a lymphoid-specific member of the G-protein-coupled receptor family (EBI-1 / CCR7), a novel human homologue to a subunit (MNLL) of the bovine ubiquinone oxidoreductase complex, and a human fibrinogen-like protein (hpT49). We found that the former three are upregulated in acute ATL and the last is down-regulated in both chronic and acute ATL. We speculate that dysregulation of the genes may account for the malignant features of ATL cells, in terms of growth, energy metabolism, and motility.

Chorioamnionitis decreased incidence of respiratory distress syndrome by elevating fetal interleukin-6 serum concentration

Respiratory distress syndrome (RDS) of newborns is one of the most important factors determining neonatal morbidity and mortality. The interleukin-6 (IL-6) titre in cord sera of RDS-free neonates born to mothers with histological chorioamnionitis was significantly higher than that in RDS-complicated neonates without chorioamnionitis. Maternal administration of glucocorticoid suppressed the IL-6 concentrations in the cord sera of fetuses with chorioamnionitis. The fetuses without chorioamnionitis who suffered from RDS even after maternal glucocorticoid administration showed a similar IL-6 titre to that of RDS-affected neonates without chorioamnionitis. Examination of the mechanism by which IL-6 decreased the incidence of fetal RDS revealed that H441-4, a human pulmonary adenocarcinoma cell line, stimulated with recombinant (r)-IL-6 started the synthesis of mRNA and protein of pulmonary surfactant protein (SP)-A. The present study shows that IL-6 elevation in fetuses with chorioamnionitis promotes fetal lung maturation by inducing SP-A synthesis, thereby decreasing the incidence of RDS in the preterm neonates.

Role of cystic fibrosis transmembrane conductance regulator in pulmonary clearance of Pseudomonas aeruginosa in vivo

Cystic fibrosis (CF)2 is a fatal genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) that is commonly associated with chronic pulmonary infections with mucoid Pseudomonas aeruginosa (PA). To test the hypothesis that CFTR plays a direct role in PA adhesion and clearance, we have used mouse lines expressing varying levels of human (h) or mouse (m) CFTR. A subacute intratracheal dose of 3 x 10(6) bacteria was cleared with similar kinetics in control wild-type (WT) and transgenic mice overexpressing hCFTR in the lung from the surfactant protein C (SP-C) promoter (SP-C-hCFTR+/-). In a second series of experiments, the clearance of an acute intratracheal dose of 1.5 x 10(7) PA bacteria was also similar in WT, hemizygous SP-C-hCFTR+/-, and bitransgenic gut-corrected FABP-hCFTR+/+-mCFTR-/-, the latter lacking expression of mCFTR in the lung. However, a small but significant decrease in bacterial killing was observed in lungs of homozygote SP-C-hCFTR+/+ mice. Lung pathology in both WT and SP-C-hCFTR+/+ mice was marked by neutrophilic inflammation and bacterial invasion of perivascular and subepithelial compartments. Bacteria were associated primarily with leukocytes and were not associated with alveolar type II or bronchiolar epithelial cells, the cellular sites of SP-C-hCFTR+/+ transgene expression. The results indicate that there is no direct correlation between levels of CFTR expression and bacterial clearance or association of bacteria with epithelial cells in vivo.

Two rat surfactant protein A isoforms arise by a novel mechanism that includes alternative translation initiation

A single gene for rat surfactant protein A (SP-A) encodes two isoforms that are distinguished by an isoleucine-lysine-cysteine (IKC) N-terminal extension (SP-A and IKC-SP-A). Available evidence suggests that the variants are generated by alternative signal peptidase cleavage of the nascent polypeptide at a primary site (Cys(-)(1)-Asn(1)) and a secondary site (Gly(-)(4)-Ile(-)(3)). In this study, we used site-directed mutagenesis and heterologous expression in vitro and in insect cells to the examine mechanisms that may lead to alternative signal peptidase cleavage including alternative translation initiation at two in-frame AUGs (Met(-)(30) and Met(-)(20)), a suboptimal context for hydrolysis at the primary cleavage site, or cotranslational protein modifications that expose an otherwise cryptic secondary cleavage site. In vitro translation of a rat cDNA for SP-A resulted in both 28 and 29 kDa primary translation products on SDS-PAGE analysis, while translation of cDNAs encoding Met-30Ala and Met-20Ala mutations resulted in only the single 28 and 29 kDa molecular mass species, respectively. These data are consistent with translation initiation at both Met(-)(30) and Met(-)(20) during in vitro synthesis of SP-A. The Met-30Ala mutation reduced expression of the longer isoform in insect cells, indicating that the Met(-)(30) site also contributes to eucaryotic protein expression. Forcing translation initiation at Met(-)(30) by optimizing the Kozak consensus sequence surrounding that codon or by mutating the Met(-)(20) codon resulted in preferential expression of the longer SP-A isoform but reduced overall expression of the protein almost 10-fold. Both isoforms were generated to some degree whether translation was initiated at the codon for Met(-)(30) or Met(-)(20), indicating that the site of translation initiation is not the sole determinant of isoform generation and suggesting that either the context of the primary cleavage site is suboptimal or that cotranslational modifications affect cleavage. Preventing N-terminal glycosylation at Asn(1) did not affect the site of signal peptidase cleavage. Disruption of interchain disulfide formation at Cys(-)(1) by substitution with serine markedly enhanced cleavage at the Gly(-)(4)-Ile(-)(3) bond, but substitution with alanine enhanced cleavage at the Cys(-)(1)-Asn(1) bond. We conclude that rat SP-A isoforms arise by a novel mechanism that includes both alternative translation initiation at two in-frame AUGs and a suboptimal context for signal peptidase hydrolysis at the primary cleavage site.

Smad7 and Smad6 differentially modulate transforming growth factor beta -induced inhibition of embryonic lung morphogenesis

Transforming growth factors beta (TGF-beta) are known negative regulators of lung development, and excessive TGF-beta production has been noted in pulmonary hypoplasia associated with lung fibrosis. Inhibitory Smad7 was recently identified to antagonize TGF-beta family signaling by interfering with the activation of TGF-beta signal-transducing Smad complexes. To investigate whether Smad7 can regulate TGF-beta-induced inhibition of lung morphogenesis, ectopic overexpression of Smad7 was introduced into embryonic mouse lungs in culture using a recombinant adenovirus containing Smad7 cDNA. Although exogenous TGF-beta efficiently reduced epithelial lung branching morphogenesis in control virus-infected lung culture, TGF-beta-induced branching inhibition was abolished after epithelial transfer of the Smad7 gene into lungs in culture. Smad7 also prevented TGF-beta-mediated down-regulation of surfactant protein C gene expression, a marker of bronchial epithelial differentiation, in cultured embryonic lungs. Moreover, we found that Smad7 transgene expression blocked Smad2 phosphorylation induced by exogenous TGF-beta ligand in lung culture, indicating that Smad7 exerts its inhibitory effect on both lung growth and epithelial cell differentiation through modulation of TGF-beta pathway-restricted Smad activity. However, the above anti-TGF-beta signal transduction effects were not observed in cultured embryonic lungs with Smad6 adenoviral gene transfer, suggesting that Smad7 and Smad6 differentially regulate TGF-beta signaling in developing lungs. Our data therefore provide direct evidence that Smad7, but not Smad6, prevents TGF-beta-mediated inhibition of both lung branching morphogenesis and cytodifferentiation, establishing the mechanistic basis for Smad7 as a novel target to ameliorate aberrant TGF-beta signaling during lung development, injury, and repair.

Corticosteroids decrease mRNA levels of SERCA pumps, whereas they increase sarcolipin mRNA in the rat diaphragm

1. In order to explore the potential role of the sarcoplasmic-endoplasmic reticulum Ca2+-ATPase (SERCA)-type pumps and of their modulators phospholamban (PLB) and sarcolipin (SLN) in the functional alterations of the diaphragm induced by corticosteroid treatment, expression of SERCA, PLB and SLN was assessed by RT-PCR in the diaphragm of rats treated daily for 5 days either with triamcinolone (80 mg kg-1, n = 8) or with saline (control; 0.6 ml, n = 8). 2. Triamcinolone treatment reduced the normalised overall amount of all SERCA mRNA in diaphragm by 70 % compared to controls (P < 0.05). This reduction was accounted for by a relatively larger decrease in the SERCA1 mRNA (-69 %, P < 0.05) whilst the decrease in SERCA2 mRNA (-49 %, P = 0.09) did not reach statistical significance. As a result the relative proportion of SERCA2 mRNA was increased from 43 +/- 7 % in control diaphragm to 52 +/- 4 % after triamcinolone treatment (P < 0.05). 3. Only the adult isoform of SERCA1 (i.e. SERCA1a) mRNA was found in the diaphragm of the 15-week-old control rats. Furthermore, triamcinolone treatment resulted in reduced levels of SERCA2a (-40 %, P < 0.05) and increased levels of SLN mRNA (+100 %, P < 0.05), while the decrease in PLB mRNA (-31 %, P = 0.277) did not reach statistical significance. SERCA1b, SERCA2b and SERCA3 mRNA levels fell below the detection limit in the diaphragm of both control and triamcinolone-treated rats. 4. Compared to control diaphragm, control rat heart showed a relatively high PLB/(SERCA1 + SERCA2) mRNA ratio of 7.88 while this ratio amounted only to 0.16 in control extensor digitorum longus (EDL) muscle. Remarkably, the SLN/(SERCA1 + SERCA2) mRNA ratio in normal cardiac muscle (0.96) was nearly the same as in diaphragm, but in EDL it amounted to only 0.05 that in diaphragm. This indicates the very low expression of SLN in rat EDL. 5. These data reveal that considerable alterations in SERCA mRNA levels accompany the functional changes seen in diaphragm after corticosteroid treatment. The relatively larger decrease in SERCA1 mRNA is in agreement with the selective type II fibre atrophy previously observed in the diaphragm of triamcinolone-treated rats, but the magnitude of SERCA alterations is more pronounced than expected on the basis of the structural changes in the diaphragm. The increase in SLN mRNA levels may represent a compensatory mechanism.