Hemoglobin is expressed in alveolar epithelial type II cells

Hemoglobin is the main oxygen carrying heme protein in erythrocytes. In an effort to study the differential gene expression of alveolar epithelial type I and type II cells using DNA microarray technique, we found that the mRNAs of hemoglobin alpha- and beta-chains were expressed in type II cells, but not in type I cells. The microarray data were confirmed by RT-PCR. The mRNA expression of both chains decreased when type II cells trans-differentiated into type I-like cells. Immunocyto/histochemistry revealed that hemoglobin protein was specifically localized in type II cells of a lung cell mixture and rat lung tissue. The endogenous synthesis of hemoglobin in alveolar epithelial cells suggests that hemoglobin may have unidentified functions other than oxygen transport in the lung.     

The hyaluronate receptor is preferentially expressed on proliferating epithelial cells

In the present study, we have examined the distribution of the hyaluronate receptor as well as hyaluronate itself in a variety of adult tissues. The hyaluronate receptor was localized with a monoclonal antibody, termed K-3, while hyaluronate was localized using proteolytic fragments of cartilage proteoglycan. Staining with the K-3 monoclonal antibody revealed that the hyaluronate receptor was present in a variety of epithelia including the skin, cheek, tongue, esophagus, vagina, intestines, oviduct, and bladder. However, it was notably absent from epithelial cells of the cornea and stomach as well as from endothelial cells of blood vessels. When present, the hyaluronate receptor was preferentially located in regions of active cell growth, such as in the basal layers of stratified epithelium and at the base of the crypts of Lieberkuhn in intestinal epithelium. A similar phenomenon was observed in cultured 3T3 cells. Cultures of 3T3 cells that were actively proliferating were found to have greater amounts of the receptor than their nonproliferating counterparts. When the various tissues were examined for hyaluronate, it was found to have a widespread distribution, being present in most of the basement membranes and between the cells in stratified epithelium. Indeed, in many cases, the distribution of hyaluronate closely paralleled that of the hyaluronate receptor. These results suggest that the interaction between hyaluronate and its receptor is involved in cell-to-substratum adhesion.     

Plexin-A4 is expressed in oligodendrocyte precursor cells and acts as a mediator of semaphorin signals

Class 3 semaphorin acts as a guidance clue for both cell migration and nerve fiber projection. The signal of class 3 semaphorin travels via a receptor complex consisting of neuropilins and Plexin-A subfamily. Although it has been reported that class 3 semaphorin acts as a repellent for oligodendrocyte precursor cells (OPCs), which migrate actively during brain development, the expression of Plexin-A subfamily has not been reported in OPCs yet. Therefore, it is currently unclear how semaphorin signals can travel in OPCs. In the present study, the expression of Plexin-A4 (PlexA4) was first demonstrated in a newly established OPC line and OPCs in developing brain. In the OPC line, repulsion for process extension was caused by both Sema3A and Sema6A, and the effect of the semaphorins was diminished in cells expressing PlexA4 lacking the cytoplasmic domain. These results strongly suggest that PlexA4 expressed in OPCs acts as a mediator of semaphorin signals.     

Somatostatin in epithelial cells of intestinal mucosa is present primarily as somatostatin 28

Region-specific antisera to [Tyr14]-SS28(1-14) were used to identify cells containing immunoreactivity to the SS28(1-14) fragment of somatostatin 28 (SS28) in gastric and intestinal mucosal epithelium and in pancreatic islets by immunoperoxidase staining. Radioimmunoassay with iodinated [Tyr14]-SS28(1-14) identified one antiserum (F4) to SS28(1-14) that cross-reacted equally with SS28(1-12), SS28(1-14) and SS28. Two other antisera (F3 and F8) to SS28(1-14) did not cross-react with SS28(1-12) and showed insignificant cross-reactivity to SS28. Immunostaining results showed that F4 stained the same cells that reacted with antiserum AS-10, which is specific for the cyclic tetradecapeptide somatostatin, SS28(15-28). Antisera F3, F4, and F8 all reacted with islet D cells and with somatostatin cells in the antral mucosa. However, only antiserum F4 detected immunoreactivity in mucosal epithelial cells; F3 and F8 did not bind to these cells. After sections of intestine were exposed to trypsin, however, epithelial cells containing immunoreactivity to SS28(1-14) were detected in intestinal mucosa with antisera F3 and F8. These results were obtained for duodenum, jejunum, ileum, and colon, but most of the epithelial cells with immunoreactivity to SS28(1-14) were in the duodenum. Both radioimmunoassay and immunostaining results suggest that F3 and F8 bind to a region of SS28(1-14) that is unavailable to antibodies in the intact SS28 molecule.(ABSTRACT TRUNCATED AT 250 WORDS)     

Poly(ADP-ribose) polymerase-1 is a survival factor for radiation-exposed intestinal epithelial stem cells in vivo

Poly(ADP-ribose) polymerase-1 (PARP-1) is a key enzyme mediating the cellular response to DNA strand breaks. It plays a critical role in genomic stability and survival of proliferating cells in culture undergoing DNA damage. Intestinal epithelium is the most proliferative tissue in the mammalian body and its stem cells show extreme sensitivity to low-level genotoxic stress. We investigated the role of PARP-1 in the in vivo damage response of intestinal stem cells in crypts of PARP-1^–/– and control mice following whole-body γ-irradiation (1 Gy). In the PARP-1^–/– mice there was a significant delay during the first 6 h in the transient p53 accumulation in stem cells whereas an increased number of cells were positive for p21^CIP1/WAF1. Either no or only marginal differences were noted in MDM2 expression, apoptosis, induction of or recovery from mitotic blockage, or inhibition of DNA synthesis. We further observed a dose-dependent reduction in crypt survival measured at 4 days post-irradiation in control mice, and this crypt-killing effect was significantly potentiated in PARP-1^–/– mice. Our results thus establish that PARP-1 acts as a survival factor for intestinal stem cells in vivo and suggest a functional link with early p53 and p21^CIP1/WAF1 responses.     

Apical membrane marker is expressed early in colonic epithelial cells

We have identified and characterized a membrane glycoprotein located at the apical plasma membrane of adult human colon epithelial cells, by the use of the monoclonal antibody technique in combination with immunocytochemical and biochemical methods. Analysis of membranes extracted with Triton X-114 and treated with specific hydrolases indicated that the antigen was an integral membrane glycoprotein. In the colon, the antigen was expressed in differentiated cells and along the entire crypt. It was also expressed at the apical membrane of the crypt cells of the distal ileum. It was not found in the proximal ileum, jejunum, or duodenum. In contrast, the antigen was found in all segments of the intestine of a 24-week-old embryo. Furthermore, the antigen had different apparent molecular weights in the adult ileum (200 kDa), adult colon (200 kDa and 301 kDa), and embryo (170 kDa). Therefore, this antigen should prove to be a useful marker to study the appearance of epithelial cell polarity during embryogenesis.     

p73 is expressed in human thymic epithelial cells.

The thymus is a heterogeneous immune organ in which immature T-cells develop and eventually specialize to make certain immune responses of their own. Among various types of stromal cells in the thymus, thymic epithelial cells (TECs) have a crucially important function for presenting self-antigens and secreting cytokines to thymocytes for their maturation into T-cells. In this study we show that the p73 gene, a homologue of the tumor suppressor gene p53, was expressed in the nucleus of the human TEC in vivo and in TEC lines in vitro. Because p73 has the capacity to be a transactivator like p53, it may contribute to T-cell development in the context of TEC biology as regulated in the cell cycle and apoptosis.     

L-MBP is expressed in epithelial cells of mouse small intestine

The mannan-binding proteins (L-MBP and S-MBP, also denoted MBL-C and MBL-A), mainly produced in liver and existing in liver and serum, play important roles in the innate immunity against a variety of pathogens. Total RNA from mouse tissues were screened for MBP mRNA by RT-PCR. In addition to liver, S-MBP mRNA was detected in lung, kidney, and testis, and L-MBP mRNA was detected in kidney, thymus, and small intestine. Quantitative RT-PCR revealed that the small intestine is a predominant site of extrahepatic expression of L-MBP. Western blotting with polyclonal Abs against rat L-MBP demonstrated this protein in Triton X-100 extracts of the small intestine obtained from mice that had undergone systemic perfusion. Immunohistochemical staining with an mAb against mouse L-MBP and in situ hybridization revealed that L-MBP is selectively expressed in some villous epithelial cells of the small intestine. These findings suggest that L-MBP plays a role in mucosal innate immunity.     

Role(s) of formyl-peptide receptors expressed in nasal epithelial cells

Chronic rhinosinusitis is one of the most frequent chronic diseases in humans. Little is known about stimuli initiating tissue remodeling process that determines the morphological expression of the disease. N-formyl peptide receptors (FPRs) are innate immunity receptors important in tissue remodeling of gastric and intestinal epithelium. The expression and functions of FPRs in nasal epithelial cells were examined to evaluate whether they could be important in the remodeling of nasal mucosa. The aim of this study is to examine FPR expression in a nasal epithelial cell line (RPMI-2650) at mRNA and protein levels. To determine whether FPRs were functional, chemotaxis experiments were carried out. In addition the effects of FPRs agonists on the expression (PCR and ELISA) of VEGF-A and TGF-beta, two key mediators of tissue remodelling, were examined. Here we demonstrate that RPMI-2650 express FPR and FPRL2, but not FPRL1. fMLP, a bacterial product active on FPR, and uPAR(84-95), an inflammatory mediator agonist for FPRL2, stimulated migration of nasal epithelial cells. fMLP and uPAR(84-95) induce expression and secretion of VEGF-A and TGF-beta. Our results suggest a possible mechanisms initiating tissue remodeling observed during chronic rhinosinusitis. This study provides further evidence that FPRs play a more complex role in human pathophysiology than bacterial recognition.     

Galectin-1 is expressed by thymic epithelial cells in myasthenia gravis

Galectin-1, a member of a family of carbohydrate binding proteins, is synthesized by thymic epithelial cells in normal juvenile thymus, and mediates adhesion of immature T cells to thymic epithelium. Because cell adhesion molecules are proposed to play a role in the thymic hyperplasia and neoplasia seen in the autoimmune disease myasthenia gravis, we examined the expression of galectin-1 in myasthenic thymi. We detected abundant galectin-1 expression in thymic epithelial cells in 27 hyperplastic and neoplastic thymi from patients with myasthenia gravis. Primary cultures of neoplastic epithelial cells from a thymoma continued to express galectin-1, and bound immature T cells; T cell binding was inhibited by the addition of the -galactosides lactose and thiodigalactoside, suggesting that galectin-1 on the thymoma cells and a saccharide ligand on the T cells participated in cell-cell adhesion. Expression of galectin-1 by thymic epithelial cells may play a role in the thymic pathology seen in myasthenia gravis.     

UCP3 expressed in yeast is primarily localized in extramitochondrial particles

Previously it was concluded (1) that, differently from UCP1, on expression in Saccharomyces cerevisiae, UCP3, and UCP3 short (UCP3s) are in a deranged state, allowing for unregulated uncoupling. Here we show that the bulk of UCP3 and UCP3s is in extramitochondrial aggregates whether expressed with high or medium expression vectors. The evidence is based on the insolubility of most UCP3 and UCP3s in nonionic detergents such as Triton X100, in contrast to UCP1. Using very high expression vector, macroscopic evidence for extramitochondrial UCP3 containing particles is a viscous white sediment surrounding the mitochondrial fraction which contains UCP3 as inclusion body type aggregate. Together with the previous data it is concluded that uncoupling due to small amounts of incorporated, deranged, and nucleotide insensitive UCP3 prevents incorporation of the bulk of UCP3 into mitochondria. This finding also provides a simple and stringent assay for the state of heterologously expressed in mitochondrial membrane proteins.     

The carbonic anhydrase domain protein nacrein is expressed in the epithelial cells of the mantle and acts as a negative regulator in calcification in the mollusc Pinctada fucata

Signals and organic matrix proteins secreted from the mantle are critical for the development of shells in molluscs. Nacrein, which is composed of a carbonic anhydrase domain and a Gly-X-Asn repeat domain, is one of the organic matrix proteins that accumulates in shells. In situ hybridization revealed that nacrein was expressed in the outer epithelial cells of the mantle of the pearl oyster Pinctada fucata. The recombinant nacrein protein inhibited the precipitation of calcium carbonate from a saturated solution containing CaCl2 and NaHCO3, indicating that it can act as a negative regulator for calcification in the shells of molluscs. Because deletion of the Gly-X-Asn repeat domain of nacrein had a significant effect on the ability of nacrein to inhibit the precipitation of calcium carbonate, it is conceivable that the repeat domain has a primary role in the inhibitory function of nacrein in shell formation. Together these studies suggest that nacrein functions as a negative regulator in calcification in the extrapallial space between the shell and the mantle by inhibiting the precipitation of CaCO3.     

Xenopus laevis FoxE1 is primarily expressed in the developing pituitary and thyroid

The members of the FoxE subfamily of Fox (forkhead) genes are expressed in the developing pituitary, thyroid and lens. Mammalian Foxe1 is expressed primarily in the developing pituitary and thyroid gland, Foxe3 is expressed in the developing lens, while Xenopus FoxE4 is expressed in the developing lens and thyroid. Here we report the identification of Xenopus FoxE1, a gene that is primarily expressed in the developing pituitary and thyroid.     

EndoPDI,a novel protein-disulfide isomerase-like protein that is preferentially expressed in endothelial cells acts as a stress survival factor

We have identified a novel protein-disulfide isomerase and named it endothelial protein-disulfide isomerase (EndoPDI) because of its high expression in endothelial cells. Isolation of the full-length cDNA showed EndoPDI to be a 48 kDa protein that has three APWCGHC thioredoxin motifs in contrast to the two present in archetypal PDI. Ribonuclease protection and Western analysis has shown that hypoxia induces EndoPDI mRNA and protein expression. In situ hybridization analysis showed that EndoPDI expression is rare in normal tissues, except for keratinocytes of the hair bulb and syncytiotrophoblasts of the placenta, but was present in the endothelium of tumors and in other hypoxic lesions such as atherosclerotic plaques. We have compared the function of EndoPDI to that of PDI in endothelial cells using specific siRNA. PDI was shown to have a protective effect on endothelial cells under both normoxia and hypoxia. In contrast, EndoPDI has a protective effect only in endothelial cells exposed to hypoxia. The loss of EndoPDI expression under hypoxia caused a significant decrease in the secretion of adrenomedullin, endothelin-1, and CD105; molecules that protect endothelial cells from hypoxia-initiated apoptosis. The identification of an endothelial PDI further extends this increasing multigene family and EndoPDI, unlike archetypal PDI, may be a molecule with which to target tumor endothelium.     

Nestin is expressed in mesenchymal and not epithelial cells of the developing mouse pancreas

Stem cell research and the prospect of stem cell based therapies depend critically on the identification of specific markers that can be used for the identification and selection of stem and progenitor cells. Nestin is expressed in neuronal progenitor cells and has also been suggested to mark multipotent pancreatic stem cells. We show here that, throughout pancreatic development, markers of pancreatic progenitor cells and differentiated pancreatic cells are expressed in E-cadherin-positive epithelial cells that do not express nestin. The data presented demonstrate that nestin is expressed in mesenchymal and not epithelial cells of the developing mouse pancreas.     

Fractalkine receptor CX(3)CR1 is expressed in epithelial ovarian carcinoma cells and required for motility and adhesion to peritoneal mesothelial cells

Epithelial ovarian carcinoma (EOC) is a deadly disease, and little is known about the mechanisms underlying its metastatic progression. Using human specimens and established cell lines, we determined that the G-protein-coupled seven-transmembrane fractalkine receptor (CX(3)CR1) is expressed in primary and metastatic ovarian carcinoma cells. Ovarian carcinoma cells robustly migrated toward CX(3)CL1, a specific ligand of CX(3)CR1, in a CX(3)CR1-dependent manner. Silencing of CX(3)CR1 reduced migration toward human ovarian carcinoma ascites fluid by approximately 70%. Importantly, adhesion of ovarian carcinoma cells to human peritoneal mesothelial cells was dependent on CX(3)CL1/CX(3)CR1 signaling. In addition, CX(3)CL1 was able to induce cellular proliferation. Together, our data suggest that the fractalkine network may function as a major contributor to the progression of EOC, and further attention to its role in the metastasis of this deadly malignancy is warranted.