Regulation of matrix metalloproteinase-9 and inhibition of tumor invasion by the membrane-anchored glycoprotein RECK

A human fibroblast cDNA expression library was screened for cDNA clones giving rise to flat colonies when transfected into v-Ki-ras-transformed NIH 3T3 cells. One such gene, RECK, encodes a membrane-anchored glycoprotein of about 110 kDa with multiple epidermal growth factor-like repeats and serine-protease inhibitor-like domains. While RECK mRNA is expressed in various human tissues and untransformed cells, it is undetectable in tumor-derived cell lines and oncogenically transformed cells. Restored expression of RECK in malignant cells resulted in suppression of invasive activity with concomitant decrease in the secretion of matrix metalloproteinase-9 (MMP-9), a key enzyme involved in tumor invasion and metastasis. Moreover, purified RECK protein was found to bind to, and inhibit the proteolytic activity of, MMP-9. Thus, RECK may link oncogenic signals to tumor invasion and metastasis.

Cardiotrophin 1 (CT-1) inhibition of cardiac myocyte apoptosis via a mitogen-activated protein kinase-dependent pathway. Divergence from downstream CT-1 signals for myocardial cell hypertrophy

Cardiac myocyte survival is of central importance in the maintenance of the function of heart, as well as in the development of a variety of cardiac diseases. To understand the molecular mechanisms that govern this function, we characterized apoptosis in cardiac muscle cells following serum deprivation. Cardiotrophin 1 (CT-1), a potent cardiac survival factor (Sheng, Z., Pennica, D., Wood, W. I., and Chien, K. R. (1996) Development (Camb.) 122, 419-428), is capable of inhibiting apoptosis in cardiac myocytes. To explore the potential downstream pathways that might be responsible for this effect, we documented that CT-1 activated both signal transducer and activator of transcription 3 (STAT3)- and mitogen-activated protein (MAP) kinase-dependent pathways. The transfection of a MAP kinase kinase 1 (MEK1) dominant negative mutant cDNA into myocardial cells blocked the antiapoptotic effects of CT-1, indicating a requirement of the MAP kinase pathway for the survival effect of CT-1. A MEK-specific inhibitor (PD098059) (Dudley, D. T., Pang, L., Decker, S.-J., Bridges, A. J., and Saltiel, A. R. (1995) Proc. Natl. Acad. Sci. USA 92, 7686-7689) is capable of blocking the activation of MAP kinase, as well as the survival effect of CT-1. In contrast, this inhibitor did not block the activation of STAT3, nor did it have any effect on the hypertrophic response elicited following stimulation of CT-1. Therefore, CT-1 promotes cardiac myocyte survival via the activation of an antiapoptotic signaling pathway that requires MAP kinases, whereas the hypertrophy induced by CT-1 may be mediated by alternative pathways, e.g. Janus kinase/STAT or MEK kinase/c-Jun NH2-terminal protein kinase.

Independent regulation of sterol regulatory element-binding proteins 1 and 2 in hamster liver

Two sterol regulatory element-binding proteins (SREBPs, designated SREBP-1 and SREBP-2), each approximately 1150 amino acids in length, are attached to membranes of the endoplasmic reticulum and nuclear envelope in human and hamster tissue culture cells. In the absence of sterols, soluble fragments of approximately 470 amino acids are released from both proteins by proteolytic cleavage. The soluble fragments enter the nucleus, where they bind to sterol regulatory elements in the promoters of genes encoding the low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl CoA synthase, thereby activating transcription. Proteolytic processing of both SREBPs is blocked coordinately by sterol overloading and enhanced coordinately when sterols are depleted by treatment with an inhibitor of cholesterol synthesis. In contrast to these findings in cultured cells, the current data show that SREBP-1 and -2 are not coordinately regulated in hamster liver. In untreated animals the soluble fragment of SREBP-1, but not of SREBP-2, was detected by immunoblotting of a liver nuclear extract. Depletion of sterols by treatment with a bile acid-binding resin (colestipol) and a cholesterol synthesis inhibitor (mevinolin) led to a marked increase in the nuclear form of SREBP-2 and a reciprocal decline in the nuclear form of SREBP-1. These findings suggest that SREBP-1 is responsible for basal transcription of the low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl CoA synthase genes in hamster liver and that SREBP-2 is responsible for the increased transcription that follows sterol depletion with a bile acid-binding resin and a cholesterol synthesis inhibitor.

Inhibition of hepatic chylomicron remnant uptake by gene transfer of a receptor antagonist

The low density lipoprotein receptor-related protein (LRP) has been proposed to mediate in concert with the LDL receptor (LDLR) the uptake of dietary lipoproteins into the hepatocytes. This hypothesis was tested by transient inactivation of LRP in vivo. Receptor-associated protein (RAP), a dominant negative regulator of LRP function, was transferred by an adenoviral vector to the livers of mice lacking LDLR (LDLR-/-). The inactivation of LRP by RAP was associated with a marked accumulation of chylomicron remnants in LDLR-/- mice and to a lesser degree in normal mice, suggesting that both LDLR and LRP are involved in remnant clearance.

Assessment of genetic changes in hepatocellular carcinoma by comparative genomic hybridization analysis: relationship to disease stage, tumor size, and cirrhosis

Hepatocellular carcinoma (HCC) is a common and highly malignant tumor that is prevalent in Southeast Asia. Although the etiological factors associated are now well recognized, the interactions between individual factors and the molecular mechanisms by which they lead to cancer remain unclear. Cytogenetic analysis on HCC has been limited because of poor hepatocyte growth in vitro. The recently developed technique of comparative genomic hybridization (CGH), however, permits screening of the entire genome without the need of cell culture. CGH was applied to the study of genomic aberrations in 67 surgically resected samples of HCC, 3 of adenomatous hyperplasia (AH), and 12 of nontumorous cirrhotic liver surrounding the tumors. All samples were from patients of a racially and etiologically homogeneous population in Southern China, where chronic hepatitis B virus infection is the main etiological factor. CGH analysis of the HCC samples revealed frequent copy number gain of 1q (48/67 cases, 72%), 8q (32/67 cases, 48%), 17q (20/67 cases, 30%), and 20q (25/67 cases, 37%) and common losses on 4q (29/67 cases, 43%), 8p (25/67 cases, 37%), 13q (25/67 cases, 37%), and 16q (20/67 cases, 30%). Our finding of a high incidence of 1q gain strongly suggested this aberration was associated with the development of HCC. Genomic abnormalities were detected in 1 of the 3 AH specimens but absent in all 12 cirrhotic tissues surrounding the tumor. Clinical staging classified 3/67 HCC cases as T1, 53 cases as T2, and 11 cases as T3. No significant difference in the pattern of genomic imbalances was detected between stages T2 and T3. A significant copy number loss of 4q11-q23 was, however, identified in those tumors larger than 3 cm in diameter. Of particular interest was the identification of 8q copy number gain in all 12 cases of HCC that arose in a noncirrhotic liver, compared with only 20/55 cases in HCC arising in a cirrhotic liver. We suggest that 8q over-representation is likely associated with a growth advantage and proliferative stimulation that have encouraged malignant changes in the noncirrhotic human liver.

Opposing effects of Jun kinase and p38 mitogen-activated protein kinases on cardiomyocyte hypertrophy

c-Jun N-terminal protein kinase (JNK) and p38, two distinct members of the mitogen-activated protein (MAP) kinase family, regulate gene expression in response to various extracellular stimuli, yet their physiological functions are not completely understood. In this report we show that JNK and p38 exerted opposing effects on the development of myocyte hypertrophy, which is an adaptive physiological process characterized by expression of embryonic genes and unique morphological changes. In rat neonatal ventricular myocytes, both JNK and p38 were stimulated by hypertrophic agonists like endothelin-1, phenylephrine, and leukemia inhibitory factor. Expression of MAP kinase kinase 6b (EE), a constitutive activator of p38, stimulated the expression of atrial natriuretic factor (ANF), which is a genetic marker of in vivo cardiac hypertrophy. Activation of p38 was required for ANF expression induced by the hypertrophic agonists. Furthermore, a specific p38 inhibitor, SB202190, significantly changed hypertrophic morphology induced by the agonists. Surprisingly, activation of JNK led to inhibition of ANF expression induced by MEK kinase 1 (MEKK1) and the hypertrophic agonists. MEKK1-induced ANF expression was also negatively regulated by expression of c-Jun. Our results demonstrate that p38 mediates, but JNK suppresses, the development of myocyte hypertrophy.

Steroid receptor co-activator is required for juvenile hormone signal transduction through a bHLH-PAS transcription factor, methoprene tolerant

Metamorphosis in insects is regulated by juvenile hormone (JH) and ecdysteroids. The mechanism of 20-hydroxyecdysone (20E), but not of JH action, is well understood. A basic helix-loop-helix (bHLH)-Per-Arnt-Sim (PAS) family member, methoprene tolerant (Met), plays an important role in JH action. Microarray analysis and RNA interference (RNAi) were used to identify 69 genes that require Met for their hydroprene-regulated expression in the red flour beetle, Tribolium castaneum. Quantitative real time PCR analysis confirmed microarray data for 13 of the 16 hydroprene-response genes tested. The members of the bHLH-PAS family often function as heterodimers to regulate gene expression and Met is a member of this family. To determine whether other members of the bHLH-PAS family are required for the expression of JH-response genes, we employed RNAi to knockdown the expression of all 11 members of the bHLH-PAS family and studied the expression of JH-response genes in RNAi insects. These studies showed that besides Met, another member of this family, steroid receptor co-activator (SRC) is required for the expression of 15 JH-response genes tested. Moreover, studies in JH responsive Aag-2 cells revealed that Aedes aegypti homologues of both Met and SRC are required for the expression of the JH-response gene, kr-h1, and SRC is required for expression of ecdysone-response genes. These data suggest the steroid receptor co-activator plays key roles in both JH and 20E action suggesting that this may be an important molecule that mediates cross-talk between JH and 20E to prevent metamorphosis.

Juvenile hormone regulates vitellogenin gene expression through insulin-like peptide signaling pathway in the red flour beetle, Tribolium castaneum

Our recent studies identified juvenile hormone (JH) and nutrition as the two key signals that regulate vitellogenin (Vg) gene expression in the red flour beetle, Tribolium castaneum. Juvenile hormone regulation of Vg synthesis has been known for a long time in several insects, but the mechanism of JH action is not known. Experiments were conducted to determine the mechanism of action of these two signals in regulation of Vg gene expression. Injection of bovine insulin or FOXO double-stranded RNA into the previtellogenic, starved, or JH-deficient female adults increased Vg mRNA and protein levels, thereby implicating the pivotal role for insulin-like peptide signaling in the regulation of Vg gene expression and possible cross-talk between JH and insulin-like peptide signaling pathways. Reduction in JH synthesis or its action by RNAi-mediated silencing of genes coding for acid methyltransferase or methoprene-tolerant decreased expression of genes coding for insulin-like peptides (ILPs) and influenced FOXO subcellular localization, resulting in the down-regulation of Vg gene expression. Furthermore, JH application to previtellogenic female beetles induced the expression of genes coding for ILP2 and ILP3, and induced Vg gene expression. FOXO protein expressed in baculovirus system binds to FOXO response element present in the Vg gene promoter. These data suggest that JH functions through insulin-like peptide signaling pathway to regulate Vg gene expression.

Cardiotrophin-1 displays early expression in the murine heart tube and promotes cardiac myocyte survival

We have recently isolated a novel cytokine, cardiotrophin-1 (CT-1), from an in vitro embryonic stem cell system of cardiogenesis that can activate embryonic markers in neonatal rat cardiac myocytes. CT-1 is a new member of the interleukin 6 (IL-6)/leukemia inhibitory factor (LIF) cytokines, which activate downstream signals via gp130-dependent pathways. To define the developmental pattern of expression of CT-1 during murine embryogenesis, we have developed antibodies directed against a CT-1 fusion protein. As assessed by immunolocalization, CT-1 is predominantly expressed in the early mouse embryonic heart tube (E8.5-10.5). In the heart, CT-1 is primarily expressed in myocardial cells, and not in endocardial cushion or outflow tract tissues. After E12.5, CT-1 expression is found in other tissues, including skeletal, liver and dorsal root ganglia. Given the effects of a related family member (ciliary neurotrophic factor, CNTF) on neuronal cell survival, we studied the ability of CT-1 to promote cardiac myocyte survival and proliferation in vitro. Both CT-1 and LIF, which share the same receptors, dramatically promote neonatal cardiac myocyte survival, while IL-6 and CNTF are without effect. A cell proliferation assay documents that CT-1 provokes an approximate 2-fold increase in embryonic cardiac myocyte proliferation. Thus, CT-1 may play an autocrine role during cardiac chamber growth and morphogenesis by promoting the survival and proliferation of immature myocytes, most likely via gp130-dependent signaling pathways.

C-type inactivation of a voltage-gated K+ channel occurs by a cooperative mechanism

The lymphocyte voltage-gated K+ channel, Kv1.3, inactivates by a C-type process. We have elucidated the molecular basis for this process using a kinetic analysis of wild-type and mutant (A413V) Kv1.3 homo- and heteromultimeric currents in a mammalian lymphoid expression system. The medians of the measured inactivation time constants for wild-type and A413V homotetrameric currents are 204 and 4 ms, respectively. Co-expression of these subunits produces heteromultimeric channels manifesting inactivation kinetics intermediate between those of wild-type and A413V homomultimers. We have considered several models in which each subunit acts either independently or cooperatively to produce the observed inactivation kinetics. The cooperative model gives excellent fits to the data for any heteromultimeric composition of subunits, clearly distinguishing it from the independent models. In the cooperative model, the difference in free energy between the open and inactivated states of the channel is invariant with subunit composition and equals approximately 1.5 kcal/mol. Each subunit contributes equally to the activation free energy for transitions between open and inactivated states, with an A413V subunit decreasing the free energy barrier for inactivation (and for recovery from inactivation) by approximately 0.6 kcal/mol. Our results are consistent with a physical model in which the outer mouth of the channel constricts during C-type inactivation (G. Yellen, D. Sodickson, T. Chen, and M.E. Jurman, 1994, Biophys. J. 66:1068-1075).

A direct regulatory role for troponin T and a dual role for troponin C in the Ca2+ regulation of muscle contraction

Troponin (Tn), containing three subunits: Ca2+ binding (TnC), inhibitory (TnI), and tropomyosin binding (TnT), plays a crucial role in the Ca2+ regulation of vertebrate striated muscle contraction. These three subunits function by interacting with each other and with the other thin filament proteins. Previous studies suggested that the primary role of TnT is to anchor the TnI.TnC complex to the thin filament, primarily through its interactions with TnI and tropomyosin. We propose here a new role for TnT. Our results indicate that, when TnT is combined with the TnI.TnC complex, there is an activation of actomyosin ATPase that is Ca(2+)-dependent. To determine whether the latter results from a direct effect of TnC on TnT or indirectly from an effect of TnC on TnI which is transmitted to TnT, we prepared a deletion mutant (deletion of residues 1-57) of TnI, TnId57 (Sheng et al. (1992) J. Biol. Chem. 267, 25407-25413), which interacts with TnC but not TnT. Both wild type (TnI.TnC.TnT) and mutant (TnId57.TnC.TnT) Tn complexes demonstrated equivalent activity in the Ca2+ regulation of actomyosin-S1 ATPase activity. Similarly, both TnI and TnId57 could equally reconstitute TnI-depleted skinned muscle fibers. Therefore, since TnId57 does not interact with TnT, these results suggest that TnT reconstitutes native Ca2+ sensitivity via direct interaction with TnC. Thus Ca2+ binding to TnC would have a dual role: 1) release of the ATPase inhibition by TnI and 2) activation of the ATPase through interaction with TnT.

Randomised placebo-controlled trial of use of topical recombinant bovine basic fibroblast growth factor for second-degree burns

BACKGROUND

Wound healing is a dynamic process that could be accelerated by growth factors. We investigated the effect of recombinant bovine basic fibroblast growth factor (rbFGF) on burn healing in a randomised placebo-controlled trial.

METHODS

We recruited 600 patients with superficial or deep second-degree burns. Patients received 150 AU/cm2 daily topical rbFGF (n=300) or placebo (n=300) plus vehicle. We assessed healing by photography, punch-biopsy, and clinical examination.

FINDINGS

All patients treated with rbFGF had faster granulation tissue formation and epidermal regeneration than those in the placebo group. Superficial and deep second-degree burns treated with rbFGF healed in a mean of 9.9 (SD 2.5) days and 17.0 (4.6) days, respectively, compared with 12.4 (2.7) and 21.2 (4.9) days (p=0.0008 and p=0.0003, respectively). No adverse effects were seen locally or systemically with rbFGF.

INTERPRETATION

rbFGF effectively decreased healing time and improved healing quality. Clinical benefits would be shorter hospital stays and the patient's skin quickly becoming available for harvesting and grafting.

Hair cell protection from aminoglycoside ototoxicity by adenovirus-mediated overexpression of glial cell line-derived neurotrophic factor

Aminoglycosides are commonly used antimicrobial drugs that often have ototoxic side effects. The ototoxicity often involves permanent loss of cochlear hair cells (HCs). Neurotrophic factors have been shown to protect a variety of tissues, including HCs, from toxic trauma. To determine if glial cell line-derived neurotrophic factor (GDNF) can protect cochlear HCs from trauma, we inoculated an adenoviral vector encoding the human GDNF gene into guinea pig cochleae via the round window membrane 4 days prior to injection of aminoglycosides. Control groups showed little or no negative influence of the viral inoculation on cochlear structure and function. In contrast, ears that were inoculated with the GDNF vector had better hearing and fewer missing HCs after exposure to the ototoxins, as compared with controls. Our results demonstrate the feasibility of gene therapy for cochlear application and suggest that virus-mediated overexpression of GDNF may be developed as a valuable prevention against trauma-induced HC death.

Juvenile hormone counteracts the bHLH-PAS transcription factors MET and GCE to prevent caspase-dependent programmed cell death in Drosophila

Juvenile hormone (JH) regulates many developmental and physiological events in insects, but its molecular mechanism remains conjectural. Here we report that genetic ablation of the corpus allatum cells of the Drosophilaring gland (the JH source) resulted in JH deficiency, pupal lethality and precocious and enhanced programmed cell death (PCD) of the larval fat body. In the fat body of the JH-deficient animals, Dronc and Drice,two caspase genes that are crucial for PCD induced by the molting hormone 20-hydroxyecdysone (20E), were significantly upregulated. These results demonstrated that JH antagonizes 20E-induced PCD by restricting the mRNA levels of Dronc and Drice. The antagonizing effect of JH on 20E-induced PCD in the fat body was further confirmed in the JH-deficient animals by 20E treatment and RNA interference of the 20E receptor EcR. Moreover, MET and GCE, the bHLH-PAS transcription factors involved in JH action, were shown to induce PCD by upregulating Droncand Drice. In the Met- and gce-deficient animals, Dronc and Drice were downregulated, whereas in the Met-overexpression fat body, Dronc and Drice were significantly upregulated leading to precocious and enhanced PCD, and this upregulation could be suppressed by application of the JH agonist methoprene. For the first time, we demonstrate that JH counteracts MET and GCE to prevent caspase-dependent PCD in controlling fat body remodeling and larval-pupal metamorphosis in Drosophila.

Ecdysteroid regulation of ovarian growth and oocyte maturation in the red flour beetle, Tribolium castaneum

Previous studies from our laboratory showed the involvement of juvenile hormone (JH) and ecdysteroid signaling in the regulation of female reproduction in the red flour beetle, Tribolium castaneum. JH regulates vitellogenin (Vg) synthesis in the fat body but the role of ecdysteroid signaling is not known. Here, we report on ecdysteroid regulation of ovarian growth and oocyte maturation. Microarray analysis of RNA isolated from ovaries showed the up-regulation of several genes coding for proteins involved in ecdysteroid signaling on the 4th day after female adult eclosion. The functional analyses of genes coding for proteins involved in ecdysteroid and JH signaling pathways by RNA interference (RNAi) revealed that ecdysteroids but not JH regulate ovarian growth and primary oocyte maturation. Ultrastructural studies showed the temporal sequences of key events in oogenesis including the development of primary oocytes, the differentiation and development of follicle epithelial cells, and the formation of intercellular spaces to facilitate uptake of Vg protein. RNAi studies showed that ecdysone receptor (EcR) and ultraspiracle (USP) are required for the ovarian growth, primary oocyte maturation and the growth and migration of the follicle cells. These studies suggest important roles for ecdysteroids in the regulation of oocyte maturation in the beetle ovaries.

Juvenile hormone and insulin regulate trehalose homeostasis in the red flour beetle, Tribolium castaneum

Insulin/IGF-1 signaling (IIS) has been well studied for its role in the control of life span extension and resistance to a variety of stresses. The Drosophila melanogaster insulin-like receptor (InR) mutant showed extended life span due to reduced juvenile hormone (JH) levels. However, little is known about the mechanism of cross talk between IIS and JH in regulation of life span extension and resistance to starvation. In the current study, we investigated the role of IIS and JH signaling in regulation of resistance to starvation. Reduction in JH biosynthesis, JH action, or insulin-like peptide 2 (ILP2) syntheses by RNA interference (RNAi)-aided knockdown in the expression of genes coding for juvenile hormone acid methyltransferase (JHAMT), methoprene-tolerant (Met), or ILP2 respectively decreased lipid and carbohydrate metabolism and extended the survival of starved beetles. Interestingly, the extension of life span could be restored by injection of bovine insulin into JHAMT RNAi beetles but not by application of JH III to ILP2 RNAi beetles. These data suggest that JH controls starvation resistance by regulating synthesis of ILP2. More importantly, JH regulates trehalose homeostasis, including trehalose transport and metabolism, and controls utilization of stored nutrients in starved adults.

Both juvenile hormone (JH) and Insulin/IGF-1 signaling (IIS) regulate life span and starvation resistance in insects. Regulation of longevity and starvation resistance by IIS has been well studied, yet little is known about the underlying mechanisms and cross talk between these two hormones. The red flour beetle, Tribolium castaneum, is a good model to study cross talk between JH and IIS because both of these pathways are important in regulation of life span and starvation resistance. The starved male beetles with either reduced JH or ILP2 levels live longer due to a lower rate in lipid and carbohydrate metabolism when compared with the control beetles. Juvenile hormone regulates starvation survival through regulation of synthesis of ILP2, trehalose transporter (TRET), and trehalase. Reduction in JH levels or its action or ILP2 expression decreased trehalase levels in the fat body, resulting in a slower rate of conversion of trehalose to glucose. Reduction in JH levels or its action also caused a decrease in TRET levels in the alimentary canal leading to a lower rate of uptake of trehalose into this tissue resulting in more trehalose available in the hemolymph. Trehalose likely regulates various processes to protect beetles from stress.

Voltage-gated K+ channels contain multiple intersubunit association sites

A domain in the cytoplasmic NH2 terminus of voltage-gated K+ channels supervises the proper assembly of specific tetrameric channels (Li, M., Jan, J. M., and Jan, L. Y.(1992) Science 257, 1225-1230; Shen, N. V., Chen X., Boyer, M. M., and Pfaffinger, P. (1993) Neuron 11, 67-76). It is referred to as a first tetramerization domain, or T1 (Shen, N. V., Chen X., Boyer, M. M., and Pfaffinger, P.(1993) Neuron 11, 67-76). However, a deletion mutant of Kv1.3 that lacks the first 141 amino acids, Kv1.3 (T1(-)) forms functional channels, suggesting that additional association sites in the central core of Kv1.3 mediate oligomerization. To characterize these sites, we have tested the abilities of cRNA Kv1.3 (T1(-)) fragments co-injected with Kv1.3 (T1(-)) to suppress current in Xenopus oocytes. The fragments include portions of the six putative transmembrane segments, S1 through S6, specifically: S1, S1-S2, S1-S2-S3, S2-S3, S2-S3-S4, S3-S4, S3-S4-S5, S2 through COOH, S3 through COOH, S4 through COOH, and S5-S6-COOH. Electrophysiologic experiments show that the fragments S1-S2-S3, S3-S4-S5, S2 through COOH, and S3 through COOH strongly suppress Kv1.3 (T1(-)) current, while others do not. Suppression of expressed current is due to specific effects of the translated peptide Kv1.3 fragments, as validated by in vivo immunoprecipitation studies of a strong suppressor and a nonsuppressor. Pulse-chase experiments indicate that translation of truncated peptide fragments neither prevents translation of Kv1.3 (T1(-)) nor increases its rate of degradation. Co-immunoprecipitation experiments suggest that suppression involves direct association of a peptide fragment with Kv1.3 (T1(-)). Fragments that strongly suppress Kv1.3 (T1(-)) also suppress an analogous NH2-terminal deletion mutant of Kv2.1 (Kv2.1 (DeltaN139)), an isoform belonging to a different subfamily. Our results indicate that sites in the central core of Kv1.3 facilitate intersubunit association and that there are suppression sites in the central core, which are promiscuous across voltage-gated K+ channel subfamilies.

Dedifferentiation of epidermal cells to stem cells in vivo

The effects of growth factors on wound healing have been studied extensively; however epidermal regeneration is not fully understood. We treated eight patients with leg ulcers with recombinant human epidermal growth factor (rhEGF) and compared biopsies of regenerating epidermis with those of controls who did not receive rhEGF. We used immunohistochemistry to identify cells expressing keratin 19 and beta1 integrin in regenerated epidermis from patients and controls. Patients treated with rhEGF had stem cells in the spinous and granular layers of regenerated epidermis. Histological analysis showed that these stem cells had reverted from differentiated to undifferentiated stem cells. Our findings provide evidence for epidermal cell reversion.

Restoration of positioning control following Disabled-2 expression in ovarian and breast tumor cells

The physical interaction of epithelial cells with the basement membrane ensures correct positioning and acts as a survival factor for epithelial cells. Cells that detach from the basement membrane often undergo apoptosis; however, in carcinomas, this positional control is absent, permitting disorganized cell proliferation. In the majority of breast and ovarian carcinomas (85-90%), the expression of a candidate tumor suppressor, Disabled-2 (Dab2), is frequently lost. The Dab2-negative tumor cells are no longer in contact with an intact basement membrane, as indicated by the absence of collagen IV (in about 90% of cases). However, in the subset (10-15%) of ovarian tumors in which Dab2 expression is positive, the presence of a basement membrane-like structure around tumor cells was observed. Recombinant adenovirus-mediated expression of Dab2 was used in Dab2-negative ovarian and breast cancer cells, and re-expression of Dab2 was found to lead to cell death or growth arrest. Dab2 expression suppressed MAPK activation and c-fos expression. Plating the infected cells on a basement membrane matrigel rescued the cells from death and growth arrest. Thus, Dab2 exhibits a negative activity for cell growth and survival, which can be countered by attachment of the cells to basement membrane matrix. We conclude that Dab2 functions in cell positioning control and mediates the exigency for basement membrane attachment of epithelial cells. Loss of Dab2 may contribute to the basement membrane-independent, disorganized proliferation of tumor cells in ovarian and breast carcinomas.

Plasmids encoding foot-and-mouth disease virus VP1 epitopes elicited immune responses in mice and swine and protected swine against viral infection

VP1 is a capsid protein of foot-and-mouth disease virus (FMDV) and contains epitopes of the virus. Plasmids encoding two VP1 epitopes (amino acid residues 141-160 and 200-213) and a host-self immunoglobulin molecule were constructed to produce a new type of FMD DNA vaccine. Two plasmids, namely, pCEIM and pCEIS, containing mouse immunoglobulin (IgG) or swine IgG were subjected to immunogenicity testing in mice and swine, respectively. In mice administrated pCEIM in the abdomen using a genegun, both FMDV-specific T-cell proliferation and neutralizing antibodies were detected. In swine immunized with pCEIS at the back of the ear, immune responses were achieved after the second administration. Swine showed a T-cell proliferative response with a stimulation index (SI) of up to 8.1 and a neutralizing antibody response that was able to protect suckling mice from 10(2) LD(50) (lethal dose 50) FMDV challenge. To compare the immunogenicity of the DNA-based vaccine candidate, versus the protein-based vaccine candidates, a second group of swine was immunized with the protein F1-scIgG, which was encoded by the plasmid pCEIS. Injection with F1-scIgG elicited a T-cell proliferative response of SI < 1.7 and a neutralizing antibody response that protected suckling mice from up to 10(5) LD(50) FMDV challenge. In the challenge test, three of three swine immunized with pCEIS were fully protected from FMDV challenge.

Transcriptional regulation of the insulin signaling pathway genes by starvation and 20-hydroxyecdysone in the Bombyx fat body

Genetic studies in the fruitfly, Drosophila melanogaster, have uncovered a conserved insulin/insulin growth factor signaling (IIS) pathway that regulates nutrition-dependent growth rates of insects. From the silkworm, Bombyx mori, we have identified and characterized several key genes involved in the IIS pathway, including InR, IRS, PI3K110, PI3K60, PTEN, PDK, and Akt. Tissue distribution analysis showed that most of these genes were highly expressed in the fat body implying that the IIS pathway is functionally important within insect adipose tissue. Developmental profile studies revealed that the expression levels of InR, IRS, PI3K110, and PDK were elevated in the fat body during molting and pupation, periods when animals ceased feeding and hemolymph levels of 20-hydroxyecdysone (20E) were high. Starvation rapidly up-regulated the mRNA levels of these same genes in the fat body, while 20E slowly induced their transcription. We conclude that 20E slowly reduces food consumption and then indirectly induces a state of starvation resulting in the elevation of the mRNA levels of InR, IRS, PI3K110, and PDK in the Bombyx fat body during molting and pupation.