Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated dynamic events during the formation of intercalated disc-like structures of adult rat cardiomyocytes (ARC) in long-term culture. Given the complexity of ARC cytoIarchitecture after de- and re-differentiation, and the non-uniform morphological development of individual cells, green fluorescent protein (GFP) technology was used to track N-cadherin in living cells. Sorting and functionality of the GFP fusion protein was tested in ARC. Isolated ARC were micro-injected with the expression construct at the onset of spreading in culture, and the fluorescence signals were tracked during contact formation and in fully redifferentiated living cells. The first contact sites were found to be established by cellular protrusions, which were marked by an ultrastructure similar to microspikes and probably have a role as exploratory units in the spreading phase. Subsequently, initial contact sites served as anchorage for the most prominent stress fibre-like structures. The fusion protein appeared before connexin-43 at newly established cell-cell contacts. Membrane invaginations at the sarcolemma facing the substratum of cultured ARC may be responsible for the appearance of a striped pattern of N-cadherin and other adherens junction proteins away from intercalated disc-like structures. The stripes were immobile in redifferentiated cells, while the distinct small fluorescent particles in the cell body were found to move directionally at speeds around 10 micro m/min. These results contribute to the understanding of the mechanisms of cell-cell contact formation of adult cardiomyocytes, which is a prerequisite for any future implantation technology.
J Mol Cell Cardiol 2000 Apr
PMID:Dynamics of early contact formation in cultured adult rat cardiomyocytes studied by N-cadherin fused to green fluorescent protein. 1075 12

beta-Catenin and plakoglobin are highly homologous components of cell-cell adherens junctions linking cadherin receptors to the actin cytoskeleton. beta-Catenin, in addition, activates transcription by forming a complex with LEF/TCF family transcription factors in the nucleus. Plakoglobin can also bind to LEF-1 and, when overexpressed in mammalian cells, enhances LEF-1-directed transcription. Plakoglobin overexpression, however, results in the elevation and nuclear translocation of endogenous beta-catenin. We show here, by DNA mobility shift analysis, that the formation of a plakoglobin-LEF/TCF-DNA complex in vitro is very inefficient compared to a complex containing beta-catenin-LEF-DNA. Moreover, in plakoglobin-transfected cells plakoglobin-LEF/TCF-DNA complexes were not formed; rather, the endogenous beta-catenin, whose level is elevated by plakoglobin transfection, formed a beta-catenin-LEF-DNA complex. Removal of the N- and C-terminal domains of both beta-catenin and plakoglobin (leaving the armadillo repeat domain intact) induced plakoglobin-LEF-DNA complex formation and also enhanced beta-catenin-LEF-DNA complexing, both with in vitro-translated components and in transfected cells. Transfection with these truncated catenins increased endogenous beta-catenin levels, but the truncated catenins acted as dominant-negative inhibitors of beta-catenin-driven transcription by forming transcriptionally inactive complexes with LEF-1. When these catenin mutants were prevented from entering the nucleus, by their fusion to the connexin transmembrane domain, they indirectly activated transcription by increasing endogenous beta-catenin levels. These results suggest that overexpression of plakoglobin does not directly activate transcription and that formation of catenin-LEF-DNA complexes is negatively regulated by the catenin N- and C-terminal domains.
Mol Cell Biol 2000 Jun
PMID:Differential mechanisms of LEF/TCF family-dependent transcriptional activation by beta-catenin and plakoglobin. 1082 88

Large non-luteinized follicles of the marmoset monkey were cultured for up to 96 h in the presence of substances that are known to induce luteinization, i.e. LH, transforming growth factor (TGF)-beta and cyclic AMP. The state of the basal lamina, and the expression of connexin-43, alpha(2) integrin subunit and TGF-beta receptor type II (TbetaR-II) were chosen as parameters to judge the progress of luteinization. Antral follicles, cultured for 1 h, were not luteinized, as shown by an intact basal lamina, strong immunoreactivity of connexin-43 in granulosa cells, and no expression of TbetaR-II in the theca layer. After 12 h, most follicles showed a dissolution of the basal lamina, a faint reactivity of connexin-43, high expression of TbetaR-II in theca- and outer granulosa cells and high expression of alpha(2) integrin subunit in granulosa cells bordering at the basement membrane; all of which indicate luteinization. After 96 h of culture, luteal structures (e.g. corpora lutea accessoria) had developed. This was true for both non-stimulated and stimulated follicles. Our results strongly suggest that antral follicles luteinize spontaneously. The decisive determinant appears to be the follicular stage.
Mol Hum Reprod 2000 Jun
PMID:Spontaneous luteinization of antral marmoset follicles in vitro. 1082 66

Myelin basic protein (MBP) plays an essential adhesive role in the formation of compact myelin in the central nervous system (CNS), but not in the peripheral nervous system (PNS). Morphologic data suggest that MBP controls the number of cytoplasmic channels or Schmidt-Lanterman incisures (SLI) present in PNS myelin. The levels of connexin-32 (Cx32) and myelin-associated glycoprotein (MAG), two components of the incisures, are inversely proportional to the levels of MBP in sciatic nerves of mice affected by the shiverer (shi) mutation, while protein zero (P0) and peripheral membrane protein 22 (PMP22), two structural components of compact myelin, remain constant. The levels of P0, PMP22, Cx32, and MAG mRNA do not vary in relationship to the levels of MBP. This indicates that MBP exerts its effect on Cx32 and MAG at a posttranscriptional level and suggests a new function for MBP in regulating gene expression in the PNS.
Mol Cell Neurosci 2000 Apr
PMID:Myelin basic protein gene dosage effects in the PNS. 1084 71

More than 130 different mutations in the gap junction integral plasma membrane protein connexin32 (Cx32) have been linked to the human peripheral neuropathy X-linked Charcot-Marie-Tooth disease (CMTX). How these various mutants are processed by the cell and the mechanism(s) by which they cause CMTX are unknown. To address these issues, we have studied the intracellular transport, assembly, and degradation of three CMTX-linked Cx32 mutants stably expressed in PC12 cells. Each mutant had a distinct fate: E208K Cx32 appeared to be retained in the endoplasmic reticulum (ER), whereas both the E186K and R142W mutants were transported to perinuclear compartments from which they trafficked either to lysosomes (R142W Cx32) or back to the ER (E186K Cx32). Despite these differences, each mutant was soluble in nonionic detergent but unable to assemble into homomeric connexons. Degradation of both mutant and wild-type connexins was rapid (t(1/2) < 3 h) and took place at least in part in the ER by a process sensitive to proteasome inhibitors. The mutants studied are therefore unlikely to cause disease by accumulating in degradation-resistant aggregates but instead are efficiently cleared from the cell by quality control processes that prevent abnormal connexin molecules from traversing the secretory pathway.
Mol Biol Cell 2000 Jun
PMID:Intracellular transport, assembly, and degradation of wild-type and disease-linked mutant gap junction proteins. 1084 20

Many lines of evidence suggest that connexin-32 gap junction is involved in the exchange of information and metabolites in the peripheral nervous system. It has been shown that connexin-32 protein and mRNA are expressed in Schwann cells that function as myelinating cells of the peripheral nervous system. The physiological importance of connexin-32 gap junctions in regulating the normal function of myelinating Schwann cell is indicated by recent findings that X-linked dominant Charcot-Marie-Tooth disease, a hereditary peripheral neuropathy, is associated with the mutations of connexin-32 gene. Recently, we encountered a Taiwanese family affected with X-linked dominant Charcot-Marie-Tooth neuropathy. Therefore, we investigated the possible mutation in the coding and noncoding regions of the connexin-32 gene of affected members of this family. Our results suggest that a G-to-A transition at the position -215 (in relation to the transcription initiation site) of the nerve-specific P2 promoter region is associated with the pathogenesis of X-linked dominant Charcot-Marie-Tooth disease. Further experiments using the promoter assay indicate that G-to-A mutation at the position -215 greatly impairs the transcriptional activity of connexin-32 P2 promoter. These findings propose that a reduced expression of connexin-32 mRNA and protein in the myelin sheath could be responsible for the development of X-linked dominant Charcot-Marie-Tooth neuropathy.
Brain Res Mol Brain Res 2000 May 31
PMID:Point mutation associated with X-linked dominant Charcot-Marie-Tooth disease impairs the P2 promoter activity of human connexin-32 gene. 1089 94

Gap junctions are transmembrane proteins comprised of six connexin subunits that facilitate direct solute transport between adjacent cells through gap junctions. Previous studies from other laboratories have documented a correlation between reduced gap-junction function and malignant transformation. In endometrial cancer, a characteristic finding is a reduction in the number of stromal cells surrounding the malignant epithelial cells. Thus, the focus of this study was to determine the effect of endometrial stromal cells on gap-junction function in normal and malignant endometrial epithelial cells. To perform these studies, we evaluated normal endometrial epithelial cells and human endometrial epithelial cells including FEEC (fetal endometrial epithelial cells immortalized with simian virus 40 large-T antigen), HEC-1A (endometrial carcinoma stage 1A), and RL-95-2 (endometrial carcinoma grade II). Gap-junctional intercellular communication (GJIC) could not be demonstrated for any of the cell lines. Low levels of GJIC were observed for normal epithelial cells and higher levels were found between stromal cells. Increased levels of GJIC were observed between the epithelial cells when they were cocultured with stromal cells. The transformed epithelial cells showed no GJIC when cultured alone or when in coculture with stromal cells. The results suggest that endometrial stromal cells may help to regulate this differentiated function of endometrial epithelial cells and that malignant endometrial epithelial cells are not responsive to these regulatory signals. Mol. Carcinog. 28:70-75, 2000.
Mol Carcinog 2000 Jun
PMID:Endometrial stromal cells regulate gap-junction function in normal human endometrial epithelial cells but not in endometrial carcinoma cells. 1090 Apr 63

Tumor cell transduction with the herpes simplex virus (HSV) thymidine kinase (tk) gene and treatment with ganciclovir (GCV) is a widely studied cancer gene therapy. Connexin (Cx)-dependent gap junctions between cells facilitate the intercellular spread of TK-activated GCV, thereby creating a bystander effect that improves tumor cell killing. However, tumor cells often have reduced connexin expression, thus thwarting bystander killing and the effectiveness of TK/GCV gene therapy. To improve the effectiveness of this therapy, we compared an HSV vector (TOCX) expressing Cx43 in addition to TK with an isogenic tk vector (TOZ.1) for their abilities to induce bystander killing of Cx-positive U-87 MG human glioblastoma cells and Cx-negative L929 fibrosarcoma cells in vitro and in vivo. The results showed that low-multiplicity infection of U-87 MG cells with TOCX only minimally increased GCV-mediated cell death compared with infection by TOZ.1, consistent with the endogenous level of Cx in these cells. In contrast, bystander killing of L929 cells was markedly enhanced by vector-mediated expression of Cx. In vivo experiments in which U-87 MG cells were preinfected at low multiplicity and injected into the flanks of nude mice showed complete cures of all animals in the TOCX group following GCV treatment, whereas untreated animals uniformly formed fatal tumors. TOCX injection into U-87 MG intradermal and intracranial tumors resulted in prolonged survival of the host animals in a GCV-dependent manner. Together, these results suggest that the combination of TK and Cx may be beneficial for the treatment of human glioblastoma.
Mol Ther 2000 Jan
PMID:Connexin 43-enhanced suicide gene therapy using herpesviral vectors. 1093 14

The effect of peptides with sequences derived from connexins, the constituent proteins of gap junctions, on mechanically stimulated intercellular Ca(2+) signaling in tracheal airway epithelial cells was studied. Three peptides with sequences corresponding to connexin extracellular loop regions reversibly restricted propagation of Ca(2+) waves to neighboring cells. Recovery of communication began within 10 min of removal of the peptides, with inhibition totally reversed by 20-40 min. The peptides were shown to be more effective in inhibiting Ca(2+) waves than glycyrrhetinic acid or oleamide. Inhibition of intercellular Ca(2+) waves by connexin mimetic peptides did not affect the Ca(2+) response to extracellular ATP. Although the intracellular Ca(2+) response of tracheal epithelial cells to ATP was greatly reduced by either pretreatment with high doses of ATP or application of apyrase, mechanically stimulated intercellular Ca(2+) signaling was not affected by these agents. We conclude that connexin mimetic peptides are effective and reversible inhibitors of gap junctional communication of physiologically significant molecules that underlie Ca(2+) wave propagation in tracheal epithelial cells and propose a potential mechanism for the mode of action of mimetic peptides.
Am J Physiol Lung Cell Mol Physiol 2000 Oct
PMID:Connexin mimetic peptides reversibly inhibit Ca(2+) signaling through gap junctions in airway cells. 1100 Jan 20

Intracellular Na(+)accumulation and K(+)loss play important roles in the pathogenesis of arrhythmias and injury in the ischemic heart. We investigated the role of metabolically sensitive connexin hemichannels as a potential route for Na(+)influx and K(+)efflux during ischemia, using dye uptake and electrophysiological measurements to assay hemichannel activity in isolated rabbit ventricular myocytes. Consistent with the known size selectivity of connexin hemichannels,;50% of myocytes exposed to either low extracellular Ca(2+)(an established method for opening connexin hemichannels) or to metabolic inhibitors (a recently described method for opening hemichannels) accumulated fluorescent dyes with <1000 MW (propidium iodide and calcein), but excluded a larger dye with 1500-3000 MW (dextran-rhodamine). Using the whole cell patch clamp technique, we found that metabolic inhibitors activated a non-selective current permeant to both small and large cations, and blocked by La(3+), similar to the properties of connexin 43 when overexpressed in human embryonic kidney (HEK) cells. These findings indicate that isolated cardiac myocytes endogenously express metabolically-sensitive connexin hemichannels. If activated during ischemia, these hemichannels could contribute significantly to altered ionic fluxes promoting arrhythmias and myocardial injury.
J Mol Cell Cardiol 2000 Oct
PMID:Metabolic inhibition activates a non-selective current through connexin hemichannels in isolated ventricular myocytes. 1101 30


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