The armadillo protein p0071 regulates Rho signalling during cytokinesis

Cytokinesis requires the spatio-temporal coordination of cell-cycle control and cytoskeletal reorganization. Members of the Rho-family of GTPases are crucial regulators of this process and assembly of the contractile ring depends on local activation of Rho signalling. Here, we show that the armadillo protein p0071, unlike its relative p120(ctn), is localized at the midbody during cytokinesis and is essential for cell division. Both knockdown and overexpression of p0071 interfered with normal cell growth and survival due to cytokinesis defects with formation of multinucleated cells and induction of apoptosis. This failure of cytokinesis seemingly correlated with the deregulation of Rho activity in response to altered p0071 expression. The function of p0071 in regulating Rho activity occurred through an association of p0071 with RhoA, as well as the physical and functional interaction of p0071 with Ect2, the one Rho guanine-nucleotide exchange factor (GEF) essential for cytokinesis. These findings support an essential role for p0071 in spatially regulating restricted Rho signalling during cytokinesis.     

The Armadillo family protein p0071 is a VE-cadherin- and desmoplakin-binding protein

p0071, a member of the armadillo protein family, localizes to both adherens junctions and desmosomes in epithelial cells and exhibits homology to the adherens junction protein p120 and the desmosomal protein plakophilin-1. p0071 is also present at dermal microvascular endothelial intercellular junctions and colocalizes with VE-cadherin, an endothelium-specific cadherin that associates with both actin and intermediate filament networks. To define the role of p0071 in junction assembly, p0071 was tested for interactions with other components of the endothelial junctional complex. In transient expression assays, p0071 colocalized with and formed complexes with both VE-cadherin and desmoplakin. Deletion analysis using the yeast two-hybrid system revealed that the armadillo repeat domain of p0071 bound directly to VE-cadherin. Site-directed mutagenesis experiments demonstrated that p0071 and p120 bound to the same region on the cytoplasmic tail of VE-cadherin and that overexpression of p0071 could displace p120 from intercellular junctions. In contrast to VE-cadherin, desmoplakin was found to associate with the non-armadillo head domain of p0071. Cotransfections and triple-label immunofluorescence analysis revealed that VE-cadherin colocalization with desmoplakin in transfected COS cells required p0071, suggesting that p0071 may couple VE-cadherin to desmoplakin. Based on previous findings that both VE-cadherin and desmoplakin play central roles in vasculogenesis, these new results suggest that p0071 may play an important role in endothelial junction assembly and in the morphogenic events associated with vascular remodeling.     

Substrate specificity of an esterase from the archaeon Sulfolobus tokodaii bearing a GGG(A)X motif

A GGG(A)X-type esterase (Est0071) from an archaeon catalyzes asymmetric hydrolysis of prochiral bulky malonic diesters in good enantioselectivity. The selectivity of Est0071 was for the opposite enantiomer to that previously shown for pig liver esterase, and the resulting enantiomeric excess of the products was higher. Est0071 could also catalyze the hydrolysis of various acetates of secondary alcohols, and showed moderate enantioselectivity in these reactions.     

PAPIN. A novel multiple PSD-95/Dlg-A/ZO-1 protein interacting with neural plakophilin-related armadillo repeat protein/delta-catenin and p0071

A neural plakophilin-related armadillo repeat protein (NPRAP)/delta-catenin interacts with one of Alzheimer disease-related gene products, presenilin 1. We have previously reported the interaction of NPRAP/delta-catenin with synaptic scaffolding molecule, which is involved in the assembly of synaptic components. NPRAP/delta-catenin also interacts with E-cadherin and beta-catenin and is implicated in the organization of cell-cell junctions. p0071, a ubiquitous isoform of NPRAP/delta-catenin, is localized at desmosomes in HeLa and A431 cells and at adherens junctions in Madin-Darby bovine kidney cells. We have identified here a novel protein interacting with NPRAP/delta-catenin and p0071 and named this protein plakophilin-related armadillo repeat protein-interacting PSD-95/Dlg-A/ZO-1 (PDZ) protein (PAPIN). PAPIN has six PDZ domains and binds to NPRAP/delta-catenin and p0071 via the second PDZ domain. PAPIN and p0071 are ubiquitously expressed in various tissues and are localized at cell-cell junctions in normal rat kidney cells and bronchial epithelial cells. PAPIN may be a scaffolding protein connecting components of epithelial junctions with p0071.     

A novel thermostable esterase from the thermoacidophilic archaeon Sulfolobus tokodaii strain 7

We have characterized an esterase expressed from the putative esterase gene (ST0071) selected from the total genome analysis from the thermoacidophilic archaeon Sulfolobus tokodaii strain 7. The ORF was cloned and expressed as a fusion protein in Escherichia coli. The protein was purified with heat treatment, affinity column chromatography, and size exclusion filtration. The optimum activity for ester cleavage against p-nitrophenyl esters was observed at around 70 degrees C and pH 7.5-8.0. The enzyme exhibited high thermostability and also showed activity in a mixture of a buffer and water-miscible organic solvents, such as acetonitrile and dimethyl sulfoxide. From the kinetic analysis, p-nitrophenyl butyrate was found to be a better substrate than caproate and caprylate.     

Protein p0071, a major plaque protein of non-desmosomal adhering junctions,is a selective cell-type marker

Protein p0071, which originally was introduced as a member of the p120-subfamily of armadillo proteins, common to desmosomes and adhaerens junctions (AJs) and to several other cell structures (centrosomes, midbodies), has been localized by using a series of novel mono- and polyclonal antibodies generated against various domains of the molecule. By protein analysis and immunolocalization techniques, protein p0071 has been localized as a plaque protein in AJs of diverse epithelia and certain vascular endothelia, in the composite junctions (areal compositae) of the intercalated disks of cardiomyocytes, and in the punctate or more extended AJs of the vast majority of cell culture types examined, including mitotic states. Using these antibodies, we have also shown that this AJ protein occurs only rarely or is even absent in tissues such as skeletal and smooth muscles, in a series of mesenchymal tissue cells, and in specific desmosome-rich cells such as those of the upper layers of the epidermis and certain other stratified epithelia and Hassall corpuscles of the thymus. We have also demonstrated that p0071 is absent from desmosomes. The occurrence of two major subtypes of lymphatic endothelial cells, one with AJs containing p0071 and one without detectable p0071, is emphasized. Possible structural and functional roles of p0071 are discussed in light of these new findings regarding its localization, and the addition of p0071 to the armamentarium of cytodiagnostic cell-type markers is recommended. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. This study was supported by project grants from the German Ministry for Education and Research (BMBF) in a cooperative research program entitled “Standardization of mesenchymal stem cells for regenerative medicine (START-MSC)” and from the Deutsche Krebshilfe (project 10–2049) to W.W. Franke.     

Interaction between Erbin and a Catenin-related protein in epithelial cells.

Integrity of epithelial tissues relies on the proper apical-basolateral polarity of epithelial cells. Members of the LAP (LRR and PDZ) protein family such as LET-413 and Scribble are involved in maintaining epithelial cell polarity in Caenorhabditis elegans and Drosophila melanogaster, respectively. We previously described Erbin as a mammalian LET-413 homologue interacting with ERBB2/HER2, an epidermal growth factor receptor family member. Erbin and ERBB2/HER2 are located in the basolateral membranes of epithelial cells. We show here that Erbin interacts with p0071 (also called plakophilin-4), an armadillo repeat protein linked to the cytoskeleton. Erbin binds to p0071 in vitro and in vivo in a PDZ domain-dependent manner, and both proteins colocalized in desmosomes of epithelial cells. Using a dominant negative approach, we found that integrity of epithelial cell monolayer is impaired when interaction between Erbin and p0071 is disrupted. We propose that Erbin is connected by p0071 to cytoskeletal networks in an interaction crucial for epithelial homeostasis.     

Protein p0071, an armadillo plaque protein of adherens junctions, is predominantly expressed in distal renal tubules

Protein p0071 is a member of the p120-subfamily of armadillo proteins and is well known as a junctional plaque component involved in cell–cell adhesion, especially in adherens junctions. By systematic immunohistochemical analysis of mouse and human kidney tissues, p0071 was prominently detected in distinct kidney tubules. Upon double-labeling immunolocalization experiments with segment-specific markers, p0071 was predominantly localized in distal straight and convoluted tubules and to a lesser extent in proximal tubules, in the ascending thin limb of loop of Henle and in the collecting ducts. In capillaries of the kidney, p0071 co-localized with VE-cadherin an endothelium-specific cadherin. Protein p0071 was also detected in both, renal cell carcinomas derived from distal tubules and in maturing nephrons of early mouse developmental stages. Immunoblotting of total extracts of cultured cells of renal origin showed that p0071 was detected in all human and murine cells analyzed. Upon immunolocalization, p0071 was observed in adherens junctions but also in distinct cytoplasmic structures at the cell periphery of cultured cells. Possible structural and functional roles of p0071 are suggested by its preferential occurrence in distinct tubule segments, and its potential use as a cytodiagnostic cell type marker in renal pathology is discussed.     

Folliculin,the Product of the Birt-Hogg-Dube Tumor Suppressor Gene,Interacts with the Adherens Junction Protein p0071 to Regulate Cell-Cell Adhesion

Birt-Hogg-Dube (BHD) is a tumor suppressor gene syndrome associated with fibrofolliculomas, cystic lung disease, and chromophobe renal cell carcinoma. In seeking to elucidate the pathogenesis of BHD, we discovered a physical interaction between folliculin (FLCN), the protein product of the BHD gene, and p0071, an armadillo repeat containing protein that localizes to the cytoplasm and to adherens junctions. Adherens junctions are one of the three cell-cell junctions that are essential to the establishment and maintenance of the cellular architecture of all epithelial tissues. Surprisingly, we found that downregulation of FLCN leads to increased cell-cell adhesion in functional cell-based assays and disruption of cell polarity in a three-dimensional lumen-forming assay, both of which are phenocopied by downregulation of p0071. These data indicate that the FLCN-p0071 protein complex is a negative regulator of cell-cell adhesion. We also found that FLCN positively regulates RhoA activity and Rho-associated kinase activity, consistent with the only known function of p0071. Finally, to examine the role of Flcn loss on cell-cell adhesion in vivo, we utilized keratin-14 cre-recombinase (K14-cre) to inactivate Flcn in the mouse epidermis. The K14-Cre-Bhd^flox/flox mice have striking delays in eyelid opening, wavy fur, hair loss, and epidermal hyperplasia with increased levels of mammalian target of rapamycin complex 1 (mTORC1) activity. These data support a model in which dysregulation of the FLCN-p0071 interaction leads to alterations in cell adhesion, cell polarity, and RhoA signaling, with broad implications for the role of cell-cell adhesion molecules in the pathogenesis of human disease, including emphysema and renal cell carcinoma.     

Direct interaction of Alzheimer's disease-related presenilin 1 with armadillo protein p0071

Alzheimer's disease-related presenilins are thought to be involved in Notch signaling during embryonic development and/or cellular differentiation. Proteins mediating the cellular functions of the presenilins are still unknown. We utilized the yeast two-hybrid system to identify an interacting armadillo protein, termed p0071, that binds specifically to the hydrophilic loop of presenilin 1. In vivo, the presenilins constitutively undergo proteolytic processing, forming two stable fragments. Here, we show that the C-terminal fragment of presenilin 1 directly binds to p0071. Nine out of 10 armadillo repeats in p0071 are essential for mediating this interaction. Since armadillo proteins, like beta-catenin and APC, are known to participate in cellular signaling, p0071 may function as a mediator of presenilin 1 in signaling events.     

<Emphasis Type="Italic">Singulispaera mucilagenosa</Emphasis> sp. nov., a novel acid-tolerant representative of the order <Emphasis Type="Italic">Planctomycetales</Emphasis>

Two novel strains of budding bacteria, Z-0071^T and Z-0072, were isolated from dystrophic humified waters formed by xylotrophic fungi in the course of spruce wood degradation. The cells of both strains are coccoid (0.95–1.80 μm), nonmotile, single or arranged in pairs. The cells have a complex system of intracellular membranes and are covered with fimbriae and surrounded by a mucous capsule up to 0.3 μm thick. Both strains are aerobic organoheterotrophic, mesophilic, and acid-tolerant microorganisms that are able to grow under microaerobic conditions. They utilize N-acetyl-glucosamine, carbohydrates, and lactate as growth substrates. The strains grow in a pH range of 4.0–7.5 with an optimum at 6.0–6.5. The temperature range for growth is 4–30°C, with an optimum at 25–28°C. Strains Z-0071^T and Z-0072, inhabitants of dystrophic low-mineral waters, are NaCl-sensitive: the NaCl content in the media above 0.5 g/l inhibited growth. The main fatty acids of strains Z-0071^T and Z-0072 are C_16:0, C_18:1ω9c, and C_{18:2ω9c, 12c}. The DNA G + C base content is 51.2–51.7 mol %. The sequences of the 16S rRNA gene fragments (1310 bp) of strains Z-0071^T and Z-0072 were found to be identical. The obtained sequences showed a 94.3% similarity with the sequences of the type strain of the most closely related species Singulisphaera acidiphila MOB10≅T. The phenotypic and phylogenetic properties of strains Z-0071^T and Z-0072 support classification of these strains within the genus Singulisphaera as a new species Singulisphaera mucilagenosa sp. nov., with the type strain Z-0071^T (VKM B-2626).     

S100 proteins interact with the N-terminal domain of MDM2

S100 proteins interact with the transactivation domain and the C-terminus of p53. Further, S100B has been shown to interact with MDM2, a central negative regulator of p53. Here, we show that S100B bound directly to the folded N-terminal domain of MDM2 (residues 2-125) by size exclusion chromatography and surface plasmon resonance experiments. This interaction with MDM2 (2-125) is a general feature of S100 proteins; S100A1, S100A2, S100A4 and S100A6 also interact with MDM2 (2-125). These interactions with S100 proteins do not result in a ternary complex with MDM2 (2-125) and p53. Instead, we observe the ability of a subset of S100 proteins to disrupt the extent of MDM2-mediated p53 ubiquitylation in vitro.

Structured summary

MINT-7905256: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100A6 (uniprotkb:P06703) by surface plasmon resonance (MI:0107)MINT-7905063: MDM2 (uniprotkb:Q00987) and s100A1 (uniprotkb:P23297) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905376: s100A4 (uniprotkb:P26447) and MDM2 (uniprotkb:Q00987) physically interact (MI:0915) by competition binding (MI:0405)MINT-7905130: s100A6 (uniprotkb:P06703) and MDM2 (uniprotkb:Q00987) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905207: s100A6 (uniprotkb:P06703) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905043: s100B (uniprotkb:P04271) and MDM2 (uniprotkb:Q00987) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905196: p53 (uniprotkb:P04637) and s100A4 (uniprotkb:P26447) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905358: p53 (uniprotkb:P04637) and s100A4 (uniprotkb:P26447) physically interact (MI:0915) by fluorescence polarization spectroscopy (MI:0053)MINT-7905220: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100B (uniprotkb:P04271) by surface plasmon resonance (MI:0107)MINT-7905104: s100A4 (uniprotkb:P26447) and MDM2 (uniprotkb:Q00987) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905229: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100A1 (uniprotkb:P23297) by surface plasmon resonance (MI:0107)MINT-7905317, MINT-7905162: s100B (uniprotkb:P04271) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905238: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100A2 (uniprotkb:P29034) by surface plasmon resonance (MI:0107)MINT-7905174, MINT-7905308: s100A1 (uniprotkb:P23297) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905247: MDM2 (uniprotkb:Q00987) binds (MI:0407) to s100A4 (uniprotkb:P26447) by surface plasmon resonance (MI:0107)MINT-7905090: s100A2 (uniprotkb:P29034) and MDM2 (uniprotkb:Q00987) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905142, MINT-7905326: MDM2 (uniprotkb:Q00987) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)MINT-7905185, MINT-7905347: s100A2 (uniprotkb:P29034) and p53 (uniprotkb:P04637) bind (MI:0407) by molecular sieving (MI:0071)     

Genomic diversity among Beijing and non-Beijing Mycobacterium tuberculosis isolates from Myanmar

Background

The Beijing family of Mycobacterium tuberculosis is dominant in countries in East Asia. Genomic polymorphisms are a source of diversity within the M. tuberculosis genome and may account for the variation of virulence among M. tuberculosis isolates. Till date there are no studies that have examined the genomic composition of M. tuberculosis isolates from the high TB-burden country, Myanmar.

Methodology/Principle Findings

Twenty-two M. tuberculosis isolates from Myanmar were screened on whole-genome arrays containing genes from M. tuberculosis H37Rv, M. tuberculosis CDC1551 and M. bovis AF22197. Screening identified 198 deletions or extra regions in the clinical isolates compared to H37Rv. Twenty-two regions differentiated between Beijing and non-Beijing isolates and were verified by PCR on an additional 40 isolates. Six regions (Rv0071-0074 [RD105], Rv1572-1576c [RD149], Rv1585c-1587c [RD149], MT1798-Rv1755c [RD152], Rv1761c [RD152] and Rv0279c) were deleted in Beijing isolates, of which 4 (Rv1572-1576c, Rv1585c-1587c, MT1798-Rv1755c and Rv1761c) were variably deleted among ST42 isolates, indicating a closer relationship between the Beijing and ST42 lineages. The TbD1 region, Mb1582-Mb1583 was deleted in Beijing and ST42 isolates. One M. bovis gene of unknown function, Mb3184c was present in all isolates, except 11 of 13 ST42 isolates. The CDC1551 gene, MT1360 coding for a putative adenylate cyclase, was present in all Beijing and ST42 isolates (except 1). The pks15/1 gene, coding for a putative virulence factor, was intact in all Beijing and non-Beijing isolates, except in ST42 and ST53 isolates.

Conclusion

This study describes previously unreported deletions/extra regions in Beijing and non-Beijing M. tuberculosis isolates. The modern and highly frequent ST42 lineage showed a closer relationship to the hypervirulent Beijing lineage than to the ancient non-Beijing lineages. The pks15/1 gene was disrupted only in modern non-Beijing isolates. This is the first report of an in-depth analysis on the genomic diversity of M. tuberculosis isolates from Myanmar.     

The p120 family of cell adhesion molecules

p120 is the prototypic member of the p120 subfamily of armadillo-related proteins that includes p0071, delta-catenin/NPRAP, ARVCF and the more distantly related plakophilins 1-3. Like armadillo, beta-catenin and plakoglobin these proteins are involved in mediating cell-cell adhesion. Besides their junctional localization they also reveal a cytoplasmic and nuclear localization. Non-cadherin-associated, cytoplasmic p120 functions in Rho signaling and regulation of cytoskeletal organization and actin dynamics. The nuclear function remains largely unsolved. Some characteristics seem to be shared by the various members of the family but it seems unlikely that p120-related proteins have solely redundant functions and compete for interactions with identical binding partners. Stabilization of cadherins at the membrane seems a common function of p120, p0071, delta-catenin and ARVCF but it is not yet known if and how these proteins confer distinct properties to cellular junctions. Moreover, p0071, NPRAP and ARVCF have a C-terminal PDZ-binding motif that is lacking in p120 pointing to distinct roles of these proteins. PDZ domains are found in a series of proteins involved in establishing cell polarity in epithelial cells. Thus, p120 proteins may not only be master regulators of cadherin abundance and activity but play additional roles in regulating cell polarity. This review focuses on the putative roles of p120 proteins in cell polarity.     

Comparisons between QST and FST—how wrong have we been?

The comparison between quantitative genetic divergence (Q(ST) ) and neutral genetic divergence (F(ST) ) among populations has become the standard test for historical signatures of selection on quantitative traits. However, when the mutation rate of neutral markers is relatively high in comparison with gene flow, estimates of F(ST) will decrease, resulting in upwardly biased comparisons of Q(ST) vs. F(ST) . Reviewing empirical studies, the difference between Q(ST) and F(ST) is positively related to marker heterozygosity. After refuting alternative explanations for this pattern, we conclude that marker mutation rate indeed has had a biasing effect on published Q(ST) -F(ST) comparisons. Hence, it is no longer clear that populations have commonly diverged in response to divergent selection. We present and discuss potential solutions to this bias. Comparing Q(ST) with recent indices of neutral divergence that statistically correct for marker heterozygosity (Hedrick's G'st and Jost's D) is not advised, because these indices are not theoretically equivalent to Q(ST) . One valid solution is to estimate F(ST) from neutral markers with mutation rates comparable to those of the loci underlying quantitative traits (e.g. SNPs). Q(ST) can also be compared to Φ(ST) (Phi(ST) ) of amova, as long as the genetic distance among allelic variants used to estimate Φ(ST) reflects evolutionary history: in that case, neutral divergence is independent of mutation rate. In contrast to their common usage in comparisons of Q(ST) and F(ST) , microsatellites typically have high mutation rates and do not evolve according to a simple evolutionary model, so are best avoided in Q(ST) -F(ST) comparisons.     

Evolutionary inference from QST

Q(ST) is a commonly used metric of the degree of genetic differentiation among populations displayed by quantitative traits. Typically, Q(ST) is compared to F(ST) measured on putatively neutral loci; if Q(ST)=F(ST), this is taken as evidence of spatially heterogeneous and diversifying selection. This paper reviews the uses, assumptions and statistics of Q(ST) and F(ST) comparisons. Unfortunately, Q(ST)/F(ST) comparisons are statistically challenging. For a single trait, Q(ST) must be compared not to the mean F(ST) but to the distribution of F(ST) values. The sources of biases and sampling error for Q(ST) are reviewed, and a new method for comparing Q(ST) and F(ST) is suggested. Simulation results suggest that the distribution of neutral F(ST) and Q(ST) values are little affected by various deviations from the island model. Consequently, the distributions of Q(ST) and F(ST) are well approximated by the Lewontin-Krakauer prediction, even with realistic deviations from the island-model assumptions.     

The effects of dominance, regular inbreeding and sampling design on Q(ST), an estimator of population differentiation for quantitative traits

To test whether quantitative traits are under directional or homogenizing selection, it is common practice to compare population differentiation estimates at molecular markers (F(ST)) and quantitative traits (Q(ST)). If the trait is neutral and its determinism is additive, then theory predicts that Q(ST) = F(ST), while Q(ST) > F(ST) is predicted under directional selection for different local optima, and Q(ST) < F(ST) is predicted under homogenizing selection. However, nonadditive effects can alter these predictions. Here, we investigate the influence of dominance on the relation between Q(ST) and F(ST) for neutral traits. Using analytical results and computer simulations, we show that dominance generally deflates Q(ST) relative to F(ST). Under inbreeding, the effect of dominance vanishes, and we show that for selfing species, a better estimate of Q(ST) is obtained from selfed families than from half-sib families. We also compare several sampling designs and find that it is always best to sample many populations (>20) with few families (five) rather than few populations with many families. Provided that estimates of Q(ST) are derived from individuals originating from many populations, we conclude that the pattern Q(ST) > F(ST), and hence the inference of directional selection for different local optima, is robust to the effect of nonadditive gene actions.