Association of ARVCF with zonula occludens (ZO)-1 and ZO-2: binding to PDZ-domain proteins and cell-cell adhesion regulate plasma membrane and nuclear localization of ARVCF

ARVCF, an armadillo-repeat protein of the p120(ctn) family, associates with classical cadherins and is present in adherens junctions, but its function is poorly understood. Here, we show that ARVCF interacts via a C-terminal PDZ-binding motif with zonula occludens (ZO)-1 and ZO-2. ARVCF and ZO-1 partially colocalize in the vicinity of the apical adhesion complex in polarized epithelial Madin-Darby canine kidney cells. ARVCF, ZO-1, and E-cadherin form a complex and are recruited to sites of initial cell-cell contact in sparse cell cultures. E-cadherin binding and plasma membrane localization of ARVCF require the PDZ-binding motif. Disruption of cell-cell adhesion releases ARVCF from the plasma membrane and an increased fraction of the protein localizes to the nucleus. Nuclear localization of ARVCF also requires the PDZ-binding motif and can be mediated by the PDZ domains of ZO-2. Thus, the interaction of ARVCF with distinct PDZ-domain proteins determines its subcellular localization. Interactions with ZO-1 and ZO-2, in particular, may mediate recruitment of ARVCF to the plasma membrane and the nucleus, respectively, possibly in response to cell-cell adhesion cues.     

Adiponectin Profile in Asian Patients Undergoing Coronary Revascularization and Its Association With Plaque Vulnerability: IDEAS‐ADIPO Study

Despite potent insulin‐sensitizing, anti‐inflammatory, and antiatherogenic effects in animal studies, the relationship between serum adiponectin level and coronary artery disease in patients remains unclear. We determined the adiponectin profile in a cohort of multiethnic Asian patients with coronary artery disease, and the association between serum adiponectin level and culprit lesion necrotic core (NC) content. Ninety‐four Asian patients (BMI, 25.3 ± 3.7 kg/m²) undergoing percutaneous coronary intervention were recruited. The serum adiponectin level was measured (n = 94), and the baseline virtual histology intravascular ultrasound examination was analyzed (n = 88). The median level of adiponectin was 3.7 µg/ml (interquartile range, 2.8–4.5 µg/ml). The serum adiponectin level was below 10 µg/ml in 90 patients (95.7%) and below 6 µg/ml in 80 patients (85.1%). There was a significant association between ethnicity and serum adiponectin level (P = 0.048). The median adiponectin level was highest among the Chinese, followed by the Malay and the Indians. Serum adiponectin levels were positively associated with culprit lesion NC content. A 1‐µg/ml increase in log adiponectin was associated with a 3.04% (95% confidence interval: 0.33–5.44) increase in culprit lesion NC content. This association remains significant after adjusting for age, sex, ethnicity, low‐density lipoprotein cholesterol, high‐density lipoprotein cholesterol, and procedural indication. We found a low serum level of adiponectin in Asian patients and a significant ethnic effect on serum adiponectin level. Increased serum adiponectin levels were independently associated with increased culprit lesion NC burden, suggesting a role for adiponectin in modulating coronary plaque vulnerability.     

An InCytes from MBC Selection: Vimentin Regulates Scribble Activity by Protecting It from Proteasomal Degradation

Scribble (Scrib), Discs large, and Lethal giant larvae form a protein complex that regulates different aspects of cell polarization, including apical–basal asymmetry in epithelial cells and anterior–posterior polarity in migrating cells. Here, we show that Scrib interacts with the intermediate filament cytoskeleton in epithelial Madin-Darby canine kidney (MDCK) cells and endothelial human umbilical vein endothelial cells. Scrib binds vimentin via its postsynaptic density 95/disc-large/zona occludens domains and in MDCK cells redistributes from filaments to the plasma membrane during the establishment of cell–cell contacts. RNA interference-mediated silencing of Scrib, vimentin, or both in MDCK cells results in defects in the polarization of the Golgi apparatus during cell migration. Concomitantly, wound healing is delayed due to the loss of directional movement. Furthermore, cell aggregation is dependent on both Scrib and vimentin. The similar phenotypes observed after silencing either Scrib or vimentin support a coordinated role for the two proteins in cell migration and aggregation. Interestingly, silencing of vimentin leads to an increased proteasomal degradation of Scrib. Thus, the upregulation of vimentin expression during epithelial to mesenchymal transitions may stabilize Scrib to promote directed cell migration.     

Active ammonia excretion in the giant mudskipper, Periophthalmodon schlosseri (Pallas), during emersion

The main objective of this study was to determine whether active NH(4) (+) excretion occurred in the giant mudskipper, Periophthalmodon schlosseri, during emersion. Our results demonstrated that continual ammonia excretion in P. schlosseri during 24 hr of emersion resulted in high concentrations ( approximately 30 mmol l(-1)) of ammonia in fluid collected from the branchial surface. For fish injected intraperitoneally with 8 mumol g(-1) ammonium acetate (CH3COONH4) followed by 24 hr of emersion, the cumulative ammonia excreted was significantly greater than that of the control injected with sodium acetate. More importantly, the ammonia excretion rate at hour 2 in fish injected with CH3COONH4 followed by emersion was greater than that in fish immersed in water as reported elsewhere, with the greatest change in the ammonia excretion rate occurring at hour 2. Assuming that the rate of endogenous ammonia production remained unchanged, 33% of the exogenous ammonia was excreted through the head region, presumably through the gills, during the first 6 hr of emersion. Indeed, at hour 6, the ammonia concentration in the branchial fluid increased to an extraordinarily high concentration of >90 mmol l(-1). Therefore, our results confirm for the first time that P. schlosseri can effectively excrete a high load of ammonia on land, and corroborate the proposition that active NH(4) (+) excretion through its gills contributes in part to its high tolerance of aerial exposure. Only 4.6% of the exogenous ammonia was detoxified to urea. The glutamate contents in the muscle and liver also increased significantly, but the glutamine contents remained unchanged.     

Effect of pulsatile growth hormone administration to the growth-restricted fetal sheep on somatotrophic axis gene expression in fetal and placental tissues

We have previously reported (Bauer MK, Breier BH, Bloomfield FH, Jensen EC, Gluckman PD, and Harding JE. J Endocrinol 177: 83-92, 2003) that a chronic pulsatile infusion of growth hormone (GH) to intrauterine growth-restricted (IUGR) ovine fetuses increased fetal circulating IGF-I levels without increasing fetal growth. We hypothesized a cortisol-induced upregulation of fetal hepatic GH receptor (GH-R) mRNA levels, secondary increases in IGF-I mRNA levels, and circulating IGF-I levels, but a downregulation of the type I IGF receptor (IGF-IR) as an explanation. We, therefore, measured mRNA levels of genes of the somatotrophic axis by real-time RT-PCR in fetal and placental tissues of fetuses with IUGR (induced by uteroplacental embolization from 110- to 116-days gestation) that received either a pulsatile infusion of GH (total dose 3.5 mg/day) or vehicle from 117-126 days and in control fetuses (n = 5 per group). Tissues were collected at 127 days (term, 145 days). Fetal cortisol concentrations were significantly increased in IUGR fetuses. However, in liver, GH-R, but not IGF-I or IGF-IR, mRNA levels were decreased in both IUGR groups. In contrast, in placenta, GH-R, IGF-I, and IGF-IR expression were increased in IUGR vehicle-infused fetuses. GH infusion further increased placental GH-R and IGF-IR, but abolished the increase in IGF-I mRNA levels. GH infusion reduced IGF-I expression in muscle and increased GH-R but decreased IGF-IR expression in kidney. IUGR increased hepatic IGF-binding protein (IGFBP)-1 and placental IGFBP-2 and -3 mRNA levels with no further effect of GH infusion. In conclusion, the modest increases in circulating cortisol concentrations in IUGR fetuses did not increase hepatic GH-R mRNA expression and, therefore, do not explain the increased circulating IGF-I levels that we found with GH infusion, which are likely due to reduced clearance rather than increased production. We demonstrate tissue-specific regulation of the somatotrophic axis in IUGR fetuses and a discontinuity between GH-R and IGF-I gene expression in GH-infused fetuses that is not explained by alterations in phosphorylated STAT5b.