Scribble-mediated membrane targeting of PHLPP1 is required for its negative regulation of Akt

PHLPP1 (PH domain leucine-rich-repeats protein phosphatase) is a Ser/Thr protein phosphatase that acts as a tumour suppressor by negatively regulating Akt. Here, we show that PHLPP1 is recruited to the cell membrane by binding to a scaffolding protein: Scribble. Knockdown of Scribble (Scrib) results in redistribution of PHLPP1 from the membrane to the cytoplasm and an increase in Akt phosphorylation, whereas overexpression of Scrib has the opposite effect. Furthermore, PHLPP1-dependent inhibition of cell proliferation is facilitated by the formation of a Scrib, PHLPP1 and Akt trimeric complex. Thus, our findings identify a functional interaction between PHLPP1 and Scrib in negatively regulating Akt signalling.     

Loss of Anti-Bax Function in Gerstmann-Str?ussler-Scheinker Syndrome-Associated Prion Protein Mutants

Previously, we have shown the loss of anti-Bax function in Creutzfeldt Jakob disease (CJD)-associated prion protein (PrP) mutants that are unable to generate cytosolic PrP (CyPrP). To determine if the anti-Bax function of PrP modulates the manifestation of prion diseases, we further investigated the anti-Bax function of eight familial Gerstmann-Sträussler-Scheinker Syndrome (GSS)-associated PrP mutants. These PrP mutants contained their respective methionine (^M) or valine (^V) at codon 129. All of the mutants lost their ability to prevent Bax-mediated chromatin condensation or DNA fragmentation in primary human neurons. In the breast carcinoma MCF-7 cells, the F198S^V, D202N^V, P102L^V and Q217R^V retained, whereas the P102L^M, P105L^V, Y145stop^M and Q212P^M PrP mutants lost their ability to inhibit Bax-mediated condensed chromatin. The inhibition of Bax-mediated condensed chromatin depended on the ability of the mutants to generate cytosolic PrP. However, except for the P102L^V, none of the mutants significantly inhibited Bax-mediated caspase activation. These results show that the cytosolic PrP generated from the GSS mutants is not as efficient as wild type PrP in inhibiting Bax-mediated cell death. Furthermore, these results indicate that the anti-Bax function is also disrupted in GSS-associated PrP mutants and is not associated with the difference between CJD and GSS.     

Relations between hydrological variables and year-class strength of sportfish in eight Florida waterbodies

Hydrological variables have influenced fish recruitment in lakes, reservoirs and rivers. We evaluated how annual and seasonal hydrological variables were related to year-class strength (i.e., residuals from catch curves) of sportfish across eight Florida waterbodies (four rivers and four lakes). Multiple regression equations computed for black bass Micropterus spp. were combined across rivers and year-class strength was negatively related to spring median flow rates and in some cases positively related to winter median flow rates (all p0.10). Conversely, Lepomis spp. residuals combined from the rivers indicated that year-class strength was positively related to median flow rates in the fall prior to spawning and negatively related to post-spawn fall median flow rates (all p0.10). Fish recruitment combined across lakes were not related to water levels in this study, although within lake relationships did occur in some instances. Ecological implications of this work include regulations such as minimum flows and levels (MFLs) regarding sportfish species. Impacts of hydrology on year-class strength of sportfish were stronger in rivers than in lakes for these Florida systems. High flows at least once every 3years in the fall may allow inundation of floodplain habitat, providing favorable environmental conditions for Lepomis spp. reproduction. Setting MFLs during periods of drought (i.e., 3years or more) should consider impacts to short-lived species such as Lepomis spp.     

Nucleotide-induced switch in oligomerization of the AAA+ ATPase ClpB

ClpB is a member of the bacterial protein-disaggregating chaperone machinery and belongs to the AAA(+) superfamily of ATPases associated with various cellular activities. The mechanism of ClpB-assisted reactivation of strongly aggregated proteins is unknown and the oligomeric state of ClpB has been under discussion. Sedimentation equilibrium and sedimentation velocity show that, under physiological ionic strength in the absence of nucleotides, ClpB from Escherichia coli undergoes reversible self-association that involves protein concentration-dependent populations of monomers, heptamers, and intermediate-size oligomers. Under low ionic strength conditions, a heptamer becomes the predominant form of ClpB. In contrast, ATP gamma S, a nonhydrolyzable ATP analog, as well as ADP stabilize hexameric ClpB. Consistently, electron microscopy reveals that ring-type oligomers of ClpB in the absence of nucleotides are larger than those in the presence of ATP gamma S. Thus, the binding of nucleotides without hydrolysis of ATP produces a significant change in the self-association equilibria of ClpB: from reactions supporting formation of a heptamer to those supporting a hexamer. Our results show how ClpB and possibly other related AAA(+) proteins can translate nucleotide binding into a major structural transformation and help explain why previously published electron micrographs of some AAA(+) ATPases detected both six- and sevenfold particle symmetry.     

Detailed account of confounding factors in interpretation of FTIR spectra of exfoliated cervical cells

The confounding variables that can potentially lead to a misinterpretation of FTIR spectroscopy of exfoliated cervical cells is described. A detailed account of the spectral effects of the following variables in FTIR spectroscopic screening of exfoliated cervical cells is presented: polymorphs; Cell degradation; and impurities such as endocervical columnar cells, metaplastic cells, cervical mucus, red cells, and debris. The interpretation of the spectra of exfoliated cervical cells must be done with subtraction analysis, which includes these factors. This is essential to prevent unacceptable false-positive rates. The above techniques are subsequently applied to two clinic populations: a dysplasia clinic in follow-up patients with negative cytology and two general gynecology clinics with patients with negative cytology. In the dysplasia clinic group 250 sequential patients with negative smears were tested. Thirty had false-positive smears as defined by the IR spectroscopy using the above methodology. Twenty of those patients subsequently had one follow-up and six had a positive abnormal smear. In the community clinic group 656 sequential patients were examined who had negative smears, of which 27 had false-positive FTIR spectra.     

Single-Cell Transcriptional Profiling Reveals Cellular Diversity and Intercommunication in the Mouse Heart

1. Download high-res image (243KB)
2. Download full-size image

     

Drinking water quality and risk implications for community health: A case study of shallow water wells and boreholes in three major communities in Northern Cross-River,Southern Nigeria

The quality of water sources and its potential health implications to adults and children populations of respective major communities in Northern Cross-River was assessed. Water samples (n = 10/water source/site) were collected from three (Okpoma, Okuku and Ugaga) communities and heavy metal concentrations (Lead (Pb), Cadmium (Cd), Chromium (Cr), Manganese (Mn), Nickel (Ni), Copper (Cu), Cobalt (Co), and Zinc (Zn)) were evaluated using Atomic Absorption Spectrometer (AAS). Overall, Pb, Cd, Ni, and Co were higher than drinking water guidelines, while only Cr, Mn, Cu, and Zn were within the permissible limits. The estimated average daily intake (EADI) and target hazard quotient (THQ) were used to determine risk implications for adult and children consumer populations. The EADI for Pb in adults for borehole water, Pb and Cr by child consumer population for borehole and shallow well water exceeded the reference dose (RfD) by USEPA. The THQ for adult population were >1 for Pb in borehole water and >1 for Pb and Cr across all sites for the child consumer population. Overall, our findings indicate toxicity and higher hazard risk for both adult (Pb) and children (Pb and Cr) populations that source drinking water from borehole and shallow well water in these communities.     

Some observations on a new type of point average molecular weight

A new type of (reduced) point average molecular weight A¹, is described. Several interesting properties are developed: (i) $\text{A}{}^1\text{=}\text{reduced}$ weight average molecular weight over the whole cell, $\text{A}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{o}}\text{A}{}^1\text{(}\text{meniscus}\text{) = A}{}_{\mathrm{<mtext>w</mtext>}}\text{(}\text{meniscus}\text{); (iii) A}{}^1\text{(}\text{zero concentration}\text{) =}\text{reduced}$ number average molecular weight, A_n (meniscus). In addition, its usefulness in extracting the meniscus concentration, J(a), and in examining heterogeneous systems such as mucus glycoproteins, are discussed. The evaluation and application of $\text{A}{}^1$ requires only simple computational facilities, without the use for large-scale multiple data acquisition and recycling techniques.     

Effect of transdermally administered hyoscine methobromide on nocturnal acid secretion in patients with duodenal ulcer.

Use of anticholinergic drugs in treatment of duodenal ulcers is limited by the side effects of widespread parasympathetic blockade evoked by usual therapeutic doses. A study was conducted into the effectiveness of transdermal delivery of hyoscine methobromide using a new system which releases the drug into the circulation at a controlled rate. In six patients whose duodenal ulcer had healed secretion of acid was measured over two nights, the first on placebo and the second on hyoscine methobromide. All patients responded to the active drug and showed a significant inhibition of acid secretion. Four subjects complained of a dry mouth after overnight treatment with hyoscine methobromide; no other side effects were reported. Transdermal delivery of anticholinergic drugs may be useful in maintenance treatment of duodenal ulcers and further clinical tests are indicated.