Internal initiation of translation of bovine viral diarrhea virus RNA.

Initiation of translation on the bovine viral diarrhea virus (BVDV) internal ribosomal entry site (IRES) was reconstituted in vitro from purified translation components to the stage of 48S ribosomal initiation complex formation. Ribosomal binding and positioning on this mRNA to form a 48S complex did not require the initiation factors eIF4A, eIF4B, or eIF4F, and translation of this mRNA was resistant to inhibition by a trans-dominant eIF4A mutant that inhibited cap-mediated initiation of translation. The BVDV IRES contains elements that are bound independently by ribosomal 40S subunits and by eukaryotic initiation factor (eIF) 3, as well as determinants that mediate direct attachment of 43S ribosomal complexes to the initiation codon.     

Modeling oculopharyngeal muscular dystrophy in myotube cultures reveals reduced accumulation of soluble mutant PABPN1 protein

Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant disease caused by an alanine tract expansion mutation in poly(A) binding protein nuclear 1 (expPABPN1). To model OPMD in a myogenic and physiological context, we generated mouse myoblast cell clones stably expressing either human wild type (WT) or expPABPN1 at low levels. Transgene expression is induced on myotube differentiation and results in formation of insoluble nuclear PABPN1 aggregates that are similar to those observed in patients with OPMD. Quantitative analysis of PABPN1 in myotube cultures revealed that expPABPN1 accumulation and aggregation is greater than that of the WT protein. We found that aggregation of expPABPN1 is more affected than WT PABPN1 by inhibition of proteasome activity. Consistent with this, in myotube cultures expressing expPABPN1, deregulation of the proteasome was identified as the most significantly perturbed pathway. Differences in the accumulation of soluble WT and expPABPN1 were consistent with differences in ubiquitination and rate of protein turnover. This study demonstrates, for the first time to our knowledge, that, in myotubes, the ratio of soluble/insoluble expPABPN1 is significantly lower compared with that of the WT protein. We suggest that this difference can contribute to muscle weakness in OPMD.     

Rubiscolin-6 activates opioid receptors to enhance glucose uptake in skeletal muscle

Rubiscolin-6 is an opioid peptide derived from plant ribulose bisphosphate carboxylase/oxygenase (Rubisco). It has been demonstrated that opioid receptors could control glucose homeostasis in skeletal muscle independent of insulin action. Therefore, Rubiscolin-6 may be involved in the control of glucose metabolism. In the present study, we investigated the effect of rubiscolin-6 on glucose uptake in skeletal muscle. Rubiscolin-6-induced glucose uptake was measured using the fluorescent indicator 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxyglucose (2-NBDG) in L6 and C2C12 cell lines. The protein expressions of glucose transporter 4 (GLUT4) and AMP-activated protein kinase (AMPK) in L6 cells were observed by Western blotting. The in vivo effects of rubiscolin-6 were characterized in streptozotocin (STZ)-induced diabetic rats. Rubiscolin-6 induced a concentration-dependent increase in glucose uptake levels. The increase of phospho-AMPK (pAMPK) and GLUT4 expressions were also observed in L6 and C2C12 cells. Effects of rubiscolin-6 were blocked by opioid receptor antagonists and/or associated signals inhibitors. Moreover, Rubiscolin-6 produced a dose-dependent reduction of blood glucose and increased GLUT4 expression in STZ-induced diabetic rats. In conclusion, rubiscolin-6 increases glucose uptake, potentially via an activation of AMPK to enhance GLUT4 translocation after binding to opioid receptors in skeletal muscle.     

Geographic access to care is not a determinant of child mortality in a rural Kenyan setting with high health facility density

Background  

Policy-makers evaluating country progress towards the Millennium Development Goals also examine trends in health inequities. Distance to health facilities is a known determinant of health care utilization and may drive inequalities in health outcomes; we aimed to investigate its effects on childhood mortality.