Mechanisms of gelsolin-dependent and -independent EGF-stimulated cell motility in a human lung epithelial cell line

Acquisition of motility is an important step in malignant progression of tumor cells and involves dynamic changes in actin filament architecture orchestrated by many actin binding proteins. A role for the actin-binding protein gelsolin has been demonstrated in fibroblast motility. In this report, we investigated the role of gelsolin in bronchial epithelial cell motility. The non-tumorigenic bronchial epithelial cell line, NL20 migrated towards EGF in a modified Boyden chamber cell motility assay. However, the tumorigenic NL20-TA cell line derived from the NL20 cells and lacking gelsolin, did not migrate towards EGF. Ectopic expression of gelsolin in NL20-TA cells restored the EGF response, while motility of NL20-TA derived cells towards serum, PDGF, and fibronectin was independent of gelsolin expression. PI3-kinase inhibition failed to block EGF-stimulated motility in gelsolin transfected NL20-TA cells. Furthermore, EGF stimulated a motility response in cells lacking gelsolin in the presence of fibronectin or fibrinogen that was blocked with PI3-kinase inhibition. Thus, EGF-stimulated motility in NL20 cells and its derivatives are gelsolin dependent and PI3-kinase independent, while fibronectin and fibrinogen enhances EGF-stimulated motility through a pathway independent of gelsolin and dependent upon PI3-kinase.     

cAMP-activated anion conductance is associated with expression of CFTR in neonatal mouse cardiac myocytes

In this study,patch-clamp techniques were applied to cultured neonatal mouse cardiacmyocytes (NMCM) to assess the contribution of cAMP stimulation to theanion permeability in this cell model. Addition of either isoproterenolor a cocktail to raise intracellular cAMP increased the whole cellcurrents of NMCM. The cAMP-dependent conductance was largely anionic,as determined under asymmetrical (low intracellular)Cl conditions and symmetrical Clin the presence of various counterions, including Na⁺,Mg²⁺, Cs⁺, andN-methyl-D-glucamine. Furthermore, thecAMP-stimulated conductance was also permeable to ATP. ThecAMP-activated currents were inhibited by diphenylamine-2-carboxylate,glibenclamide, and an anti-cystic fibrosis transmembrane conductanceregulator (CFTR) monoclonal antibody. The anti-CFTR monoclonal antibodyfailed, however, to inhibit an osmotically activated anion conductance,indicating that CFTR is not linked to osmotically stimulated currentsin this cell model. Immunodetection studies of both neonatal mouse heart tissue and cultured NMCM revealed that CFTR is expressed in thesepreparations. The implication of CFTR in the cAMP-stimulated Cl- and ATP-permeable conductance was furtherverified with NMCM of CFTR knockout mice[cftr(/)] in which cAMP stimulationwas without effect on the whole cell currents. In addition, stimulation with protein kinase A and ATP induced Cl-permeablesingle-channel activity in excised, inside-out patches from control,but not cftr(/) NMCM. The data in this report indicate that cAMP stimulation of NMCM activates an anion-permeable conductance with functional properties similar to those expected forCFTR, thus suggesting that CFTR may be responsible for the cAMP-activated conductance. CFTR may thus contribute to the permeation and/or regulation of Cl- and ATP-permeable pathwaysin the developing heart.

     

The role of upregulated miRNAs and the identification of novel mRNA targets in prostatospheres

TICs are characterized by their ability to self-renew, differentiate and initiate tumor formation. miRNAs are small noncoding RNAs that bind to mRNAs resulting in regulation of gene expression and biological functions. The role of miRNAs and TICs in cancer progression led us to hypothesize that miRNAs may regulate genes involved in TIC maintenance. Using whole genome miRNA and mRNA expression profiling of TICs from primary prostate cancer cells, we identified a set of up-regulated miRNAs and a set of genes down-regulated in PSs. Inhibition of these miRNAs results in a decrease of prostatosphere formation and an increase in target gene expression. This study uses genome-wide miRNA profiling to analyze expression in TICs. We connect aberrant miRNA expression and deregulated gene expression in TICs. These findings can contribute to a better understanding of the molecular mechanisms governing TIC development/maintenance and the role that miRNAs have in the fundamental biology of TICs.     

A nuclear magnetic resonance study of the helix–coil transition of poly(L-glutamic acid)

There have been many reports that the nuclear magnetic resonance (nmr) spectra of a large number of polypeptides exhibit peak doubling of the α-carbon and the α-carbon proton in the helix–coil transition region. One apparent exception to this generalization has been polypeptides with ionizable side chains, where the helix–coil transition is induced by changes in pH in aqueous solution. Because it is important to establish the proper theoretical reason for the peak doubling and its relation to the rate of conformational change of amino acid residues, we have reexamined the proton and carbon-13 nmr spectra, at high field, for two polydisperse samples of poly(L -glutamic acid). Doubling of the α-carbon proton resonance as well as those of the α- and β-carbon, and backbone carbonyl are observed for a low-molecular-weight sample (DP = 54), while a higher molecular weight sample (DP = 309), exhibits only single resonances. Thus, polydispersity by itself is not sufficient to observe peak doubling; low-molecular weight is also required.