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The present study investigates choline transport processes and regulation of choline transporter-like protein-1 (CTL1) in human THP-1 monocytic cells and phorbol myristate 13-acetate (PMA)-differentiated macrophages. Choline uptake is saturable and therefore protein-mediated in both cell types, but its transport characteristics change soon after treatments with PMA. The maximal rate of choline uptake intrinsic to monocytic cells is greatly diminished in differentiated macrophages as demonstrated by alterations in V(max) values from 1,973 +/- 118 to 380 +/- 18 nmol x mg(-1) x min(-1), when the binding affinity did not change significantly (K(m) values 56 +/- 8 and 53 +/- 6 microM, respectively). Treatments with hemicholinim-3 effectively inhibit most of the choline uptake, establishing that a choline-specific transport protein rather than a general transporter is responsible for the observed kinetic parameters. mRNA screening for the expression of various transporters reveals that CTL1 is the most plausible candidate that possesses the described kinetic and inhibitory properties. Fluorescence-activated cell sorting analyses at various times after PMA treatments further demonstrate that the disappearance of CTL1 protein from the cell surface follows the same trend as the reduction in choline uptake. Importantly, the loss of functional CTL1 from the cell surface occurs without significant changes in total CTL1 protein or its mRNA level indicating that an impaired CTL1 trafficking is the key contributing factor to the reduced choline uptake, subsequent to the PMA-induced THP-1 differentiation to macrophages.

Fluorescence correlation spectroscopy (FCS) was used to study the diffusion behavior of the glucocorticoid dexamethasone on the cell membrane of the mouse pituitary cell line AtT-20 to investigate the putative membrane glucocorticoid receptor (mGR). This putative membrane receptor is thought to mediate glucocorticoid effects independent from protein synthesis and the well-known intracellular glucocorticoid receptor (iGR), the so-called "nongenomic" effects. The high spatial resolution of the FCS technique allowed for focusing exclusively on the cell membrane; measurements were taken on living cells in solution after incubation with 60 nM fluoresceindexamethasone for 1 h without manipulation of the cells. FCS measurements were performed by moving the position of the laser focus in 1 µm steps through a single cell. In a scan through the cell a component typical for a receptor-bound ligand (diffusion constant 3 x 10 -10 cm 2 sec -1 ) becomes apparent in the autocorrelation function (ACF) at the position of the cell membrane whereas another component (diffusion constant 2 x 10 -8 cm 2 sec -1 ) typical for a ligand diffusing in the cytosol becomes predominant in the ACF curves inside the cell. After pre-incubation with unlabeled dexamethasone in 1000-fold excess the "receptor-typical" component on the cell membrane was absent. This result is the first direct evidence for the existence of a mGR on a living cell.

Legionella jamestowniensis can be found in the environment in various water samples, in wet soil, and in compost facilities, but evidence of its human pathogenicity has not yet been demonstrated. Here, we report the first draft genome sequence of an L. jamestowniensis isolate, derived from a patient suffering from a chronic respiratory disease.

Vancomycin-resistant enterococci have emerged as major nosocomial pathogens worldwide. While antimicrobial pressure promotes nosocomial colonization with these enterococci, prolonged exposure to vancomycin may foster the transition from vancomycin resistance to vancomycin dependence. Here, we report the draft genome sequence of a vancomycin-dependent Enterococcus faecium isolate showing partial teicoplanin dependence.