Editorial: Conflicts

The Editorial Board reflects on the theme of 'conflict', as observed in the work published in this issue, and in the wider world

Role of PSCs in Regeneration of Remnant Pancreas after PX

Background and objectives Mechanism of regeneration of remnant pancreas after partial pancreatectomy (PX) is still unknown. In this study, effect of siRNA against the collagen specific chaperone, HSP47, which inhibits collagen secretion from activated pancreas stellate cells (aPSCs), and induces their apoptosis, on regeneration of remnant pancreas was determined. Methods Pancreatectomy was performed according to established methods. Proliferation of cells was assessed by BrdU incorporation. Immunostaining of HSP47 was employed to identify PSCs. Progenitor cells were identified by SOX9 staining. Acinar cells were immunostained for amylase. Co-culture of acinar cells with aPSCs were carried out in a double chamber with a cell culture insert. siRNA HSP47 encapsulated in vitamin A-coupled liposome (VA-lip siRNA HSP47) was delivered to aPSCs by iv injection. Results In remnant pancreas of 90% PX rat, new areas of foci were located separately from duodenal areas with normal pancreatic features. After PX, BrdU uptake of acinar cells and islet cells significantly increased, but was suppressed by treatment with VA-lip siRNA HSP47. BrdU uptake by acinar cells was augmented by co-culturing with aPSCs and the augmentation was nullified by siRNA HSP47. BrdU uptake by progenitor cells in foci area was slightly enhanced by the same treatment. New area which exhibited intermediate features between those of duodenal and area of foci, emerged after the treatment. Conclusion aPSCs play a crucial role in regeneration of remnant pancreas, proliferation of acinar and islet cells after PX through the activity of secreted collagen. Characterization of new area emerged by siRNA HSP47 treatment as to its origin is a future task

Screening for FtsZ Dimerization Inhibitors Using Fluorescence Cross-Correlation Spectroscopy and Surface Resonance Plasmon Analysis

FtsZ is an attractive target for antibiotic research because it is an essential bacterial cell division protein that polymerizes in a GTP-dependent manner. To find the seed chemical structure, we established a high-throughput, quantitative screening method combining fluorescence cross-correlation spectroscopy (FCCS) and surface plasmon resonance (SPR). As a new concept for the application of FCCS to polymerization-prone protein, Staphylococcus aureus FtsZ was fragmented into the N-terminal and C-terminal, which were fused with GFP and mCherry (red fluorescent protein), respectively. By this fragmentation, the GTP-dependent head-to-tail dimerization of each fluorescent labeled fragment of FtsZ could be observed, and the inhibitory processes of chemicals could be monitored by FCCS. In the first round of screening by FCCS, 28 candidates were quantitatively and statistically selected from 495 chemicals determined by in silico screening. Subsequently, in the second round of screening by FCCS, 71 candidates were also chosen from 888 chemicals selected via an in silico structural similarity search of the chemicals screened in the first round of screening. Moreover, the dissociation constants between the highest inhibitory chemicals and Staphylococcus aureus FtsZ were determined by SPR. Finally, by measuring the minimum inhibitory concentration, it was confirmed that the screened chemical had antibacterial activity against Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus (MRSA)

Results of 2nd FCCS screening of 888 chemicals.

<p>A. Bar graph of averaged binding ratios of 3 independent screenings. Error bar indicates the standard deviation (n = 3). The red line indicates the average binding ratio obtained after addition of DMSO and GTP (= 0.411). The white arrow indicates the chemical that most effectively inhibited FtsZ dimerization. B. The Venn diagram shows a summary of the 2nd screening results.</p

The structure and fragmentation of FtsZ.

<p>A. The crystal structure of the <i>S</i>. <i>aureus</i> FtsZ monomer bound to GTP-γS (Protein Data Bank: 3WGN). B. FtsZ polymerizes into tubulin-like protofilaments by head-to-tail association with GTP. C. FtsZ is shown schematically. The black arrowhead indicates the α-helix in the middle of FtsZ as shown in Fig 1A. D. For FCCS, FtsZ protein was fragmented. The N- and C-terminal FtsZ were fused with EGFP and mCherry (red fluorescent protein), respectively. The mutation at K175D in the N-terminal fragment was inserted to prevent further bundling FtsZ. E. To avoid interaction independent of GTP addition, the α-helix was retained in both the N- and C-terminal fragments (black arrowheads in A and C) in the middle of FtsZ structure. F. By binding to GTP, FtsZ^K175D_N-terminal-EGFP and FtsZ_C-terminal-mCherry could be dimerized in a head-to-tail manner.</p

Relationship between inhibition % and dissociation constant (Kd).

<p>Relationship between inhibition % and dissociation constant (Kd).</p

Typical scatter plot of R_eq/theoretical R_max versus concentrations of chemicals and fitting.

<p>The filled squares represent the values of R_<b>eq</b>/theoretical R_<b>max</b> at corresponding concentrations of each chemical. The black lines represent fitting on the points. Fitting analysis was performed using Origin software.</p