PBP 10

Interaction of the gelsolin-derived antibacterial PBP 10 peptide with lipid bilayers and cell membranes.[Pubmed:16940084]

Antimicrob Agents Chemother. 2006 Sep;50(9):2932-40.

PBP 10, an antibacterial, cell membrane-permeant rhodamine B-conjugated peptide derived from the polyphosphoinositide binding site of gelsolin, interacts selectively with both lipopolysaccharides (LPS) and lipoteichoic acid (LTA), the distinct components of gram-negative and gram-positive bacteria, respectively. Isolated LPS and LTA decrease the antimicrobial activities of PBP 10, as well as other antimicrobial peptides, such as cathelicidin-LL37 (LL37) and mellitin. In an effort to elucidate the mechanism of bacterial killing by PBP 10, we compared its effects on artificial lipid bilayers and eukaryotic cell membranes with the actions of the mellitin, magainin II, and LL37 peptides. This study reveals that pore formation is unlikely to be involved in PBP 10-mediated membrane destabilization. We also investigated the effects of these peptides on platelets and red blood cells (RBCs). Comparison of these antimicrobial peptides shows that only mellitin has a toxic effect on platelets and RBCs in a concentration range concomitant with its bactericidal activity. The hemolytic activities of the PBP 10 and LL37 peptides significantly increase when RBCs are osmotically swollen in hypotonic solution, indicating that these antibacterial peptides may take advantage of the more extended form of bacterial membranes in exerting their killing activities. Additionally, we found that LL37 hemolytic activity was much higher when RBCs were induced to expose phosphatidylserine to the external leaflet of their plasma membranes. This finding suggests that asymmetrical distribution of phospholipids in the external membranes of eukaryotic cells may represent an important factor in determining the specificity of antibacterial peptides for targeting bacteria rather than eukaryotic cells.

Structural characterization and inhibitory profile of formyl peptide receptor 2 selective peptides descending from a PIP2-binding domain of gelsolin.[Pubmed:22706076]

J Immunol. 2012 Jul 15;189(2):629-37.

The neutrophil formyl peptide receptors, FPR1 and FPR2, play critical roles for inflammatory reactions, and receptor-specific antagonists/inhibitors can possibly be used to facilitate the resolution of pathological inflammatory reactions. A 10-aa-long rhodamine-linked and membrane-permeable peptide inhibitor (PBP10) has such a potential. This FPR2 selective inhibitor adopts a phosphatidylinositol 4,5-bisphosphate-binding sequence in the cytoskeletal protein gelsolin. A core peptide, RhB-QRLFQV, is identified that displays inhibitory effects as potent as the full-length molecule. The phosphatidylinositol 4,5-bisphosphate-binding capacity of PBP10 was not in its own sufficient for inhibition. A receptor in which the presumed cytoplasmic signaling C-terminal tail of FPR2 was replaced with that of FPR1 retained the PBP10 sensitivity, suggesting that the tail of FPR2 was not on its own critical for inhibition. This gains support from the fact that the effect of cell-penetrating lipopeptide (a pepducin), suggested to act primarily through the third intracellular loop of FPR2, was significantly inhibited by PBP10. The third intracellular loops of FPR1 and FPR2 differ in only two amino acids, but an FPR2 mutant in which these two amino acids were replaced by those present in FPR1 retained the PBP10 sensitivity. In summary, we conclude that the inhibitory activity on neutrophil function of PBP10 is preserved in the core sequence RhB-QRLFQV and that neither the third intracellular loop of FPR2 nor the cytoplasmic tail of the receptor alone is responsible for the specific inhibition.

Cell permeant polyphosphoinositide-binding peptides that block cell motility and actin assembly.[Pubmed:11533030]

J Biol Chem. 2001 Nov 16;276(46):43390-9.

Polyphosphoinositides (PPIs) affect the localization and activities of many cellular constituents, including actin-modulating proteins. Several classes of polypeptide sequences, including pleckstrin homology domains, FYVE domains, and short linear sequences containing predominantly hydrophobic and cationic residues account for phosphoinositide binding by most such proteins. We report that a ten-residue peptide derived from the phosphatidylinositol 4,5-bisphosphate (PIP(2)) binding region in segment 2 of gelsolin, when coupled to rhodamine B has potent PIP(2) binding activity in vitro; crosses the cell membrane of fibroblasts, platelets, melanoma cells, and neutrophils by a process not involving endocytosis; and blocks cell motility. This peptide derivative transiently disassembles actin filament structures in GFP-actin-expressing NIH3T3 fibroblasts and prevents thrombin- or chemotactic peptide-stimulated actin assembly in platelets and neutrophils, respectively, but does not block the initial [Ca(2+)] increase caused by these agonists. The blockage of actin assembly and motility is transient, and cells recover motility within an hour after their immobilization by 5-20 microm peptide. This class of reagents confirms the critical relation between inositol lipids and cytoskeletal structure and may be useful to probe the location and function of polyphosphoinositides in vivo.