TY  - JOUR
A1  - Pollitt, Alice Y.
A1  - Poulter, Natalie S.
A1  - Gitz, Eelo
A1  - Navarro-Nuñez, Leyre
A1  - Wang, Ying-Jie
A1  - Hughes, Craig E.
A1  - Thomas, Steven G.
A1  - Nieswandt, Bernhard
A1  - Douglas, Michael R.
A1  - Owen, Dylan M.
A1  - Jackson, David G.
A1  - Dustin, Michael L.
A1  - Watson, Steve P.
T1  - Syk and Src Family Kinases Regulate C-type Lectin Receptor 2 (CLEC-2)-mediated Clustering of Podoplanin and Platelet Adhesion to Lymphatic Endothelial Cells*
JF  - The Journal of Biological Chemistry
N2  - The interaction of CLEC-2 on platelets with Podoplanin on lymphatic endothelial cells initiates platelet signalling events that are necessary for prevention of blood-lymph mixing during development. In the present study, we show that CLEC-2 signalling via Src family and Syk tyrosine kinases promotes platelet adhesion to primary mouse lymphatic endothelial cells at low shear. Using supported lipid bilayers containing mobile Podoplanin, we further show that activation of Src and Syk in platelets promotes clustering of CLEC-2 and Podoplanin. Clusters of CLEC-2-bound Podoplanin migrate rapidly to the centre of the platelet to form a single structure. Fluorescence life-time imaging demonstrates that molecules within these clusters are within 10 nm of one another and that the clusters are disrupted by inhibition of Src and Syk family kinases. CLEC-2 clusters are also seen in platelets adhered to immobilised Podoplanin using direct stochastic optical reconstruction microscopy (dSTORM). These findings provide mechanistic insight by which CLEC-2 signalling promotes adhesion to Podoplanin and regulation of Podoplanin signalling thereby contributing to lymphatic vasculature development.
KW  - endothelial cell
KW  - lipid bilayer
KW  - platelet receptor
KW  - tyrosine-protein kinase
KW  - CLEC-2 ITAM
KW  - podoplanin
KW  - Src family
KW  - kinase Syk
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-120770
VL  - 289
IS  - 52
ER  - 
TY  - JOUR
A1  - Benz, Roland
A1  - Maier, Elke
A1  - Bauer, Susanne
A1  - Ludwig, Albrecht
T1  - The Deletion of Several Amino Acid Stretches of Escherichia coli Alpha-Hemolysin (HlyA) Suggests That the Channel-Forming Domain Contains Beta-Strands
JF  - PLOS ONE
N2  - Escherichia coli α-hemolysin (HlyA) is a pore-forming protein of 110 kDa belonging to the family of RTX toxins. A hydrophobic region between the amino acid residues 238 and 410 in the N-terminal half of HlyA has previously been suggested to form hydrophobic and/or amphipathic α-helices and has been shown to be important for hemolytic activity and pore formation in biological and artificial membranes. The structure of the HlyA transmembrane channel is, however, largely unknown. For further investigation of the channel structure, we deleted in HlyA different stretches of amino acids that could form amphipathic β-strands according to secondary structure predictions (residues 71–110, 158–167, 180–203, and 264–286). These deletions resulted in HlyA mutants with strongly reduced hemolytic activity. Lipid bilayer measurements demonstrated that HlyAΔ71–110 and HlyAΔ264–286 formed channels with much smaller single-channel conductance than wildtype HlyA, whereas their channel-forming activity was virtually as high as that of the wildtype toxin. HlyAΔ158–167 and HlyAΔ180–203 were unable to form defined channels in lipid bilayers. Calculations based on the single-channel data indicated that the channels generated by HlyAΔ71–110 and HlyAΔ264–286 had a smaller size (diameter about 1.4 to 1.8 nm) than wildtype HlyA channels (diameter about 2.0 to 2.6 nm), suggesting that in these mutants part of the channel-forming domain was removed. Osmotic protection experiments with erythrocytes confirmed that HlyA, HlyAΔ71–110, and HlyAΔ264–286 form defined transmembrane pores and suggested channel diameters that largely agreed with those estimated from the single-channel data. Taken together, these results suggest that the channel-forming domain of HlyA might contain β-strands, possibly in addition to α-helical structures.
KW  - membrane potential
KW  - molecular mass
KW  - cations
KW  - membrane structures
KW  - membrane proteins
KW  - lipid bilayer
KW  - red blood cells
KW  - toxins
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-118115
SN  - 1932-6203
VL  - 9
IS  - 12
ER  -