Latest news and publications from inflammation and infections group.
The Complement group had eight visiting medical students from HUMANITAS University Milan, Italy from which two students, Luigia Ferrante & Marta Pagano, were working in our group. They stayed for four weeks in August - September 2021.
Syed et al. Streptococcus pneumoniae pneumolysin and neuraminidase A convert high density lipoproteins into pro-atherogenic particles.
Figure 6. Schematic presentation on the role of PLY and NanA in converting HDL from anti-inflammatory to pro-inflammatory and pro-atherogenic particles. Binding of PLY to HDL particles (green spheres) and desialylation of HDL by NanA modify the proteome and lipidome of HDL. In the arterial endothelium and intima the modified HDL particles (orange spheres) activate the complement system and macrophages and exhibit reduced ability to remove cholesterol (red arrow) from macrophages. HDL particles are further modified by oxidation. Macrophages are loaded with cholesterol from LDL particles (yellow spheres). The macrophages with large amounts of cholesterol become foam cells and undergo apoptosis, where after the cells will activate the complement system. Complement component C1q and C-reactive protein (CRP) have significant roles in complement-mediated clearance of apoptotic cells. In addition to HDL modification and cell lysis by PLY and NanA promote activation of platelets.
Hiking trip in the Nuuksio National Park 13th of October together with Seppo Meri's group
17th European Meeting on Complement in Human Disease (EMCHD 2019) participants (Spain,14-17 September, 2019): Larisa Viazmina, Karita Haapasalo and Shahan Syed
Syed, S et al. Role of Pneumococcal NanA Neuraminidase Activity in Peripheral Blood
Schematic illustration of the putative mechanism how NanA could reduce complement regulation by factor H on the cells and sensitize cells for attack by complement and thereby lead to cell damage. In addition, NanA increases the susceptibility of cells to attack by pneumolysin (PLY) or other virulence factors.
Haapasalo, K. et al. Staphylococcus aureus toxin LukSF dissociates from its membrane receptor target to enable renewed ligand sequestration. October 2018. The FASEB Journal
Model for LukSF-receptor binding and the mechanism of LukSF-induced inflammation. (A). LukS (PDB ID: 1T5R) binds on hC5aR (structure based on angiotensin receptor data PDB ID: 4YAY, cyan dashed box) as a soluble monomer on the cell membrane. Each LukS monomer binds one hC5aR molecule via the receptor interacting residues R73, Y184, Y250, T244 (marked with blue dots) within a cluster of approximately 4-5 hC5aR homo-oligomers. Upon binding to hC5aR LukS exposes residues for LukF (PDB ID: 1LKF) binding (interface indiacted by dashed ellipse). In these tight clusters each LukF can bind to two LukS monomers via two interfaces. (B) Binding of LukF on LukS and formation of the octameric pore (PDB ID: 3B07) causes dissociation of the receptors from the complex because of leakage of the cell membrane and possibly also since the receptor binding region (marked with a circle) is buried between the monomers in the complex. (C) The detached hC5aR molecule can be reused by its ligands LukS or C5a anaphylatoxin (PDB ID: 1KJS). (D) Zoom out of (A-C), illustrating the putative mechanism of LukSF induced inflammation.
Eija Nissilä, E et al. Complement factor H and apolipoprotein E participate in regulation of inflammation in THP-1 macrophages, Front. Immunol. 2018. doi: 10.3389/fimmu.2018.02701
Schematic illustrating the putative mechanism of the effect of factor H-apoE interaction in reducing inflammation in atherosclerotic lesions. Binding of factor H on apoE containing HDL particles reduces plasma complement activation while elevated binding of apoE on monocytes/macrophages/foam cells via FH reduces local inflammation and cholesterol efflux.