CaGpm1p is a surface protein as demonstrated by immunostaining and flow cytometry. A C. albicans gpm1؊/؊ mutant strain was generated that did not grow on glucose-supplemented but on ethanol-and glycerol-supplemented medium. Reduced binding of Factor H and plasminogen to the null mutant strain is in agreement with the presence of additional binding proteins. Attached to CaGpm1p, each of the three host plasma proteins is functionally active. Factor H and FHL-1 show cofactor activity for cleavage of C3b, and bound plasminogen is converted by urokinase-type plasminogen activator to proteolytically active plasmin. Thus, the surface-expressed CaGpm1p is a virulence factor that utilizes the host Factor H, FHL-1, and plasminogen for immune evasion and degradation of extracellular matrices.

BackgroundAge-related macular degeneration (AMD) is the leading cause of blindness in developed countries. The polymorphism rs10490924 in the ARMS2 gene is highly associated with AMD and linked to an indel mutation (del443ins54), the latter inducing mRNA instability. At present, the function of the ARMS2 protein, the exact cellular sources in the retina and the biological consequences of the rs10490924 polymorphism are unclear.MethodsRecombinant ARMS2 was expressed in Pichia pastoris, and protein functions were studied regarding cell surface binding and complement activation in human serum using fluoresence-activated cell sorting (FACS) as well as laser scanning microscopy (LSM). Biolayer interferometry defined protein interactions. Furthermore, endogenous ARMS2 gene expression was studied in human blood derived monocytes and in human induced pluripotent stem cell-derived microglia (iPSdM) by PCR and LSM. The ARMS2 protein was localized in human genotyped retinal sections and in purified monocytes derived from AMD patients without the ARMS2 risk variant by LSM. ARMS2 expression in monocytes under oxidative stress was determined by Western blot analysis.ResultsHere, we demonstrate for the first time that ARMS2 functions as surface complement regulator. Recombinant ARMS2 binds to human apoptotic and necrotic cells and initiates complement activation by recruiting the complement activator properdin. ARMS2-properdin complexes augment C3b surface opsonization for phagocytosis. We also demonstrate for the first time expression of ARMS2 in human monocytes especially under oxidative stress and in microglia cells of the human retina. The ARMS2 protein is absent in monocytes and also in microglia cells, derived from patients homozygous for the ARMS2 AMD risk variant (rs10490924).ConclusionsARMS2 is likely involved in complement-mediated clearance of cellular debris. As AMD patients present with accumulated proteins and lipids on Bruch’s membrane, ARMS2 protein deficiency due to the genetic risk variant might be involved in drusen formation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0776-3) contains supplementary material, which is available to authorized users.

Atherosclerotic cardiovascular disease (ACVD) is a lipid-driven inflammatory disease and one of the leading causes of death worldwide. Lipid deposits in the arterial wall lead to the formation of plaques that involve lipid oxidation, cellular necrosis, and complement activation, resulting in inflammation and thrombosis. The present study found that homozygous deletion of the CFHR1 gene, which encodes the plasma complement protein factor H-related protein 1 (FHR-1), was protective in two cohorts of patients with ACVD, suggesting that FHR-1 accelerates inflammation and exacerbates the disease. To test this hypothesis, FHR-1 was isolated from human plasma and was found to circulate on extracellular vesicles and to be deposited in atherosclerotic plaques. Surface-bound FHR-1 induced the expression of pro-inflammatory cytokines and tissue factor in both monocytes and neutrophils. Notably, plasma concentrations of FHR-1, but not of factor H, were significantly (p < 0.001) elevated in patients with ACVD, and correlated with the expression of the inflammation markers C-reactive protein, apolipoprotein serum amyloid protein A, and neopterin. FHR-1 expression also significantly correlated with plasma concentrations of low-density lipoprotein (LDL) (p < 0.0001) but not high-density lipoprotein (HDL). Taken together, these findings suggest that FHR-1 is associated with ACVD.

The phosphatidylinositol (PtdIns) 3-kinase Vps34p of the human pathogenic yeast Candida albicans participates in virulence and in protein transport. In order to dissect these two functions, a search for proteins interacting with C. albicans Vps34p was performed using a yeast two-hybrid system. This study demonstrates the physical interaction between Vps34p and Ade5,7p, which is the bifunctional enzyme of the de novo purine nucleotide biosynthetic pathway. The interaction initially observed in a yeast two-hybrid system was confirmed in vitro with recombinant proteins. Given the complex formation between Ade5,7p and the virulence-regulating Vps34p, it was of interest to characterize the function of Ade5,7p in C. albicans. To this end, ade5,7 null mutants were generated. The resulting mutants were adenine deficient, and sensitive to the presence of metal ions. In addition, the ade5,7 null mutants were avirulent in a mouse model of systemic candidiasis, and showed reduced hyphal growth in an agar matrix under embedded conditions. In summary, Ade5,7p interacts with the multifunctional virulence regulator PtdIns 3-kinase Vps34p, and ade5,7 and vps34 null mutant strains show similar phenotypes regarding sensitivity to metal ions, hyphal growth and virulence.