Taxonomic group: bacteria, algae / Proteobacteria, Ochrophyta (Phylum: Proteobacteria, Ochrophyta)
Organ / tissue: cell wall
 
NCBI PubMed ID: 21878570
Publication DOI: 10.1128/mBio.00178-11
Journal NLM ID: 101519231
Publisher: Washington, DC: American Society for Microbiology
Correspondence: sarika.agarwalumassmed.edu
Institutions: Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA, Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA

Fungal cell walls are predominantly composed of glucans, mannans, and chitin. Recognition of these glycans by the innate immune system is a critical component of host defenses against the mycoses. Complement, an important arm of innate immunity, plays a significant role in fungal pathogenesis, especially the alternative pathway (AP). Here we determine that the glycan monosaccharide composition and glycosidic linkages affect AP activation and C3 deposition. Furthermore, properdin, a positive regulator of the AP, contributes to these functions. AP activation by glycan particles that varied in composition and linkage was measured by C3a generation in serum treated with 10 mM EGTA and 10 mM Mg(2+) (Mg-EGTA-treated serum) (AP specific; properdin functional) or Mg-EGTA-treated serum that lacked functional properdin. Particles that contained either β1→3 or β1→6 glucans or both generated large and similar amounts of C3a when the AP was intact. Blocking properdin function resulted in 5- to 10-fold-less C3a production by particulate β1→3 glucans. However, particulate β1→6 glucans generated C3a via the AP only in the presence of intact properdin. Interestingly, zymosan and glucan-mannan particles (GMP), which contain both β-glucans and mannans, also required properdin to generate C3a. The β1→4 glycans chitin and chitosan minimally activated C3 even when properdin was functional. Finally, properdin binding to glucan particles (GP) and zymosan in serum required active C3. Properdin colocalized with bound C3, suggesting that in the presence of serum, properdin bound indirectly to glycans through C3 convertases. These findings provide a better understanding of how properdin facilitates AP activation by fungi through interaction with the cell wall components.

properdin

Structure type: homopolymer
Location inside paper: Table 1, curdlan, laminarin
Trivial name: glucan, β-1,3-glucan, curdlan, curdlan-type polysaccharide 13140, paramylon, curdlan, laminarin, β-glucan, curdlan, β-(1,3)-glucan, β-(1,3)-glucan, curdlan, curdlan, β-1,3-glucan, paramylon, reserve polysaccharide, b-glucan, β-1,3-D-glucan, laminaran, botryosphaeran, laminaran type β-D-glucan, latiglucan I, pachymaran, Curdlan, zymosan A, β-glucan, curdlan, laminarin, zymosan, zymosan, glucan particles, zymosan, β-(1-3)-glucan, β-(1,3)-glucan, β-(1,3)glucan, pachymaran, D-glucan (DPn)540, pachyman, laminaran, curdlan, zymosan, zymosan, β-(1,3)-glucan, zymosan A, zymosan, β-1,3-glucan, curdlan, β-1,3-glucan, curdlan, β-1,3-glucan, curdlan, pachyman, β-(1,3)-glucan, curdlan, callose, a water-insoluble β-(1→3)-glucan, fermentum β-polysaccharide, water-insoluble glucan, alkali-soluble β-glucan (PeA3), alkali-soluble polysaccharide (PCAP), callose, laminarin
Compound class: EPS, O-polysaccharide, cell wall polysaccharide, lipophosphoglycan, glycoprotein, LPG, glucan, polysaccharide, glycoside, β-glucan, β3-glucan, cell wall glucan
Contained glycoepitopes: IEDB_1397514,IEDB_142488,IEDB_146664,IEDB_153543,IEDB_158555,IEDB_161166,IEDB_2278476,IEDB_2278477,IEDB_558869,IEDB_857743,IEDB_983931,SB_192
 
Methods: enzyme immunoassay, electrophoresis, extraction, confocal microscopy, flow cytometry
Biological activity: activates complement C3 from normal human serum in an antibody-independent manner through the alternative pathway in vitro
Comments, role: laminarin is soluble glucan; laminarin contains -6)bDGlcp(1- branches
 
Related record ID(s): 42294, 43303, 43304, 47304, 47707, 48305, 48371, 48410, 48411, 48472, 49256, 49257, 49258, 49266, 49290
NCBI Taxonomy refs (TaxIDs): 511, 80365
Reference(s) to other database(s): GTC:G51056AN, GlycomeDB:157, CCSD:50049, CBank-STR:4225, CA-RN: 51052-65-4, GenDB:FJ3380871.1
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