Evidence for Proinflammatory β-1,6 Glucans in the Pneumocystis carinii Cell Wall.
Inflammation is a major cause of respiratory impairment during Pneumocystis pneumonia. Studies support a significant role for cell wall β-glucans in stimulating inflammatory responses. Fungal β-glucans are comprised of d-glucose homopolymers containing β-1,3-linked glucose backbones with β-1,6-linked glucose side chains. Prior studies in Pneumocystis carinii have characterized β-1,3 glucan components of the organism. However, recent investigations in other organisms support important roles for β-1,6 glucans, predominantly in mediating host cellular activation. Accordingly, we sought to characterize β-1,6 glucans in the cell wall of Pneumocystis and to establish their activity in lung cell inflammation. Immune staining revealed specific β-1,6 localization in P. carinii cyst walls. Homology-based cloning facilitated characterization of a functional P. carinii kre6 (Pckre6) β-1,6 glucan synthase in Pneumocystis that, when expressed in kre6-deficient Saccharomyces cerevisiae, restored cell wall stability. Recently synthesized β-1,6 glucan synthase inhibitors decreased the ability of isolated P. carinii preparations to generate β-1,6 carbohydrate. In addition, isolated β-1,6 glucan fractions from Pneumocystis elicited vigorous tumor necrosis factor alpha (TNF-α) responses from macrophages. These inflammatory responses were significantly dampened by inhibition of host cell plasma membrane microdomain function. Together, these studies indicate that β-1,6 glucans are present in the P. carinii cell wall and contribute to lung cell inflammatory activation during infection.
Thoracic Diseases Research Unit, Departments of Medicine and Biochemistry, Mayo Clinic College of Medicine, Rochester, Minnesota, USA University of Iceland School of Health Sciences, Reykjavík, Iceland.
Theodore J
TJ
Kottom
Thoracic Diseases Research Unit, Departments of Medicine and Biochemistry, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
Deanne M
DM
Hebrink
Thoracic Diseases Research Unit, Departments of Medicine and Biochemistry, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
Paige E
PE
Jenson
University of Iceland School of Health Sciences, Reykjavík, Iceland.
Gunnar
G
Gudmundsson
Thoracic Diseases Research Unit, Departments of Medicine and Biochemistry, Mayo Clinic College of Medicine, Rochester, Minnesota, USA limper.andrew@mayo.edu.
Andrew H
AH
Limper
D000818:Animals; D002460:Cell Line; D002473:Cell Wall / Q000737:chemistry* / Q000276:immunology*; D003001:Cloning, Molecular; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000276:immunology* / Q000382:microbiology; D051379:Mice; D045363:Pneumocystis carinii / Q000737:chemistry* / Q000201:enzymology / Q000276:immunology*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D047071:beta-Glucans / Q000032:analysis / Q000276:immunology* / Q000633:toxicity*
D047071:beta-Glucans; D005964:Glucosyltransferases