Am. J. Respir. Cell Mol. Biol., Vol 11, No. 3, Sep 1994, 262-269.
Isolation of Pneumocystis carinii gp120 by fibronectin affinity: evidence for manganese dependence
P Wisniowski, R Pasula and WJ Martin 2nd
Indiana University School of Medicine, Department of Internal Medicine, Indianapolis.
Pneumocystis carinii is a major opportunistic lung pathogen and a leading
cause of death among patients with the human immunodeficiency virus.
Adherence of P. carinii to type I alveolar epithelial cells is essential
for growth and replication and has been shown to be mediated in part by
fibronectin (Fn). To better understand the mechanisms underlying this
attachment, P. carinii-Fn interaction was characterized with respect to
divalent and monovalent ion concentration and pH using an 125I-Fn binding
assay to P. carinii. The results suggest that P. carinii has a receptor for
Fn that was partially dependent on Ca2+, enhanced by Mn2+, and diminished
somewhat by Mg2+. Additional data demonstrated that P. carinii-Fn
interaction was sensitive to ionic strength. The pH profile revealed that
P. carinii-Fn interaction increased with decreasing pH. The results from
the binding assay provided the rationale for a simple isolation of the Fn
receptor from P. carinii using a Fn-affinity column involving nondenaturing
conditions. The isolated receptor appeared highly purified by SDS-PAGE
analysis, with apparent molecular weights of 114 to 118 kD and 66 kD.
Western blot analysis indicated that this receptor was gp120, a major
surface glycoprotein of P. carinii. Furthermore, the isolated receptor
inhibited Fn binding to P. carinii. Finally, a monoclonal antibody raised
against the affinity-purified gp120 blocked Fn binding to P. carinii.
