Pneumocvstis carinii infection alters GTP-binding proteins in lungs

Pneumocvstis carinii is a common cause of life-threatening pneumonitis in the acquired immunodeficiency syndrome (AIDS),and other immuncompromised patients. The GTP-binding proteins were compared in parenchyma! lung membrane preparations from normal; immunosuppressed without P. carinii pneumonitis (PCP); and, immunosuppressed with PCP ferrets and rats. Pertussis toxin (PT) and cholera toxin (CT) ADP-ribosylated respectively a 41kDa, and two distinct 44/48KDa polypeptides in lung fractions. The 44/48KDa proteins were highly suppressed in PCP-infected compared to PCP-free membranes. Western blot analysis using specific antibodies to G-proteins, a, to detect CT, acomm ,.2 0 for PT substrates, Gq/a|, and subunit, exposed these proteins. PCP altered these proteins. Pan-ras antibody revealed a 21 KJDa peptide corresponding to small G-proteins in PCP-free, however PCP membranes expressed only 30% of this peptide. Comparison of studies performed with ferret and rat lung membranes revealed similar findings with only minor differences. These data are evidence for extensive changes induced by PCP in the GTP-binding proteins independent of the state of immunosuppression.