GAP JUNCTION DISAPPEARANCE IN ASTROCYTES AND LEPTOMENINGEAL CELLS AS A CONSEQUENCE OF PROTOZOAN INFECTION

Trypanosoma cruzi and Toxoplasma gondii are protozoan parasites capabl e of causing infections of the nervous system. In order to determine e ffects of infection by these organisms on intercellular communication in the brain, dye coupling and connexin abundance and distribution wer e examined in leptomeningeal cells and astrocytes infected with T. cru zi or T. gondii. For both cell types infected with either type of prot ozoan parasite, intercellular diffusion of intracellularly injected Lu cifer Yellow was dramatically reduced. Immunocytochemistry with antibo dies specific for connexin43 (in astrocytes) or both connexin43 and co nnexin26 (for leptomeningeal cells) demonstrated that punctate gap jun ctional staining was much reduced in infected cells, although uninfect ed neighbors could display normal connexin abundance and distribution. Western blot analyses revealed that connexin43 abundance in both cell types infected with either parasite was similar to that in uninfected cells. Phosphorylation state of connexin43 (inferred from electrophor etic mobility of connexin43 isoforms) was not significantly affected b y the infection process. Immunocytochemistry of whole brains from anim als acutely infected with either parasite also showed a marked reducti on in connexin43 expression. We conclude that infection of both types of brain cells with either protozoan parasite results in a loss of int ercellular communication and organized gap junction plaques without af fecting expression levels or posttranslational processing of gap junct ion proteins. Presumably, these changes in gap junction distribution r esult from altered targeting of the junctional protein to the plasma m embrane, and/or from changes in assembly of subunits into functional c hannels. (C) 1998 Elsevier Science B.V.