A. Santiago et al., ENTAMOEBA-HISTOLYTICA - PKC TRANSDUCTION PATHWAY ACTIVATION IN THE TROPHOZOITE FIBRONECTIN INTERACTION, Experimental parasitology, 79(3), 1994, pp. 436-444
Interaction of Entamoeba histolytica trophozoites with fibronectin (FN
) induces reorganization of the actin cytoskeleton and an increase in
proteolytic activities that results in the degradation of the bound pr
otein. The binding is mediated by a 37-kDa FN ''receptor'' localized i
n the trophozoite surface and associated to the cytoskeleton. The intr
acellular signals triggered by the ligand-receptor interaction are not
well understood but it is plausible that they drive the observed resp
onses. To address this issue, the activation of protein kinase C (PKC)
pathways by FN binding was explored. Stimulation with phorbol myrista
te acetate (PMA) or FN produced a rapid increase in the amebas adhesio
n to the substrate and local release of proteases. Two PKC inhibitors,
H7 and staurosporine, reverted the PMA stimulus and inhibited the res
ponse induced by FN. Interaction with FN as well as treatment with PMA
produced transient changes of F-actin levels susceptible to inhibitio
n by H7. Furthermore, phosphorylation of amebic proteins was enhanced
in response to FN binding and PMA, while the presence of the PKC inhib
itor diminished their phosphorylation. Inositol triphosphate productio
n was stimulated by the FN binding, and PKC activation and translation
was registered in cell extracts obtained from the stimulated amebas.
Our results suggest that PKC pathways are activated in amebas by infor
mation transduced as a result of trophozoite binding to FN. (C) 1994 A
cademic Press, Inc.