AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 6 1051-R1058, Copyright © 1986 by American Physiological Society
Calmodulin: biochemical, physiological, and morphological effects on Schistosoma mansoni
D. P. Thompson, G. Z. Chen, A. K. Sample, D. R. Semeyn and J. L. Bennett
Results of radioimmunoassays for the Ca2+-binding protein, calmodulin,
revealed that this receptor constitutes 0.53 +/- 0.12% of the total protein
in adult male Schistosoma mansoni. Schistosome calmodulin purified by
Ca2+-dependent hydrophobic interaction chromatography showed an apparent
molecular weight of 19 kDa, and its mobility on sodium dodecyl sulfate
polyacrylamide gels was influenced by the presence of Ca2+ but not the
antischistosomal drug praziquantel. Calmodulin from the parasite effected a
four-fold stimulation of bovine heart adenosine 3',5'-cyclic monophosphate
phosphodiesterase; this process was inhibited by removal of Ca2+ with
ethyleneglycol-bis(B-aminoethylether)-N,N'-tetraacetic acid but not by
praziquantel. Inhibition of calmodulin-activated processes with
antipsychotic compounds in vitro resulted in a number of time- and
concentration-dependent changes, including inhibition of schistosome
calmodulin stimulation of bovine heart phosphodiesterase, disruption and
depolarization of the parasite's tegument, and positive inotropic effects
on longitudinal musculature. Results of this study indicate that calmodulin
is a functional component of schistosomes and suggest that the role it
serves is analogous to that obtained in other eukaryotes; i.e., it is an
important component of numerous processes regulated, in part, by Ca2+.
