The Journal of Cell Biology, Vol 100, 1834-1838, Copyright © 1985 by The Rockefeller University Press
The microsporidian spore invasion tube. IV. Discharge activation begins with pH-triggered Ca2+ influx
J Pleshinger and E Weidner
The microsporidian spore extrusion apparatus activates with a calcium
influx from Spraguea lophii spore wall/plasma membrane; this influx
requires preconditioning with an extrasporular shift in medium pH to the
alkaline in the presence of the polyanions mucin or polyglutamate.
Undischarged S. lophii spores display calcium bound to the wall/plasma
membrane with a characteristic calcium-chlorotetracycline fluorescence;
this fluorescence declines significantly during spore discharge. S. lophii
spores do not discharge when spore wall/plasma membrane calcium is removed
with EGTA. Extrasporular mucin or polyglutamate and a pH shift to the
alkaline appear to be necessary preconditions for the triggering of the
influx of spore wall/plasma membrane-bound 45Ca2+. Ionophore A-23187 also
effectively activates spore discharge without other extrasporular
polyanions. Micromolar concentrations of the calcium antagonists lanthanum
or verapamil prevent spore discharge, and micromolar concentrations of
calmodulin inhibitors chlorpromazine and trifluroperazine prevent spore
discharge. Calmodulin, visualized with a calmodulin antibody and a
peroxidase conjugate, is localized particularly on the plasma membrane and
the polaroplast membranes of the extrusion apparatus.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
