Inositol 1,4,5-trisphosphate releases Ca2+ from vacuolar membrane vesicles of Saccharomyces cerevisiae.
Inositol 1,4,5-trisphosphate (IP3) induces a release of Ca2+ from vacuolar membrane vesicles of Saccharomyces cerevisiae. The amount released is dependent on IP3 concentration (concentration for half maximal effect, Km, apparent = 0.4 microM). Myo-inositol, and inositol 1,4-bisphosphate up to 50 microM have no effect on Ca2+ levels in the vesicles. The IP3-induced Ca2+ release is blocked by dantrolene and 8-(N,N-diethylamino)-octyl 3,4,5-trimethoxybenzoate-HCl (TMB-8), which are known to block Ca2+ release from Ca2+ stores in animal cells. IP3-induced release of Ca2+ also occurs when Ca2+ is accumulated by means of an artificial pH gradient, indicating that the effect of IP3 is not due to an effect on the vacuolar H(+)-ATPase. The IP3-induced Ca2+ release is not accompanied by a change in the pH gradient, which indicates that it is not due to a reversal of the Ca2+/nH+ antiport or to a decrease in delta pH by IP3. The present results suggest that IP3 may act as a second messenger in the mobilization of Ca2+ in yeast cells. As in plant cells, the vacuolar membrane of yeast seems to contain a Ca2+ channel, which can be opened by IP3. In this respect the vacuole could function as an IP3-regulated intracellular Ca2+ store, equivalent to the endoplasmic- and sarcoplasmic reticulum in animal cells, and play a role in Ca(2+)-dependent signal transduction in yeast cells.
Laboratory of Cell Biology, Faculty of Science, University of Nijmegen, The Netherlands.
P J
PJ
Belde
J H
JH
Vossen
G W
GW
Borst-Pauwels
A P
AP
Theuvenet
D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000648:ultrastructure; D014617:Vacuoles / Q000378:metabolism*
D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D002118:Calcium