Previous Article | Next Article ![]()
Molecular and Cellular Biology, September 2000, p. 6686-6694, Vol. 20, No. 18
Department of Biology, Johns Hopkins
University, Baltimore, Maryland 21218
Received 10 May 2000/Accepted 16 June 2000
In animal cells, capacitative calcium entry (CCE) mechanisms become
activated specifically in response to depletion of calcium ions
(Ca2+) from secretory organelles. CCE serves to replenish
those organelles and to enhance signaling pathways that respond to
elevated free Ca2+ concentrations in the cytoplasm. The
mechanism of CCE regulation is not understood because few of its
essential components have been identified. We show here for the first
time that the budding yeast Saccharomyces cerevisiae
employs a CCE-like mechanism to refill Ca2+ stores within
the secretory pathway. Mutants lacking Pmr1p, a conserved
Ca2+ pump in the secretory pathway, exhibit higher rates of
Ca2+ influx relative to wild-type cells due to the
stimulation of a high-affinity Ca2+ uptake system.
Stimulation of this Ca2+ uptake system was blocked in
pmr1 mutants by expression of mammalian SERCA pumps. The
high-affinity Ca2+ uptake system was also stimulated in
wild-type cells overexpressing vacuolar Ca2+ transporters
that competed with Pmr1p for substrate. A screen for yeast mutants
specifically defective in the high-affinity Ca2+ uptake
system revealed two genes, CCH1 and MID1,
previously implicated in Ca2+ influx in response to mating
pheromones. Cch1p and Mid1p were localized to the plasma membrane,
coimmunoprecipitated from solubilized membranes, and shown to function
together within a single pathway that ensures that adequate levels of
Ca2+ are supplied to Pmr1p to sustain secretion and growth.
Expression of Cch1p and Mid1p was not affected in pmr1
mutants. The evidence supports the hypothesis that yeast maintains a
homeostatic mechanism related to CCE in mammalian cells. The homology
between Cch1p and the catalytic subunit of voltage-gated
Ca2+ channels raises the possibility that in some
circumstances CCE in animal cells may involve homologs of Cch1p and a
conserved regulatory mechanism.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
A Homolog of Voltage-Gated Ca2+
Channels Stimulated by Depletion of Secretory Ca2+ in
Yeast
*
Corresponding author. Mailing address: Department of
Biology, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218. Phone: (410) 516-7844. Fax: (410) 516-5213. E-mail:
kwc{at}jhu.edu.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|