title: PCaPs, possible regulators of PtdInsP signals on plasma membrane.
abstract: In plants, Ca(2+), phosphatidylinositol phosphates (PtdInsPs) and inositol phosphates are major components of intracellular signaling. Several kinds of proteins and enzymes, such as calmodulin (CaM), protein kinase, protein phosphatase, and the Ca(2+) channel, mediate the signaling. Two new Ca(2+)-binding proteins were identified from Arabidopsis thaliana and named PCaP1 and PCaP2 [plasma membrane (PM)-associated Ca(2+) (cation)-binding protein 1 and 2]. PCaP1 has an intrinsically disordered region in the central and C-terminal parts. The PCaP1 gene is expressed in most tissues and the PCaP2 gene is expressed predominantly in root hairs and pollen tubes. We recently demonstrated that these proteins are N-myristoylated, stably anchored in the PM, and are bound with phosphatidylinositol phosphates, especially PtdInsP2s. Here we propose a model for the switching mechanism of Ca (2+)-signaling mediated by PtdInsPs. Ca(2+) forms a complex with CaM (Ca(2+)-CaM) when there is an increase in the cytosol free Ca(2+). The binding of PCaPs with Ca(2+)-CaM causes PCaPs to release PtdInsPs. Until the release of PtdInsPs, the signaling is kept in the resting state.
authors.affiliation: Graduate School of Bioagricultural Sciences; Nagoya University, Nagoya, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Kato
authors.forename: Nahoko
authors.initials: N
authors.lastname: Nagasaki-Takeuchi
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ide
authors.forename: Rie
authors.initials: R
authors.lastname: Tomioka
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Maeshima
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