Intracellular localisation of PPI1 (proton pump interactor, isoform 1), a regulatory protein of the plasma membrane H plus -ATPase of Arabidopsis thaliana

PPI1 (proton pump interactor isoform 1) is a novel protein able to interact
with the C-terminal autoinhibitory domain of the Arabidopsis thaliana
plasma membrane (PM) H+-ATPase. In vitro, PPI1 binds the PM H+-ATPase
in a site different from the known 14-3-3 binding site and stimulates its
activity. In this study, we analysed the intracellular localisation of PPI1. The
intracellular distribution was monitored in A. thaliana cultured cells by
immunolocalisation using an antiserum against the PPI1 N-terminus and in
Vicia faba guard cells and epidermal cells by transient expression of a
GFP::PPI1 fusion. The results indicate that the bulk of PPI1 is localised at
the endoplasmic reticulum, from which it might be recruited to the PM for
interaction with the H+-ATPase in response to as yet unidentified signals.