Intracellular pH regulation by Na+/H+ exchange requires phosphatidylinositol 4,5-bisphosphate

Citation
O. Aharonovitz et al., Intracellular pH regulation by Na+/H+ exchange requires phosphatidylinositol 4,5-bisphosphate, J CELL BIOL, 150(1), 2000, pp. 213-224
Citations number
47
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cell & Developmental Biology
Journal title
JOURNAL OF CELL BIOLOGY
ISSN journal
0021-9525 → ACNP
Volume
150
Issue
1
Year of publication
2000
Pages
213 - 224
Database
ISI
SICI code
0021-9525(20000710)150:1<213:IPRBNE>2.0.ZU;2-J
Abstract
The carrier-mediated, electroneutral exchange of Na+ for H+ across the plas ma membrane does not directly consume metabolic energy. Nevertheless, acute depletion of cellular ATP markedly decreases transport. We analyzed the po ssible involvement of polyphosphoinositides in the metabolic regulation of NHE1, the ubiquitous isoform of the Na+/H+ exchanger. Depletion of ATP was accompanied by a marked reduction of plasmalemmal phosphatidylinositol 4,5- bisphosphate (PIP2) content. Moreover, sequestration or hydrolysis of plasm alemmal PIP2, in the absence of ATP depletion, was associated with profound inhibition of NHE1 activity. Examination of the primary structure of the C OOH-terminal domain of NHE1 revealed two potential PIP2-binding motifs. Fus ion proteins encoding these motifs bound PIP2 in vitro. When transfected in to antiport-deficient cells, mutant forms of NHE1 lacking the putative PIP2 -binding domains had greatly reduced transport capability, implying that as sociation with PIP2 is required for optimal activity. These findings sugges t that NHE1 activity is modulated by phosphoinositides and that the inhibit ory effect of ATP depletion may be attributable, at least in part, to the a ccompanying net dephosphorylation of PIP2.