RT Journal Article
SR Electronic
T1 Na+/H+ Exchanger 1 is Regulated Via its Lipid-Interacting Domain which Functions as a Molecular Switch: A Pharmacological Approach Using Indolocarbazole Compounds
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.113.089268
DO 10.1124/mol.113.089268
A1 Shimada-Shimizu Naoko
A1 Takashi Hisamitsu
A1 Tomoe Y Nakamura
A1 Noriaki Hirayama
A1 Shigeo Wakabayashi
YR 2013
UL http://molpharm.aspetjournals.org/content/early/2013/10/17/mol.113.089268.abstract
AB The plasma membrane Na+/H+ exchanger 1 (NHE1) is rapidly activated in response to various stimuli. The membrane-proximal cytoplasmic region (~60 residues), termed the lipid-interacting domain (LID), is an important regulatory domain of NHE1. Here, we used a pharmacological approach to further characterize the role of LID in the regulation of NHE1. Pharmacological analysis using staurosporine-like indolocarbazole and bisindolylmaleimide compounds suggested that the phorbol ester- and receptor agonist-induced activation of NHE1 occurs through a protein kinase C-independent mechanism. In particular, only indolocarbazole compounds that inhibited NHE1 activation were able to interact with the LID, suggesting that the inhibition of NHE1 activation is achieved through the direct action of these compounds on the LID. Furthermore, in addition to phorbol esters and a receptor agonist, okadaic acid and hyperosmotic stress, which are known to activate NHE1 through unknown mechanisms, were also found to promote membrane association of the LID concomitant with NHE1 activation; these effects were inhibited by staurosporine as well as by a mutation in the LID. Binding experiments using the fluorescent ATP analog trinitrophenyl ATP revealed that ATP and the NHE1 activator phosphatidylinositol 4,5-bisphosphate bind competitively to the LID. These findings suggest that modulation of NHE1 activity by various activators and inhibitors occurs through the direct binding of these molecules to the LID, which alters the association of the LID with the plasma membrane.