Investigating the Regulation of Cell Proliferation and Stress Fiber Formation Due to the Palmitoylation and Phosphorylation of the Na + ‐H + Exchanger Isoform 1 (NHE1): MAPK Signaling Pathway Kinases

Abstract

The Na+-H+ Exchanger Isoform 1 (NHE1) is key to the regulation of cell proliferation and stress fiber formation. NHE1 is a 12-pass transmembrane transport protein that exchanges one extracellular Na+ for one intracellular H+ with the primary function of intracellular pH regulation. This pH regulation is essential to the control of cell proliferation and migration. The regulation of NHE1 is extremely complex and involves protein and lipid binding sites including phosphorylation and palmitoylation sites. NHE1 transport activity is regulated by a series of signaling pathways which include kinases of the MAPK signaling pathway such as Erk and Rsk. Recently it has been demonstrated that reduced signaling through the MAPK pathway by the inhibition of MEK using PD98059 decreases palmitoylation of NHE1. To investigate the role of this interaction between palmitoylation and phosphorylation in the regulation of cellular function we assessed cell proliferation and stress fiber formation in PSN cells. It is hypothesized that inhibition of palmitoylation and phosphorylation will differentially regulate cell proliferation and stress fiber formation. PSN cells are Chinese hamster lung fibroblasts, which express human NHE1. Proliferation and stress fiber formation were evaluated in the presence and absence of combinations of inhibitors that alter NHE1 regulation and transport activity including, PD98059 (MEK), SCH772934 (ERK), BI-D1870 (RSK), 2-Bromopalmitate (Palmitoylation), and Ethylisopropylamiloride (NHE1).