SLC9A1 (NHE1), a member of the Na+/H+ exchanger family, is a ubiquitous membrane protein that regulates intracellular pH and cell volume. Furthermore, SLC9A1 is known to interact with the actin cytoskeleton. Fibroblasts expressing mutated NHE1 that fails to interact with actin-related proteins show impaired organization of focal adhesion points and actin stress fibers, and an irregular cell shape. Polymorphisms of the SLC9A1 gene have been reported in association with essential hypertension.