PEPTIDE BLOCK OF CONSTITUTIVELY ACTIVATED NA+ CHANNELS IN LIDDLES DISEASE

Hypertension is a multifactorial disorder that results in an increased risk of cardiovascular and end-stage renal disease. Liddle's disease represents a specific hypertensive disease and expresses itself in the human population as an autosomal dominant trait. Recent experimental evidence indicates that patients with Liddle's disease have constituti vely active amiloride-sensitive Na+ channels and that these channels a re phenotypically expressed in lymphocytes obtained from normal and af fected members of the original Liddle's kindred. Linkage analysis indi cates that this disease results from a deletion of the carboxy-termina l region of the beta-subunit of a recently cloned epithelial Na+ chann el (ENaC). We report the successful immunopurification and reconstitut ion of both normal and constitutively active lymphocyte Na+ channels i nto planar lipid bilayers. These channels display all of the character istics typical of renal Na+ channels, including sensitivity to protein kinase A phosphorylation. We demonstrate that gating of normal Na+ ch annels is removed by cytoplasmic trypsin digestion and that the consti tutively active Liddle's Na+ channels are blocked by a beta- or gamma- ENaC carboxy-terminal peptide in a GTP-dependent fashion.