Dataset Information

DHHC7-mediated palmitoylation of barttin is a risk factor for Bartter syndrome

ABSTRACT: Chloride permeability in the thin and thick ascending limbs of the loop of Henle is a crucial component for urine concentration, with ClC-K/barttin chloride channels as a central component in establishing the cortico-medullary osmotic gradient. Barttin is an accessory subunit of human ClC-K channels, promoting trafficking of the ClC-K/barttin complex to the plasma membrane, increasing channel stability, and switching ClC-K/barttin channels into an active state. Barttin undergoes post-translational palmitoylation, which is essential for channel activation. Here, we identified DHHC7 as a major barttin palmitoyl-acyltransferase, the depletion of which reduced barttin palmitoylation and the macroscopic current amplitudes in cells expressing ClC-K/barttin channels. To investigate a functional role of barttin palmitoylation in vivo, we established Zdhhc7-/- mice. Although barttin palmitoylation was significantly decreased in the kidneys of Zdhhc7-/- animals, it did not result in any pathological consequences for kidney structure or function under physiological conditions. However, when Zdhhc7-/- animals were fed a low-salt diet, they developed hyponatremia and mild metabolic alkalosis, symptoms characteristic of human Bartter syndrome (BS) Type IV with mild progression. Notably, decreased barttin palmitoylation was also found for the R8L barttin mutant identified in human BS Type IV. These data suggest that barttin palmitoylation plays an important role in chloride channel dysfunction in certain variants of BS. Thus, our study provides evidence of the downregulation of barttin palmitoylation as a possible mechanism in the etiology of BS, making the restoration of barttin palmitoylation a promising clinical strategy for the treatment of Type IV BS.

INSTRUMENT(S):

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Kidney

SUBMITTER: Monika Zareba-Koziol