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): Q Exactive

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Kidney

SUBMITTER: Monika Zareba-Koziol

LAB HEAD: Jakub Włodarczyk

PROVIDER: PXD017231 | Pride | 2020-03-31

REPOSITORIES: Pride

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Publications

DHHC7-mediated palmitoylation of the accessory protein barttin critically regulates the functions of ClC-K chloride channels.

Gorinski Nataliya N Wojciechowski Daniel D Guseva Daria D Abdel Galil Dalia D Mueller Franziska E FE Wirth Alexander A Thiemann Stefan S Zeug Andre A Schmidt Silke S Zareba-Kozioł Monika M Wlodarczyk Jakub J Skryabin Boris V BV Glage Silke S Fischer Martin M Al-Samir Samer S Kerkenberg Nicole N Hohoff Christa C Zhang Weiqi W Endeward Volker V Ponimaskin Evgeni E

The Journal of biological chemistry 20200317 18

Barttin is the accessory subunit of the human ClC-K chloride channels, which are expressed in both the kidney and inner ear. Barttin promotes trafficking of the complex it forms with ClC-K to the plasma membrane and is involved in activating this channel. Barttin undergoes post-translational palmitoylation that is essential for its functions, but the enzyme(s) catalyzing this post-translational modification is unknown. Here, we identified zinc finger DHHC-type containing 7 (DHHC7) protein as an ...[more]

PMID: 32184353

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Project description:Although sex differences in the brain are prevalent, the knowledge about mechanisms underlying sex-related effects on normal and pathological brain functioning is rather poor. It is known that female and male brains differ in size and connectivity. Moreover, those differences are related to neuronal morphology and activity, synapse molecular organization, synaptic plasticity, and molecular signalling pathways. Among different processes assuring proper synapse function are posttranslational modifications, and among them, S-palmitoylation emerges as a crucial mechanism underlying synaptic integrity. Protein S-palmitoylation (S-PALM) refers to the covalent attachment of palmitic acid (C16:0) to cysteine residue(s) via the formation of a thioester bond. Protein S-PALM is governed by a family of PATs, also known as DHHC proteins. Here we focused on the sex-related functional importance of DHHC7 acyltransferase. Under physiological conditions, DHHC7 emerges of particular interest because it palmitoylates various synaptic proteins involved in the regulation of cellular polarity and proliferation as well as in stress and anxiety-related pathology. Moreover, DHHC7 is responsible for S-PALM of sex steroid receptors. Functionally, S-PALM of these receptors regulates their trafficking to the plasma membrane as well as their rapid responses to sex steroid hormones. Using mass spectrometry-based method PANIMoni we identified sex-dependent differences in the S-palmitoylation of synaptic proteins, potentially involved in the regulation of passive membrane properties and excitability (e.g. potassium voltage-gated channels), synaptic transmission (e.g. subunits of glutamate or kainate receptors, voltage-dependent calcium channels) as well as signalling proteins involved in structural plasticity of dendritic spines (e.g. G-proteins and Rab GTPase). Furthermore, to determine a mechanistic source for sex-dependent changes in protein S-palmitoylation we used synaptoneurosomes from DHHC-7 knock-out -/- (DHHC7 KO) female and male mice. Our data showed sex-dependent action of DHHC-7 acyltransferase. Such discovery will facilitate the development of novel and targeted treatments congruous with biological sex.

Dataset Information

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

Publications

DHHC7-mediated palmitoylation of the accessory protein barttin critically regulates the functions of ClC-K chloride channels.

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