A mutation in the Na‐K‐2Cl cotransporter‐1 leads to changes in cellular metabolism. Issue 10 (10th February 2020)

• Record Type: Journal Article
• Authors: Omer, Salma; Koumangoye, Rainelli; Delpire, Eric
• Is Part Of: Journal of cellular physiology. Volume 235:Issue 10(2020:Oct.)
• Page Start: 7239
• Page End: 7250
• Publication Date: 2020-02-10
• Subjects: epithelial cells -- fibroblasts -- glycolysis -- mitochondrial respiration -- Na‐K‐2Cl cotransport; Physiology -- Periodicals; Cell physiology -- Periodicals; 571.6
• DOI: 10.1002/jcp.29623
• Languages: English
• ISSNs: 0021-9541

Abstract

Abstract: The Na‐K‐Cl cotransporter‐1 (NKCC1), by mediating the electroneutral transport of Na +, K +, and Cl − plays an important role in cell volume regulation, epithelial transport, and the control of neuronal excitability. Recently, we reported the first known human mutation in SLC12A2, the gene encoding NKCC1. The 17‐year old patient suffers from multiorgan failure. Laboratory tests conducted on muscle and liver biopsies of the patient showed abnormal increase in mitochondrial DNA copy number and increased glycogen levels, indicating the possibility that the transporter may play a role in energy metabolism. Here, we show that fibroblasts isolated from the patient demonstrate a significant increase in mitochondrial respiration, compared to fibroblasts isolated from healthy individuals. Similarly, Madin Darby canine kidney (MDCK) cells transfected with enhanced green fluorescent protein (EGFP)‐tagged mutant NKCC1 DNA demonstrated increased mitochondrial respiration when compared to MDCK cells expressing EGFP‐tagged wild‐type (WT) cotransporter. Direct inhibition of the cotransporter through addition of bumetanide did not change the rate of basal respiration, but led to increased maximal mitochondrial respiration. Fibroblasts extracted from NKCC1 WT/DFX and NKCC1 DFX/DFX mice also demonstrated a significant elevation in mitochondrial respiration, compared to fibroblasts isolated from their WT littermates. Expression of the mutant protein was associated with an increase in hydrogen peroxide and peroxidase activity and a decrease in messenger RNA transcript levels for protein involved in the unfolded protein response. These data reveal that cells expressing the mutant cotransporter demonstrate increased mitochondrial respiration and behave like they are experiencing a state of starvation. Abstract : Truncation mutation in Na‐K‐Cl cotransporter‐1 (NKCC1) leads to increased mitochondrial respiration in fibroblasts isolated from a patient and fibroblasts isolated from its mouse model. The increase results from expression of an abnormal protein instead of decreased function of the cotransporter.