Lysosomal storage disease upon disruption of the neuronal chloride transport protein ClC-6

Abstract

Mammalian CLC proteins function as Cl ؊ channels or as electrogenic Cl ؊ ͞H ؉ exchangers and are present in the plasma membrane and intracellular vesicles. We now show that the ClC-6 protein is almost exclusively expressed in neurons of the central and peripheral nervous systems, with a particularly high expression in dorsal root ganglia. ClC-6 colocalized with markers for late endosomes in neuronal cell bodies. The disruption of ClC-6 in mice reduced their pain sensitivity and caused moderate behavioral abnormalities. Neuronal tissues showed autofluorescence at initial axon segments. At these sites, electron microscopy revealed electron-dense storage material that caused a pathological enlargement of proximal axons. These deposits were positive for several lysosomal proteins and other marker proteins typical for neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disease. However, the lysosomal pH of Clcn6 ؊/؊ neurons appeared normal. CLCN6 is a candidate gene for mild forms of human NCL. Analysis of 75 NCL patients identified ClC-6 amino acid exchanges in two patients but failed to prove a causative role of CLCN6 in that disease.acidification ͉ anion transport ͉ Batten disease ͉ channelopathy ͉ Kufs' disease

Role of the Vesicular Chloride Transporter ClC-3 in Neuroendocrine Tissue

“…This neurodegeneration is not associated with the massive intraneuronal deposits of lysosomal storage material found in mice lacking ClC-6 (Poët et al, 2006), ClC-7 (Kasper et al, 2005), or Ostm1 (Lange et al, 2006). Although CNS degeneration is the salient feature of ClC-3 knock-out (KO) mice (Stobrawa et al, 2001;Dickerson et al, 2002;Yoshikawa et al, 2002), ClC-3 is expressed in many other tissues (Kawasaki et al, 1994;Borsani et al, 1995;Stobrawa et al, 2001).…”

“…The disruption of vesicular CLCs has diverse effects including impaired renal endocytosis and kidney stones with a loss of ClC-5 (Lloyd et al, 1996;Piwon et al, 2000;Wang et al, 2000), lysosomal storage disease with a loss of ClC-6 (Poët et al, 2006), and osteopetrosis associated with lysosomal storage disease with a loss of either ClC-7 (Kornak et al, 2001;Kasper et al, 2005) or its ␤-subunit Ostm1 (Lange et al, 2006).…”

Neuronal ceroid-lipofuscinoses

“…Animal studies suggest that other proteins of known function may be candidates for yet unclassified human NCLs. For instance, mice deficient in cathepsin F had previously been shown to develop late-onset neuronal ceroid-lipofuscinosis thus predicting CLN13 [12], and deficiencies of chloride channel proteins CLC-3, CLC-6, and CLC-7 produce neuronal ceroid-lipofuscinosis phenotypes in mice [13][14][15]. A truncating mutation in ATP13A2 that encodes an ATPase transporter of inorganic cations has been described in Tibetan terriers with adult onset NCL [16].…”

Functional Characterization of Na⁺/H⁺ Exchangers of Intracellular Compartments Using Proton-killing Selection to Express Them at the Plasma Membrane

“…It has been shown that the pH gradient between cytosol and vesicular content is generated by vacuolar H + ATPases 1 , coupled to vesicular ClC chloride transporters 2 . Both in knock-out (KO) mice and human patients, the importance of these transporters has been highlighted by the heavy phenotypes caused by mutations in their genes [3][4][5][6] .…”