Intracellular targeting of copper-transporting ATPase ATP7A in a normal andAtp7b^−/−kidney

Abstract

Kidneys regulate their copper content more effectively than many other organs in diseases of copper deficiency or excess. We demonstrate that two copper-transporting ATPases, ATP7A and ATP7B, contribute to this regulation. ATP7A is expressed, to a variable degree, throughout the kidney and shows age-dependent intracellular localization. In 2-wk-old mice, ATP7A is located in the vicinity of the basolateral membrane, whereas in 20-wk-old mice, ATP7A is predominantly in intracellular vesicles. Acute elevation of serum copper, via intraperitoneal injection, results in the in vivo redistribution of ATP7A from intracellular compartments toward the basolateral membrane, illustrating a role for ATP7A in renal response to changes in copper load. Renal copper homeostasis also requires functional ATP7B, which is coexpressed with ATP7A in renal cells of proximal and distal origin. The kidneys of Atp7b−/−mice, an animal model of Wilson disease, show metabolic alterations manifested by the appearance of highly fluorescent deposits; however, in marked contrast to the liver, renal copper is not significantly elevated. The lack of notable copper accumulation in the Atp7b−/−kidney is likely due to the compensatory export of copper by ATP7A. This interpretation is supported by the predominant localization of ATP7A at the basolateral membrane of Atp7b−/−cortical tubules. Our results suggest that both Cu-ATPases regulate renal copper, with ATP7A playing a major role in exporting copper via basolateral membranes and protecting renal tissue against copper overload.

Research Tools and Techniques for Copper Metabolism in Mammals

“…In addition, antibodies against Ctr1, 5,75) Atp7a, 76) Atp7b, 77) Atox1, 21) Cox17, 78) and Ccs 79) were produced by researches.…”

The multi-layered regulation of copper translocating P-type ATPases

“…As we learn more about the recently discovered Cu-ATPase complementary function and differential localization, it is likely to emerge that similar to the examples described above, MNK and WND are subject to Cuindependent regulation in many tissues. For example, investigations into renal Cu distribution demonstrate a role for WND in apical Cu excretion and storage in Cu-loaded vesicles, whereas Cu-stimulated MNK trafficking from internal secretory compartments to the basolateral membrane aids Cu re-absorption (Linz et al 2008). Enterocytes are an important site for Cu uptake in the body.…”

“…They share *60% amino acid identity and the ability to perform two key functions: delivery of Cu to Cu-dependent enzymes in the secretory pathway (a physiological function), and Cu export via active efflux (a homeostatic function). The dual function is a result of a regulated trafficking process where MNK or WND can be expressed and localized to: (1) the trans Golgi network (TGN) for Cu transfer to enzymes in the secretory pathway such as tyrosinase and peptidylglycine a-amidating monooxygenase (by MNK) and ceruloplasmin (by WND) under basal conditions; or (2) endosomes or rapidly recycling vesicles in the vicinity of the cell surface to facilitate Cu efflux or secretion when intracellular Cu concentrations become elevated (Hellman and Gitlin 2002;Linz et al 2008;Nyasae et al 2007;Pase et al 2004;Petris et al 2000;Setty et al 2008;Steveson et al 2003).…”

“…In the last decade, the expression profile and localization of Cu-ATPases has been examined in a range of tissues. This includes hepatocytes (Huster et al 2003;Schaefer et al 1999), cultured kidney epithelial cells , mouse cerebellum and kidney (Linz et al 2008;Linz and Lutsenko 2007), hippocampal neurons (Schlief et al 2005), retina (Krajacic et al 2006) and intestinal epithelia (Monty et al 2005;Nyasae et al 2007). Initial CHO cell expression studies revealed Custimulated WND translocation to cytoplasmic vesicles (La Fontaine et al 1998).…”

“…Initial CHO cell expression studies revealed Custimulated WND translocation to cytoplasmic vesicles (La Fontaine et al 1998). These vesicles have since been more accurately associated with the membrane of bile ducts in the liver, and studies in non-hepatic cells indicate that the vesicles are large, apical/sub-apicallocalized Cu-storage compartments destined for secretion (Hardman et al 2004;Huster et al 2003;La Fontaine et al 2001;Linz et al 2008). In contrast, Cu stimulation results in MNK localization to vesicles throughout the secretory pathway, with particular enrichment within basolateral regions of polarized endothelial and epithelial cells for Cu efflux Nyasae et al 2007;Pascale et al 2003;Petris et al 1996).…”