Abstract:.-We report for the first time on the copper-dependent behavior of endogenous ATP7A in two types of polarized intestinal epithelia, rat enterocytes in vivo and filter-grown Caco-2 cells, an accepted in vitro model of human small intestine. We used high-resolution, confocal immunofluorescence combined with quantitative cell surface biotinylation and found that the vast majority of endogenous ATP7A was localized intracellularly under all copper conditions. In copper-depleted cells, virtually all of the ATP7A loc… Show more
“…MD is an X-linked copper deficiency disorder that arises due to mutation of ATP7A (OMIM 309400). The primary site of the defect are the intestinal enterocytes, which take up dietary copper, but absorption into the portal circulation is impaired due to defective ATP7A-mediated copper efflux (2,3). Consequently, systemic copper deficiency accounts for the wide range of neurological and developmental defects (1).…”
Section: Menkes (Md)mentioning
confidence: 99%
“…ATP7A and ATP7B reside at the trans-Golgi network, where they receive copper from the copper chaperone ATOX1. With increased intracellular copper levels, ATP7A and ATP7B traffic to exocytic vesicles near the basolateral or apical membranes, respectively (2,3,5,6). When copper levels are restored, they recycle back to the trans-Golgi network (5).…”
The copper-transporting P 1B -type ATPases (Cu-ATPases) ATP7A and ATP7B are key regulators of physiological copper levels. They function to maintain intracellular copper homeostasis by delivering copper to secretory compartments and by trafficking toward the cell periphery to export excess copper. Mutations in the genes encoding ATP7A and ATP7B lead to copper deficiency and toxicity disorders, Menkes and Wilson diseases, respectively. This report describes the interaction between the Cu-ATPases and clusterin and demonstrates a chaperone-like role for clusterin in facilitating their degradation. Clusterin interacted with both ATP7A and ATP7B in mammalian cells. This interaction increased under conditions of oxidative stress and with mutations in ATP7B that led to its misfolding and mislocalization. A Wilson disease patient mutation (G85V) led to enhanced ATP7B turnover, which was further exacerbated when cells overexpressed clusterin. We demonstrated that clusterin-facilitated degradation of mutant ATP7B is likely to involve the lysosomal pathway. The knockdown and overexpression of clusterin increased and decreased, respectively, the Cu-ATPase-mediated copper export capacity of cells. These results highlight a new role for intracellular clusterin in mediating Cu-ATPase quality control and hence in the normal maintenance of copper homeostasis, and in promoting cell survival in the context of disease. Based on our findings, it is possible that variations in clusterin expression and function could contribute to the variable clinical expression of Menkes and Wilson diseases.
“…MD is an X-linked copper deficiency disorder that arises due to mutation of ATP7A (OMIM 309400). The primary site of the defect are the intestinal enterocytes, which take up dietary copper, but absorption into the portal circulation is impaired due to defective ATP7A-mediated copper efflux (2,3). Consequently, systemic copper deficiency accounts for the wide range of neurological and developmental defects (1).…”
Section: Menkes (Md)mentioning
confidence: 99%
“…ATP7A and ATP7B reside at the trans-Golgi network, where they receive copper from the copper chaperone ATOX1. With increased intracellular copper levels, ATP7A and ATP7B traffic to exocytic vesicles near the basolateral or apical membranes, respectively (2,3,5,6). When copper levels are restored, they recycle back to the trans-Golgi network (5).…”
The copper-transporting P 1B -type ATPases (Cu-ATPases) ATP7A and ATP7B are key regulators of physiological copper levels. They function to maintain intracellular copper homeostasis by delivering copper to secretory compartments and by trafficking toward the cell periphery to export excess copper. Mutations in the genes encoding ATP7A and ATP7B lead to copper deficiency and toxicity disorders, Menkes and Wilson diseases, respectively. This report describes the interaction between the Cu-ATPases and clusterin and demonstrates a chaperone-like role for clusterin in facilitating their degradation. Clusterin interacted with both ATP7A and ATP7B in mammalian cells. This interaction increased under conditions of oxidative stress and with mutations in ATP7B that led to its misfolding and mislocalization. A Wilson disease patient mutation (G85V) led to enhanced ATP7B turnover, which was further exacerbated when cells overexpressed clusterin. We demonstrated that clusterin-facilitated degradation of mutant ATP7B is likely to involve the lysosomal pathway. The knockdown and overexpression of clusterin increased and decreased, respectively, the Cu-ATPase-mediated copper export capacity of cells. These results highlight a new role for intracellular clusterin in mediating Cu-ATPase quality control and hence in the normal maintenance of copper homeostasis, and in promoting cell survival in the context of disease. Based on our findings, it is possible that variations in clusterin expression and function could contribute to the variable clinical expression of Menkes and Wilson diseases.
“…Previously, most similar studies have focused on mammalian ATP7A regulation at the post-translational level and several of these studies have shown that the translocation of ATP7A from a compartment localized within the trans-Golgi network to a compartment near the plasma membrane is required for regulation of intracellular Cu levels (Nyasae et al, 2007;Lutsenko et al, 2008). Transcriptional regulation of ATP7A levels in liver and intestine of zebrafish and sea bream exposed to waterborne Cu (Craig et al, 2009;Minghetti et al, 2010) and in rat intestine after Cu-exposure (Bauerly et al, 2005) indicate an additional mechanism of regulation in Cu efflux.…”
Copper transporting ATPase, ATP7A, is an ATP dependent copper pump present in all vertebrates, critical for the maintenance of intracellular and whole body copper homeostasis.
Effects of copper treatment on
“…The Cu-ATPases predominantly reside at the trans-Golgi network (TGN) under basal conditions for metallation of copper-dependent enzymes of the secretory pathway. In response to elevated intracellular copper levels, they traffic to vesicles located near the basolateral (ATP7A) (3,4) or apical (ATP7B) (5-7) membranes where they sequester and mediate export of the excess copper. When intracellular copper levels are restored, the Cu-ATPases recycle back to the TGN.…”
mentioning
confidence: 99%
“…In MD, a fatal X-linked copper deficiency disorder, the intestinal enterocytes are the primary site of the defect. Defective copper transport across the basolateral membrane of these cells into the portal circulation leads to a systemic copper deficiency with devastating consequences (3,4,9,10). Biochemical abnormalities lead to neurological and developmental defects among many other symptoms (9,11).…”
Background: Clusterin and COMMD1 interact to down-regulate copper transporters ATP7A and ATP7B. Results: Clusterin and COMMD1 act independently and under different conditions to target ATP7B degradation via different pathways. Conclusion: Clusterin and COMMD1 regulate the quality control of ATP7A/ATP7B and directly impact copper homeostasis. Significance: Clusterin and COMMD1 allelic variations may influence the clinical expression of Menkes and Wilson diseases.
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