OBJECTIVE: Wilson\'s disease (WD) in children and adolescents is predominantly asymptomatic or oligo-symptomatic. The symptoms are nonspecific and difficult to distinguish from other hepatic or neuropsychiatric disorders. In this study, we present the experience of a pediatric referral center for WD diagnosis and treatment.
METHODS: We retrospectively analyzed clinical and laboratory data from 99 patients with WD of Sardinian origin, including physical examination, laboratory biochemical testing, liver biopsy, and genetic analysis.
RESULTS: Patients were prevalently oligo-symptomatic or asymptomatic. The median age of diagnosis was 8.78 years. Ceruloplasmin values were lower than normal values in all analyzed patients. Twenty-four-hour urinary copper levels were higher than 40 μg/24-h in 92/96 patients. In all analyzed patients with the exception of one, liver copper was higher than 250 μg/g of dry weight but all had >75 μg/g of dry weight. Statistical analysis showed correlation between the age at diagnosis, serum copper, and 24-h urinary copper. Correlation was also found between serum copper and 24-h urinary copper. Molecular analysis of ATP7B gene allowed complete characterization in all the analyzed patients.
CONCLUSIONS: A high index of clinical suspicion and biochemical tests including liver tests, serum ceruloplasmin, and basal 24-h urinary copper excretion and genotype determination are key to WD diagnosis. The long experience that a referral center for WD possesses is an important factor in making WD diagnosis a more accurate process. Studies in animal models on WD could be used as a guide to further investigate the molecular mechanisms that regulate copper metabolism and influence the natural history of WD.

Copper is a critical trace element in biological systems due the vast number of essential enzymes that require the metal as a cofactor, including cytochrome c oxidase, superoxide dismutase and dopamine-β-hydroxylase. Due its key role in oxidative metabolism, antioxidant defence and neurotransmitter synthesis, copper is particularly important for neuronal development and proper neuronal function. Moreover, increasing evidence suggests that copper also serves important functions in synaptic and network activity, the regulation of circadian rhythms, and arousal. However, it is important to note that because of copper\'s ability to redox cycle and generate reactive species, cellular levels of the metal must be tightly regulated to meet cellular needs while avoiding copper-induced oxidative stress. Therefore, it is essential that the intricate system of copper transporters, exporters, copper chaperones and copper trafficking proteins function properly and in coordinate fashion. Indeed, disorders of copper metabolism such as Menkes disease and Wilson disease, as well as diseases linked to dysfunction of copper-requiring enzymes, such as SOD1-linked amyotrophic lateral sclerosis, demonstrate the dramatic neurological consequences of altered copper homeostasis. In this review, we explore the physiological importance of copper in the nervous system as well as pathologies related to improper copper handling.

Wilson disease (WD), also known as hepatolenticular degeneration, is an autosomal recessive disorder characterized by disorganized copper metabolism caused by mutations in the ATP7B gene. Currently, the main treatment options for WD involve medications such as d-penicillamine, trientine hydrochloride, zinc acetate, and liver transplantation. However, there are challenges that encompass issues of poor compliance, adverse effects, and limited availability of liver sources that persist. Stem cell therapy for WD is currently a promising area of research. Due to the advancement in stem cell directed differentiation technology in vitro and the availability of sufficient stem cell donors, it is expected to be a potential treatment option for the permanent correction of abnormal copper metabolism. This article discusses the research progress of stem cell therapy for WD from various sources, as well as the challenges and future prospects of the clinical application of stem cell therapy for WD.

Human copper transporters ATP7B and ATP7A deliver copper to biosynthetic pathways and maintain copper homeostasis in the cell. These enzymes combine several challenges for structural biology because they are large low abundance membrane proteins with many highly mobile domains and long disordered loops. No method has yet succeeded in solving the structure of the complete fully functional protein. Still, X-ray crystallography, Cryo-EM and NMR helped to piece together a structure based model of the enzyme activity and regulation by copper. We review the structures of ATP7B and ATP7A with an emphasis on the mechanistic insights into the unique aspects of the transport function and regulation of the human copper ATPases that have emerged from more than twenty years of research.

Selective retrograde transport from endosomes back to the trans-Golgi network (TGN) is important for maintaining protein homeostasis, recycling receptors, and returning molecules that were transported to the wrong compartments. Two important transmembrane proteins directed to this pathway are the Cation-Independent Mannose-6-phosphate receptor (CI-MPR) and the ATP7B copper transporter. Among CI-MPR functions is the delivery of acid hydrolases to lysosomes, while ATP7B facilitates the transport of cytosolic copper ions into organelles or the extracellular space. Precise subcellular localization of CI-MPR and ATP7B is essential for the proper functioning of these proteins. This study shows that both CI-MPR and ATP7B interact with a variant of the clathrin adaptor 1 (AP-1) complex that contains a specific isoform of the γ-adaptin subunit called γ2. Through synchronized anterograde trafficking and cell-surface uptake assays, we demonstrated that AP-1γ2 is dispensable for ATP7B and CI-MPR exit from the TGN while being critically required for ATP7B and CI-MPR retrieval from endosomes to the TGN. Moreover, AP-1γ2 depletion leads to the retention of endocytosed CI-MPR in endosomes enriched in retromer complex subunits. These data underscore the importance of AP-1γ2 as a key component in the sorting and trafficking machinery of CI-MPR and ATP7B, highlighting its essential role in the transport of proteins from endosomes.

Wilson\'s disease is a complicated medical condition caused by the accumulation of copper, mostly in the liver and brain. The genetic basis of Wilson\'s disease is attributed to the presence of pathogenic variants in the ATP7B copper-transporting gene, which prevents the excretion of copper through the biliary tract. To date, ATP7B remains the only identified gene that has been linked to the development of this disease. Our understanding of the disease has been associated with the identification of particular disease-causing variants that present specific impairments in copper transporters. It is crucial to identify the most frequent variant in terms of ethnicity to facilitate testing of its functionality. This study represents the initial comprehensive analysis of ATP7B variants, providing insights into the extensive range of disease-causing mutations. Here, we describe the 1275 distinct ATP7B variants documented so far, with particular emphasis on their regional and ethnic prevalence. The H1069Q missense variant is the most frequently reported in Europe, Northern America, and North Africa, whereas the R778L, C271*, and M645R variants are the most prevalent in the East Asian, Middle Eastern-South Asian, and South American populations, respectively. Acquiring such knowledge would facilitate the implementation of a selective mutation screening approach, targeting the most predominant variant identified within a specific ethnic group or geographic region for better diagnosis of the disease.

Copper, a vital element in various physiological processes, is transported from the gastrointestinal tract to tissues and cells through diverse copper transporters. Among these transporters, ATP7A and ATP7B play significant roles in regulating systemic copper metabolism and exhibit precise regulation in their intracellular trafficking. These transporters undergo dynamic shuttling between the trans-Golgi network (TGN) and the plasma membrane via the endocytic recycling mechanism, which involves the retromer and other associated factors. Interestingly, the antimicrobial attribute of copper implies a potential connection between microbial infection and copper metabolism. Several microbes, including Salmonella enterica, Cryptococcus, Influenza A virus (IAV) and Zika virus (ZIKV) have been observed to impact the regulatory mechanisms of ATP7A/B, either directly or indirectly, as a means of survival. This review summarizes the key features and trafficking mechanisms of the copper transporters ATP7A/B, and examines the intricate interplay between microbes and copper metabolism. Ultimately, it highlights how microbes can perturb copper homeostasis through interactions with host factors, offering valuable insights into the mechanistic aspects of host-microbe interactions.

Wilson disease, a rare genetic disorder resulting from mutations in the ATP7B gene disrupts copper metabolism, leading to its harmful accumulation in hepatocytes, the brain, and other organs. It affects roughly 1 in 30,000 individuals, with 1 in 90 being gene carriers. Beyond gene mutations, the disease involves complex factors contributing to copper imbalance. Ongoing research seeks to unravel intricate molecular pathways, offering fresh insights into the disease\'s mechanisms. Simultaneously, there is a dedicated effort to develop effective therapeutic strategies. Nanotechnology-driven formulations are showing promise for both treatment and early diagnosis of Wilson disease. This comprehensive review covers the entire spectrum of the condition, encompassing pathophysiology, potential biomarkers, established and emerging therapies, ongoing clinical trials, and innovative nanotechnology applications. This multifaceted approach holds the potential to improve our understanding, diagnosis, and management of Wilson\'s disease, which remains a challenging and potentially life-threatening disorder.

ATP7B is a copper-transporting protein that contributes to the chemo-resistance of human cancer cells. It remains unclear what the molecular mechanisms behind ATP7B are in cancer, as well as its role in human pan-cancer studies.
Our study evaluated the differential expression of ATP7B in cancer and paracancerous tissues based on RNA sequencing data from the GTEx and TCGA. Kaplan-Meier and Cox proportional hazards regressions were used to estimate prognostic factors associated with ATP7B.The correlations between the expression of ATP7B and immune cell infiltration, tumor mutation burden, microsatellite instability and immune checkpoint molecules were analyzed. Co-expression networks and mutations in ATP7B were analyzed using the web tools. An analysis of ATP7B expression difference on drug sensitivity on tumor cells was performed using the CTRP, GDSC and CMap database.
ATP7B expression differed significantly between cancerous and paracancerous tissues. The abnormal expression of ATP7B was linked to prognosis in LGG and KIRC. Infiltration of immune cells, tumor mutation burden, microsatellite instability and immunomodulators had all been linked to certain types of cancer. Cancer cells exhibited a correlation between ATP7B expression and drug sensitivity.
ATP7B might be an immunotherapeutic and prognostic biomarker based on its involvement in cancer occurrence and development.

The homologous P-type copper-ATPases (Cu-ATPases) ATP7A and ATP7B are the key regulators of copper homeostasis in mammalian cells. In polarized epithelia, upon copper treatment, ATP7A and ATP7B traffic from the trans-Golgi network (TGN) to basolateral and apical membranes, respectively. We characterized the sorting pathways of Cu-ATPases between TGN and the plasma membrane and identified the machinery involved. ATP7A and ATP7B reside on distinct domains of TGN in limiting copper conditions, and in high copper, ATP7A traffics to basolateral membrane, whereas ATP7B traverses common recycling, apical sorting and apical recycling endosomes en route to apical membrane. Mass spectrometry identified regulatory partners of ATP7A and ATP7B that include the adaptor protein-1 complex. Upon knocking out pan-AP-1, sorting of both Cu-ATPases is disrupted. ATP7A loses its trafficking polarity and localizes on both apical and basolateral surfaces in high copper. By contrast, ATP7B loses TGN retention but retained its trafficking polarity to the apical domain, which became copper independent. Using isoform-specific knockouts, we found that the AP-1A complex provides directionality and TGN retention for both Cu-ATPases, whereas the AP-1B complex governs copper-independent trafficking of ATP7B solely. Trafficking phenotypes of Wilson disease-causing ATP7B mutants that disrupts putative ATP7B-AP1 interaction further substantiates the role of AP-1 in apical sorting of ATP7B.