Delivery of the Cu-transporting ATPase ATP7B to the plasma membrane in Xenopus oocytes

The effects of H22 tumor on the quality of oocytes and the development of early embryos from host mice: A single-cell RNA sequencing approach

The association between cancer and female reproduction remains largely unknown. Here we investigated the quality of oocytes and the developmental potential of zygotes using H22 tumor-bearing mice model. The results showed that the number of oocytes was decreased in tumor-bearing mice compared with the control mice, and accompanied scattered chromosomes was observed. Further study revealed an abnormal epigenetic reprogramming occurred in the zygotes from the H22 tumor-bearing mice, as exemplified by the aberrant 5hmC/5mC modifications in the pronuclei. Finally, single-cell RNA sequencing was performed on the oocytes collected from the H22 tumor-bearing mice. Our data showed that 45 of the 202 differentially expressed genes in tumor-bearing group were closely associated with oocyte quality. Protein interaction analysis indicated that the potential interaction among these 45 genes. Collectively, our study uncovered that the quality of oocytes and early embryonic development were affected by H22 tumor bearing via the altered expression patterns of genes related with reproduction, providing new insights into the reproductive capability of female cancer patients.

Copper Sulfide Facilitates Hepatobiliary Clearance of Gold Nanoparticles through the Copper-Transporting ATPase ATP7B

Metallic gold (Au) nanoparticles have great potential for a wide variety of biomedical applications. Yet, slow clearance of Au nanoparticles significantly hinders their clinical translation. Herein, we describe a strategy of utilizing the endogenous copper (Cu) clearance to improve the elimination of Au nanoparticles. Our mechanistic study reveals that a Cu-transporting P-type ATPase, ATP7B, mediates the exocytosis of CuS nanoparticles into bile canaliculi for their rapid hepatobiliary excretion. The efflux of CuS nanoparticles is adopted to facilitate the hepatobiliary clearance of Au nanoparticles through CuS-Au conjugation. Using two different CuS-Au nanoconjugates, we demonstrate that CuS increases the biliary Au excretion of CuS-Au nanospheres or CuS-Au nanorods in mice or rats in comparison to that of their respective unconjugated Au nanoparticles postintravenous injection. The current CuS-Au conjugation approach provides a feasible strategy to enhance the hepatobiliary clearance of Au nanoparticles that may be applicable to various structures.

The six metal binding domains in human copper transporter, ATP7B: molecular biophysics and disease-causing mutations

Wilson Disease (WD) is a hereditary genetic disorder, which coincides with a dysfunctional copper (Cu) metabolism caused by mutations in ATP7B, a membrane-bound P1B-type ATPase responsible for Cu export from hepatic cells. The N-terminal part (~ 600 residues) of the multi-domain 1400-residue ATP7B constitutes six metal binding domains (MBDs), each of which can bind a copper ion, interact with other ATP7B domains as well as with different proteins. Although the ATP7B's MBDs have been investigated in vitro and in vivo intensively, it remains unclear how these domains modulate overall structure, dynamics, stability and function of ATP7B. The presence of six MBDs is unique to mammalian ATP7B homologs, and many WD causing missense mutations are found in these domains. Here, we have summarized previously reported in vitro biophysical data on the MBDs of ATP7B and WD point mutations located in these domains. Besides the demonstration of where the research field stands today, this review showcasts the need for further biophysical investigation about the roles of MBDs in ATP7B function. Molecular mechanisms of ATP7B are important not only in the development of new WD treatment but also for other aspects of human physiology where Cu transport plays a role.

Role of N-glycosylation in renal betaine transport

The osmolyte and folding chaperone betaine is transported by the renal Na(+)-coupled GABA (γ-aminobutyric acid) symporter BGT-1 (betaine/GABA transporter 1), a member of the SLC6 (solute carrier 6) family. Under hypertonic conditions, the transcription, translation and plasma membrane (PM) insertion of BGT-1 in kidney cells are significantly increased, resulting in elevated betaine and GABA transport. Re-establishing isotonicity involves PM depletion of BGT-1. The molecular mechanism of the regulated PM insertion of BGT-1 during changes in osmotic stress is unknown. In the present study, we reveal a link between regulated PM insertion and N-glycosylation. Based on homology modelling, we identified two sites (Asn(171) and Asn(183)) in the extracellular loop 2 (EL2) of BGT-1, which were investigated with respect to trafficking, insertion and transport by immunogold-labelling, electron microscopy (EM), mutagenesis and two-electrode voltage clamp measurements in Xenopus laevis oocytes and uptake of radiolabelled substrate into MDCK (Madin-Darby canine kidney) and HEK293 (human embryonic kidney) cells. Trafficking and PM insertion of BGT-1 was clearly promoted by N-glycosylation in both oocytes and MDCK cells. Moreover, association with N-glycans at Asn(171) and Asn(183) contributed equally to protein activity and substrate affinity. Substitution of Asn(171) and Asn(183) by aspartate individually caused no loss of BGT-1 activity, whereas the double mutant was inactive, suggesting that N-glycosylation of at least one of the sites is required for function. Substitution by alanine or valine at either site caused a dramatic loss in transport activity. Furthermore, in MDCK cells PM insertion of N183D was no longer regulated by osmotic stress, highlighting the impact of N-glycosylation in regulation of this SLC6 transporter.

Structural organization of human Cu-transporting ATPases: learning from building blocks

Copper-transporting ATPases (Cu-ATPases) ATP7A and ATP7B play an essential role in human physiological function. Their primary function is to deliver copper to the secretory pathway and export excess copper from the cell for removal or further utilization. Cells employ Cu-ATPases in numerous physiological processes that include the biosynthesis of copper-dependent enzymes, lactation, and response to hypoxia. Biochemical studies of human Cu-ATPases and their orthologs have demonstrated that Cu-ATPases share many common structural and mechanistic characteristics with other members of the P-type ATPase family. Nevertheless, the Cu-ATPases have a unique coordinate environment for their ligands, copper and ATP, and additional domains that are required for sophisticated regulation of their intracellular localization and activity. Here, we review recent progress that has been made in understanding the structure of Cu-ATPases from the analysis of their individual domains and orthologs from microorganisms, and speculate about the implications of these findings for the function and regulation of human copper pumps.

Cellular multitasking: the dual role of human Cu-ATPases in cofactor delivery and intracellular copper balance

The human copper-transporting ATPases (Cu-ATPases) are essential for dietary copper uptake, normal development and function of the CNS, and regulation of copper homeostasis in the body. In a cell, Cu-ATPases maintain the intracellular concentration of copper by transporting copper into intracellular exocytic vesicles. In addition, these P-type ATPases mediate delivery of copper to copper-dependent enzymes in the secretory pathway and in specialized cell compartments such as secretory granules or melanosomes. The multiple functions of human Cu-ATPase necessitate complex regulation of these transporters that is mediated through the presence of regulatory domains in their structure, posttranslational modification and intracellular trafficking, as well as interactions with the copper chaperone Atox1 and other regulatory molecules. In this review, we summarize the current information on the function and regulatory mechanisms acting on human Cu-ATPases ATP7A and ATP7B. Brief comparison with the Cu-ATPase orthologs from other species is included.