Golgi Metal Ion Homeostasis in Human Health and Diseases

High-Fidelity Spatiotemporal Recognition of Golgi ALP through an Initial-Accumulation and Postactivation Strategy

Various signal molecules mediate complex physiological processes collectively in the Golgi. However, most currently accessible probes are questionable in illuminating the functions of these reactive species in Golgi because of the inability to irradiate these probes only at the desired Golgi location, which compromises specificity and accuracy. In this study, we rationally designed the first photocontrollable and Golgi-targeted fluorescent probe to in situ visualize the Golgi alkaline phosphatase (ALP). The designed probe with natural yellow fluorescence can provide access into Golgi and monitor the exact timing of accumulation in Golgi. On-demand photoactivation at only the desired Golgi location affords a significant emission response to ALP with illuminating red fluorescence at 710 nm. Through the photocontrollable fluorescence responsiveness to ALP, precise spatiotemporal recognition of Golgi ALP fluctuations is successfully performed. With this probe, for the first time, we revealed the Golgi ALP levels during cisplatin-induced acute kidney injury (AKI), which will further facilitate and complement the comprehensive exploration of ALP kinetics during physiological and pathological processes.

ZNT5-6 and ZNT7 play an integral role in protein N-glycosylation by supplying Zn2+ to Golgi α-mannosidase II

The stepwise addition of monosaccharides to N-glycans attached to client proteins to generate a repertoire of mature proteins involves a concerted action of many glycosidases and glycosyltransferases. Here, we report that Golgi α-mannosidase II (GMII), a pivotal enzyme catalyzing the first step in the conversion of hybrid- to complex-type N-glycans, is activated by Zn2+ supplied by the early secretory compartment-resident ZNT5-ZNT6 heterodimers (ZNT5-6) and ZNT7 homodimers (ZNT7). Loss of ZNT5-6 and ZNT7 function results in marked accumulation of hybrid-type and complex/hybrid glycans with concomitant reduction of complex- and high-mannose-type glycans. In cells lacking the ZNT5-6 and ZNT7 functions, the GMII activity is substantially decreased. In contrast, the activity of its homolog, lysosomal mannosidase (LAMAN), is not decreased. Moreover, we show that the growth of pancreatic cancer MIA PaCa-2 cells lacking ZNT5-6 and ZNT7 is significantly decreased in a nude mouse xenograft model. Our results indicate the integral roles of ZNT5-6 and ZNT7 in N-glycosylation and highlight their potential as novel target proteins for cancer therapy.

Exogeneous metal ions as therapeutic agents in cardiovascular disease and their delivery strategies

Metal ions participate in many metabolic processes in the human body, and their homeostasis is crucial for life. In cardiovascular diseases (CVDs), the equilibriums of metal ions are frequently interrupted, which are related to a variety of disturbances of physiological processes leading to abnormal cardiac functions. Exogenous supplement of metal ions has the potential to work as therapeutic strategies for the treatment of CVDs. Compared with other therapeutic drugs, metal ions possess broad availability, good stability and safety and diverse drug delivery strategies. The delivery strategies of metal ions are important to exert their therapeutic effects and reduce the potential toxic side effects for cardiovascular applications, which are also receiving increasing attention. Controllable local delivery strategies for metal ions based on various biomaterials are constantly being designed. In this review, we comprehensively summarized the positive roles of metal ions in the treatment of CVDs from three aspects: protecting cells from oxidative stress, inducing angiogenesis, and adjusting the functions of ion channels. In addition, we introduced the transferability of metal ions in vascular reconstruction and cardiac tissue repair, as well as the currently available engineered strategies for the precise delivery of metal ions, such as integrated with nanoparticles, hydrogels and scaffolds.

The organization and function of the Golgi apparatus in dendrite development and neurological disorders

Dendrites are specialized neuronal compartments that sense, integrate and transfer information in the neural network. Their development is tightly controlled and abnormal dendrite morphogenesis is strongly linked to neurological disorders. While dendritic morphology ranges from relatively simple to extremely complex for a specified neuron, either requires a functional secretory pathway to continually replenish proteins and lipids to meet dendritic growth demands. The Golgi apparatus occupies the center of the secretory pathway and is regulating posttranslational modifications, sorting, transport, and signal transduction, as well as acting as a non-centrosomal microtubule organization center. The neuronal Golgi apparatus shares common features with Golgi in other eukaryotic cell types but also forms distinct structures known as Golgi outposts that specifically localize in dendrites. However, the organization and function of Golgi in dendrite development and its impact on neurological disorders is just emerging and so far lacks a systematic summary. We describe the organization of the Golgi apparatus in neurons, review the current understanding of Golgi function in dendritic morphogenesis, and discuss the current challenges and future directions.

Structure and transport mechanism of the human calcium pump SPCA1

Secretory-pathway Ca2+-ATPases (SPCAs) play critical roles in maintaining Ca2+ homeostasis, but the exact mechanism of SPCAs-mediated Ca2+ transport remains unclear. Here, we determined six cryo-electron microscopy (cryo-EM) structures of human SPCA1 (hSPCA1) in a series of intermediate states, revealing a near-complete conformational cycle. With the aid of molecular dynamics simulations, these structures offer a clear structural basis for Ca2+ entry and release in hSPCA1. We found that hSPCA1 undergoes unique conformational changes during ATP binding and phosphorylation compared to other well-studied P-type II ATPases. In addition, we observed a conformational distortion of the Ca2+-binding site induced by the separation of transmembrane helices 4L and 6, unveiling a distinct Ca2+ release mechanism. Particularly, we determined a structure of the long-sought CaE2P state of P-type IIA ATPases, providing valuable insights into the Ca2+ transport cycle. Together, these findings enhance our understanding of Ca2+ transport by hSPCA1 and broaden our knowledge of P-type ATPases.

Trans-Golgi protein TVP23B regulates host-microbe interactions via Paneth cell homeostasis and Goblet cell glycosylation

A key feature in intestinal immunity is the dynamic intestinal barrier, which separates the host from resident and pathogenic microbiota through a mucus gel impregnated with antimicrobial peptides. Using a forward genetic screen, we have found a mutation in Tvp23b, which conferred susceptibility to chemically induced and infectious colitis. Trans-Golgi apparatus membrane protein TVP23 homolog B (TVP23B) is a transmembrane protein conserved from yeast to humans. We found that TVP23B controls the homeostasis of Paneth cells and function of goblet cells, leading to a decrease in antimicrobial peptides and more penetrable mucus layer. TVP23B binds with another Golgi protein, YIPF6, which is similarly critical for intestinal homeostasis. The Golgi proteomes of YIPF6 and TVP23B-deficient colonocytes have a common deficiency of several critical glycosylation enzymes. TVP23B is necessary for the formation of the sterile mucin layer of the intestine and its absence disturbs the balance of host and microbe in vivo.

Mesoporous TiO2 Coatings Regulate ZnO Nanoparticle Loading and Zn2+ Release on Titanium Dental Implants for Sustained Osteogenic and Antibacterial Activity

Two major issues are currently hindering the clinical practice of titanium dental implants for the lack of biological activities: immediate/early loading risks and peri-implantitis. To solve these issues, it is urgent to develop multifunctional implants modified with effective osteogenic and antibacterial properties. Zinc oxide nanoparticles (ZnO NPs) possess superior antibacterial activity; however, they can rapidly release Zn²⁺, causing cytotoxicity. In this study, a potential dental implant modification was creatively developed as ZnO nanoparticle-loaded mesoporous TiO₂ coatings (nZnO/MTC-Ti) via the evaporation-induced self-assembly method (EISA) and one-step spin coating. The mesoporous TiO₂ coatings (MTCs) regulated the synthesis and loading of ZnO NPs inside the nanosized pores. The synergistic effects of MTC and ZnO NPs on nZnO/MTC-Ti not only controlled the long-term steady-state release of Zn²⁺ but also optimized the charge distribution on the surface. Therefore, the cytotoxicity of ZnO NPs was resolved without triggering excessive reactive oxygen species (ROS). The increased extracellular Zn²⁺ further promoted a favorable intracellular zinc ion microenvironment through the modulation of zinc transporters (ZIP1 and ZnT1). Owing to that, the adhesion, proliferation, and osteogenic activity of bone mesenchymal stem cells (BMSCs) were improved. Additionally, nZnO/MTC-Ti inhibited the proliferation of oral pathogens (Pg and Aa) by inducing bacterial ROS production. For in vivo experiments, different implants were implanted into the alveolar fossa of Sprague-Dawley rats immediately after tooth extraction. The nZnO/MTC-Ti implants were found to possess a higher capability for enhancing bone regeneration, antibiosis, and osseointegration in vivo. These findings suggested the outstanding performance of nZnO/MTC-Ti implants in accelerating osseointegration and inhibiting bacterial infection, indicating a huge potential for solving immediate/early loading risks and peri-implantitis of dental implants.

A Golgi-Located Transmembrane Nine Protein Gene TMN11 Functions in Manganese/Cadmium Homeostasis and Regulates Growth and Seed Development in Rice

Metal transporters play crucial roles in plant nutrition, development, and metal homeostasis. To date, several multi-proteins have been identified for metal transport across the plasma membrane and tonoplast. Nevertheless, Golgi endomembrane metal carriers and their mechanisms are less documented. In this study, we identified a new transmembrane nine (TMN) family gene, TMN11, which encodes a Mn transport protein that was localized to the cis-Golgi endomembrane in rice. OsTMN11 contains a typically conserved long luminal N-terminal domain and nine transmembrane domains. OsTMN11 was ubiquitously expressed over the lifespan of rice and strongly upregulated in young rice under excess Mn(II)/Cd(II) stress. Ectopic expression of OsTMN11 in an Mn-sensitive pmr1 mutant (PMR1 is a Golgi-resident Mn exporter) yeast (Saccharomyces cerevisiae) restored the defective phenotype and transported excess Mn out of the cells. As ScPMR1 mediates cellular Mn efflux via a vesicle-secretory pathway, the results suggest that OsTMN11 functions in a similar manner. OsTMN11 knockdown (by RNAi) compromised the growth of young rice, manifested as shorter plant height, reduced biomass, and chlorosis under excessive Mn and Cd conditions. Two lifelong field trials with rice cropped in either normal Mn supply conditions or in Cd-contaminated farmland demonstrated that knockdown of OsTMN11 impaired the capacity of seed development (including panicle, spikelet fertility, seed length, grain weight, etc.). The mature RNAi plants contained less Mn but accumulated Cd in grains and rice straw, confirming that OsTMN11 plays a fundamental role in metal homeostasis associated with rice growth and development even under normal Mn supply conditions.

New insights into the role of the Golgi apparatus in the pathogenesis and therapeutics of human diseases

The Golgi apparatus is an essential cellular organelle that mediates homeostatic functions, including vesicle trafficking and the post-translational modification of macromolecules. Its unique stacked structure and dynamic functions are tightly regulated, and several Golgi proteins play key roles in the functioning of unconventional protein secretory pathways triggered by cellular stress responses. Recently, an increasing number of studies have implicated defects in Golgi functioning in human diseases such as cancer, neurodegenerative, and immunological disorders. Understanding the extraordinary characteristics of Golgi proteins is important for elucidating its associated intracellular signaling mechanisms and has important ramifications for human health. Therefore, analyzing the mechanisms by which the Golgi participates in disease pathogenesis may be useful for developing novel therapeutic strategies. This review articulates the structural features and abnormalities of the Golgi apparatus reported in various diseases and the suspected mechanisms underlying the Golgi-associated pathologies. Furthermore, we review the potential therapeutic strategies based on Golgi function.