The GOLPH3 pathway regulates Golgi shape and function and is activated by DNA damage

Golgi apparatus targeted therapy in cancer: Are we there yet?

Membrane trafficking within the Golgi apparatus plays a pivotal role in the intracellular transportation of lipids and proteins. Dysregulation of this process can give rise to various pathological manifestations, including cancer. Exploiting Golgi defects, cancer cells capitalise on aberrant membrane trafficking to facilitate signal transduction, proliferation, invasion, immune modulation, angiogenesis, and metastasis. Despite the identification of several molecular signalling pathways associated with Golgi abnormalities, there remains a lack of approved drugs specifically targeting cancer cells through the manipulation of the Golgi apparatus. In the initial section of this comprehensive review, the focus is directed towards delineating the abnormal Golgi genes and proteins implicated in carcinogenesis. Subsequently, a thorough examination is conducted on the impact of these variations on Golgi function, encompassing aspects such as vesicular trafficking, glycosylation, autophagy, oxidative mechanisms, and pH alterations. Lastly, the review provides a current update on promising Golgi apparatus-targeted inhibitors undergoing preclinical and/or clinical trials, offering insights into their potential as therapeutic interventions. Significantly more effort is required to advance these potential inhibitors to benefit patients in clinical settings.

GOLPH3 inhibits erastin-induced ferroptosis in colorectal cancer cells

Ferroptosis is a novel form of programmed cell death and is considered to be a druggable target for colorectal cancer (CRC) therapy. However, the role of ferroptosis in CRC and its underlying mechanism are not fully understood. In the present study we found that a protein enriched in the Golgi apparatus, Golgi phosphoprotein 3 (GOLPH3), was overexpressed in human CRC tissue and in several CRC cell lines. The expression of GOLPH3 was significantly correlated with the expression of ferroptosis-related genes in CRC. The overexpression of GOLPH3 in Erastin-induced Caco-2 CRC cells reduced ferroptotic phenotypes, whereas the knockdown of GOLPH3 potentiated ferroptosis in HT-29 CRC cells. GOLPH3 induced the expression of prohibitin-1 (PHB1) and prohibitin-2 (PHB2), which also inhibited ferroptosis in Erastin-treated CRC cells. Moreover, GOLPH3 interacted with PHB2 and nuclear factor erythroid 2-related factor 2 (NRF2) in Caco-2 cells. These observations indicate that GOLPH3 is a negative regulator of ferroptosis in CRC cells. GOLPH3 protects these cells from ferroptosis by inducing the expression of PHB1 and PHB2, and by interacting with PHB2 and NRF2.

Early signs of neurodegenerative diseases: Possible mechanisms and targets for Golgi stress

The Golgi apparatus plays a crucial role in mediating the modification, transport, and sorting of intracellular proteins and lipids. The morphological changes occurring in the Golgi apparatus are exceptionally important for maintaining its function. When exposed to external pressure or environmental stimulation, the Golgi apparatus undergoes adaptive changes in both structure and function, which are known as Golgi stress. Although certain signal pathway responses or post-translational modifications have been observed following Golgi stress, further research is needed to comprehensively summarize and understand the related mechanisms. Currently, there is evidence linking Golgi stress to neurodegenerative diseases; however, the role of Golgi stress in the progression of neurodegenerative diseases such as Alzheimer's disease remains largely unexplored. This review focuses on the structural and functional alterations of the Golgi apparatus during stress, elucidating potential mechanisms underlying the involvement of Golgi stress in regulating immunity, autophagy, and metabolic processes. Additionally, it highlights the pivotal role of Golgi stress as an early signaling event implicated in the pathogenesis and progression of neurodegenerative diseases. Furthermore, this study summarizes prospective targets that can be therapeutically exploited to mitigate neurodegenerative diseases by targeting Golgi stress. These findings provide a theoretical foundation for identifying novel breakthroughs in preventing and treating neurodegenerative diseases.

GOLPH3 Participates in Mitochondrial Fission and Is Necessary to Sustain Bioenergetic Function in MDA-MB-231 Breast Cancer Cells

In this study, we investigated the inter-organelle communication between the Golgi apparatus (GA) and mitochondria. Previous observations suggest that GA-derived vesicles containing phosphatidylinositol 4-phosphate (PI(4)P) play a role in mitochondrial fission, colocalizing with DRP1, a key protein in this process. However, the functions of these vesicles and potentially associated proteins remain unknown. GOLPH3, a PI(4)P-interacting GA protein, is elevated in various types of solid tumors, including breast cancer, yet its precise role is unclear. Interestingly, GOLPH3 levels influence mitochondrial mass by affecting cardiolipin synthesis, an exclusive mitochondrial lipid. However, the mechanism by which GOLPH3 influences mitochondria is not fully understood. Our live-cell imaging analysis showed GFP-GOLPH3 associating with PI(4)P vesicles colocalizing with YFP-DRP1 at mitochondrial fission sites. We tested the functional significance of these observations with GOLPH3 knockout in MDA-MB-231 cells of breast cancer, resulting in a fragmented mitochondrial network and reduced bioenergetic function, including decreased mitochondrial ATP production, mitochondrial membrane potential, and oxygen consumption. Our findings suggest a potential negative regulatory role for GOLPH3 in mitochondrial fission, impacting mitochondrial function and providing insights into GA-mitochondria communication.

GOLPH3 promotes endotoxemia-induced liver and kidney injury through Golgi stress-mediated apoptosis and inflammatory response

Sepsis is a serious clinical condition characterized by a systemic inflammatory response, a leading cause of acute liver and kidney injury, and is associated with a high morbidity and mortality. Understanding the molecular mechanisms underlying the acute liver and kidney injury is crucial for developing an effective therapy. Golgi apparatus plays important roles and has various substrates mediating cellular stress responses. Golgi phosphoprotein 3 (GOLPH3), linking Golgi membranes to the cytoskeleton, has been identified as an important oncogenic regulator; however, its role in endotoxemia-induced acute liver and kidney injury remains elusive. Here, we found that upregulation of GOLPH3 was associated with endotoxemia-induced acute liver and kidney injury. Lipopolysaccharide (LPS) treatment increased Golgi stress and fragmentation, and associated pro-inflammatory mediator (Tnfα, IL-6, and IL-1β) production in vivo and in vitro. Interestingly, the downregulation of GOLPH3 significantly decreased LPS-induced Golgi stress and pro-inflammatory mediators (Tnfα, IL-6, Mcp1, and Nos2), and reversed apoptotic cell deaths in LPS-treated hepatocytes and renal tubular cells. GOLPH3 knockdown also reduced inflammatory response in LPS-treated macrophages. The AKT/NF-kB signaling pathway was suppressed in GOLPH3 knockdown, which may be associated with a reduction of inflammatory response and apoptosis and the recovery of Golgi morphology and function. Taken together, GOLPH3 plays a crucial role in the development and progression of acute liver and kidney injury by promoting Golgi stress and increasing inflammatory response and apoptosis, suggesting GOLPH3 as a potential therapeutic target for endotoxemia-induced tissue injury.

Development of a Golgi-targeted superoxide anion fluorescent probe for elucidating protein GOLPH3 function in myocardial ischemia-reperfusion injury

Superoxide anion (O₂^•-) is an important reactive oxygen species (ROS) and participates in various physiological and pathological processes in the organism. The O₂^•- burst induced by ischemia-reperfusion (I/R) is associated with cardiovascular disease and promotes the cell apoptosis. In this work, a turn-on type Golgi-targeting fluorescent probe Gol-Cou-O₂^•- was rationally designed for sensitive and selective detection of O₂^•-. The minimum detection limit concentration for O₂^•- was about 3.9 × 10^-7 M in aqueous solution. Gol-Cou-O₂^•- showed excellent capacity of detecting exogenous and endogenous O₂^•- in living cells and zebrafish, and was also used to capture the up-regulated O₂^•- level during the duration of I/R process in cardiomyocytes. Golgi Phosphoprotein 3 (GOLPH3) is a potential Golgi stress marker protein and plays a key role in cells apoptosis during I/R. The fluorescence imaging and flow cytometry assay results indicated that silencing GOLPH3 through siRNA could give rise to the down-regulated O₂^•- level and alleviation of apoptosis in I/R myocardial cells. Thus, development of Gol-Cou-O₂^•- provides a diagnostic tool for myocardial oxidative stress injury and distinct insights on roles of GOLPH3 in myocardial I/R injury.

Metformin antagonizes nickel-refining fumes-induced cell pyroptosis via Nrf2/GOLPH3 pathway in vitro and in vivo

Nickel compounds, an international carcinogen in the industrial environment, increased the risk of lung inflammation even lung cancer in Ni refinery workers. Metformin has displayed the intense anti-inflammation and anti-cancer properties through regulating pyroptosis. This study was designed to explore whether Nickel-refining fumes (NiRF) can induce cell pyroptosis and how AMPK/CREB/Nrf2 mediated the protection afforded by metformin against Ni particles-induced lung impairment. Our results represented that Ni fumes exposure evoked pyroptosis via GOLPH3 and induced oxidative stress, while, metformin treatment alleviated Ni particles-mediated above changes. Moreover, nuclear factor erythroid 2-related factor 2 (Nrf2) involved in the protection of metformin, and the deficiency of Nrf2 attenuated the beneficial protection. We also determined that Nrf2 was a downstream molecule of AMPK/CREB pathway. Furthermore, male C57BL/6 mice were administered with Ni at a dose of 2 mg/kg by non-exposed endotracheal instillation and metformin (100, 200 and 300 mg/kg) via oral gavage for 4 weeks. The results indicated that NiRF promoted GOLPH3 and pyroptosis by stimulating NLRP3, caspase-1, N-GSDMD, IL-18 and IL-1β expression. However, various doses of metformin reduced GOLPH3 and the above protein levels of pyroptosis, also improved AMPK/CREB/Nrf2 expression. In summary, we found that metformin suppressed NiRF-connected GOLPH3-prompted pyroptosis via AMPK/CREB/Nrf2 signaling pathway to confer pulmonary protection.

Golgi Phosphoprotein 3 Regulates the Physical Association of Glycolipid Glycosyltransferases

Glycolipid glycosylation is an intricate process that mainly takes place in the Golgi by the complex interplay between glycosyltransferases. Several features such as the organization, stoichiometry and composition of these complexes may modify their sorting properties, sub-Golgi localization, enzymatic activity and in consequence, the pattern of glycosylation at the plasma membrane. In spite of the advance in our comprehension about physiological and pathological cellular states of glycosylation, the molecular basis underlying the metabolism of glycolipids and the players involved in this process remain not fully understood. In the present work, using biochemical and fluorescence microscopy approaches, we demonstrate the existence of a physical association between two ganglioside glycosyltransferases, namely, ST3Gal-II (GD1a synthase) and β3GalT-IV (GM1 synthase) with Golgi phosphoprotein 3 (GOLPH3) in mammalian cultured cells. After GOLPH3 knockdown, the localization of both enzymes was not affected, but the fomation of ST3Gal-II/β3GalT-IV complex was compromised and glycolipid expression pattern changed. Our results suggest a novel control mechanism of glycolipid expression through the regulation of the physical association between glycolipid glycosyltransferases mediated by GOLPH3.

Role of the Mosaic Cisternal Maturation Machinery in Glycan Synthesis and Oncogenesis

Tumorigenesis is associated with the deregulation of multiple processes, among which the glycosylation of lipids and proteins is one of the most extensively affected. However, in most cases, it remains unclear whether aberrant glycosylation is a cause, a link in the pathogenetic chain, or a mere consequence of tumorigenesis. In other cases, instead, studies have shown that aberrant glycans can promote oncogenesis. To comprehend how aberrant glycans are generated it is necessary to clarify the underlying mechanisms of glycan synthesis at the Golgi apparatus, which are still poorly understood. Important factors that determine the glycosylation potential of the Golgi apparatus are the levels and intra-Golgi localization of the glycosylation enzymes. These factors are regulated by the process of cisternal maturation which transports the cargoes through the Golgi apparatus while retaining the glycosylation enzymes in the organelle. This mechanism has till now been considered a single, house-keeping and constitutive function. Instead, we here propose that it is a mosaic of pathways, each controlling specific set of functionally related glycosylation enzymes. This changes the conception of cisternal maturation from a constitutive to a highly regulated function. In this new light, we discuss potential new groups oncogenes among the cisternal maturation machinery that can contribute to aberrant glycosylation observed in cancer cells. Further, we also discuss the prospects of novel anticancer treatments targeting the intra-Golgi trafficking process, particularly the cisternal maturation mechanism, to control/inhibit the production of pro-tumorigenic glycans.

Proteomics Profiling with SWATH-MS Quantitative Analysis of Changes in the Human Brain with HIV Infection Reveals a Differential Impact on the Frontal and Temporal Lobes

The chronic irreversible regression of cognitive ability and memory function in human immunodeficiency virus (HIV)-associated dementia (HAND) is linked with late-stage HIV infection in the brain. The molecular-level signatures of neuroinflammation and neurodegeneration are linked with dysfunction in HAND patients. Protein expression changes and posttranslational modification are epigenetic cues for dementia and neurodegenerative disease. In this study quantitative proteome analysis was performed to comprehensively elucidate changes in protein profiles in HIV-positive (HIV+) human brains. Frontal and temporal lobes of normal and HIV+ brains were subjected to label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis using the data-independent acquisition method. Comprehensive proteomic identification and quantification analysis revealed that 3294 total proteins and 251 proteins were differentially expressed in HIV+ brains; specifically, HIV+ frontal and temporal lobes had 132 and 119 differentially expressed proteins, respectively. Proteomic and bioinformatic analyses revealed protein alterations predominantly in the HIV+ frontal lobe region. The expression of GOLPH3, IMPDH2, DYNLL1, RPL11, and GPNMB proteins was significantly altered in HIV+ frontal lobes compared to that in normal brains. These proteins are associated with metabolic pathways, neurodegenerative disorders, and dementia. These proteomic-level changes may be potential biological markers and therapeutic targets to relieve the dementia-associated symptoms in individuals with HAND.

Identification of GOLPH3 Partners in Drosophila Unveils Potential Novel Roles in Tumorigenesis and Neural Disorders

Golgi phosphoprotein 3 (GOLPH3) is a highly conserved peripheral membrane protein localized to the Golgi apparatus and the cytosol. GOLPH3 binding to Golgi membranes depends on phosphatidylinositol 4-phosphate [PI(4)P] and regulates Golgi architecture and vesicle trafficking. GOLPH3 overexpression has been correlated with poor prognosis in several cancers, but the molecular mechanisms that link GOLPH3 to malignant transformation are poorly understood. We recently showed that PI(4)P-GOLPH3 couples membrane trafficking with contractile ring assembly during cytokinesis in dividing Drosophila spermatocytes. Here, we use affinity purification coupled with mass spectrometry (AP-MS) to identify the protein-protein interaction network (interactome) of Drosophila GOLPH3 in testes. Analysis of the GOLPH3 interactome revealed enrichment for proteins involved in vesicle-mediated trafficking, cell proliferation and cytoskeleton dynamics. In particular, we found that dGOLPH3 interacts with the Drosophila orthologs of Fragile X mental retardation protein and Ataxin-2, suggesting a potential role in the pathophysiology of disorders of the nervous system. Our findings suggest novel molecular targets associated with GOLPH3 that might be relevant for therapeutic intervention in cancers and other human diseases.

Alterations of Golgi Structural Proteins and Glycosylation Defects in Cancer

As the central hub in the secretory and endocytic pathways, the Golgi apparatus continually receives the flow of cargos and serves as a major processing station in the cell. Due to its dynamic nature, a sophisticated and constantly remodeling mechanism needs to be set up to maintain the Golgi architecture and function in the non-stop trafficking of proteins and lipids. Abundant evidence has been accumulated that a well-organized Golgi structure is required for its proper functions, especially protein glycosylation. Remarkably, altered glycosylation has been a hallmark of most cancer cells. To understand the causes of Golgi defects in cancer, efforts have been made to characterize Golgi structural proteins under physiological and pathological conditions. This review summarizes the current knowledge of crucial Golgi structural proteins and their connections with tumor progression. We foresee that understanding the Golgi structural and functional defects may help solve the puzzle of whether glycosylation defect is a cause or effect of oncogenesis.

Golgi phosphoprotein 3 promotes the proliferation of gallbladder carcinoma cells via regulation of the NLRP3 inflammasome

Golgi phosphoprotein 3 (GOLPH3) has been demonstrated to promote tumor progression in various gastrointestinal malignancies. However, its effects in gallbladder carcinoma (GBC) remain unknown. In the present study, the expression levels of GOLPH3 and nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor 3 (NLRP3) in human GBC tissues were detected by immunohistochemistry, and the clinical data and survival of these patients were analyzed. Next, whether GOLPH3 could affect tumor proliferation via regulation of the NLRP3 inflammasome was investigated in vitro. The results demonstrated that GOLPH3 could promote GBC cell proliferation, and that it regulated protein expression levels of NLRP3, as well as Caspase-1 P10. Conversely, knockdown of NLRP3 reversed the effects of GOLPH3 overexpression on GBC cell proliferation. GOLPH3 and NLRP3 expression levels were found to be upregulated in GBC tissues and their expression was positively correlated. The expression of GOLPH3 and NLRP3 was associated with the expression of the proliferative marker Ki-67 in tissues, and associated with poor survival, tumor stage, degree of differentiation, depth of invasion, carbohydrate antigen 19-9 and C-reactive protein levels in patients with GBC. In summary, these results indicate that GOLPH3 promotes GBC cell proliferation via a NLRP3/Caspase-1 pathway. GOLPH3 and NLRP3 participate in the process of human GBC growth and may serve as a potential therapeutic targets.

Golgi Apparatus: A Potential Therapeutic Target for Autophagy-Associated Neurological Diseases

Autophagy has dual effects in human diseases: appropriate autophagy may protect cells from stress, while excessive autophagy may cause cell death. Additionally, close interactions exist between autophagy and the Golgi. This review outlines recent advances regarding the role of the Golgi apparatus in autophagy. The signaling processes of autophagy are dependent on the normal function of the Golgi. Specifically, (i) autophagy-related protein 9 is mainly located in the Golgi and forms new autophagosomes in response to stressors; (ii) Golgi fragmentation is induced by Golgi-related proteins and accompanied with autophagy induction; and (iii) the endoplasmic reticulum-Golgi intermediate compartment and the reticular trans-Golgi network play essential roles in autophagosome formation to provide a template for lipidation of microtubule-associated protein 1A/1B-light chain 3 and induce further ubiquitination. Golgi-related proteins regulate formation of autophagosomes, and disrupted formation of autophagy can influence Golgi function. Notably, aberrant autophagy has been demonstrated to be implicated in neurological diseases. Thus, targeted therapies aimed at protecting the Golgi or regulating Golgi proteins might prevent or ameliorate autophagy-related neurological diseases. Further studies are needed to investigate the potential application of Golgi therapy in autophagy-based neurological diseases.

Myosin XVIII

Class XVIII myosins represent a branch of the myosin family tree characterized by the presence of large N- and C-terminal extensions flanking a generic myosin core. These myosins display the highest sequence similarity to conventional class II muscle myosins and are compatible with but not restricted to myosin-2 contractile structures. Instead, they fulfill their functions at diverse localities, such as lamella, actomyosin bundles, the Golgi apparatus, focal adhesions, the cell membrane, and within sarcomeres. Sequence comparison of active-site residues and biochemical data available thus far indicate that this myosin class lacks active ATPase-driven motor activity, suggesting that its members function as structural myosins. An emerging body of evidence indicates that this structural capability is essential for the organization, maturation, and regulation of the contractile machinery in both muscle and nonmuscle cells. This is supported by the clear association of myosin-18A (Myo18A) and myosin-18B (Myo18B) dysregulation with diseases such as cancer and various myopathies.

[Golgi phosphoprotein 3 overexpression inhibits paclitaxel-induced apoptosis in HeLa cells by promoting autophagy]

OBJECTIVE

To investigate the effect of Golgi phosphoprotein 3 (Golph3) on paclitaxel- induced apoptosis and autophagy in HeLa cells.

METHODS

HeLa cells were transfected with a lentiviral vector expressing Golph3 or a small interfering RNA (siRNA) targeting Golph3 for up-regulation or down-regulation of Golph3 which was verified by Western blotting. The autophagic bodies in the cells were observed using transmission electron microscopy. The expression of autophagy markers p62 and LC3 were detected using Western blotting, and the cell apoptosis was examined by PI/Anexin V-FITC double staining and flow cytometry. The effects of blocking autophagy was evaluated by treatment of the cells with the autophagy inhibitor 3-MA.

RESULTS

Transmission electron microscopy showed that the lentivirus-mediated overexpression of Golph3 significantly increased the number of autophagic bodies and interference of Golph3 expression significantly decreased autophagic bodies in HeLa cells. Western blotting showed that Golph3 overexpression caused an increased expression of LC3 and decreased the accumulation of p62 in the cells, and interference of Golph3 resulted in the reverse changes. The cell apoptosis induced by paclitaxel was significantly decreased in Golph3-overexpressing HeLa cells and increased in the cells with Golph3 knockdown (P>0.01). Treatment with 3-MA alone did not obviously affect HeLa cell apoptosis, but in cells with Golph3 knockdown, 3-MA significantly enhanced paclitaxel-induced apoptosis (P>0.01).

CONCLUSIONS

Up-regulation of Golph3 promotes autophagy and inhibits paclitaxel-induced apoptosis, whereas suppression of Golph3 inhibits autophagy and enhances paclitaxel- induced apoptosis in HeLa cells.

Role of GOLPH3 and TPX2 in Neuroblastoma DNA Damage Response and Cell Resistance to Chemotherapy

Neuroblastoma (NB) is an aggressive, relapse-prone infancy tumor of the sympathetic nervous system and is the leading cause of death among preschool age diseases, so the search for novel therapeutic targets is crucial. Golgi phosphoprotein 3 (GOLPH3) has been reported to be involved in the development, and in the DNA damage response, of various human cancers. Golgi dispersal is a common feature of DNA damage response in mammalian cells. Understanding how cells react to DNA damage is essential in order to recognize the systems used to escape from elimination. We induced DNA damage in two human neuroblastoma cell lines by curcumin. The exposure of neuroblastoma cells to curcumin induced: (a) up-regulation of GOLPH3⁺ cells; (b) augmentation of double-strand breaks; (c) Golgi fragmentation and dispersal throughout the cytoplasm; (d) increase of apoptosis and autophagy; (e) increased expression of TPX2 oncoprotein, able to repair DNA damage. Primary neuroblastoma samples analysis confirmed these observations. Our findings suggest that GOLPH3 expression levels may represent a clinical marker of neuroblastoma patients’ responsiveness to DNA damaging therapies—and of possible resistance to them. Novel molecules able to interfere with GOLPH3 and TPX2 pathways may have therapeutic benefits when used in combination with standard DNA damaging therapeutic agents in neuroblastoma

Chondroitin Sulfate-Linked Prodrug Nanoparticles Target the Golgi Apparatus for Cancer Metastasis Treatment

Metastasis is a multistep biological process regulated by multiple signaling pathways. The integrity of the Golgi apparatus plays an important role in these signaling pathways. Inspired by the mechanism and our previous finding about accumulation of chondroitin sulfate in Golgi apparatus in hepatic stellate cells, we developed a Golgi apparatus-targeting prodrug nanoparticle system by synthesizing retinoic acid (RA)-conjugated chondroitin sulfate (CS) (CS-RA). The prodrug nanoparticles appeared to accumulate in the Golgi apparatus in cancer cells and realized RA release under an acidic environment. We confirmed that CS-RA exhibited successful inhibition of multiple metastasis-associated proteins expression in vitro and in vivo by disruption of the Golgi apparatus structure. Following loading with paclitaxel (PTX), the CS-RA based nanoformulation (PTX-CS-RA) inhibited migration, invasion, and angiogenesis in vitro and suppressed tumor growth and metastasis in 4T1-Luc bearing mice. This multistep targeted nanoparticle system potentially enhanced the effect of antimetastasis combined with chemotherapy.

Efficient Golgi Forward Trafficking Requires GOLPH3-Driven, PI4P-Dependent Membrane Curvature

Vesicle budding for Golgi-to-plasma membrane trafficking is a key step in secretion. Proteins that induce curvature of the Golgi membrane are predicted to be required, by analogy to vesicle budding from other membranes. Here, we demonstrate that GOLPH3, upon binding to the phosphoinositide PI4P, induces curvature of synthetic membranes in vitro and the Golgi in cells. Moreover, efficient Golgi-to-plasma membrane trafficking critically depends on the ability of GOLPH3 to curve the Golgi membrane. Interestingly, uncoupling of GOLPH3 from its binding partner MYO18A results in extensive curvature of Golgi membranes, producing dramatic tubulation of the Golgi, but does not support forward trafficking. Thus, forward trafficking from the Golgi to the plasma membrane requires the ability of GOLPH3 both to induce Golgi membrane curvature and to recruit MYO18A. These data provide fundamental insight into the mechanism of Golgi trafficking and into the function of the unique Golgi secretory oncoproteins GOLPH3 and MYO18A.

Dark side of the epididymis: tails of sperm maturation

BACKGROUND

The Hermes body (HB) previously called the cytoplasmic droplet is a focal distension of the flagellar cytoplasm of epididymal spermatozoa consisting mainly of isolated flattened Golgi cisternae.

OBJECTIVE

To define a functional role for the HB of epididymal spermatozoa.

METHODS

Isolated fractions of HBs of epididymal spermatozoa were prepared and by quantitative tandem mass spectrometry revealed 1511 proteins.

RESULTS

The glucose transporter GLUT-3 was the most abundant protein followed by hexokinase 1, which along with the presence of all glycolytic enzymes suggested a role for the HB in glycolysis. Several TMED/p24 Golgi trafficking proteins were abundant with TMED7/p27 and TMED2/p24 defining the identity of the flattened cisternae within the HB as Golgi, along with the known Golgi proteins, GBF1, GOLPH3, Man2α1, and ManIIX. The Golgi trafficking protein TMED7/p27 via small 50-nm vesicles emanating from the Golgi cisternae was proposed to transport GLUT-3 to the plasma membrane for ATP production related to sperm motility. The internal membranes revealed abundant proteins not only of Golgi cisternae, but also of endoplasmic reticulum and endosomes. COPI and COPII coats, clathrin, SNAREs, annexins, atlastins, and GTPases were identified for vesicular trafficking and membrane fusion, in addition to ribosomes, stress proteins for protection, proteasome proteins involved in degradation, and cytoskeletal elements for migration of the HB along the flagellum. The biogenesis of the HB occurring at step 19 spermatids of the testis just prior to their release was uncovered as a key step in germ cell differentiation, where several proteins were expressed, some for the first time.

CONCLUSION

As epididymal spermatozoa undergo remodeling of their protein makeup through selective degradation of sperm proteins during epididymal transit, then remodeling as a consequence of new protein synthesis is not excluded by our observations.

Intersectin-1 interacts with the golgin GCC88 to couple the actin network and Golgi architecture

The maintenance of the Golgi ribbon relies on a dynamic balance between the actin and microtubule networks; however, the pathways controlling actin networks remain poorly defined. Previously, we showed that the trans-Golgi network (TGN) membrane tether/golgin, GCC88, modulates the Golgi ribbon architecture. Here, we show that dispersal of the Golgi ribbon by GCC88 is dependent on actin and the involvement of nonmuscle myosin IIA. We have identified the long isoform of intersectin-1 (ITSN-1), a guanine nucleotide exchange factor for Cdc42, as a novel Golgi component and an interaction partner of GCC88 responsible for mediating the actin-dependent dispersal of the Golgi ribbon. We show that perturbation of Golgi morphology by changes in membrane flux, mediated by silencing the retromer subunit Vps26, or in a model of neurodegeneration, induced by Tau overexpression, are also dependent on the ITSN-1-GCC88 interaction. Overall, our study reveals a role for a TGN golgin and ITSN-1 in linking to the actin cytoskeleton and regulating the balance between a compact Golgi ribbon and a dispersed Golgi, a pathway with relevance to pathophysiological conditions.

Golgi Structure and Function in Health, Stress, and Diseases

The Golgi apparatus is a central intracellular membrane-bound organelle with key functions in trafficking, processing, and sorting of newly synthesized membrane and secretory proteins and lipids. To best perform these functions, Golgi membranes form a unique stacked structure. The Golgi structure is dynamic but tightly regulated; it undergoes rapid disassembly and reassembly during the cell cycle of mammalian cells and is disrupted under certain stress and pathological conditions. In the past decade, significant amount of effort has been made to reveal the molecular mechanisms that regulate the Golgi membrane architecture and function. Here we review the major discoveries in the mechanisms of Golgi structure formation, regulation, and alteration in relation to its functions in physiological and pathological conditions to further our understanding of Golgi structure and function in health and diseases.

Selected Golgi-Localized Proteins and Carcinogenesis: What Do We Know?

The role of the Golgi apparatus in carcinogenesis still remains unclear. A number of structural and functional cis-, medial-, and trans-Golgi proteins as well as a complexity of metabolic pathways which they mediate may indicate a central role of the Golgi apparatus in the development and progression of cancer. Pleiotropy of cellular function of the Golgi apparatus makes it a "metabolic heart" or a relay station of a cell, which combines multiple signaling pathways involved in carcinogenesis. Therefore, any damage to or structural abnormality of the Golgi apparatus, causing its fragmentation and/or biochemical dysregulation, results in an up- or downregulation of signaling pathways and may in turn promote tumor progression, as well as local nodal and distant metastases. Three alternative or parallel models of spatial and functional Golgi organization within tumor cells were proposed: (1) compacted Golgi structure, (2) normal Golgi structure with its increased activity, and (3) the Golgi fragmentation with ministacks formation. Regardless of the assumed model, the increased activity of oncogenesis initiators and promoters with inhibition of suppressor proteins results in an increased cell motility and migration, increased angiogenesis, significantly activated trafficking kinetics, proliferation, EMT induction, decreased susceptibility to apoptosis-inducing factors, and modulating immune response to tumor cell antigens. Eventually, this will lead to the increased metastatic potential of cancer cells and an increased risk of lymph node and distant metastases. This chapter provided an overview of the current state of knowledge of selected Golgi proteins, their role in cytophysiology as well as potential involvement in tumorigenesis.

GOLPH3: a Golgi phosphatidylinositol(4)phosphate effector that directs vesicle trafficking and drives cancer

GOLPH3 is a peripheral membrane protein localized to the Golgi and its vesicles, but its purpose had been unclear. We found that GOLPH3 binds specifically to the phosphoinositide phosphatidylinositol(4)phosphate [PtdIns(4)P], which functions at the Golgi to promote vesicle exit for trafficking to the plasma membrane. PtdIns(4)P is enriched at the trans-Golgi and so recruits GOLPH3. Here, a GOLPH3 complex is formed when it binds to myosin18A (MYO18A), which binds F-actin. This complex generates a pulling force to extract vesicles from the Golgi; interference with this GOLPH3 complex results in dramatically reduced vesicle trafficking. The GOLPH3 complex has been identified as a driver of cancer in humans, likely through multiple mechanisms that activate secretory trafficking. In this review, we summarize the literature that identifies the nature of the GOLPH3 complex and its role in cancer. We also consider the GOLPH3 complex as a hub with the potential to reveal regulation of the Golgi and suggest the possibility of GOLPH3 complex inhibition as a therapeutic approach in cancer.

The Golgi architecture and cell sensing

An array of signalling molecules are located at the Golgi apparatus, including phosphoinositides, small GTPases, kinases, and phosphatases, which are linked to multiple signalling pathways. Initially considered to be associated predominantly with membrane trafficking, signalling pathways at the Golgi are now recognised to regulate a diverse range of higher-order functions. Many of these signalling pathways are influenced by the architecture of the Golgi. In vertebrate cells, the Golgi consists of individual stacks fused together into a compact ribbon structure and the function of this ribbon structure has been enigmatic. Notably, recent advances have identified a role for the Golgi ribbon in regulation of cellular processes. Fragmentation of the Golgi ribbon results in modulation of many signalling pathways. Various diseases and disorders, including cancer and neurodegeneration, are associated with the loss of the Golgi ribbon and the appearance of a dispersed fragmented Golgi. Here, we review the emerging theme of the Golgi as a cell sensor and highlight the relationship between the morphological status of the Golgi in vertebrate cells and the modulation of signalling networks.

More than just sugars: Conserved oligomeric Golgi complex deficiency causes glycosylation-independent cellular defects

The conserved oligomeric Golgi (COG) complex controls membrane trafficking and ensures Golgi homeostasis by orchestrating retrograde vesicle trafficking within the Golgi. Human COG defects lead to severe multisystemic diseases known as COG-congenital disorders of glycosylation (COG-CDG). To gain better understanding of COG-CDGs, we compared COG knockout cells with cells deficient to 2 key enzymes, Alpha-1,3-mannosyl-glycoprotein 2-beta-N-acetylglucosaminyltransferase and uridine diphosphate-glucose 4-epimerase (GALE), which contribute to proper N- and O-glycosylation. While all knockout cells share similar defects in glycosylation, these defects only account for a small fraction of observed COG knockout phenotypes. Glycosylation deficiencies were not associated with the fragmented Golgi, abnormal endolysosomes, defective sorting and secretion or delayed retrograde trafficking, indicating that these phenotypes are probably not due to hypoglycosylation, but to other specific interactions or roles of the COG complex. Importantly, these COG deficiency specific phenotypes were also apparent in COG7-CDG patient fibroblasts, proving the human disease relevance of our CRISPR knockout findings. The knowledge gained from this study has important implications, both for understanding the physiological role of COG complex in Golgi homeostasis in eukaryotic cells, and for better understanding human diseases associated with COG/Golgi impairment.

The Function of the Golgi Ribbon Structure - An Enduring Mystery Unfolds!

The Golgi apparatus in vertebrate cells consists of individual Golgi stacks fused together in a continuous ribbon structure. The ribbon structure per se is not required to mediate the classical functions of this organelle and the relevance of the "ribbon" structure has been a mystery since first identified ultrastructurally in the 1950s. Recent advances recognize a role for the Golgi apparatus in a range of cellular processes, some mediated by signaling networks which are regulated at the Golgi. Here we review the cellular processes and signaling events regulated by the Golgi apparatus and, in particular, explore an emerging theme that the ribbon structure of the Golgi contributes directly to the regulation of these higher order functions.

STK16 regulates actin dynamics to control Golgi organization and cell cycle

STK16 is a ubiquitously expressed, myristoylated, and palmitoylated serine/threonine protein kinase with underexplored functions. Recently, it was shown to be involved in cell division but the mechanism remains unclear. Here we found that human STK16 localizes to the Golgi complex throughout the cell cycle and plays important roles in Golgi structure regulation. STK16 knockdown or kinase inhibition disrupts actin polymers and causes fragmented Golgi in cells. In vitro assays show that STK16 directly binds to actin and regulates actin dynamics in a concentration- and kinase activity-dependent way. In addition, STK16 knockdown or kinase inhibition not only delays mitotic entry and prolongs mitosis, but also causes prometaphase and cytokinesis arrest. Therefore, we revealed STK16 as a novel actin binding protein that resides in the Golgi, which regulates actin dynamics to control Golgi structure and participate in cell cycle progression.

Emerging themes of regulation at the Golgi

The Golgi is generally recognized for its central role in the secretory pathway to orchestrate protein post-translational modification and trafficking of proteins and lipids to their final destination. Despite the common view of the Golgi as an inert sorting organelle, emerging data demonstrate that important signaling events occur at the Golgi, including those that regulate the trafficking function of the Golgi. The phosphatidylinositol-4-phosphate/GOLPH3/MYO18A/F-actin complex serves as a hub for signals that regulate Golgi trafficking function. Furthermore, the Golgi is increasingly appreciated for its important role in cell growth and in driving oncogenic transformation, as illuminated by the discovery that GOLPH3 and MYO18A are cancer drivers.

The Role of GOLPH3L in the Prognosis and NACT response in Cervical Cancer

Background: We previously reported GOLPH3L is a novel oncogene associated with ovarian cancer. The role of GOLPH3L in cervical cancer and its cellular functions has not been determined. This study investigated clinical significance of GOLPH3L and potential proteins and pathways associated with GOLPH3L in cervical squamous cell carcinoma.

Methods: Immunohistochemistry and western blot were used to examine the expression of GOLPH3L in cervical squamous cell carcinoma tissue specimens and adjacent non-cancerous tissues. The clinical and prognostic significance of GOLPH3L expression was statistically analyzed. Cell proliferation rate, cell cycle progression, apoptosis and cisplatin response in GOLPH3L silenced SiHa and HeLa cells were also examined. Phospho-antibody array was used to identify changes in protein phosphorylation and the corresponding signaling pathways associated with these changes.

Results: GOLPH3L overexpressed in cervical cancer tissue specimens compared with normal adjacent non-cancerous tissues. Increased GOLPH3L expression was associated with FIGO staging (P=0.033), cervical stromal invasion (P=0.037), cervical canal stromal invasion (P=0.027), lymph node metastasis (P=0.016) and positive surgical margins (P=0.015). Patients with lower expression of GOLPH3L demonstrated longer progression-free survival and overall survival compared with those with higher expression. The tissue samples from patients who poorly responded to neoadjuvant chemotherapy (NACT) exhibited increased GOLPH3L expression levels compared with tissue samples from patients who achieved a pathologic complete response (pCR). Patients with lower GOLPH3L expression level, poorer tumor differentiation, shorter NACT treatment intervals and smaller tumor sizes were more likely to achieve a pCR after NACT. Knockdown GOLPH3L in cells was associated with an induction of cell cycle arrest, increased apoptosis and cisplatin sensitivity, and a reduction in cellular viability. Phospho-antibody array suggested GOLPH3L plays a role in mediating cell cycle arrest.

Conclusions: This study provides a potential biomarker for predicting prognosis and NACT response in patients with cervical squamous cell carcinoma. The functional role of GOLPH3L in cervical cancer merits further investigation.

Epithelial-to-mesenchymal transition drives a pro-metastatic Golgi compaction process through scaffolding protein PAQR11

Tumor cells gain metastatic capacity through a Golgi phosphoprotein 3-dependent (GOLPH3-dependent) Golgi membrane dispersal process that drives the budding and transport of secretory vesicles. Whether Golgi dispersal underlies the pro-metastatic vesicular trafficking that is associated with epithelial-to-mesenchymal transition (EMT) remains unclear. Here, we have shown that, rather than causing Golgi dispersal, EMT led to the formation of compact Golgi organelles with improved ribbon linking and cisternal stacking. Ectopic expression of the EMT-activating transcription factor ZEB1 stimulated Golgi compaction and relieved microRNA-mediated repression of the Golgi scaffolding protein PAQR11. Depletion of PAQR11 dispersed Golgi organelles and impaired anterograde vesicle transport to the plasma membrane as well as retrograde vesicle tethering to the Golgi. The N-terminal scaffolding domain of PAQR11 was associated with key regulators of Golgi compaction and vesicle transport in pull-down assays and was required to reconstitute Golgi compaction in PAQR11-deficient tumor cells. Finally, high PAQR11 levels were correlated with EMT and shorter survival in human cancers, and PAQR11 was found to be essential for tumor cell migration and metastasis in EMT-driven lung adenocarcinoma models. We conclude that EMT initiates a PAQR11-mediated Golgi compaction process that drives metastasis.

GOLPH3 drives cell migration by promoting Golgi reorientation and directional trafficking to the leading edge

The GOLPH3 oncogene functions in Golgi trafficking. GOLPH3 promotes cell migration, which is important in cancer. GOLPH3, by linking the Golgi to F-actin, promotes both Golgi reorientation and forward trafficking, which together drive trafficking to the leading edge. These findings provide insight into how GOLPH3 drives cell migration.

The mechanism of directional cell migration remains an important problem, with relevance to cancer invasion and metastasis. GOLPH3 is a common oncogenic driver of human cancers, and is the first oncogene that functions at the Golgi in trafficking to the plasma membrane. Overexpression of GOLPH3 is reported to drive enhanced cell migration. Here we show that the phosphatidylinositol-4-phosphate/GOLPH3/myosin 18A/F-actin pathway that is critical for Golgi–to–plasma membrane trafficking is necessary and limiting for directional cell migration. By linking the Golgi to the actin cytoskeleton, GOLPH3 promotes reorientation of the Golgi toward the leading edge. GOLPH3 also promotes reorientation of lysosomes (but not other organelles) toward the leading edge. However, lysosome function is dispensable for migration and the GOLPH3 dependence of lysosome movement is indirect, via GOLPH3’s effect on the Golgi. By driving reorientation of the Golgi to the leading edge and driving forward trafficking, particularly to the leading edge, overexpression of GOLPH3 drives trafficking to the leading edge of the cell, which is functionally important for directional cell migration. Our identification of a novel pathway for Golgi reorientation controlled by GOLPH3 provides new insight into the mechanism of directional cell migration with important implications for understanding GOLPH3’s role in cancer.