ARTICLE | doi:10.20944/preprints201810.0521.v1
Subject: Medicine And Pharmacology, Gastroenterology And Hepatology Keywords: alcohol-induced Golgi disorganization; Golgi recovery; giantin; hepatic proteins; ethanol withdrawal
Online: 23 October 2018 (06:10:04 CEST)
Background: In hepatocytes and alcohol-metabolizing cultured cells, Golgi undergoes ethanol (EtOH)-induced disorganization. Periniclear and organized Golgi is important in liver homeostasis, but how the Golgi remains intact is unknown. Work from our laboratories showed that EtOH-altered cellular function could be reversed after alcohol removal; we wanted to determine whether this recovery would apply to Golgi. Methods: We used alcohol-metabolizing HepG2 (VA-13) cells (cultured with or without EtOH for 72 h) and rat hepatocytes (control and EtOH-fed (Lieber-DeCarli diet). For recovery, EtOH was removed and replenished with control medium (48 hours for VA-13 cells) or control diet (10 days for rats). Results: EtOH-induced Golgi disassembly was associated with de-dimerization of the largest Golgi matrix protein giantin, along with impaired transport of selected hepatic proteins. After recovery from EtOH, Golgi regained their compact structure, and alterations in giantin and protein transport were restored. In VA-13 cells, when we knocked down giantin, Rab6a GTPase or non-muscle Myosin IIB, minimal changes were observed in control conditions, but post-EtOH recovery was impaired. Conclusions: These data provide a link between Golgi organization and plasma membrane protein expression and identify several proteins whose expression is important to maintain Golgi structure during the recovery phase after EtOH administration.
REVIEW | doi:10.20944/preprints202310.0839.v1
Subject: Biology And Life Sciences, Cell And Developmental Biology Keywords: GOMED; alternative autophagy; Golgi
Online: 13 October 2023 (07:47:25 CEST)
Autophagy is a cellular mechanism that utilizes lysosomes to degrade its own components and is performed using Atg5 and other molecules originating from the endoplasmic reticulum membrane. On the other hand, we identified an alternative type of autophagy, namely, Golgi membrane-associated degradation (GOMED), which also utilizes lysosomes to degrade its own components, but does not use Atg5 originating from the Golgi membranes. The GOMED pathway involves Ulk1, Wipi3, Rab9 and other molecules, and plays crucial roles in a wide range of biological phenomena, such as the regulation of insulin secretion and neuronal maintenance. We here describe the overview of GOMED, the methods to detect autophagy and GOMED, and to distinguish GOMED from autophagy.
REVIEW | doi:10.20944/preprints202007.0601.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: traffic; endocytosis; sorting; Aspergillus nidulans; UapA; Golgi; fungi
Online: 25 July 2020 (11:00:02 CEST)
Eukaryotic plasma membrane (PM) transporters face critical challenges that are not widely present in prokaryotes. The two most important issues are proper subcellular traffic and targeting to the PM, and regulated endocytosis in response to physiological, developmental or stress signals. Sorting of transporters from their site of synthesis, the Endoplasmic Reticulum (ER), to the PM has been long thought, but not formally shown, to occur via the conventional Golgi-dependent vesicular secretory pathway. Endocytosis of specific eukaryotic transporters has been studied more systematically and shown to involve ubiquitination, internalization, and sorting to early endosomes, followed by turnover in the MVB/lysosomes/vacuole system. In specific cases internalized transporters have been shown to recycle back to the PM. However, the mechanisms of transporter forward trafficking and turnover have been overturned recently through systematic work in the model fungus Aspergillus nidulans. In this review we present evidence that shows that transporter traffic to the PM takes place through Golgi-bypass and transporter endocytosis operates via a mechanism that is distinct from that of recycling membrane cargoes essential for fungal growth. We discuss these findings in relation to adaptation to challenges imposed by cell polarity in fungi as well as in other eukaryotes and provide a rationale why transporters and possibly other housekeeping membrane proteins ‘avoid’ routes of polar trafficking.
ARTICLE | doi:10.20944/preprints202306.1295.v1
Subject: Biology And Life Sciences, Neuroscience And Neurology Keywords: CHMP2B; N1E-115 cell; neuronal differentiation; Arf4; Golgi stress.
Online: 19 June 2023 (05:13:12 CEST)
Frontotemporal dementia and/or amyotrophic lateral sclerosis type 7 (FTD/ALS7) is an autosomal dominant neurodegenerative disorder characterized by the onset of ALS and/or FTD mainly in adulthood. Patients with some types of mutations, including the Thr104Asn (T104N) mutation of charged multivesicular body protein 2B (CHMP2B), have predominantly ALS phenotypes, whereas patients with other mutations have predominantly FTD phenotypes. A few patients with further other mutations have both phenotypes approximately equally; however, the reason why phenotypes differ depending on the position of the mutation is unknown. CHMP2B composes one part of the endosomal sorting complexes required for transport (ESCRT), specifically ESCRT-III, in the cytoplasm. We describe here, for the first time, that CHMP2B with the T104N mutation inhibits neuronal process elongation in the N1E-115 cell line, a model of neuronal differentiation. The inhibitory phenotype was accompanied by changes in marker protein expression. It is noteworthy that CHMP2B with the T104N mutation but not its wild-type was preferentially accumulated in the Golgi body. Of the four major Golgi stress signaling pathways currently known, the pathway through Arf4, as the small GTPase, was specifically upregulated in cells expressing CHMP2B with the T104N mutation. Conversely, knockdown of Arf4 with the cognate small interfering (si)RNA recovered the neuronal process elongation inhibited by the T104N mutation. These results suggest that the T104N mutation of CHMP2B inhibits neuronal morphological differentiation by triggering Golgi stress signaling, revealing a possible therapeutic molecular target for recovering potential molecular and cellular phenotypes underlying FTD/ALS7.
Subject: Medicine And Pharmacology, Pathology And Pathobiology Keywords: Epilepsy; Brain damage; Golgi determinations; Ramon y Cajal: axons
Online: 27 March 2020 (12:35:20 CET)
As a medical student (Granada University Medical School, Spain), interested in Pediatrics, expended countless hours at the hospital pediatric facilities and got to know many of the children and their medical problems. A particular case, still vivid on my mind, awaken my scientific curiosity. One day, walking and talking with a seven years old child he unexpectedly felt down unconscious with multiple, incontrollable and erratic muscular contractions involving face, body and extremities and salivating. I was overwhelmed thinking it was the child’ last hour. At the time, my knowledge of epilepsy was nil. Following the seizures, the child was up, talking and walking with me as if nothing has happened and without any knowledge of the event. What could have caused the brain motor cortex to suddenly discharge that amount of altered activity causing generalized and erratic muscular contractions remains inexplicable. I migrated to USA, become a Pediatric (Developmental) Pathologist and Director of the Pediatrics Autopsy Service (1962-1999) at the Dartmouth-Hitchcock Medical Center, New Hampshire. I carried out countless postmortem studied of children brains, normal (unaltered) as well as those altered by hemorrhagic, hypoxic-ischemic and/or traumatic damage. With an NIH Fellowship, I spend one year (1967-68) at the Cajal Institute (Madrid, Spain) studying Cajal’ old Golgi preparations and learning about the method. Some of my Golgi studies of children’ brains have been published: The Human Brain. Prenatal Development and Structure, Springer, Heidelberg, Germany, 2012. The present monograph explores the developmental neuropathology of selected perinatal cortical injuries through their acute, subacute and chronic stages. Including: a) how an altered neuronal activity evolves in a damaged cortical region; b) how it moves through the cortex (epileptic auras); and c) how it reaches the motor cortex to be discharged as erratic and incontrollable muscular contractions. Understanding these processes should provide insights into the pathogenesis of epilepsy secondary to perinatal brain damage.
ARTICLE | doi:10.20944/preprints202308.0324.v1
Subject: Chemistry And Materials Science, Biomaterials Keywords: Golgi apparatus; carbon nanodots; polymer dots; Near infrared fluorescence; High photostability
Online: 4 August 2023 (11:11:48 CEST)
As an important organelle in eukaryotic cells, Golgi apparatus is responsible for processing and transporting proteins and lipids in cells. Precise monitoring the status of Golgi apparatus by targeting fluorescence imaging technology is of enormous importance but remains an attractive yet dramatically challenging task. In this study, we report the construction of the first Golgi apparatus targeted sensor with bright near-infrared fluorescence, termed as Golgi-Pdots. As a start point of our investigation, hydrophobic CDs with bright NIR fluorescence at 674 nm (fluorescence quantum yield : 12.18%), narrow emission band of 23 nm, and excellent stability were facilely prepared from Magnolia Denudata flowers through an ultrasonic method. Incorporating the CDs into a polymer matrix modified with Golgi-targeting molecules can produce the water-soluble Golgi-Pdots, which showed high colloidal stability and similar optical properties as compared to CDs. Further studies revealed that the Golgi-Pdots showed good biocompatibility and Golgi-targeting ability. Based on these fascinating properties, Golgi-Pdots have been successfully used for long term bioimaging of Golgi apparatus inside live cells.
Subject: Biology And Life Sciences, Biophysics Keywords: cytosolic phospholipase A2; electron microscopy; C2 domain; Golgi; membrane bending; membrane curvature; oligomerization
Online: 12 March 2020 (04:10:52 CET)
Group IV phospholipase A2α (cPLA2α) regulates the production of prostaglandins and leukotrienes via the formation of arachidonic acid from membrane phospholipids. The targeting and membrane binding of cPLA2α to the Golgi involves the N-terminal C2 domain whereas the catalytic domain produces arachidonic acid. Although most studies of cPLA2α concern its catalytic activity, it is also linked to homeostatic processes involving the generation of vesicles that traffic material from the Golgi to the plasma membrane. Here we investigate how membrane curvature influences the homeostatic role of cPLA2α in vesicular trafficking. The cPLA2α C2 domain is known to induce changes in positive membrane curvature, a process which is dependent on cPLA2α membrane penetration. We show that cPLA2α undergoes C2 domain-dependent oligomerization on membranes in vitro and in A549 cells. We found that the association of the cPLA2α C2 domain with membranes is limited to membranes with positive curvature, and enhanced C2 domain oligomerization was observed on vesicles ~50 nm in diameter. We demonstrated that the cPLA2α C2 domain generates cholesterol enriched Golgi-derived vesicles independently of cPLA2α catalytic activity. Our results therefore provide novel insight into the molecular forces that mediate C2 domain-dependent membrane localization in vitro and in cells.
ARTICLE | doi:10.20944/preprints201908.0027.v1
Subject: Biology And Life Sciences, Plant Sciences Keywords: plant specific insert; aspartic proteinase; vacuolar sorting; unconventional trafficking; endoplasmic reticulum; Golgi, N-linked glycosylation
Online: 2 August 2019 (10:05:06 CEST)
In plant cells the conventional route to the vacuole involves the endoplasmic reticulum, the Golgi and the prevacuolar compartment. However, over the years, unconventional sorting to the vacuole, bypassing the Golgi, has been described, which is the case of the Plant Specific Insert (PSI) of the aspartic proteinase cardosin A. Interestingly, this Golgi-bypass ability is not a characteristic shared by all PSIs, since two related PSIs showed to have different sensitivity to ER-to-Golgi blockage. Given the high sequence similarity between the PSIs domains, we sought to depict the differences in terms of post-translational modifications. In fact, one feature that draws our attention is that one is N-glycosylated and the other one is not. Using site-directed mutagenesis to obtain mutated versions of the two PSIs, with and without the glycosylation motif, we observed that altering the glycosylation pattern interferes with the trafficking of the protein as the non-glycosylated PSI-B, unlike its native glycosylated form, is able to bypass ER-to-Golgi blockage and accumulate in the vacuole. This is also true when the PSI domain is analyzed in the context of the full-length cardosin. Regardless of opening exciting research gaps, the results obtained so far need a more comprehensive study of the mechanisms behind this unconventional direct sorting to the vacuole.
REVIEW | doi:10.20944/preprints202308.1053.v1
Subject: Biology And Life Sciences, Neuroscience And Neurology Keywords: axons; nerves; plasma membrane; endoplasmic reticulum; Golgi apparatus; mitochondria; crayfish; gap junctions; sulfhydryl groups; electrical stimulation; asphyxia
Online: 14 August 2023 (15:19:49 CEST)
This review describes and discusses unusual axonal structural details and evidence for unmasking of sulfhydryl groups (-SH) in axoplasmic membranes resulting from electrical stimulation or asphyxia. Crayfish axons contain fenestrated septa (FS) that in phase contrast micrographs appear as repeated striations. In the electron microscope each septum is made of two cross-sectioned membranes containing ~550 Å pores, each occupied by a microtubule. Thin filaments, likely to be made of kinesin, bridge the microtubule to the edge of the pore. FS are believed to play a role in axoplasmic flow. The axons also display areas in which axon and sheath-glial cell plasma membranes are sharply curved and project into the axoplasm. In freeze-fractures, the protoplasmic leaflet (P-face) of the projections appears as elongated indentations containing parallel chains of particles. The sheath-glial cell plasma membrane also contains particles, but they are irregularly aggregated. The axons also display areas where axonal and glial plasma membranes fuse, creating intercellular pores. In axons fixed during electrical stimulation the plasma membrane, the outer membrane of mitochondria, membranes of other cytoplasmic organelles and gap junctions increase in electron opacity and thickness, resulting from unmasking of sulfhydryl groups (-SH). Similar changes occur in asphyxiated nerve cords.
COMMUNICATION | doi:10.20944/preprints202210.0383.v2
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: structural biology; organelles; Golgi Apparatus (GA); Parkinson’s disease (PD); cryo-ET; alpha-synuclein; neurodegenerative diseases; soft X-ray tomography (SXT); cancer; NDDs
Online: 5 December 2022 (02:27:26 CET)
The Golgi apparatus (GA) dysfunctions in Parkinson’s Disease (PD), neurodevelopmental disorders (NDDs), cancer, and organelle structural biology (OSB) can provide insights into therapeutic targets, gene therapy, and drug design. Primary defects and fragmentation within the GA are implicated in a wide range of neurodegenerative diseases. GA defects typically result in mislocation of proteins, accumulation of undegraded proteins, and impaired glycosylation of proteins. Inhibition of vesicular trafficking by α-synuclein (aSyn) may affect the dopamine-producing neurons and neuromodulators. GA regulates apoptosis during pathological mechanisms of neurological diseases and could provide new avenues in treatments through translation research. PD patients bearing the hereditary E46K disease mutation manifest the clinical picture of parkinsonism. How do we provide high resolution nanoimages of the GA during disease to capture dysfunction? Could we visualize the aSyn traffic jam between vesicles in the organelles ER and GA? OSB is emerging as a field as more technology advances and is more accessible. Structural studies of the GA will advance the field of neurological disease forward with an in depth understanding of dysfunction, fragmentation, and defects. Discoveries of the GA in PD, NDDs, and cancer would break new ground and provide translational medicine data of these diseases. Future research could be visualizing high angle annular dark field-STEM (HAADF-STEM) tomograms, cryogenic electron tomography (cryo-ET), multiplex correlative light and electron microscopy (cryo-CLEM), nanobody-assisted tissue immunostaining for volumetric EM (NATIVE) and using soft X-ray tomography (SXT) and computational reconstruction of the GA.