Supply chain logistics – the role of the Golgi complex in extracellular matrix production and maintenance

ABSTRACT The biomechanical and biochemical properties of connective tissues are determined by the composition and quality of their extracellular matrix. This, in turn, is highly dependent on the function and organisation of the secretory pathway. The Golgi complex plays a vital role in directing matrix output by co-ordinating the post-translational modification and proteolytic processing of matrix components prior to their secretion. These modifications have broad impacts on the secretion and subsequent assembly of matrix components, as well as their function in the extracellular environment. In this Review, we highlight the role of the Golgi in the formation of an adaptable, healthy matrix, with a focus on proteoglycan and procollagen secretion as example cargoes. We then discuss the impact of Golgi dysfunction on connective tissue in the context of human disease and ageing.

The cellular characterisation of SARS-CoV-2 spike protein in virus-infected cells using Receptor Binding Domain-binding specific human monoclonal antibodies.

A human monoclonal antibody panel (PD4, PD5, PD7, SC23 and SC29) was isolated from the B cells of convalescent patients and used to examine the S protein in SARS-CoV-2-infected cells. While all five antibodies bound conformational-specific epitopes within SARS-CoV-2 Spike (S) protein, only PD5, PD7, and SC23 were able to bind to the Receptor Binding Domain (RBD). Immunofluorescence microscopy was used to examine the S protein RBD in cells infected with the Singapore isolates SARS-CoV-2/0334 and SARS-CoV-2/1302. The RBD-binders exhibited a distinct cytoplasmic staining pattern that was primarily localised within the Golgi complex and was distinct from the diffuse cytoplasmic staining pattern exhibited by the non-RBD binders (PD4 and SC29). These data indicated that the S protein adopted a conformation in the Golgi complex that enabled the RBD recognition by the RBD-binders. The RBD-binders also recognised the uncleaved S protein indicating that S protein cleavage was not required for RBD recognition. Electron microscopy indicated high levels of cell-associated virus particles, and multiple cycle virus infection using RBD-binder staining provided evidence for direct cell-to-cell transmission for both isolates. Although similar levels of RBD-binder staining was demonstrated for each isolate, the SARS-CoV-2/1302 exhibited slower rates of cell-to-cell transmission. These data suggest that a conformational change in the S protein occurs during its transit through the Golgi complex that enables RBD recognition by the RBD-binders, and suggests that these antibodies can be used to monitor S protein RBD formation during the early stages of infection.

Flavivirus infections induce a Golgi stress response in vertebrate and mosquito cells

The stress of the Golgi apparatus is an autoregulatory mechanism that is induced to compensate for greater demand in the Golgi functions. No examples of Golgi stress responses due to physiological stimuli are known. Furthermore, the impact on this organelle of viral infections that occupy the vesicular transport during replication is unknown. In this work, we evaluated if a Golgi stress response is triggered during dengue and Zika viruses replication, two flaviviruses whose replicative cycle is heavily involved with the Golgi complex, in vertebrate and mosquito cells. Using GM-130 as a Golgi marker, and treatment with monensin as a positive control for the induction of the Golgi stress response, a significant expansion of the Golgi cisternae was observed in BHK-21, Vero E6 and mosquito cells infected with either virus. Activation of the TFE3 pathway was observed in the infected cells as indicated by the translocation from the cytoplasm to the nucleus of TFE3 and increased expression of pathway targeted genes. Of note, no sign of activation of the stress response was observed in CRFK cells infected with Feline Calicivirus (FCV), a virus released by cell lysis, not requiring vesicular transport. Finally, dilatation of the Golgi complex and translocation of TFE3 was observed in vertebrate cells expressing dengue and Zika viruses NS1, but not NS3. These results indicated that infections by dengue and Zika viruses induce a Golgi stress response in vertebrate and mosquito cells due to the increased demand on the Golgi complex imposed by virion and NS1 processing and secretion.

BIOLOGICAL PECULIARITIES OF ADIPOSE TISSUE-DERIVED MESENCHYMAL STEM CELLS AT DIFFERENT PASSAGES OF CULTIVATION

The studies were conducted on 2–3-months-old males of C57BL/6 mice weighing 20–24 g. Obtaining and operating with adipose tissue-derived mesenchymal stem cell (MSC) culture was performed in a sterile laminar box under conditions of asepsis and antiseptics. The adipose tissue-derived MSC of the 2, 4, 7 and 12 passages were analyzed. Morphometric analysis was performed using a light microscopy. Morphometric parameters such as cell and nucleus area or nuclear-cytoplasmic ratio were calculated using the Axiovision light microscope (Carl Zeiss, Germany) and Image J 1.45 software. Trypan blue dye used for investigation of the viability of MSC. The morphological characteristics of adipose tissue-derived MSC during the process of cultivation changes: at the first passages of cultivation, the cells are spindle-shaped with two, at least three, long cytoplasmic processes, which are located bipolar. Near the nucleus, the Golgi complex is clearly visible – a sign of active cells. At later passages, cells have a small cytoplasmic processes and the bipolar arrangement of processes changes by stellar arrangement. Golgi complex is also clearly visualized. The indicator of the nuclear-cytoplasmic ratio in MSC from adipose tissue is significantly reduced at the 7th passage to 0.2189 ± 0.0122 (P < 0.01), and at the 12th passage to 0.1111 ± 0.0086 (P < 0.001) compared to the 2nd passage. The coefficient of proliferation of adipose tissue-derived MSC is significantly reduced at 12th passage. The viability of MSC from adipose tissue with an increasing of a number of passages significantly reduces and at the 12th passage of cultivation reaches 84.67 ± 1.36 (P < 0.05). The content of apoptotic cells that exhibited sensitivity to serum-free cultivation significantly increased at the 7th and 12th passages and was 21.33 ± 1.36 (P < 0.05) and 23.67 ± 0.97% (P < 0.05), respectively.

The Spliced Leader RNA Silencing (SLS) Pathway in Trypanosoma brucei Is Induced by Perturbations of Endoplasmic Reticulum, Golgi Complex, or Mitochondrial Protein Factors: Functional Analysis of SLS-Inducing Kinase PK3

In this study, we found that SLS is induced by depletion of the essential ER-resident chaperones BiP and calreticulin, ER oxidoreductin 1 (ERO1), and the Golgi complex-localized quiescin sulfhydryl oxidase (QSOX). Most strikingly, silencing of Rhomboid-like 1 (TIMRHOM1), involved in mitochondrial protein import, also induces SLS.

WFS1 functions in ER export of vesicular cargo proteins in pancreatic β-cells

The sorting of soluble secretory proteins from the endoplasmic reticulum (ER) to the Golgi complex is mediated by coat protein complex II (COPII) vesicles and thought to required specific ER membrane cargo-receptor proteins. However, these receptors remain largely unknown. Herein, we show that ER to Golgi transfer of vesicular cargo proteins requires WFS1, an ER-associated membrane protein whose loss of function leads to Wolfram syndrome. Mechanistically, WFS1 directly binds to vesicular cargo proteins including proinsulin via its ER luminal C-terminal segment, whereas pathogenic mutations within this region disrupt the interaction. The specific ER export signal encoded in the cytosolic N-terminal segment of WFS1 is recognized by the COPII subunit SEC24, generating mature COPII vesicles that traffic to the Golgi complex. WFS1 deficiency leads to abnormal accumulation of proinsulin in the ER, impeding the proinsulin processing as well as insulin secretion. This work identifies a vesicular cargo receptor for ER export and suggests that impaired peptide hormone transport underlies diabetes resulting from pathogenic WFS1 mutations.

Ubiquitination drives COPI priming and Golgi SNARE localization

Deciphering mechanisms controlling SNARE localization within the Golgi complex is crucial to understanding protein trafficking patterns within the secretory pathway. SNAREs are also thought to prime COPI assembly to ensure incorporation of these essential cargoes into vesicles but the regulation of these events is poorly understood. Here we report roles for ubiquitin recognition by COPI in SNARE trafficking and in stabilizing interactions between Arf, COPI, and Golgi SNAREs. The ability of COPI to bind ubiquitin through its N-terminal WD repeat domain of β′COP or through an unrelated ubiquitin-binding domain (UBD) is essential for the proper localization of Golgi SNAREs Bet1 and Gos1. We find that COPI, the ArfGAP Glo3, and multiple Golgi SNAREs are ubiquitinated. Notably, the binding of Arf and COPI to Gos1 is markedly enhanced by ubiquitination of these components. Glo3 is thought to prime COPI-SNARE interactions; however, Glo3 is not enriched in the ubiquitin-stabilized SNARE-Arf-COPI complex but is instead enriched with COPI complexes that lack SNAREs. These results support a new model for how posttranslational modifications drive COPI priming events crucial for Golgi SNARE localization.

Clinical and genetic parallels in congenital brain lesions without epilepsy

Background. The problem of preventing the development of gross congenital brain lesions and their successful treatment is more than relevant now. It is known that approximately in every third case of the development of congenital cerebral palsy (CP), it is impossible to identify the main pathogenetic factor. This determines the activity of the search for gene mechanisms for the formation of this phenotype. G. McMichael et al. were among the first to identify the most relevant directions of the influence of genes on the formation of the CP phenotype.Objective: to study the influence of gene determinants on the formation of the phenotype of CP, which is not accompanied by epilepsy.Materials and methods. Gene abnormalities in 18 patients with CP were divided into groups of determinable physiological processes. Genetic mutations were confirmed by next generation sequencing (NGS) and Sanger trio methods. For the study, samples of the patients' venous blood were taken.Results and discussion. The analysis showed that genes from different groups by determinants are to varying degrees associated with the formation of the CP phenotype. The “map of determinants” in the pathogenesis of CP is specific. The pathogenesis involves genetically determined disorders of cell division and neuroontogenesis (neuronal migration, sprouting, myelination, partly apoptosis), cell metabolism, including those whose disturbance leads to the formation of storage diseases, transmembrane transport, the exchange of neurotransmitters and the functioning of synapses, the formation of and the functioning of the cytoskeleton, as well as the regulation of immunity and oncogenesis. Malformations of the brain are more often associated with determinants of the regulation of the formation and functioning of the cytoskeleton, neuroontogenesis, as well as the processes of cell division (chromatin modification, transcription, replication). The pathogenesis of congenital cerebral palsy does not involve (according to our data) the determinants of canalopathy, energy supply of the cell, intracellular synthesis with the Golgi complex, and ribosomal synthesis.Conclusions. Genetically determined CP is a universal phenotype that implements the multidirectional effect of the genome. The influence of the genome does not apply to the energy supply of the cell, ribosomal synthesis and the functioning of the Golgi complex. In the absence of epilepsy in the phenotype, there is no influence of the genes of canalopathies.