Camillo Golgi and the discovery of the Golgi apparatus

 Camillo Golgi (1843–1926) was born at Corteno, near Brescia, in northern Italy. After graduating in Medicine at the ancient University of Pavia, the former seat of great scientists and naturalists, Golgi continued a long-standing Italian tradition by studying the histology of the nervous system. While working as a modest physician at Abbiategrasso, a small town near Pavia, he developed a silver–osmium technique, the ”reazione nera” (black reaction), for which he was awarded the Nobel Prize in 1906. In the late 1890’s, 25 years after the publication of his black reaction and while Professor of General Pathology in Pavia, Golgi noticed a fine internal network in only partially silver-osmium-blackened Purkinje cells. Following confirmation by his assistant Emilio Veratti, Golgi published the discovery, called the ”apparato reticolare interno”, in the Bollettino della Società medico-chirurgica di Pavia in 1898, which is now considered the birthday of the ”Golgi apparatus”. The discovery of the Golgi apparatus can be added to the long list of accidental discoveries. The man after whom it is named was not a cytologist engaged in studying the inner structure of the cell, but a pathologist searching to prove a neuroanatomical theory. Accepted: 24 October 1997     

The Golgi silver impregnation method: commemorating the centennial of the Nobel Prize in medicine (1906) shared by Camillo Golgi and Santiago Ramón y Cajal

The Golgi silver impregnation technique is a simple histological procedure that reveals complete three-dimensional neuron morphology. This method is based in the formation of opaque intracellular deposits of silver chromate obtained by the reaction between potassium dichromate and silver nitrate (black reaction). Camillo Golgi, its discoverer, and Santiago Ramón y Cajal its main exponent, shared the Nobel Prize of Medicine and Physiology in 1906 for their contribution to the knowledge of the nervous system structure, Their successes were largely due to the application of the silver impregnation method. However, Golgi and Cajal had different views on the structure of nervous tissue. According to the Reticular Theory, defended by Golgi, the nervous system was formed by a network of cells connected via axons within a syncytium. In contrast, Cajal defended the Neuron Doctrine which maintained that the neurons were independent cells. In addition, Golgi had used a variant of his "black reaction" to discover the cellular organelle that became known as the Golgi apparatus. Electron microscopy studies confirmed the postulates of the Neuron Doctrine as well as the existence of the Golgi complex and contributed to a resurgence of use of the Golgi stain. Although modern methods of intracellular staining reveal excellent images of neuron morphology, the Golgi technique is an easier and less expensive method for the study of normal and pathological morphology of neurons.     

Gut thoughts on the Golgi complex

The new millennium coincides within 1 year of Camillo Golgi's centennial celebrations. It is quite remarkable that the structure and formation of this organelle is as controversial today as was its mere existence from Golgi's time to the 1950s, when EM approaches were introduced. Since the late 1950s, two opposing models of Golgi structure and function have split the Golgi scientific community, namely vesicular transport versus organelle maturation. Although a few years ago Golgi maturation seemed to be 'out for the count', it has recently seen an almost messianic revival. In this review, I argue that this large-scale desertion from the vesicle transport model to the maturation camp is premature. I propose an alternative, dynamic steady-state model, in which transient tubular connections function in parallel to vesicular transport and that the biosynthetic pathway is made up of three major distinct compartments: the ER, the Golgi and the TGN.     

Deciphering the Golgi apparatus: from imaging to genes

The Golgi apparatus is a vital organelle in eukaryotic cells. It grabs and processes secretory materials synthesized by the endoplasmic reticulum (ER) before sorting them to their destination. The Golgi also receives materials from vacuoles/lysosomes and the plasma membrane for further recycling to other compartments within the cell (1) (Figure 1). Given the vital role of the Golgi in a cell, it is important to understand how this organelle attains and maintains its structural and functional integrity during the intense processes of membrane traffic. Despite an equally central role of the Golgi in membrane traffic in eukaryotes, the organization of this organelle has some unique features in each cell system. Therefore, the wealth of information available on the structure and activity of the Golgi in one system is not always directly transferable to others. However, certain morphological and functional aspects are common among cell systems. Therefore, studying the factors that regulate organelle biogenesis and organization of the Golgi apparatus is important in basic cell biology of eukaryotes and may also contribute to a better understanding of how different cell systems have evolved. In this study, we report on the identification of Golgi mutants in plant cells. We have developed a screen that is a promising strategy not only for the identification of genes responsible for the morphological and functional integrity of the plant Golgi but could also provide fundamental information on other multicellular systems for which the power of forward genetics cannot be exploited as easily as in Arabidopsis.     

Golgi apparatus buds — vesicles or coated ends of tubules?

Summary Based on cell-free processing whereby membrane glycoproteins from one cell type were processed by enzymes located in Golgi apparatus from another cell type, J. Rothman and colleagues postulated that vesicles budding from one Golgi apparatus stack migrated to and fused with cisternal membranes of other Golgi apparatus stacks in the cell-free milieu. An extension of this hypothesis was that these same or similar vesicles were involved in the trafficking of membrane material from one cisterna to the next even in the same Golgi apparatus stack [W. G. Dunphy, J. E. Rothman: Compartmental organization of the Golgi stack. Cell 42: 13–21 (1985)]. A coated bud revealed by tannic acid-containing fixatives was the morphological entity associated with this intercompartment Golgi apparatus transfer. This report summarizes information from the author's laboratories that suggests that perhaps the majority of these coated buds, while associated with the Golgi apparatus, are not vesicles per se but rather coated ends of tubules. Golgi apparatus tubules have been postulated to permit interconnections among adjacent Golgi apparatus stacks but not to function in transport between contiguous cisternae of the same Golgi apparatus stack.In the interest of scientific discourse, reasoned and constructive replies to views expressed under New Ideas in Cell Biology will be considered for publication. In this case, the responsible editor, to be contacted by respondents, is E. Schnepf.     

Maintenance of Golgi structure and function depends on the integrity of ER export.

The Golgi apparatus comprises an enormous array of components that generate its unique architecture and function within cells. Here, we use quantitative fluorescence imaging techniques and ultrastructural analysis to address whether the Golgi apparatus is a steady-state or a stable organelle. We found that all classes of Golgi components are dynamically associated with this organelle, contrary to the prediction of the stable organelle model. Enzymes and recycling components are continuously exiting and reentering the Golgi apparatus by membrane trafficking pathways to and from the ER, whereas Golgi matrix proteins and coatomer undergo constant, rapid exchange between membrane and cytoplasm. When ER to Golgi transport is inhibited without disrupting COPII-dependent ER export machinery (by brefeldin A treatment or expression of Arf1[T31N]), the Golgi structure disassembles, leaving no residual Golgi membranes. Rather, all Golgi components redistribute into the ER, the cytoplasm, or to ER exit sites still active for recruitment of selective membrane-bound and peripherally associated cargos. A similar phenomenon is induced by the constitutively active Sar1[H79G] mutant, which has the additional effect of causing COPII-associated membranes to cluster to a juxtanuclear region. In cells expressing Sar1[T39N], a constitutively inactive form of Sar1 that completely disrupts ER exit sites, Golgi glycosylation enzymes, matrix, and itinerant proteins all redistribute to the ER. These results argue against the hypothesis that the Golgi apparatus contains stable components that can serve as a template for its biogenesis. Instead, they suggest that the Golgi complex is a dynamic, steady-state system, whose membranes can be nucleated and are maintained by the activities of the Sar1-COPII and Arf1-coatomer systems.     

GRASP55 regulates intra‐Golgi localization of glycosylation enzymes to control glycosphingolipid biosynthesis

The Golgi apparatus, the main glycosylation station of the cell, consists of a stack of discontinuous cisternae. Glycosylation enzymes are usually concentrated in one or two specific cisternae along the cis‐trans axis of the organelle. How such compartmentalized localization of enzymes is achieved and how it contributes to glycosylation are not clear. Here, we show that the Golgi matrix protein GRASP55 directs the compartmentalized localization of key enzymes involved in glycosphingolipid (GSL) biosynthesis. GRASP55 binds to these enzymes and prevents their entry into COPI‐based retrograde transport vesicles, thus concentrating them in the trans‐Golgi. In genome‐edited cells lacking GRASP55, or in cells expressing mutant enzymes without GRASP55 binding sites, these enzymes relocate to the cis‐Golgi, which affects glycosphingolipid biosynthesis by changing flux across metabolic branch points. These findings reveal a mechanism by which a matrix protein regulates polarized localization of glycosylation enzymes in the Golgi and controls competition in glycan biosynthesis.     

1998: The centenary of the discovery of the Golgi apparatus

1998 is the year of the centenary of the discovery of the Golgi apparatus. This event is considered in its historical context: the first cell theory of 1838–1839, the first polemics in cytology and the research on the cell organelles at the turn of the century. The first approaches to clarify the physiological significance of the apparatus is traced from Golgi (1909) to Bowen (1929).     

蛋白的高尔基体定位

高尔基体既是蛋白质修饰、分选、水解加工的场所,又是分泌物质的转运站,每时每刻都有大量的蛋白进出高尔基体。在这种情况下,高尔基体仍能保持完整且高度有序的结构,表明高尔基体驻留蛋白有精确的定位信号,以保证它们定位于正确的区隔,而不会沿着分泌途径被运输出去。高尔基体内有几种不同类别的膜蛋白,包括糖基转移酶、周缘膜蛋白、病毒蛋白和受体等。研究显示,有多种定位信号和定位机制参与了蛋白的高尔基体定位。     

Low temperature compartment formation in feline immunodeficiency virus-infected and uninfected feline kidney cells

Summary This study was to determine if feline immunodeficiency virus (FIV)-infected and uninfected Crandall feline kidney (CRFK) cells exhibited a low temperature (16°C) block in membrane trafficking between transitional endoplasmic reticulum and Golgi apparatus represented by intermediate compartment formation. Cells were cultured at different temperatures and membrane changes involving the Golgi apparatus and Golgi apparatus-associated membrane structures were monitored by electron microscopy and quantitated. With 30 min of incubation, membranes of the Golgi apparatus stack increased in amount at temperatures of 16°C and below compared to temperatures above 18°C. The increase was greatest along the major polarity axis as evidenced by an increased stack height. Neither the number of cisternae per stack nor the average stack diameter (width) was affected by temperature. The response was maximal between 15 and 30 min of low temperature treatment of the cells. Results with cells infected and uninfected with feline immunodeficiency virus were similar. The increase in stack height was due primarily to an increase of membranes at the cis face (cis Golgi apparatus network). At 18°C, membranes of the trans Golgi apparatus network accumulated suggesting that import from the cis Golgi network could proceed at this temperature, whereas exit from the trans Golgi network was still at least partially blocked. Also increased at 16°C and below were numbers of transition vesicles in the space between the Golgi apparatus and the transitional endoplasmic reticulum associated with the cis Golgi apparatus face. The results suggested interruption of the orderly flux of membranes into the Golgi apparatus at 16°C and below. Moreover, the block appeared to be reversible. Upon transfer from 16°C to 37°C, there was a time-dependent decrease in the accumulations of cis compartment membrane accompanied by a corresponding equivalent increase in the membranes of the trans Golgi apparatus compartment.     

The centrosome–Golgi apparatus nexus

A shared feature among all microtubule (MT)-dependent processes is the requirement for MTs to be organized in arrays of defined geometry. At a fundamental level, this is achieved by precisely controlling the timing and localization of the nucleation events that give rise to new MTs. To this end, MT nucleation is restricted to specific subcellular sites called MT-organizing centres. The primary MT-organizing centre in proliferating animal cells is the centrosome. However, the discovery of MT nucleation capacity of the Golgi apparatus (GA) has substantially changed our understanding of MT network organization in interphase cells. Interestingly, MT nucleation at the Golgi apparently relies on multiprotein complexes, similar to those present at the centrosome, that assemble at the cis-face of the organelle. In this process, AKAP450 plays a central role, acting as a scaffold to recruit other centrosomal proteins important for MT generation. MT arrays derived from either the centrosome or the GA differ in their geometry, probably reflecting their different, yet complementary, functions. Here, I review our current understanding of the molecular mechanisms involved in MT nucleation at the GA and how Golgi- and centrosome-based MT arrays work in concert to ensure the formation of a pericentrosomal polarized continuous Golgi ribbon structure, a critical feature for cell polarity in mammalian cells. In addition, I comment on the important role of the Golgi-nucleated MTs in organizing specialized MT arrays that serve specific functions in terminally differentiated cells.     

Adelchi Negri and Schools of General Pathology in Italy between the end of the nineteenth and beginning of the twentieth century

The long lasting scientific collaboration of Adelchi Negri with Camillo Golgi in the Laboratory of General Pathology and Histology of Pavia began in 1898–99, when he was still a medical student, and at about the time basic knowledge about human malaria transmission cycle (to which Golgi himself had given important contributions) was completed. On the occasion of the 100^th anniversary of the discovery of Negri bodies, this article provides a short overview of the scientific and cultural context in whichNeurocytes hydrophobiae hypothesis matured. To the same intent and purposes, this article also delineates some of the important scientific achievements in the field of General Pathology by Negri’s contemporaries, reflecting both the influence of the two great pioneers in the field (Bizzozero and Golgi), and the close contact with European science in the 1890’s to the end of the first World War, when biological science in Italy entered a new crisis.

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Adelchi Negri e le Scuole di Patologia generale nel passaggio dall’Ottocento al Novecento

Riassunto  La lunga collaborazione scientifica di Adelchi Negri con Camillo Golgi, nel Laboratorio di Patologia generale ed Istologia di Pavia, ebbe inizio nel 1898–99, quando questi era ancora studente di Medicina, e la conoscenza di base sul ciclo di trasmissione della malaria nell’uomo (alla quale lo stesso Golgi aveva dato importanti contributi in studi pionieristici) era completata. In occasione del Centenario della scoperta dei Corpi del Negri, questo articolo offre una rassegna sintetica del contesto scientifico-culturale in cui maturò l’ipotesi delNeurocytes hydrophobiae come agente causale della rabbia. Con questo intento e per lo stesso scopo, questo articolo traccia anche alcuni degli importanti raggiungimenti scientifici nel campo della Patologia generale da parte dei contemporanei di Negri, nei quali è rinvenibile, sia l’influenza dei grandi pionieri della disciplina (Bizzozero e Golgi), sia lo stretto contatto con la scienza europea, tra il 1890 circa e la fine della prima guerra mondiale, allorché la scienza biologica italiana entrò in una nuova crisi.

     

Studies on the submicrosomal fractions of bovine oligodendroglia: Lipid composition and glycolipid biosynthesis

Oligodendroglia were isolated from bovine brain, and a crude, microsomal fraction obtained from cell homogenates was subfractionated into myelin (MP), plasma membranes (PM), Golgi (GF), smooth (SER) and rough (RER) endoplasmic membranes using discontinuous-sucrose gradient centrifugation. The submicrosomal fractions were characterized by ultrastructural examination and analysis of the specific organelle markers. The myelin and plasma membrane rich fractions contained characteristically the highest amounts of the lipid with lower mole percentages of total phospholipids and phosphatidylcholine, and higher concentrations of phosphatidylethanolamine (+plasmalogens), cholesterol and galactolipids. Considerable amounts of the typical myelin galactolipids (galacto-cerebrosides, sulfatides and monogalactosyl diglycerides) were also found in the Golgi fraction (GF). The GF fraction had the greatest enrichment of glycolipid-forming galactosyltransferases, and the distribution of these enzymes correlated well with that of the Golgi marker enzymes. The results give evidence that intracellular Golgi apparatus of oligodendroglia is rich in the myelin-specific lipids, and suggest its involvement in the synthesis and processing of myelin lipids.     

BFA‐induced compartments from the Golgi apparatus and trans‐Golgi network/early endosome are distinct in plant cells

Brefeldin A (BFA) is a useful tool for studying protein trafficking and identifying organelles in the plant secretory and endocytic pathways. At low concentrations (5–10 μg ml^?1), BFA caused both the Golgi apparatus and trans‐Golgi network (TGN), an early endosome (EE) equivalent in plant cells, to form visible aggregates in transgenic tobacco BY‐2 cells. Here we show that these BFA‐induced aggregates from the Golgi apparatus and TGN are morphologically and functionally distinct in plant cells. Confocal immunofluorescent and immunogold electron microscope (EM) studies demonstrated that BFA‐induced Golgi‐ and TGN‐derived aggregates are physically distinct from each other. In addition, the internalized endosomal marker FM4‐64 co‐localized with the TGN‐derived aggregates but not with the Golgi aggregates. In the presence of the endocytosis inhibitor tyrphostin A23, which acts in a dose‐ and time‐dependent manner, SCAMP1 (secretory carrier membrane protein 1) and FM4‐64 are mostly excluded from the SYP61‐positive BFA‐induced TGN aggregates, indicating that homotypic fusion of the TGN rather than de novo endocytic trafficking is important for the formation of TGN/EE‐derived BFA‐induced aggregates. As the TGN also serves as an EE, continuously receiving materials from the plasma membrane, our data support the notion that the secretory Golgi organelle is distinct from the endocytic TGN/EE in terms of its response to BFA treatment in plant cells. Thus, the Golgi and TGN are probably functionally distinct organelles in plants.     

Cytochemical studies on the internal polarity of the golgi apparatus and the relationship between this organelle and GERL

Summary Cytochemical studies were performed to clarify the occurrence of an internal polarity of the Golgi apparatus and the relationship between this organelle and GERL in many kinds of cells having different morphologies and functions. The fine structural localizations of thiamine pyrophosphatase (TPPase) and acid phosphatase (AcPase) were examined in anterior pituitary cells, thyroid epithelial cells, gastric chief and parietal cells, duodenal absorptive epithelial cells, hepatocytes, adrenal cortical and medullary cells of mice, and thyroid epithelial cells of domestic fowls. TPPase activity is usually localized in the cisternae of 1–3 stacks and vesicles on the trans-side of the Golgi apparatus of all the cells examined, and in some immature secretory granules of anterior pituitary cells and of gastric chief cells. Rigid lamellae and multivesicular bodies are rarely positive to this reaction, in several kinds of cells. AcPase activity was usually demonstrable in the cisternae of 1–3 stacks and vesicles on the trans-side of the Golgi apparatus, and also in rigid lamellae, coated vesicles, multivesicular bodies and lysosomes in all varieties of cells studied. Some immature secretory granules are positive to the AcPase reaction in anterior pituitary cells and gastric chief cells. The areas positive for both enzyme activities were partially or almost completely overlapping in all the cells examined, though there were minor variations among them. The grades of overlap are classified into three types. Prolonged osmication was performed on thyroid epithelial cells, duodenal absorptive epithelial cells, hepatocytes, adrenal cortical cells, Leydig cells, the epithelial cells of the vas deferens and the theca cells of mice. Cisternae of 1–3 stacks on the cis-side of the Golgi apparatus of all the cells examined were stained with osmium tetroxide. In all these cells we observed that the Golgi apparatus has an internal polarity and that GERL is a part of this organelle in cytochemical respects.This study was supported by grants from the Japan Ministry of Education     

The Golgi apparatus in parasitic protists

This review summarizes the current reports on the Golgi apparatus of parasitic protists. Numerous recent publications have demonstrated that studies on intracellular traffic in parasites essentially advanced our knowledge on the Golgi structure and function, which has been traditionally based on research on yeast and mammalian cultured cells. It has been reported that the parasitic lifestyle determines the functional and structural peculiarities of the secretory systems in unrelated groups of unicellular parasites that make them different from those in mammalian and yeast cells. This review covers the best-studied protists, predominantly those of high medical importance, belonging to the following taxa: Parabasalia (Trichomonas), Diplomonada (Giardia), Entamoebidae (Entamoeba), parasitic Alveolata of the phyllum Apicomplexa (Toxoplasma, Plasmodium), and Kinetoplastida (Trypanosoma, Leishmania). The morphology of the Golgi organelle in eukaryotes from various taxonomic groups has been compared. Within three of the six highest taxa of Eukaryota (Adl et al., 2005) a minimum of eight groups are represented by species lacking Golgi dictiosomes. However, biochemical and/or molecular (genomic) evidence indicate that an organelle with the functions of the Golgi was present in every lineage of eukaryotes studied thus far. Loss of the Golgi organelle is a secondary event as proven by identification of Golgi genes in the genomes of Golgi-lacking lineages. The loss might have occurred independently several times in evolution. Neither the number of stacks, nor the size of the organelle correlates with the intensity of secretion or the position of the species on the evolutionary tree (in terms of presumably early/lately diverged lineages).     

Golvesin-GFP fusions as distinct markers for Golgi and post-Golgi vesicles in Dictyostelium cells

Golvesin is a new protein associated with membranes of the Golgi apparatus and post-Golgi vesicles in Dictyostelium cells. An internal hydrophobic sequence of 24 amino-acid residues is responsible for anchoring golvesin to the membranes of these organelles. In an attempt to visualize organelle dynamics in vivo, we have used specific antibody and other labels to localize golvesin-green fluorescent protein (GFP) constructs to different cellular compartments. With a GFP tag at its N-terminus, golvesin shows the same localization as the untagged protein. It is transferred to two post-Golgi compartments, the endosomal and contractile vacuole systems. Endosomes are decorated with GFP-golvesin within less than 10 min of their internalisation, and keep the label during the acidic phase of the pathway. Blockage of the C-terminus with GFP causes entrapment of the protein in the Golgi apparatus, indicating that a free C-terminus is required for transfer of golvesin to any of the post-Golgi compartments. The C-terminally tagged golvesin proved to be a reliable Golgi marker in Dictyostelium cells revealing protrusion of Golgi tubules at peak velocities of 3 to 4 microm x s(-1). The fusion protein is retained in Golgi vesicles during mitosis, visualizing Golgi disassembly and reorganization in line with cytokinesis.     

Targeting of proteins to the Golgi apparatus

The Golgi apparatus maintains a highly organized structure in spite of the intense membrane traffic which flows into and out of this organelle. Resident Golgi proteins must have localization signals to ensure that they are targeted to the correct Golgi compartment and not swept further along the secretory pathway. There are a number of distinct groups of Golgi membrane proteins, including glycosyltransferases, recyclingtrans-Golgi network proteins, peripheral membrane proteins, receptors and viral glycoproteins. Recent studies indicate that there are a number of different Golgi localization signals and mechanisms for retaining proteins to the Golgi apparatus. This review focuses on the current knowledge in this field.     

The Golgi complex: a hub of the secretory pathway

The Golgi complex plays a central role in protein secretion by regulating cargo sorting and trafficking. As these processes are of functional importance to cell polarity, motility, growth, and division, there is considerable interest in achieving a comprehensive understanding of Golgi complex biology. However, the unique stack structure of this organelle has been a major hurdle to our understanding of how proteins are secreted through the Golgi apparatus. Herein, we summarize available relevant research to gain an understanding of protein secretion via the Golgi complex. This includes the molecular mechanisms of intra-Golgi trafficking and cargo export in the trans-Golgi network. Moreover, we review recent insights on signaling pathways regulated by the Golgi complex and their physiological significance.     

Intermediate organelles of the plant secretory pathway: identity and function

The secretory pathway of eukaryotic cells comprises a network of organelles that connects three large membranes, the plasma membrane, the vacuole and the endoplasmic reticulum. The Golgi apparatus and the various post-Golgi organelles that control vacuolar sorting, secretion and endocytosis can be regarded as intermediate organelles of the endocytic and biosynthetic routes. Many processes in the secretory pathway have evolved differently in plants and cannot be studied using yeast or mammalian cells as models. The best characterized organelles are the Golgi apparatus and the prevacuolar compartment, but recent work has shed light on the role of the trans Golgi network, which has to be regarded as a separate organelle in plants. In this study, we wish to highlight recent findings regarding the late secretory pathway and its crosstalk with the early secretory pathway as well as the endocytic route in plants. Recently published findings and suggested models are discussed within the context of known features of the equivalent pathway in other eukaryotes.