Golgi Complex

Mark Stamnes , in Encyclopedia of Biological Chemistry, 2004

Morphology of the Golgi Complex

The Golgi complex is often found as a set of 3-5 stacked saccules or cisternae ( Figure 1A) . The cisternae are organized with a polarity such that there is a cis-cisterna where proteins arriving from the endoplasmic reticulum enter and a trans-cisterna where proteins exit the Golgi complex. Proteins pass through the medial cisternae that are present between the cis- and trans-cisternae. The cis and transfaces of the Golgi apparatus are often reticulated and thus referred to as the cis-Golgi network and the trans-Golgi network.

Figure 1. The morphology and localization of Golgi complexes. (A) Shown is a transmission electron micrograph of a Golgi complex from a rat kidney cell. Note that it is composed of three stacked cisternae: cis, medial, and trans. Transport vesicles are apparent near the Golgi complex as circular profiles. (B) Shown is a fluorescence micrograph of normal rat kidney cells that are decorated with an antibody against the Golgi enzyme, mannosidase II. Note that the labeled Golgi stacks (red) are concentrated in a region next to the cell nucleus.

The stacked Golgi complexes are frequently localized together at a single site adjacent to the cell nucleus (Figure 1B). This site is near the centrosome, a cellular structure involved in the assembly and organization of microtubules, which are one of the key components of the cell cytoskeleton. In mammalian cells, the juxtanuclear localization of the Golgi complex involves the translocation of pre-Golgi vesicles along microtubules using a molecular motor protein called dynein. The Golgi stacks are often organized into interconnected ribbon-like structures. Although there is some variability in the morphology and organization of the Golgi complex among eukaryotic cells, in all cases, the Golgi is a critical site for processing and sorting of proteins that are transiting the secretory pathway.

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Golgi Complex

M. Stamnes , in Encyclopedia of Biological Chemistry (Second Edition), 2013

Protein aggregation as a sorting mechanism

Another way that proteins are sorted in the Golgi complex is through aggregation. Some resident Golgi proteins, such as the enzyme mannosidase II, form aggregates with themselves and other Golgi-resident proteins. Golgi proteins may be retained at the proper cisternae through the exclusion of the large aggregates from transport vesicles. By contrast, some proteins – for example, insulin and many other hormones – may cluster within the trans-Golgi network to facilitate their concentration and packaging into vesicles. Aggregation continues in the secretory vesicles before its delivery to the plasma membrane and release into the extracellular space.

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General Characteristics of the Euprotista (Protozoa)

Burton J. Bogitsh , ... Thomas N. Oeltmann , in Human Parasitology (Fifth Edition), 2019

Golgi Complex

The Golgi complex is a cytoplasmic organelle whose specific function in protozoans is essentially identical to that in other eukaryotes. The Golgi is the seat of glycosylation of a number of secretory products of the cell. It is in the cisternae of the Golgi complex, for instance, that the final carbohydrate moieties are added to the glycocalyx associated with the plasma membrane. The arrangement and number of Golgi complexes vary during the life cycle of many protozoans. Thus, cyst-forming protistans may lose their Golgi complexes during encystation, only to resynthesize them when they excyst. The so-called parabasal body of protozoans is homologous to the Golgi complex of other eukaryotic cells but with several morphological differences, the most notable of which is the frequent presence of a fibril, the parabasal filament, running from the cisternae of the Golgi complex to one or more basal bodies.

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Mechanisms and Morphology of Cellular Injury, Adaptation, and Death1

Margaret A. Miller , James F. Zachary , in Pathologic Basis of Veterinary Disease (Sixth Edition), 2017

Golgi Complex

The Golgi complex, also commonly called the Golgi apparatus, is a series of flattened membrane-bound sacs with its inner face ( cis or entry face) near the rER in a paranuclear position (see Fig. 1-3). Proteins made in the rER are delivered to the entry face of the Golgi complex by transport vesicles. As the proteins traverse the Golgi complex, they are processed (e.g., carbohydrate moieties added through glycosylation) and packaged into secretory vesicles to be released from the outer (trans) face of the Golgi complex into the cytosol, either for use by the cell that produced them, as in the case of lysosomal enzymes, or (more commonly) for delivery to the plasma membrane for export. Transmission electron microscopy is usually required to visualize the Golgi complex. However, an active Golgi complex, such as that needed for processing and packaging of immunoglobulin molecules, is large enough to impart a paranuclear eosinophilic pallor to plasma cells in a hematoxylin and eosin (H&E)–stained histologic section.

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Golgi Complex and Endosome Antibodies

Marvin J. Fritzler , Edward K.L. Chan , in Autoantibodies (Third Edition), 2014

Disease association

Disease prevalence

AGA was first identified in the serum of a Sjögren syndrome (SjS) patient with lymphoma. This was followed by other reports that described AGAs in SjS, systemic lupus erythematosus (SLE), rheumatoid arthritis, mixed connective tissue disease, Wegener granulomatosis, and human immunodeficiency virus (HIV) infection (Table 32.2 and reviewed in [8]). Immunoblotting and immunoprecipitation studies have shown that the proteins recognized by human AGA are remarkably heterogeneous [3]. Although AGAs are generally considered to be rare, at Mitogen Advanced Diagnostics Laboratory at the University of Calgary they are seen at least as common as antibodies to Sm. In a study of 80 sera, the frequency of AGA directed to specific Golgi components was correlated with the molecular masses of the golgins [3]. Thus, autoantibodies to giantin/macrogolgin, the highest molecular weight golgin, were the most frequent, being found in 50% of the AGA sera. By contrast, antibodies to golgin 97 were the least common, being found in only approximately 4% of the AGA sera. The most reactive of the giantin/macrogolgin epitopes were those that included the C-terminal transmembrane domain [3]. There is emerging consensus that AGA are not disease specific [4,17], although high titers of AGA have been suggested to constitute an early sign of systemic autoimmune diseases even in the absence of clear clinical manifestations [18].

Table 32.2. Diseases Associated with Anti-Golgi and Anti-endosome Antibodies

Golgi Complex
(golgins-67, -95, -97, -160, -245, Giantin, BHMT1)		 Endosomes
(EEA1, CLIP-170, GRASP-1, LBPA)
Rheumatic diseases Rheumatic diseases
Sjögren syndrome Sjögren syndrome
Rheumatoid arthritis Rheumatoid arthritis
Systemic lupus erythematosus Subacute cutaneous lupus
Scleroderma Systemic lupus erythematosus
Mixed connective tissue disease Seronegative polyarthritis
Granulomatosis with polyangiitis Granulomatosis with polyangiitis
Fibromyalgia Undifferentiated connective tissue disease
Raynaud phenomenon Scleroderma
Neurological disease Raynaud phenomenon
Cerebellar degeneration Neurological disease
Ataxia Lower motor neuron disease
Malignancy Ataxia and vertigo
Lymphoma Demyelinating polyneuropathy
Adenocarcinoma Malignancy
Nasopharyngeal carcinoma Glioblastoma
Other Other
Glomerulonephritis Hypothyroidism
Viral hepatitis Anemia
Human immunodeficiency virus Interstitial pulmonary fibrosis
Epstein-Barr virus Immune deficiency

BHMT1: betaine homocysteine methyl transferase 1; CLIP-170: cytoplasmic linker protein-170; EEA1: early endosome antigen 1; GRASP-1: glutamate receptor interacting protein-associated protein-1; LBPA: lysobisphosphatidic acid.

Autoantibodies to EEA1 have been associated with neurologic diseases and a variety of systemic and organ-specific autoimmune diseases (Table 32.2 and reviewed in [8,14]). Further study of the sera that reacted with EEA1 showed that 94% reacted with the partial length EEA1 constructs that included the C-terminal zinc finger (+FYVE) and the methyl accepting domain (amino acids 82–1411) in an addressable laser bead assay [14]. A study of the epitopes bound by sera from patients with neurologic diseases and patients with other conditions suggested that the later sera from patients recognized epitopes in the central and C-terminal EEA1 domains, whereas the patients with neurologic disease recognized a more restricted set of epitopes in the C-terminal domain [14].

The prevalence of AGA and anti-endosome antibodies in cohorts of SjS, SLE, and systemic sclerosis, as detected by screening IIF assays, suggest that the prevalence of these autoantibodies in those conditions is less than 1%.

Diagnostic value

Further studies of multi-institutional serologic cohorts are required to determine the specificity and sensitivity of antibodies to the Golgi complex and endosome autoantigens.

Prognostic value

Longitudinal studies of patients with AGA or anti-endosome antibodies have not been reported.

Disease activity

There are no studies of the relationship of these autoantibodies to disease activity.

Organ involvement/damage

To date there are no studies of organ involvement or damage that can be directly attributed to AGA or endosome autoantibodies.

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GOLGI COMPLEX AND ENDOSOME ANTIBODIES

MARVIN. J. FRITZLER , EDWARD K.L. CHAN , in Autoantibodies (Second Edition), 2007

TAKE-HOME MESSAGES

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The Golgi complex and endosomes are unique cytoplasmic structures that contain a number of proteins involved in the synthesis, posttranslational modification, and intracellular trafficking of proteins.

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Antibodies to Golgi complex have a distinct pattern of staining but antibodies to endosomes can be mistaken for antibodies to lysosomes or GW bodies.

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Patients with antibodies to Golgi complex antigens, also referred to as golgins, and to endosomal autoantigens have a variety of conditions.

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Special tests such as immunoprecipitation, ALBIA, or other assays are required to definitely identify antibodies to components of the Golgi complex or endosomes.

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Platelet Structure

James G. White , in Platelets (Third Edition), 2013

1 Golgi Complexes

Golgi complexes consisting of parallel-associated, flattened sacules are prominent in the perinuclear cytoplasm of the megakaryocyte during granulopoiesis. When organelle formation is completed, the extensively developed, highly complex Golgi zones move to the periphery of the megakaryocyte cytoplasm and almost completely disappear before proplatelets develop. Only residual elements consisting of a few parallel-associated, flattened sacules with no budding vesicles are found in less than 1% of circulating platelets (Fig. 7-62). Its mission was accomplished before the circulating platelet was born.

But not always. Platelets from patients with some of the hypogranular platelet syndromes carry significant numbers of Golgi complexes to the peripheral blood. 75 This is particularly true for WPS. 56 Patients with this disorder have mild thrombocytopenia, increased mean platelet volume, decreased sensitivity to aggregating agents, and prolonged bleeding times. Four to thirteen percent of their platelets contain large, fully developed Golgi complexes actively budding smooth and coated vesicles and frequently associated with centrioles (Figs. 7-63 and 7-64). As many as seven Golgi complexes and five centrioles have been observed in single platelets. The findings indicate that platelets from patients with some hypogranular platelet disorders are continuing the process of granulopoiesis into circulating platelets. Recognition that this phenomenon can occur and is characteristic of WPS will prevent the patients from being diagnosed incorrectly to have a leukemic disorder.

Figure 7-63. Platelet from a patient with the White platelet syndrome.

There are five well-developed Golgi complexes (↑) shedding numerous smooth and coated vesicles in the cytoplasm. Mitochondria (M) are more numerous than α granules (G). Mag.×22,000.

Figure 7-64. White platelet syndrome platelet containing a large Golgi complex (Gc) and four centrioles (↑).

Mag.×22,000.

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Organelles

Merri Lynn Casem BA, PhD , in Case Studies in Cell Biology, 2016

Introduction

The Golgi complex is an organelle that consists of multiple, independent membrane compartments called cisternae. Individual cisternae are organized into a stack with each compartment in close physical proximity to the others. The classic appearance of the Golgi complex as a set of "flattened sacs" is conserved across a wide range of eukaryotic cells. Stacking of Golgi membrane compartments creates an orientation where the cisterna closest to the ER is designated the cis Golgi while the cisterna farthest away is the trans Golgi. The term medial Golgi is applied to the cisternal compartments between cis and trans.

The Golgi complex contributes to the modification and sorting of proteins and lipids as part of a cell's endomembrane system. Each cisterna is associated with a specific modification based on the enzymes that are located within the lumen of that compartment. For example, the enzyme mannosidase I is found in the cis Golgi, mannosidase II is present in the medial Golgi, and sialyltransferase is located in the trans Golgi. A consequence of the packaging of specific enzymes within specific cisternae is the sequential modification of proteins and lipids as they move from the cis to trans Golgi. Physical stacking of the cisternae is thought to contribute to maintaining the sequential nature of Golgi function.

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Conduct a search to find images of the Golgi complex. Compare the images you find. How are they similar? How are they different?

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What is the significance of the observation that the shape of the Golgi complex is highly conserved?

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Research/review the function of the enzymes mannosidase I, mannosidase II, and sialyltransferase in the Golgi complex.

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Peptide Hormones, Subcellular Structure

Priscilla S. Dannies , in Encyclopedia of Endocrine Diseases, 2004

The Golgi Complex

The Golgi complex is a stack of flattened membrane cisternae ( Fig. 1) usually located near the nucleus of the cell. In three dimensions, it resembles a broad ribbon-like structure. In cells secreting large amounts of proteins, there may be more than one such stack. Proteins arrive at the Golgi complex on the cis side and process to the trans side. It had long been assumed that proteins were carried forward from one layer of the complex to the next by small vesicles, but it has become generally accepted that each of the layers of the Golgi complex progresses through the stack, so that the cis-layer eventually becomes the trans-layer. Each layer metamorphoses in turn from a cis to a medial to a trans cisterna as small vesicles transport the enzymes that characterize the different layers of the Golgi complex back to the layer behind. A cis-layer takes on the characteristics of later compartments sequentially as vesicles or possibly tubular structures derived from later compartments cycle back the appropriate enzymes. The enzymes in the different layers further covalently modify some of the proteins as they process through the Golgi complex; possible modifications include further glycosylation, as well as phosphorylation and sulfation. The concept that it is the layers that process through the stack provides the simplest explanation why some proteins process through the stack in forms that are too large to be included in the small vesicles seen around the stacks by electron microscopy. Atrial natriuretic peptide, for example, appears in a dense aggregated form too large to be carried in vesicles in all layers of the Golgi complex in atrial cardiomyocytes.

When a Golgi layer reaches the trans side of the Golgi complex, small vesicles still bud to return enzymes and other constituents to the more newly formed layers; in addition, clathrin-coated vesicles bud off to transport vesicles to the lysosome and other vesicles bud to take soluble proteins to the plasma membrane, so that the entire trans-layer of the Golgi complex is consumed by budding of small vesicles to be replaced by the layer that formed after it. Proteins clearly have been sorted when they leave the trans-Golgi region, but the sites of sorting of different proteins may vary, as suggested by the finding of Howell and colleagues, who examined the Golgi complex in three dimensions, that only one type of vesicle is seen budding from regions of the trans-Golgi layer.

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Methods for Analysis of Golgi Complex Function

Erik Lee Snapp , in Methods in Cell Biology, 2013

Abstract

The Golgi complex (GC) is a highly dynamic organelle that constantly receives and exports proteins and lipids from both the endoplasmic reticulum and the plasma membrane. While protein trafficking can be monitored with traditional biochemical methods, these approaches average the behaviors of millions of cells, provide modest temporal information and no spatial information. Photobleaching methods enable investigators to monitor protein trafficking in single cells or even single GC stacks with subsecond precision. Furthermore, photobleaching can be exploited to monitor the behaviors of resident GC proteins to provide insight into mechanisms of retention and trafficking. In this chapter, general photobleaching approaches with laser scanning confocal microscopes are described. Importantly, the problems associated with many fluorescent proteins (FPs) and their uses in the secretory pathway are discussed and appropriate choices are suggested. For example, Enhanced Green Fluorescent Protein (EGFP) and most red FPs are extremely problematic. Finally, options for data analyses are described.

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