Nucleophosmin, Coilin, and Argentophilic (AgNOR) Proteins in the Neurons of Human Substantia Nigra
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eophosmin, Coilin, and Argentophilic (AgNOR) Proteins in the Neurons of Human Substantia Nigra V. V. Guselnikovaa, *, D. A. Sufievaa, and D. E. Korzhevskya aInstitute
of Experimental Medicine, St. Petersburg, 197376 Russia *e-mail: [email protected]
Received December 24, 2019; revised January 16, 2020; accepted January 16, 2020
Abstract—The aim of the work was to study the intranuclear distribution of nucleophosmin (B23), coilin (p80), AgNOR proteins, and nonheme iron in the neurons of the human substantia nigra. Fragments of the human midbrain (n = 10) were shown to have no signs of neurodegeneration. The material was fixed in zinc– ethanol–formaldehyde, a special fixative that provides high preservation of antigenic determinants and tissue structures. This work revaled a new data on molecular and structural organization of the nucleoli of neurons in human substantia nigra. It was found that, in the nuclei of substantia nigra neurons, there is only one large nucleolus, and its size varies between individuals (from 4.2 ± 0.4 to 6.2 ± 0.6 μm in diameter). Nucleophosmin is concentrated solely in the nucleolus and is unevenly distributed in it. Cajal bodies found in the nucleus of most substantia nigra neurons are coiline-containing structures of round or oval shape and about 1 μm in size. Coilin accumulation has also been noted in numerous intranuclear microstructures, which significantly differ in their localization and morphological characteristics from typical Cajal bodies. AgNOR proteins are present in the substantia nigra neurons and are very variably distributed. Nonheme iron was detected in the nucleoli ofof some substantia nigra neurons. In some cases iron was concentrated in the giant fibrillar center (GFC). The data obtained will contribute to a clearer understanding of the role of nucleolar proteins in the functioning of dopaminergic neurons in the human brain and the determination of molecular sensors of nucleolar stress observed during neurodegeneration. Keywords: nucleolus, substantia nigra, nucleophosmin, coilin, AgNOR proteins, non-heme iron, immunohistochemistry DOI: 10.1134/S1990519X20050041
The nucleolus is an evolutionarily conservative and the largest structural domain of the cell nucleus present in the vast majority of eukaryotic cells. The main function of this nuclear compartment is the formation of ribosome subunits. In mammalian cells, the nucleolus includes three main structural components— fibrillar centers (FCs), a dense fibrillar component (PFC, DFC), and a granular component (HA, GC) (Raška et al., 2006; Farley et al., 2015). Genes encoding rRNA and some proteins necessary for transcription of RNA genes—RNA polymerase I and its specific cofactor UBF, as well as topoisomerase I—are located in FCs. DFC is a site for rRNA synthesis. It contains primary pre-rRNA transcripts and proteins such as C23 (nucleolin) and the main protein snoRNP Abbreviations: DOPA—L-dioxiphenylalanine, DFC—dense fibrillar component of the nucleolus (dense fibrillar component), FC—fibrillar center of
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