scholarly journals Basic proteins of the perinuclear theca of mammalian spermatozoa and spermatids: a novel class of cytoskeletal elements.

1987 ◽  
Vol 105 (3) ◽  
pp. 1105-1120 ◽  
Author(s):  
F J Longo ◽  
G Krohne ◽  
W W Franke
Keyword(s):  
Plasma Membrane ◽  
Complex Structure ◽  
Sperm Head ◽  
Cytoskeletal Proteins ◽  
Electron Microscopic Level ◽  
Intermediate Filament Proteins ◽  
Basic Proteins ◽  
Nuclear Lamins ◽  
Perinuclear Theca ◽  
Cytoskeletal Elements

The nuclei of bovine spermatids and spermatozoa are surrounded by dense cytoplasmic webs sandwiched between the nuclear envelope and the acrosome and plasma membrane, respectively, filling most of the cytoplasmic space of the sperm head. This web contains a complex structure, the perinuclear theca, which is characterized by resistance to extractions in nondenaturing detergents and high salt buffers, and can be divided into two major subcomponents, the subacrosomal layer and the postacrosomal calyx. Using calyces isolated from bull and rat spermatozoa we have identified two kinds of basic proteins as major constituents of the thecal structure and have localized them by specific antibodies at the light and electron microscopic level. These are an Mr 60,000 protein, termed calicin, localized almost exclusively to the calyx, and a group of multiple-band polypeptides (MBP; Mr 56,000-74,000), which occur in both the calyx and the subacrosomal layer. The polypeptides of the MBP group are immunologically related to each other, but unrelated, by antibody reactions and peptide maps, to calicin. We show that these basic cytoskeletal proteins are first detectable in the round spermatid stage. As we have not detected any intermediate filament proteins and proteins related to nuclear lamins of somatic cells in sperm heads, we conclude that the perinuclear theca and its constituents, calicin and MBP proteins, are the predominant cytoskeletal elements of the sperm head. Immunologically cross-reacting polypeptides with similar properties have been identified in the heads of rat and human spermatozoa. We speculate that these insoluble basic proteins contribute, during spermiogenesis, to the formation of the perinuclear theca as an architectural element involved in the shape changes and the intimate association of the nucleus with the acrosome and the plasma membrane.

scholarly journals Cytoskeletal distribution and function during the maturation and enucleation of mammalian erythroblasts.

1989 ◽  
Vol 109 (6) ◽  
pp. 3005-3013 ◽  
Author(s):  
S T Koury ◽  
M J Koury ◽  
M C Bondurant
Keyword(s):  
Plasma Membrane ◽  
Cytochalasin D ◽  
Cytoskeletal Proteins ◽  
Filamentous Actin ◽  
Accessory Cells ◽  
Vitro Model ◽  
And Function ◽  
Cytoskeletal Elements

We have used murine splenic erythrolasts infected with the anemia-inducing strain of Friend virus (FVA cells), as an in vitro model to study cytoskeletal elements during erythroid maturation and enucleation. FVA cells are capable of enucleating in suspension culture in vitro, indicating that associations with an extracellular matrix or accessory cells are not required for enucleation to occur. The morphology of FVA cells undergoing enucleation is nearly identical to erythroblasts enucleating in vivo. The nucleus is segregated to one side of the cell and then appears to be pinched off resulting in an extruded nucleus and reticulocyte. The extruded nucleus is surrounded by an intact plasma membrane and has little cytoplasm associated with it. Newly formed reticulocytes have an irregular shape, are vacuolated and contain all cytoplasmic organelles. The spatial distribution of several cytoskeletal proteins was examined during the maturation process. Spectrin was found associated with the plasma membrane of FVA cells at all stages of maturation but was segregated entirely to the incipient reticulocyte during enucleation. Microtubules formed cages around nuclei in immature FVA cells and were found primarily in the incipient reticulocyte in cells undergoing enucleation. Reticulocytes occasionally contained microtubules, but a generalized diffuse distribution of tubulin was more common. Vimentin could not be detected at any time in FVA cell maturation. Filamentous actin (F-actin) had a patchy distribution at the cell surface in the most immature erythroblasts, but F-actin bundles could be detected as the cells matured. F-actin was found concentrated between the extruding nucleus and incipient reticulocyte in enucleating erythroblasts. Newly formed reticulocytes exhibited punctate actin fluorescence whereas extruded nuclei lacked F-actin. Addition of colchicine, vinblastine, or taxol to cultures of FVA cells did not affect enucleation. In contrast, cytochalasin D caused a complete inhibition of enucleation that could be reversed by washing out the cytochalasin D. These results demonstrate that F-actin plays a role in enucleation while the complete absence of microtubules or excessive numbers of polymerized microtubules do not affect enucleation.

scholarly journals Revealing the Roles of Keratin 8/18-Associated Signaling Proteins Involved in the Development of Hepatocellular Carcinoma

2021 ◽  
Vol 22 (12) ◽  
pp. 6401
Author(s):  
Younglan Lim ◽  
Nam-On Ku
Keyword(s):  
Hepatocellular Carcinoma ◽  
Transcription Factors ◽  
Liver Damage ◽  
Cell Shape ◽  
Mutation Frequency ◽  
Cytoskeletal Proteins ◽  
Signaling Proteins ◽  
Intermediate Filament Proteins ◽  
Keratin 8 ◽  
Keratin 18

Although hepatocellular carcinoma (HCC) is developed with various etiologies, protection of hepatocytes seems basically essential to prevent the incidence of HCC. Keratin 8 and keratin 18 (K8/K18) are cytoskeletal intermediate filament proteins that are expressed in hepatocytes. They maintain the cell shape and protect cells under stress conditions. Their protective roles in liver damage have been described in studies of mouse models, and K8/K18 mutation frequency in liver patients. Interestingly, K8/K18 bind to signaling proteins such as transcription factors and protein kinases involved in HCC development. Since K8/K18 are abundant cytoskeletal proteins, K8/K18 binding with the signaling factors can alter the availability of the factors. Herein, we discuss the potential roles of K8/K18 in HCC development.

scholarly journals Specific release of membrane-bound annexin II and cortical cytoskeletal elements by sequestration of membrane cholesterol.

1997 ◽  
Vol 8 (3) ◽  
pp. 533-545 ◽  
Author(s):  
T Harder ◽  
R Kellner ◽  
R G Parton ◽  
J Gruenberg
Keyword(s):  
Actin Cytoskeleton ◽  
Cytoskeletal Proteins ◽  
Annexin Ii ◽  
Dependent Manner ◽  
Cortical Actin ◽  
Independent Manner ◽  
Low Concentrations ◽  
Early Endosomes ◽  
Associated Proteins ◽  
Cytoskeletal Elements

Annexin II is an abundant protein which is present in the cytosol and on the cytoplasmic face of plasma membrane and early endosomes. It is generally believed that this association occurs via Ca(2+)-dependent binding to lipids, a mechanism typical for the annexin protein family. Although previous studies have shown that annexin II is involved in early endosome dynamics and organization, the precise biological role of the protein is unknown. In this study, we found that approximately 50% of the total cellular annexin was associated with membranes in a Ca(2+)-independent manner. This binding was extremely tight, since it resisted high salt and, to some extent, high pH treatments. We found, however, that membrane-associated annexin II could be quantitatively released by low concentrations of the cholesterol-sequestering agents filipin and digitonin. Both treatments released an identical and limited set of proteins but had no effects on other membrane-associated proteins. Among the released proteins, we identified, in addition to annexin II itself, the cortical cytoskeletal proteins alpha-actinin, ezrin and moesin, and membrane-associated actin. Our biochemical and immunological observations indicate that these proteins are part of a complex containing annexin II and that stability of the complex is sensitive to cholesterol sequestering agents. Since annexin II is tightly membrane-associated in a cholesterol-dependent manner, and since it seems to interact physically with elements of the cortical actin cytoskeleton, we propose that the protein serves as interface between membranes containing high amounts of cholesterol and the actin cytoskeleton.

scholarly journals Murine endodermal cytokeratins Endo A and Endo B are localized in the same intermediate filament.

1986 ◽  
Vol 34 (6) ◽  
pp. 785-793 ◽  
Author(s):  
W E Howe ◽  
F G Klier ◽  
R G Oshima
Keyword(s):  
Immunoelectron Microscopy ◽  
Intermediate Filament ◽  
Microscopic Level ◽  
Cytoskeletal Proteins ◽  
Electron Microscopic Level ◽  
Electron Microscopic ◽  
Double Label ◽  
Secondary Antibodies ◽  
Endodermal Cells ◽  
20 Nm

The intracellular distribution of extra-embryonic endodermal, cytoskeletal proteins A (Endo A) and B (Endo B) was investigated by double-label immunofluorescent microscopy and double-label immunoelectron microscopy. In parietal endodermal cells, the immunofluorescent distribution of Endo B was always coincident with that of Endo A and could be distinguished from vimentin, particularly at the periphery of the cell. At the electron microscopic level, antibodies against both Endo A and Endo B recognized both bundles and individual intermediate filaments. Double-label immunoelectron microscopy was achieved by use of two sizes of colloidal gold particles (5 nm and 20 nm) that were stabilized with secondary antibodies. These results show that Endo A and B are found in the same intermediate filament and probably co-polymerize to form such structures.

A cDNA from Drosophila melanogaster encodes a lamin C-like intermediate filament protein

1993 ◽  
Vol 104 (4) ◽  
pp. 1263-1272 ◽  
Author(s):  
C.A. Bossie ◽  
M.M. Sanders
Keyword(s):  
Drosophila Melanogaster ◽  
Intermediate Filament ◽  
Blot Analysis ◽  
Polytene Chromosomes ◽  
Intermediate Filament Protein ◽  
Chromosome 2 ◽  
Cross Hybridization ◽  
Intermediate Filament Proteins ◽  
Nuclear Lamins ◽  
Filament Protein

A novel intermediate filament cDNA, pG-IF, has been isolated from a Drosophila melanogaster embryonic expression library screened with a polyclonal antiserum produced against a 46 kDa cytoskeletal protein isolated from Kc cells. This 46 kDa protein is known to be immunologically related to vertebrate intermediate filament proteins. The screen resulted in the isolation of four different cDNA groups. Of these, one has been identified as the previously characterized Drosophila nuclear lamin cDNA, Dm0, and a second, pG-IF, demonstrates homology to Dm0 by cross hybridization on Southern blots. DNA sequence analysis reveals that pG-IF encodes a newly identified intermediate filament protein in Drosophila. Its nucleotide sequence is highly homologous to nuclear lamins with lower homology to cytoplasmic intermediate filament proteins. pG-IF predicts a protein of 621 amino acids with a predicted molecular mass of 69,855 daltons. In vitro transcription and translation of pG-IF yielded a protein with a SDS-PAGE estimated molecular weight of approximately 70 kDa. It contains sequence principles characteristic of class V intermediate filament proteins. Its near neutral pI (6.83) and the lack of a terminal CaaX motif suggests that it may represent a lamin C subtype in Drosophila. In situ hybridization to polytene chromosomes detects one band of hybridization on the right arm of chromosome 2 at or near 51A. This in conjunction with Southern blot analysis of various genomic digests suggests one or more closely placed genes while Northern blot analysis detects two messages in Kc cells.

scholarly journals GRAMP 100: a membrane protein concentrated on secretory granule membranes and the apical cell surface in exocrine acinar cells.

1992 ◽  
Vol 40 (12) ◽  
pp. 1827-1835 ◽  
Author(s):  
S M Laurie ◽  
M B Mixon ◽  
J D Castle
Keyword(s):  
Plasma Membrane ◽  
Apical Cell ◽  
Reduced Form ◽  
Electron Microscopic Level ◽  
Apical Plasma Membrane ◽  
Cell Fractionation ◽  
Immunocytochemical Localization ◽  
Electron Microscopic ◽  
Common Component ◽  
Rat Parotid

Using a monoclonal antibody (SG10A6) raised against secretion granule membranes of the rat parotid gland, we have identified an antigen that is a common component of both exocrine pancreatic and parotid granule membranes. SG10A6 (an IgM) immunoprecipitates antigen that migrates as a single band (M(r) approximately 80 KD unreduced; M(r) approximately 100 KD reduced) and immunoblots at least two polypeptides that are similar to the reduced and nonreduced immunoprecipitated antigen. This granule-associated membrane polypeptide (GRAMP 100; named for the apparent M(r) in reduced form) is also a prominent component of plasma membrane fractions. Immunocytochemical localization at the electron microscopic level demonstrates the presence of GRAMP 100 on granule membranes, especially condensing vacuoles and exocytotic figures, and the apical plasma membrane. Lower levels of antigen are detected on basolateral plasma membrane and on peri-Golgi membranes that may be part of the endosomal system. Both the cell fractionation and immunocytochemical localization indicate that GRAMP 100 differs in distribution from GRAMP 92 and 30K SCAMPs, two other components of exocrine granule membranes identified with monoclonal antibodies. To date, no polypeptides have been identified with this approach that are exclusive components of exocrine granule membranes.

Translocation of the neuronal cytoskeleton and axonal locomotion

1982 ◽  
Vol 299 (1095) ◽  
pp. 313-327 ◽  
Keyword(s):  
Plasma Membrane ◽  
Axonal Transport ◽  
Cell Body ◽  
Cytoskeletal Proteins ◽  
The Other ◽  
Current Understanding ◽  
Axonal Elongation ◽  
Neuronal Cytoskeleton ◽  
Other Hand ◽  
Neuron Cell Body

Recent studies of axonal transport indicate that cytoskeletal proteins are assembled into polymers in the neuron cell body and that these polymers move from the cell body toward the end of the axon. On the other hand, membranous elements appear to be inserted into the axonal plasma membrane preferentially at the end of the axon. These new observations are explored in relation to our current understanding of axonal elongation.

Expression of intermediate filament proteins during development of Xenopus laevis. I. cDNA clones encoding different forms of vimentin

Development ◽  
1989 ◽  
Vol 105 (2) ◽  
pp. 279-298
Author(s):  
H. Herrmann ◽  
B. Fouquet ◽  
W.W. Franke
Keyword(s):  
Amino Acid ◽  
Xenopus Laevis ◽  
Intermediate Filament ◽  
De Novo ◽  
Mesenchymal Cell ◽  
Amino Acid Sequences ◽  
Cytoskeletal Proteins ◽  
Cdna Clones ◽  
Mammalian Development ◽  
Intermediate Filament Proteins

To provide a basis for studies of the expression of genes encoding the diverse kinds of intermediate-filament (IF) proteins during embryogenesis of Xenopus laevis we have isolated and characterized IF protein cDNA clones. Here we report the identification of two types of Xenopus vimentin, Vim1 and Vim4, with their complete amino acid sequences as deduced from the cloned cDNAs, both of which are expressed during early embryogenesis. In addition, we have obtained two further vimentin cDNAs (Vim2 and 3) which are sequence variants of closely related Vim1. The high evolutionary conservation of the amino acid sequences (Vim1: 458 residues; Mr approximately 52,800; Vim4: 463 residues; Mr approximately 53,500) to avian and mammalian vimentin and, to a lesser degree, to desmin from the same and higher vertebrate species, is emphasized, including conserved oligopeptide motifs in their head domains. Using these cDNAs in RNA blot and ribonuclease protection assays of various embryonic stages, we observed a dramatic increase of vimentin RNA at stage 14, in agreement with immunocytochemical results obtained with antibody VIM-3B4. The significance of very weak mRNA signals detected in earlier stages is discussed in relation to negative immunocytochemical results obtained in these stages. The first appearance of vimentin has been localized to a distinct mesenchymal cell layer underlying the neural plate or tube, respectively. The results are discussed in relation to programs of de novo synthesis of other cytoskeletal proteins in amphibian and mammalian development.

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