scholarly journals Keratin 7 Is a Constituent of the Keratin Network in Mouse Pancreatic Islets and Is Upregulated in Experimental Diabetes

2021 ◽  
Vol 22 (15) ◽  
pp. 7784
Author(s):  
Catharina M. Alam ◽  
Sarah Baghestani ◽  
Ada Pajari ◽  
M. Bishr Omary ◽  
Diana M. Toivola
Keyword(s):  
Experimental Diabetes ◽  
Streptozotocin Diabetes ◽  
Intermediate Filament Protein ◽  
Β Cells ◽  
Diabetes Model ◽  
Cytoplasmic Filaments ◽  
Mouse Pancreatic Islets ◽  
Filament Networks ◽  
Filament Protein ◽  
Keratin 7

Keratin (K) 7 is an intermediate filament protein expressed in ducts and glands of simple epithelial organs and in urothelial tissues. In the pancreas, K7 is expressed in exocrine ducts, and apico-laterally in acinar cells. Here, we report K7 expression with K8 and K18 in the endocrine islets of Langerhans in mice. K7 filament formation in islet and MIN6 β-cells is dependent on the presence and levels of K18. K18-knockout (K18‒/‒) mice have undetectable islet K7 and K8 proteins, while K7 and K18 are downregulated in K8‒/‒ islets. K7, akin to F-actin, is concentrated at the apical vertex of β-cells in wild-type mice and along the lateral membrane, in addition to forming a fine cytoplasmic network. In K8‒/‒ β-cells, apical K7 remains, but lateral keratin bundles are displaced and cytoplasmic filaments are scarce. Islet K7, rather than K8, is increased in K18 over-expressing mice and the K18-R90C mutation disrupts K7 filaments in mouse β-cells and in MIN6 cells. Notably, islet K7 filament networks significantly increase and expand in the perinuclear regions when examined in the streptozotocin diabetes model. Hence, K7 represents a significant component of the murine islet keratin network and becomes markedly upregulated during experimental diabetes.

scholarly journals Viscoelastic properties of vimentin compared with other filamentous biopolymer networks.

1991 ◽  
Vol 113 (1) ◽  
pp. 155-160 ◽  
Author(s):  
P A Janmey ◽  
U Euteneuer ◽  
P Traub ◽  
M Schliwa
Keyword(s):  
Viscoelastic Properties ◽  
Intermediate Filament Protein ◽  
Linear Polymers ◽  
Cell Integrity ◽  
Interphase Cell ◽  
Shear Moduli ◽  
Lower Shear ◽  
Cytoplasmic Filaments ◽  
Filament Protein

The cytoplasm of vertebrate cells contains three distinct filamentous biopolymers, the microtubules, microfilaments, and intermediate filaments. The basic structural elements of these three filaments are linear polymers of the proteins tubulin, actin, and vimentin or another related intermediate filament protein, respectively. The viscoelastic properties of cytoplasmic filaments are likely to be relevant to their biologic function, because their extreme length and rodlike structure dominate the rheologic behavior of cytoplasm, and changes in their structure may cause gel-sol transitions observed when cells are activated or begin to move. This paper describes parallel measurements of the viscoelasticity of tubulin, actin, and vimentin polymers. The rheologic differences among the three types of cytoplasmic polymers suggest possible specialized roles for the different classes of filaments in vivo. Actin forms networks of highest rigidity that fluidize at high strains, consistent with a role in cell motility in which stable protrusions can deform rapidly in response to controlled filament rupture. Vimentin networks, which have not previously been studied by rheologic methods, exhibit some unusual viscoelastic properties not shared by actin or tubulin. They are less rigid (have lower shear moduli) at low strain but harden at high strains and resist breakage, suggesting they maintain cell integrity. The differences between F-actin and vimentin are optimal for the formation of a composite material with a range of properties that cannot be achieved by either polymer alone. Microtubules are unlikely to contribute significantly to interphase cell rheology alone, but may help stabilize the other networks.

Immunocytochemical localization of desmin and vimentin in chick embryonic myocardial cells

1990 ◽  
Vol 48 (3) ◽  
pp. 448-449
Author(s):  
Yukiko Sugi
Keyword(s):  
Sodium Methoxide ◽  
Intermediate Filament Protein ◽  
Chick Embryos ◽  
Immunocytochemical Localization ◽  
Myocardial Cells ◽  
Immunofluorescence Study ◽  
Immunofluorescent Localization ◽  
Rabbit Igg ◽  
Semithin Sections ◽  
Filament Protein

In cultured skeletal muscle cells of chick, one intermediate filament protein, vimentin, is primarily formed and then synthesis of desmin follows. Coexistence of vimentin and desmin has been immunocytochemically confirmed in chick embryonic skeletal musclecells. Immunofluorescent localization of vimentin and desmin has been described in developing myocardial cells of hamster. However, initial localization of desmin and vimentin in early embryonic heart has not been reported in detail. By quick-freeze deep-etch method a loose network of intermediate filaments was revealed to exist surrounding myofibrils. In this report, immunocytochemical localization of desmin and vimentin is visualized in early stages of chick embryonic my ocardium.Chick embryos, Hamburger-Hamilton (H-H) stage 8 to hatch, and 1 day old postnatal chicks were used in this study. For immunofluorescence study, each embryo was fixed with 4% paraformaldehyde and embedded in Epon 812. De-epoxinized with sodium methoxide, semithin sections were stained with primary antibodies (rabbit anti-desmin antibody and anti-vimentin antibody)and secondary antibody (RITC conjugated goat-anti rabbit IgG).

scholarly journals The Intermediate Filament Protein Vimentin Is a New Target for Epigallocatechin Gallate

2005 ◽  
Vol 280 (17) ◽  
pp. 16882-16890 ◽  
Author(s):  
Svetlana Ermakova ◽  
Bu Young Choi ◽  
Hong Seok Choi ◽  
Bong Seok Kang ◽  
Ann M. Bode ◽  
...  
Keyword(s):  
Intermediate Filament ◽  
Epigallocatechin Gallate ◽  
Intermediate Filament Protein ◽  
Filament Protein

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.

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