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#intermediate filaments

11 public questions tagged with this topic.

Cytoskeleton

What is a major function of intermediate filaments in cells?

Intermediate filaments constitute one of three major cytoskeletal polymers alongside actin microfilaments and microtubules, classified by ten nanometer diameter and apolar rope-like assembly through parallel coiled-coil dimers antiparallel tetramers laterally associating into filaments without polarity. Major classes include keratins in epithelia, vimentin in mesenchyme, desmin in muscle, glial fibrillary acidic protein in astrocytes, neurofilaments in neurons, lamins in nucleus. Their primary mechanical role is tensile resistance to shear and stretching, absorbing deformation through flexible

Ref: Herrmann J Cell Sci; IF 10nm tensile strength, anchored at desmosomes hemidesmosomes, no polarity.

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Cytoskeleton

Which protein links intermediate filaments to actin filaments and microtubules?

Plectin is a giant cytolinker of the plakin family that simultaneously recognizes actin, microtubules and intermediate filaments, integrating cytoskeletal networks into a cohesive mechanical continuum. Its structure includes an N-terminal actin-binding domain composed of two calponin-homology motifs, a central 200-nm coiled-coil rod dimerization domain, and a C-terminal repeat domain that binds vimentin, keratin, desmin and glial fibrillary acidic protein with distinct isoform specificity. Alternative splicing of first exons targets isoforms to hemidesmosomes via integrin beta4, to focal adhes

Ref: Alberts Ch 16; Fuchs & Cleveland, Science 1998 plakin plectin crosslinks IF, actin, microtubules.

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Cytoskeleton

How does phosphorylation affect intermediate filaments?

Intermediate filaments are apolar polymers of tetrameric coiled-coil dimers that lack intrinsic nucleotide turnover, so dynamic regulation relies on post-translational modification. Phosphorylation within the N-terminal head domain by mitotic kinases such as Cdk1, Plk1, Aurora B, as well as PKA, PKC and MAP kinases, introduces dense negative charge that disrupts head-to-rod electrostatic interactions essential for filament elongation. The result shifts equilibrium toward soluble tetramers and monomers, enabling mitotic disassembly of vimentin networks and nuclear lamina breakdown at prometapha

Ref: Alberts Ch 16 Cytoskeleton; Lodish Ch 18; IF phosphorylation controls disassembly via head domain serine.

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Cytoskeleton

In epithelial cells, intermediate filaments are mainly composed of:

Epithelial tissues covering skin intestine lung alveoli renal tubules subject to friction stretch requiring robust mechanical buffering and polarity maintenance. Keratin intermediate filaments provide this resilience forming dense cable network 10 nm diameter spanning cytoplasm inserting into desmosomes and hemidesmosomes creating continuous transcellular network distributing tensile forces across sheet preventing cell separation under shear. Expression program tissue specific precisely regulated: basal epidermal keratinocytes keratin 5 and 14 pair suprabasal differentiating keratin 1 and 10 s

Ref: Herrmann et al., Nat Rev Mol Cell Biol 2007 – Keratin main intermediate filament protein in epithelial cells.

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Cytoskeleton

Which of the following proteins is a component of intermediate filaments?

Intermediate filament protein family comprises over 70 members classified by sequence homology and expression pattern regulated developmentally. Signature central rod domain about 310 amino acids alpha helical coiled coil flanked by variable head tail domains mediating assembly and interactions. Major subgroups include type I acidic keratins 28 genes and type II basic keratins 26 genes obligate heteropolymers in epithelia forming extensive cytoskeleton; type III includes vimentin mesenchymal fibroblasts endothelial desmin skeletal cardiac smooth muscle GFAP astrocytes peripherin peripheral neu

Ref: Eriksson et al., Physiol Rev 2009 – Intermediate filament proteins including keratin as component classification.

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Cytoskeleton

Intermediate filaments differ from actin filaments because:

Three cytoskeletal filament systems differ chemically mechanically and kinetically defining cytoplasmic organization. Actin filaments polar 7 nm helical polymers of ATP G actin assembling barbed plus fast pointed minus slow exhibiting treadmilling ATP hydrolysis dependent turnover myosin motors. Microtubules polar 25 nm tubes of GTP tubulin dimers showing dynamic instability and kinesin dynein transport highways plus end tracking. Intermediate filaments 10 nm rope like nonpolar exceptionally stable structures without polarity unique to metazoans. Lack of polarity stems from assembly pathway: p

Ref: Alberts et al., Molecular Biology of the Cell, Chapter 16: Intermediate filaments lack polarity distinction from actin and microtubules.

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Cytoskeleton

Which of the following cytoskeletal elements provides tensile strength to cells?

Cytoskeletal polymers provide complementary mechanical functions. F actin, 7 nanometer double helical polymer of ATP loaded G actin, drives protrusion and contraction via myosin II and generates branched networks via Arp2/3 at 70 degrees. Microtubules, 25 nanometer hollow cylinders of alpha beta tubulin heterodimers with GTP cap, resist compression and act as long range highways for kinesin plus end and dynein minus end motors transporting organelles and chromosomes. Intermediate filaments, 10 nanometer non polar fibers, provide outstanding tensile strength and resilience. Assembly hierarchy i

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 16: Cytoskeleton and Intermediate Filaments.

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Cell Communication and Cell Adhesion

Desmosomes connect to cytoskeleton via

Intermediate filaments, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Communication and Cell Adhesion

Intermediate filaments in hemidesmosomes are mainly

Keratin, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Communication and ECM

Intermediate filaments in epithelia are linked to ECM by

Hemidesmosomes, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Protein

Which of the following describes the function of keratin intermediate filaments in cells?

Provides tensile strength to epithelial cells is the accurate answer because it correctly identifies the biological function or role described in this question. In Protein, understanding the specific functions of molecules, enzymes, or structures is fundamental. Provides tensile strength to epithelial cells fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (Assists in DNA replication, Acts as an enzyme in metabolic pathways, and Regulates transcription factors) serve different biological func

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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