Updated: 2/12/2018

Intermediate Filaments

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Overview
  •  Structure
    • stable polymers
      • unlike microtubules and actin → does not undergo dynamic treadmilling
      • must be degraded via the ubiquitin pathway
        • sends to proteasomes
    • intermediate in size between microfilaments (7 nm) and microtubules (25 nm)
  • Function 
    • give strength to the cytoskeleton
    • 5 types

     

TypeFilament nameLocationsStain
I-II Keratin Epithelial cells Cytokeratin
III Desmin Muscle (smooth, cardiac, and skeletal) Desmin
  Peripherin Peripheral nerve axons  -
  Vimentin Fibroblasts and endothelium Vimentin
  Glial fibrillary acidic protein (GFAP) Astrocytes and Schawnn cells GFAP
IV Neurofilaments Neurons Neurofilament (NF)
V Lamins Nuclear envelope of all cells -
  • Clinical importance
    • alcoholic liver disease
      • ubiquitinated cytokeratin filaments accumulate in hepatocytes
        • eosinophilic inclusions called Mallory bodies 
    • Parkinson's disease
      • alpha-synuclein and ubiquitinated neurofilaments accumulate in neurons of substantia nigra
      • eosinophilic inclusions called Lewy bodies

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Questions (1)

(M1.BC.17.4753) A 55-year-old female presents to her primary care physician complaining of a mass in her mid-thigh. The mass has grown slowly over the past six months and is not painful. The patient’s past medical history is notable for hypertension and hyperlipidemia. She takes lisinopril and rosuvastatin. On examination, there is a firm, immobile mass on the medial aspect of the distal thigh. She has full range of motion and strength in her lower extremities and patellar reflexes are 2+ bilaterally. A biopsy of the mass reveals multiple pleomorphic smooth muscle cells with nuclear atypia. The patient subsequently initiates radiation therapy with plans to undergo surgical resection. This tumor will most strongly stain for which of the following? Tested Concept

QID: 108852
1

Chromogranin

22%

(22/101)

2

Desmin

58%

(59/101)

3

Cytokeratin

7%

(7/101)

4

Glial fibrillary acidic protein

5%

(5/101)

5

Neurofilament

6%

(6/101)

M 1 C

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