Download Cell Architecture 2 Dr Mahjabeen

Dr Mah Jabeen Muneera
Assistant Professor
Department of Anatomy
KEMU
• Shape: double sranded helix
• Diameter: 7nm
• Basic protein subunit: monomer
of G-actin (globular or free
actin) polymerizes to F- actin
(filamentous), in presence of K
& Mg.
• Formin
• Polarity: _ pointed end and +
barbed end
• Treadmilling
• Stable- muscle cells and
microvilli
• Dissociate and reassemble
• Profilin & Cofilin
• Prevent polymerization
• Prevent depolymerization
(phalloidin found in
poisosnous mushrooms)
• Disrupt the dynamic
equilibrium between
F-actin and G-actin
causing cell death
Core of actin filaments
ABPs- Actin Binding Proteins
• Villin and fimbrin
• Tropomyosin
• Spectrin
• Myosin 1 and 2
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10-12nm
Structural function
Intercellular junctions
Nuclear lamina
Identification by means
of immunocytochemical
methods
• Tissue specificity
Desmosomes
Zonula adherens
Fibroblasts: Cells of
mesenchymal origin- ? IF
›50 different types divided into
05 classes
• 1. Keratins- epithelium
• 2. Vimentin- mesenchymal
cells and vascular smooth
muscle
• 3. Desmin- muscle except
vascular smooth muscle
• 4. Glial fibrillary acidic
proteins- glial cells
• 5. Neurofilaments- neurons
• Presence of a specific type of intermediate filament in tumors
can reveal which cell originated the tumor
• Identification of intermediate filament proteins by means of
immunocytochemical methods is a routine procedure
• Microvilli bearing cells
• Microfilaments &
intermediate filaments
• Desmosomes anchorage
• ABP: spectrin & Myosin II
• Neurofibrillary tangles: presence of structurally abnormal but
phosphorylated neurofilaments and microtubule associated
proteins ??
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Disorder of CNS
Mutations in the coding region of GFAP gene
Altered GFAP prevents the assembly of intermediate filaments
Accumulation of intermediate filament protein GFAP leads to
cytoplasmic inclusions in astrocytes (Rosenthal fibres)