Dr Mah Jabeen Muneera Assistant Professor Department of Anatomy KEMU.
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Transcript of Dr Mah Jabeen Muneera Assistant Professor Department of Anatomy KEMU.
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Dr Mah Jabeen MuneeraAssistant Professor Department of AnatomyKEMU
Cell architecture; structure and functions of cytoskeletal framework
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Microfilaments • 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
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Toxins that bind to actin
• Prevent polymerization
• Prevent depolymerization (phalloidin found in poisosnous mushrooms)
• Disrupt the dynamic equilibrium between
F-actin and G-actin causing cell death
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Cytokinesis
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Microvillus
Core of actin filamentsABPs- Actin Binding
Proteins • Villin and fimbrin• Tropomyosin• Spectrin• Myosin 1 and 2
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Cell cortex
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Stress fibers
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Intermediate filaments
• 10-12nm• Structural function• Intercellular
junctions• Nuclear lamina• Identification by
means of immunocytochemical methods
• Tissue specificity
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Intercellular adhesions
Desmosomes Zonula adherens
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Tissue specificityFibroblasts: 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
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Information for diagnosis and treatment of cancer
• 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
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Terminal Web
• Microvilli bearing cells• Microfilaments &
intermediate filaments• Desmosomes
anchorage• ABP: spectrin & Myosin
II
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Alzheimers disease• Neurofibrillary tangles: presence of structurally
abnormal but phosphorylated neurofilaments and microtubule associated proteins ??
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Alexander disease• 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)