intermediá rne filamenty · microfilaments intermediate filaments (if) 10 nm. actin focal...
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Intermediá rne Filamenty
Katarína GaplovskáKatedra genetiky
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25 nm
Microtubules
5-9 nm
Microfilaments
Intermediate Filaments (IF)
10 nm
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Actin Focal adhesions
MicrotubulesGolgi apparatus
CytokeratinsDesmosomes
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transmit mechanicalforces between adjacent cells
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Lamin A
Two types of IF in metazoan cells
Vimentin
J Clin Invest. 2009 July 1; 119(7): 1772– 1783.
DNA
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Two distinct cytoplasmic IFs in one cell
Human alveolar carcinoma cells
J Clin Invest. 2009 July 1; 119(7): 1763– 1771
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General features of IF• encoded in human genome by 70 different genes
• conserved α-helical rod domain, N- and C-terminal domains of different sizes
• lamins generally expressed, cytoplasmic IF – tissue specificexpression, each class of IF unique properties
• IF evolution – Lamin gene duplication -> deletion of NLS and CAAX box = cytoplasmic intermediate filaments
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Major classes of IF in Mammals
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IF structure
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IF structure
• common core structure
• contain above-averrage hydrophobic residues and sequences
• alpha-helical conformation with heptad repeats
• 2 monomers form Coiled-coil structure
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Coiled-coil structure is typical for IF
• 3,6 amino acid per α-helix turn• position a and d of heptad repeat
= hydrophobic amino acidsLeu Val Met
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Assembly of IF
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J Biol Chem. 2007 Jun 22;282(25):18563-72.
IF assembly in vitro
ULF = UnitLengthFilament
soluble tetrameric complexes of wild-type desmin
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IF assembly in vivo
End to and assembly
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Posttranslational modification of IF
Phosphorylation
• lamin & vimentin = disassembly nuclear Lamina and vimentin filaments
• keratins et al. = partial disassembly
• neurofilaments = heavily phosphorylated C-termstabilization
Disulfide and amide bonds formation
• keratins = „fiberglass-like“ material
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IF dynamicsIntermediate filaments: • have long half-lives and biochemicaly are stable
• disassembly and reassembly during cell spreading, wound healing and cell division etc.
vimentin subunit exchange –FRAP experiment
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Mechanical properties of microfilaments,microtubules and intermediate filaments
J. Cell Biol., 1991 113:155– 160
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Atomic Force Microscopy
Soft - flexible –nearly unbreakable
Herrmann et al., Nat Rev Mol CellBiol. 2007 Jul;8(7):562-73
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IF-pathies
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Keratins• major proteins in skin, epithelial cells, hair and nails• most diverse IF family (>50)• form heterodimers = acidic + basic keratin• diagnostic tool for carcinomas• disulfide bridges
Basal Lamina
Epidermis
>10%
>70%
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Defects in Keratins cause disease
Epidermolysis bullosa simplex
• rare genetic disorder with bullous lesions
• skin is fragile and blisters
• K5 & K14 impaired
type I and II intermediate filament
• basal keratinocytes become fragile
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Epidermolysis bullosa simplex
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Vimentin
lymphocyte
vimentin IF network in cage configuration = resistance to
haemodynamic and mechanic stresses
1. chemokine induced chemotaxis
2. Site-specific phosphorylation
3. perinuclear relocalization
4. extravasationinflamation
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Desmin• connects contractile apparatus and structural elements of the cell
• in structures surrounding Z- disk(skeletal muscle)ordesmosomes (cardiac muscle)
Desmin
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Normal myocyte
Goldfarb & Dalakas, J Clin Invest. 2009;119(7):1806– 1813
Desminopathy
mutant advanced stage
myofibrillar myopathy, cardiomyopathy etc. => aggregation ofmisfolded protein
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Glial fibrillary acidic protein (GFAP)
• in astroglial cells • support and nurishment of neurons in brain• probably involved in controlling the shape, movement,
and function of astroglial cells
GFAP - astrocyte
Neuronal tubulin - neurons
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Alexandre disease
• neurodegenerative disorder
• loss of myelin (degeneration of white matter in brain)
• enlarged brain and head size, etc.
• mutant protein acts in gain-of-function fashion
wild type astrocytes
Mignot et al., Exp Cell Res. 2007, 313(13):2766-79. video
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Motor neuron
Axon
NF-H MT
NF-M
NF-HC- terminal tail domains = IF spacing
Subcortical actin
Neurofilaments
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Lamins
• Lamin A/C – in differentiated cells
• Lamin B1 and Lamin B2- essential
• Form nuclear lamina
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Lamins
Role in:
• controling nuclear shape
& size
• DNA replication
• DNA transcription
• Cell signaling
• Structural, functional and
epigenetic organization of
chromatin etc.
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Lamins & cell division
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Lamin B & Mitotic Spindle Matrix
Lamin Bessential for spindle matrix formation
Spindle matrixpromotes microtubule assembly and
organization in mitosis
Tsai at al., Science. 2006 Mar 31;311(5769):1887-93
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Laminopathies
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Hutchinson-Gilford Progeria syndrom(HGPS)
• Lamin A mutated• premature aging disorder• incidence 1 per 4– 8 million live births • average life expectancy for a patient is 13 years (7 – 27y)• 97% caucasian origin
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Coutinho et al., Immunity & Ageing 2009, 6:4
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Lamin A
Lamin A-Progerin
Mutant Lamin A alters mitosis & cell cycle progression
Dechat et al., Proc Natl Acad Sci U S A. 2007 Mar 20;104(12):4955-60
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Plectin cross-links IF to Microtubules