Transcript Guillain-Barre syndrome (GBS)

GCCTCAATGGATCCACCACCCTTTTTGGGCA
GCCTCAATGGATCCACCACCCTTTTTGGTGCA
AGCCTCAATGGATCCACCACCCTTTTTGGTGC
AAGCCTCAATGGATCCACCACCCTTTTTGGTG
CAAGCCTCAATGGATCCACCACCCTTTTTGGT
GCAAGCCTCAATGGATCCACCACCCTTTTTGG
TGCAAGCCTCAATGGATCCACCACCCTTTTTG
GTGCAGCCTCAATGGATCCACCACCCTTTTTG
GGCAGCCTCAATGGATCCACCACCCTTTTTG
GTGCAAGCCTCAATGGATCCACCACCCTTTTT
GGTGCAAGCCTCAATGGATCCACCTCCACCA
CCCTTTTTGGTGCATGTGCCATGGC
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Gene expression
 Transcription
 Translation
 Functional proteins: post-translational modifications
 Phosphorylation
 Glycosylation
 Sorting: targeting to appropriate organelles
 Modulation by extracellular signals
 Covalent modification
 Association with other molecules
 Degradation

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Sorting and Secretory pathways
diverged
in trans-Golgi
Constitutive pathway
many soluble proteins
Regulated pathway
stored in secretory vesicles
active transport from cytosol
to vesicles
complexed with
macromolecules (e.g.
proteglycans)
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Regulated secretory pathway
 In
response to extracellular stimuli: hormone,
transmitters, digestive enzymes
stored
in secretory vesicles
active transport from cytosol to vesicles
complexed with macromolecules (e.g.
proteglycans) to reach high concentration
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Three pathways in Golgi
 to
lysosome
 with
mannose-6-phosphate, via late endosome to
lysosome
 to
secretory pathways
 Constitutive:
to apical or basolateral domain
 Regulated
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“Roadmap” for traffic
Transport
Gated
transport: cytosol and
nucleus via nuclear pore
complexes
Membrane transport: via
membrane-bound
translocators; unfolded
Vesicle transport: vesicles
Sorting
signals
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Membrane transport
 Membrane-bound
translocators
 Unfolding of protein to be transported
 Passing through a topologically distinct space:
cytosol to ER; cytosol to mitochondria
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Equivalent space for transport
 Cycles
of budding and fusion permits
transport of molecules
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Sorting signals
 Signal
sequences
 15-60
aa
 Removed by signal peptidase when reaching the
target
 Signal
patch
 Usually
non-continuous stretch of sequences
 Exposed when appropriately folded
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Sorting signals
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Signal sequences
 Function:
specify the direction for destination
 for initial transfer to the ER: with a signal sequence
at N-terminus; consisting of 5-10 hydrophobic aa
Go forward Golgi: most proteins
Return to ER (ER residents): with a specific
sequence of 4 aa at C-terminus
Go to mitochondria: positively charged amino
acids alternate with hydrophobic ones
Go to peroxisome: with a signal peptide of 3
characteristic at C terminus
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Signal sequences
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Experiments to demonstrate “zip code”
 Swap
the signal sequence:
 e.g.: adding the ER signal sequences to a
cytosolic protein results in the retention of this
protein in ER
 Hyprophobicilty: maybe a determing factor of
signal sequences
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Günter Blobel
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Effect of misdirected protein
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Overview of protein sorting
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Protein sorting
 ER
 ER-Golgi
intermediate
 Glogi network
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Glycosylation in ER
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Lysosomal protein:
phosphorylation of mannose
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Sorting in Golgi
 Export
 Lysosome
 Secretion
Constitute
Regulated
 Retain
in Golgi
 transmembrane
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Transport to
plasma membrane
 TGN
 Apical
domain
 Basolateral
domain
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Endocytosis
 Phagocytosis
(cell eating)
 Ingestion
of large particles (e.g. bacteria)
 In specialized cells
 Pinocytosis
(cell drinking)
 Up-take
of fluids or macromolecules in small vesicles
 Receptor-mediated endocytosis
 Common among eukaryotic cells
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Phagocytosis
 Pseudopodia
 Phagosome
 Phagolysosome
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Receptor-mediated
endocytosis
 Clathrin-coated
pits
 Clathrin-coated vesicles
 Example: cholesterol, LDL,
LDL receptor
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LDL: low density lipoprotein
 Core
 ~1500
Cholesterol ester
 Coat
 ~500
cholesterol
 ~ 800 phospholipid
 1 Apoprotein B100
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LDL receptor
 MS
Brown, JL Goldstein
 Familial
hypercholesterolemia
 LDL-binding domain
 Internalization signal
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LDL receptor
 Internalization
signal: Tyr
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Clathrin-coated pits
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Lysosomal proteins in clathrin-coated pits
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Sorting in early
endosome
ph by H+
pump for
dissociation of
proteins
 Acidic
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Recycling of synaptic vesicles
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Protein sorting
by transcytosis
 Membrane
protein in
apical domain
 Secretory
proteins from
bloodstream
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Lysosomal system
 For
membrane-bound proteins and proteins
taken by endocytosis
 Multiple acid proteases (cathepsins) and
other hydrolases
 Studied with weak bases to inhibit lysosomal
acidification or lysosomal inhibitors (E64)
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