Transcript Crystallographic studies of ABC transporters

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Many serious genetic diseases can
be traced to ion channel mutations
in the gene encoding protein
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Most diseases are because some of these cells
to produce and transmit impulses capacity is
reduced - excitable cells (eg, muscle cells, nerve
cells and sensory cells) affected the membrane
ion permeability
Compared with other diseases, cystic fibrosis
(CF) is the most common epithelial cells by
acting on ion channel defects caused by disease,
but also the most thoroughly studied diseases.
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Cystic fibrosis is a chronic, progressive,
hereditary disease, exocrine glands, is the
most common Caucasian shortened life
expectancy will cause the genetic disease.
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The disease of the defective gene will cause
the body to produce excessive mucus,
especially on the respiratory system and
digestive tract of the impact of the drama.
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Airway glands produce thick, thick
secretions, airway obstruction, and cause
pulmonary infection
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When the pulmonary alveolar collapse, the
pneumonia will often follow. Pneumonia in
cystic fibrosis patients is the most
susceptible, and easy to recurrent infections.
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In Scandinavia, there is an average of 25 individuals
carrying one of a cystic fibrosis can be copied from
the gene. because they do not show the phenotype
of mutant genes, so most will not find that
heterozygous carriers of them. Therefore, This white
group, there are about 1 / 2500 of the infant is
homozygous recessive, which are born with cystic
fibrosis.
Usually the children suffering from cystic fibrosis
call their disease will be the "65 Roses", because the
English pronunciation in the Sixty-five roses and
Cystic fibrosis is very close to
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Cystic fibrosis gene was isolated in 1989,
treatment of the disease has entered a new
era!
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The cystic fibrosis transmembrane
conductance regulator(CFTR) is a chloride
channel located in the apical membrane of
many epithelial cells.
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Gating studies before
crystallization
Structure Research of
CFTR
Gating of CFTR
channels
Crystallographic
studies of ABC
transporters
Gating studies after
crystallization
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Gating of CFTR channels
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The first piece of evidence for CFTR being
an ATP-gated ion channel comes from
patch-clamp experiments by Anderson
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The role of ATP hydrolysis in CFTR gating
was implied by Anderson’s studies since the
CFTR channel failed to open in the presence
of nonhydrolyzable ATP analogs such as
AMP-PNP or ATPγS.
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The first piece of evidence for CFTR being
an ATP-gated ion channel comes from
patch-clamp experiments by Anderson
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In addition to nonhydrolyzable ATP analogs,
ADP was the other commonly used
nucleotide for CFTR gating studies.
Anderson et al.[9] showed that ADP by itself
cannot stimulate the channel activity, but in
the presence of ATP it inhibits CFTR activity.
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Crystallographic studies of ABC
transporters
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Gating studies after crystallization
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An explanation for the debilitating effects on lung
function from the absence of the CFTR protein.
More than 1000 different mutations
70% of the alleles contain the same genetic
alteration
All missing 3bp of DNA that encode a
phenylalanine at position 508
Fail to be processed normally within the
membrances of the endoplasmic reticulum
Can not reach the surface of epithelial cells
At lower temperature, it functions quite well.
small molecules that can bind to these mutant CFTR
molecules, preventing destruction , reach the cell surface.
Several promising candidates have been identified, but
none has yet to be proven effective in clinical trials.
The ΔF508 mutation had to have originated more than
50,000 years ago to have reached such a high frequency.
Heterozygotes may receive some selective advantage.
Cholera
No record of cholera epidemics in Europe until
the 1820s.
Typhoid fever
Bacterium adheres poorly to the wall of an intestine
Antibiotics
Bronchodilator
Five types of drugs
Mucus solvent
Antioxidant
Gene therapy
gene therapy—replacement of the defective gene
with normal
Cystic fibrosis is a good candidate for gene therapy
because the worst symptoms of the disease result
from the defective activities of epithelial cells that
line the airways
are accessible to agents that can be delivered by
inhalation of an aerosol.
delivery systems:
one group of trials:
the normal CFTR gene was incorporated into the DNA
of a defective adenovirus. The recombinant virus infect
the cells of the airway, delivering the normal gene to the
genetically deficient cells.
disadvantage
the viral DNA does not become integrated into host cell
induces an immune response
eliminates the virus
and leads to lung inflammation.
for fear of initiating the formation of cancers.
In other trials:
the DNA encoding the normal CFTR gene has been
linked to positively charged liposomes that can fuse
with the plasma membranes of the airway cells,
delivering their DNA contents into the cytoplasm.
advantage
less likely to stimulate a destructive immune response
disadvantage
less effective in modification
To date, none of the clinical trials of gene
therapy has resulted in significant
improvement of either physiologic
processes or disease symptoms.
Natural Compound:
Theophylline
Curcumin
Denufosol Tetrasodium