Water Channels 2003 Chemistry Nobel Prize

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Water Channels2003 Chemistry Nobel Prize

• Kristi McKee
• SFASU Fall 2003
• Scientific Discovery

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Importance of this Award

• 70 of living systems are made up of water.
• Have to have some type of mechanism to move water
  and important ions around.

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Cell Membrane

• The cell membrane is important in protecting the
  cells organelles from the environment and
  transporting nutrients in and waste out of the
  cell.

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Cell Membrane

• The cell membrane is made up of mostly
  phospholipidis and proteins.

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Cell Membrane

• Phospholipids have a hydrophilic and hydrophobic
  ends.
• The phosphate head is charged while the carbon
  tail is not charged.

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Phopholipid Structure
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Cell Membrane

• Three types of predominant proteins in the
  membrane
• Transport Proteins
• Marker Proteins
• Receptor Proteins

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Cell Membrane

• Transport Proteins regulate transport and
  diffusion across membrane. There are two forms
• Carrier
• Channel

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Carrier Proteins

• They do not extend the whole distance of
  membrane, instead move back and forth carrying
  nutrients and waste in and out.

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Channel Proteins

• Some act as a passive pore to allow diffusion of
  water and some other molecules.
• Does not require energy.

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History

• 1890 Wilhelm Ostwald proposed the idea that
  electric signals were produced by ions moving in
  and out of the cell. He was awarded the Nobel
  Prize in 1909 for the discovery.

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History

• John Eccles, Alan Hodgkin and Andrew Huxley were
  able to show how potassium and sodium ions were
  involved in chemical cascades (i.e. eyes
  watering, muscles contracting) They were awarded
  a Nobel Prize in the 1963.

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HIstory

• Jens Skou awarded the Nobel Prize in Chemistry in
  1997 for discovery of Sodium-Potassium Pumps.

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History

• In the 1970s scientists were able to prove that
  some channels were specific to only particular
  type of ions.
• However, no one had yet been able to see what a
  water channel actually does, how it looks.

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Advance of Science

• In the late 1980s protein science had advanced
  for the study of molecular machinery of how
  proteins may work and function.
• By 1992 scientists were able to identify which
  proteins were involved in channels.

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• Peter Agre

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Peter Agre

• BA in Chemistry 1970 Augsburg College
• MD 1974 from Johns Hopkins University School of
  Medicine
• 1974 75 Postdoctoral Fellowship Johns Hopkins
  Dept of Pharamacology

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Agre

• 1975 78 Internship and Residency at Case
  Western Reserve University Dept. of Medicine
• 1978 80 Postdoctoral Fellowship At Univ. of N.
  Carolina at Chapel Hill Dept. of Medicine
  Hematology/Oncology Div.
• 1980 81 Clinical Asst. Professor of Medicine
  Univ. of N. Carolina at Chapel Hill

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Agre

• 1980 81 Senior Clinical Research Scientist
• 1981 83 Research Associate Johns Hopkins School
  of Medicine Dept. of Cell Biology/Anatomy and
  Medicine
• 1984 93 Asst. Professor Johns Hopkins
• 1990 94 Co-Director Office of Research Planning
  Dept. of Medicine

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Agre

• 1993 present Professor Johns Hopkins School of
  Medicine Departments of Biological Chemistry and
  Medicine
• 1996 1999 Director of John Hopkins Graduate
  Program in Cellular and Molecular Medicine (CMM)
• 1999 present Chair Advisory Board Johns Hopkins
  Graduate Program in CCM

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Agres Work

• In mid-1980s he studied various proteins found
  in the membrane of red blood cells and also found
  one in the kidneys and was able to determine the
  peptide sequence and the corresponding DNA
  sequence. (CHIP28 28kDa)

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Agres Work

• Expressed the CHIP28 in Xenopus oocytes and
  placed in hypo-osmotic medium and noticed the
  cells swelling rapidly.

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Agres Work

• He tested his theory by a simple experiment by
  comparing two cells one with this protein and one
  without. When exposed to water the ones with the
  protein swelled and one without remain unchanged.
  

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Agres Work
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Agres Work

• Also ran trials on artificial cells called
  liposome (type of soap bubble with water on
  inside and out) Also found the cells with the
  protein (CHIP28) inserted in membrane acted as
  previous cells.
• He termed these channel proteins aquaporin,
  water pore.

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Agres Work

• From knowledge that Hg2 blocks water movement in
  cells he was able to show the cells with the
  protein were also rendered inactive by the
  mercury ions. This finding made him believe that
  his discovery was actually a water channel.

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Agres Work

• In 2000 with other research scientists, he was
  able to show the first three-dimensional of an
  aquaporin (Aquaporin-1 from human red blood
  cell).

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Agres Work
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Phylogenetic Tree
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The Other Half

• Roderick MacKinnon

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Roderick MacKinnon

• BS 1978 Brandeis University in Biochemistry
• MD 1982 Tufts Medical School in Boston
• 1985 Completed residency at Beth Israel Hospital,
  Harvard, board Certified in internal medicine.

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MacKinnon

• 1985 86 Postdoctoral Fellowship in Dept of
  Medicine at Beth Israel Hospital.
• 1986 89 Postdoctoral Fellowship in Dept. of
  Biochemistry at Brandeis.
• 1989 91 Asst Professor in Dept. of Cellular and
  Molecular Physiology, Harvard Medical School.

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MacKinnon

• 1991 92 Asst. Professor in Dept. of
  Neurobiology, Harvard Medical School.
• 1992 received PEW Scholar in Biomedical Sciences
  and McKnight Scholars Award
• 1995 Received Biophysical Society Young
  Investigator Award and was promoted to full
  Professor at Harvard Medical School Dept. of
  Neurobiology.

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MacKinnon

• 1996 Present Professor in Laboratory of
  Molecular Neurobiology and Biophysics and
  Rockefeller University, New York City. Also an
  Investigator at the Howard Hughes Medical
  Institute.
• 1999 Awarded Lasker Award for Basic Medical
  Research on work with ion channels.

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MacKinnon

• Took a new approach to try and crack the
  controversy of ion channel proteins.
• First worked with scorpion toxin that was
  discovered to block potassium channels that lead
  to the discovery of the shaker gene.

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MacKinnon

• Discovered that potassium channels had to be
  tetramers by binomial statistics and the toxin
  experiments.

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MacKinnon

• Using his skills and the advancements of X-ray
  crystallography, MacKinnon taught himself the
  fundamentals and presented the structure of an
  ion channel in April of 1998 (KcsA from the
  bacterium Streptomyces lividans).
• Also revealed how ion channel functions at an
  atomic level.

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MacKinnon
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MacKinnon

• Two types of ion channels studied and discovered
  how they differentiated between ions
• Potassium channels
• Sodium channels

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MacKinnon

• The channels had a selective filter in the
  P-loop, and a sensor to determine when to let the
  ions in and out of the cell.
• Discovered in the potassium channel that the
  spacing between the K and the oxygen atoms in
  the filter and the sodium ions do not fit so they
  remain behind in the water solution.

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MacKinnon
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MacKinnon

• Ion Channel GatingIon channel gating refers to
  opening and closing of the ion conduction pore in
  response to a specific stimulus.
• Certain channels open when ligands bind
  (ligand-gated channels) others open in response
  to membrane voltage (voltage-gated channels).

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MacKinnon

• Studied diffusion-limited rates by analysis of
  ion conduction on potassium channels using K and
  Rb
• Used Rb because they are know to penetrate K
  channels.
• Found K ion is passed and rehydrated in
  approximently ten nanoseconds.

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Channels

• Types of channels
• Water They are responsible to transportation of
  water in and out of the cell.
• Ion Move ions in and out to conduct such things
  as signal cascades.
• Aquaglyceroporins Trasport glycerol and other
  small molecules across membrane.

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Channels

• There are now 11 different variants of these
  channels in the human body and more may still be
  discovered.
• They are responsible for many reactions in the
  body one major function is done in the kidneys.

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Body Functions

• 170 liters of primary urine produced in 24 hours
  but only approximently 1 liter is excreted per
  day.
• This is due to the mechanisms in kidneys
• 70 of water reabsorbed by AQP1 into blood
• 10 of water reabsorbed by AQP2

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Kidney Tubules
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Diseases related to Ion Channels

• Several disease states are related to
  dysfunctional ion channels.
• cardiac arrhythmias
• diabetes
• hypertension
• angina pectoris
• epilepsy

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Diseases Related to Defects with Ion Channels

• Alzheimers Disease
• Parkinsons
• Schizophrenia
• Thought to result from dysfunction of voltage
  gated channels

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Defects in Ion Channels

• 1989 cystic fibrosis was first discovered to be
  as a defect in ion channels.
• Epilepsy caused from synchronised bursts in nerve
  cells in the brain that result in seizures.
  Disorder was found in the beta subunit or in the
  alpha subunit in voltage-gated sodium channel.
  Defect in a single change of amio acid residue.

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Defect in Aquaporins

• A deficiency in the antidiureti hormone,
  vasopressin, may be affected by diabetes
  insipidus and show an increase of urine excretion
  to 10 15 liters a day.

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Drug Targeting

• Already today, drugs targeting ion channels
  generates over 6 billion dollars in sales per
  annum. According to the FDA, the number of new
  approved drugs targeting ion channels is equal to
  or even higher than that for drugs targeting
  proteases, polymerases and reverse transcriptases.

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Resources

• Agre, Peter Bonhivers, Melanie Borgnia, Mario
  J. The Aquaporins, Blueprints for Cellular
  Plumbing Systems, Jounal of Biological
  Chemistry Vol. 273, Issue 24. June 12, 1998. pp
  14659 14662.
• An Interview with Roderick MacKinnon, Lasker
  Foundation. www.laskerfoundation.org/awards/libra
  ry/1999b_int_mr2.shtml.
• Boigraphy of Roderick MacKinnon Lasker
  Foundation. www.laskerfoundation.org/awards/libra
  ry/ 1999b_boi_mr.shtml
• Bowen, R. Aquaporins Water Channels
  www.arbl.cvmbs.colostate.edu/hbooks/molecules/aqua
  porins.html

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Resources

• Cell Membrane Cartoon. www.people.virginia.edu/r
  jh9u/cellmembrane.html
• Chemistry Channels Spotlight
  www.psigate.ac.uk/spotlight/issue13b/chemistry.htm
  l
• Dworakowska, Beata Dolowy, Krzysztof. Ion
  Channels-related Diseases, Acta Biochimica
  Polonica Vol. 47 No. 3, July 27, 2000. pp. 685
  703.
• Hard, Trude. Potassium Channels in Guard Cells
  From Phenomenon to Structural Analysis,
  www.iwf.de/iwfeng/3medien/33db/333/c7041.html

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Resources

• Jensen, Morten O Tajkhorshid, Emad Schulten,
  Klaus. Electrostatic Tuning of Permeation and
  Selectivity in Aquaporin Water Channels,
  Boiphysical Journal. Vol 85. November 2003. pp
  2884 2899.
• Karow, Julia. Interview with Roderick
  MacKinnon, March 4, 2002. Scientific American.
  www.sciam.com
• Keeley, Jim. Researchers Discover Structure of
  Natures Circuit Breaker, April 30, 2003.
  www.eurekalert.org/pub_releases/2003-04/hhmi-rds04
  2903.php

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Resources

• Morals-Cabral, Joao H Zhou Yufeng MacKinnon,
  Roderick. Energetic Optimization of Ion
  Conduction Rate by the K Selectivity Filter,
  
  
  Nature. Vol. 414, November 2001pp. 37 42.
• Morrill, James A. MacKinnon, Roderick.
  Isolation of a Single Carboxyl-Carboxylate
  Proton Binding Site in the Pore of a Cyclic
  Nucleotide-gated Channel, Journal of General
  Physiology. Vol. 114 July 1999. pp. 71 83.

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Resources

• Nobel Prize in Chemistry. Advanced Information
  for Public. www.nobel.se
• Nobel Prize in Chemistry 2003 - Information for
  the Public www.nobel.se/chemistry/laureates/2003
  /public.html
• Phospholipid Structure. www.bact.wisc.edu/microte
  xtbook/bacterialstructure/membraneGen.html
• Structure and Mechanism of Ion Channels,
  www.hhmi.org/research/investigators/mackinnon.html

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Resources

• Shaping better Understanding of Potassium
  Channels, www.hhmi.org/news/mackinnon6.html
• Structural Studies Reveal How Potassium Channels
  are Inactivated, www.hhmi.org/newsmackinnon4.htm
  l
• The Virtual Cell Web Page Ch 3 Cell Biology.
  www.personal.tmlp.com/Jimr57/textbook/chapter3.htm
  
• Voltage Dependent Potassium Channel. Roderick
  MacKinnon, Ion Channels. www.osti.gov/accomplishm
  ents/mackinnon.html