Removing toxic aggregates that our cells can’t break down

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Removing toxic aggregates that our cells cant
break down Aubrey de Grey Department of
Genetics, University of Cambridge Email
ag24_at_gen.cam.ac.uk Website http//www.gen.cam.ac.
uk/sens/
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The lysosome the cells garbage disposal
machinery of last resort
Amino acids
P
Lyso-some
R
?
M
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The problem the lysosome is not
omnipotent Livers solution exocytosis
Lyso-some
Lyso-some
Not done elsewhere kidneys would suffer?
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All other cells solution sequestration Obvious
ly fails eventually Cellular function
impaired Cell becomes toxic Cell dies
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• Lysosomal junk
• The four major types
• Lipofuscin. Universal marker of postmitotic cell
  aging reaches 10 of total cell mass in heart
  and motor neurons. No clear proof of
  pathogenesis, but in vitro evidence is strong

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• Lysosomal junk
• The four major types
• 2) A2E -- weird molecule created by reaction of
  the membrane lipid phosphatidylethanolamine with
  the photoreceptor pigment retinal. More or less
  proven to be pathogenic causes age-related
  macular degeneration.

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• Lysosomal junk
• The four major types
• 3) Hyperphosphorylated tau in neurons. Widely
  believed to be a major cause of Alzheimers
  disease. Similar aggregates form in other
  neurodegenerative diseases and normal aging.

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• Lysosomal junk
• The four major types
• 4) Oxidised (etc) cholesterol and cholesteryl
  esters (oxysterols) in arterial macrophages.
  Causes them to become foam cells, then fatty
  streaks, and eventually atherosclerotic plaques.

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• Why dont graveyards fluoresce?
• de Grey 2002, Trends in Biotechnology 20452-455
• These (often fluorescent) materials do not
  accumulate in nature, even in areas rich in the
  remains of animals that produce them. Thus,
  something degrades them. They are energy-rich,
  so micro-organisms could live off them.
• Bacterial strains exist with astonishingly varied
  catabolic activities, and are being used by many
  groups for bioremediation purposes. They degrade
  rubber, TNT, PCBs, dioxin, ... Some fungi are
  similarly versatile.
• Can micro-organisms capable of degrading
  lysosomal junk be isolated from the soil???

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• Some FAQs
• Q Arent foam cell lysosomes mainly native
  cholesterol?
• A Yes - the major lysosomal component is not
  necessarily the culprit - the culprit may impair
  lysosomal trafficking of normally benign things
• Q Wont we need an awful lot of different
  enzymes?
• A Probably not - degradation is synergistic -
  one step will often form a substrate for an
  enzyme we already have
• Q What about immune rejection?
• A Same problem/solutions as for normal gene
  therapy

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• Steps to biomedical application
• Isolate competent strains select by starvation
• Identify the enzymes (mutagenesis, chemistry,
  genomics)
• Make lysosome-targeted transgenes, assay cell
  toxicity
• Assay competence in vitro (more
  mutagenesis/selection)
• Construct transgenic mice, assay toxicity in vivo
• Assay competence in disease models (apoE-/- mice,
  etc.)
• Test in humans as for lysosomal storage diseases

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Funding the story so far 2001, 2002 Kronos deem
it too sciencey -( 2003 Archer wows NIA
officials at IABG10 -) 2004 SENS 5 (July
26th, NIA offices, Bethesda) Jay Jerome
atherogenic junk Ralph Nixon neurotoxic
junk Janet Sparrow ophthalmotoxic junk Ana Maria
Cuervo gene engineering for lysosomal
targeting Roscoe Brady protein engineering for
lysosomal targeting Bruce Rittmann, Perry
McCarty, Pedro Alvarez biorem. Fingers crossed.