disease in which aggregating misfolded host pro-
teins—a class referred to as amyloid—seem to prop-
agate and wreak havoc either. In Parkinson’s dis-
ease, misfolded alpha-synuclein proteins spread
through the brain, and in amyotrophic lateral sclero-
sis (Lou Gehrig’s disease), the misfolded, accumu-
lating protein is TDP-43. We should investigate the
transmission potential of these diseases as well.
The only thing that seemed to separate these
conditions from classic prion diseases was trans-
missibility. But now that that barrier has been
breached for at least one, I also wonder: What is
the difference between amyloid and prions? Are
they part of a spectrum? Are they one and the
same? If not, what is the difference? Can what
we’ve learned about the biology of prions help our
efforts to fight amyloid dementias? Of course,
since we still can’t cure prion diseases, it may not
be much help even if so.
The realization that the peptides involved in
some of the most common and feared dementias
on Earth may be transmissible under even limited
conditions is a sobering and humbling reminder of
how very little we still understand about them. Giv-
en what we know about prions, I think we would be
wise not to underestimate their abilities.
Opinion