Oddly Microbial: Prions by Marcia Stone (Noticias)

PrionsPrions can turn their victims into zombies—they punch holes in their brains and steal their souls. The infected stumble about, might take a bite out of someone if hungry, certainly don’t think straight and, most important, lose their memories and with them the very essence of their humanity or “soul.” Zombie enthusiast and Harvard psychiatrist Steven Schlozman made the connection and has even written a science fiction novel, soon to be a film, about a prion-caused apocalypse called The Zombie Autopsies. In the book, influenza-like viruses with prion payloads, possibly concocted by mad scientists, cause a zombie pandemic that kill off a goodly portion of the planet’s humans; but not before the newly minted zombies stagger about trying to eat, and likely infecting, anyone they manage to fall into. Schlozman’s hypothetical disease, “ANSD” or Ataxic Neurodegenerative Satiety Deficiency Syndrome, is readily transmitted by coughing or sneezing.

OK. That neurologic prions turn people into “zombies” is a good analogy; sadly, that’s what seems to happen when Alzheimer’s and raft of other protein-instigated neurodegenerative diseases take hold. However, it’s unlikely that any amount of microbiological savvy could keep a tiny RNA virus schlepping around a prion or two afloat. And even if a few overloaded viruses manage to accidently plummet into an open nostril while struggling to stay aerosolized, it isn’t in the nature of prions to cause immediate disease.

Pathogenic proteins accepted as infectious agents… but not without a fight

Notably, before Stanley Prusiner, a neurologist, stood his ground in the 1980s insisting that dementias could be caused by nucleic acid-deficient infecting agents, virologists were adamant in their belief that these strange diseases were caused by “slow viruses.” Emphasis was on the “slow.” Furthermore, dogma at the time held that “conveyers of transmissible diseases required genetic material composed of nucleic acid (DNA or RNA) in order to establish infection in a host,” Prusiner writes.

Prusiner lost both his promotion to tenure at the University of California San Francisco and his Howard Hughes Medical Institute (HHMI) grant by stubbornly defending his then heretical belief that “proteinaceous infectious particles“—or “prions”—could underlie inherited, as well as communicable, diseases. Such dual behavior was unknown and thus unthinkable at the time. “Virologists were generally incredulous, and some investigators working on scrapie and Creutzfeldt-Jakob disease were irate.” Prusiner got even at the Nobel Prize ceremony in 1997 and cautions in his autobiography: “While it is quite reasonable for scientists to be skeptical of new ideas that do not fit within the accepted realm of scientific knowledge, the best science often emerges from situations where results carefully obtained do not fit within the accepted paradigms.” He also got his tenure at UCSF and a much larger grant, but not from HHMI. Now, 30 years after he and his colleagues isolated a rogue protein that could cause disease in healthy animals, Prusiner says there’s enough evidence to support a unifying prion-like mechanism in neurodegenerative and, perhaps, other diseases.

Alzheimer’s prions prove protein-caused disease is transmittable

Prion infectivity depends on a normal cellar prion protein (PrPC) misfolding into what’s known as the “scrapie” protein (PrPSC), and then corrupting the normal surrounding proteins. PrPSC is prone to aggregation, thus the misfolded prion proteins tangle themselves up as, for example, in Alzheimer’s disease, forming brain-destroying Aβ amyloid plaques. Alzheimer’s has recently proved transmissible in marmosets, thus proving beyond a doubt that prions can cause disease. And distressingly, grafted fetal brain cells can become infected with α-synuclein prions after they’ve been transplanted into patients with Parkinson’s disease. Prusiner conjectures that the disease-causing prions cross from the neurons of the recipient and corrupt the healthy fetal cells…

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