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Thanks. It is also not clear to me after a quick search whether any amyloid has been called "infectious" other than ones derived from the PRNP sequence. It is v

• subroutine 8y ago
  I'm telling you-- i went down the prion rabbit hole myself recently and the entire path is littered with misconception and inconsistencies in how the term "prion" is being used. One place to start other than wikipedia is this cdc site that lists know prion diseases... https://www.cdc.gov/prions/index.html https://www.cdc.gov/prions/index.html After some digging, I concluded that all the diseases they listed are related to PRNP. Please, please, correct me if I'm wrong. I'm actually going to chat with a friend in a few minutes who is a postdoc at MIT studying protein (mis)folding, and said he could help clarify. (i'll relay any new insights...)
  • subroutine 8y ago
    Follow-up -- Spoke with my postdoc friend who informed me there are basically 3 definitions of prion being used in the literature (outside formal reports, he contends that, just as 'epigenetics' evolved to mean nothing in particular, the term 'prion' could mean almost anything). The big three: 1. The purists say prions are protein-only infectious agent; and they have a strong case since the word prion was coined as an abbreviation for "proteinaceous infectious particle". However the specific prion protein underlying these various diseases were all turning out to be the same thing. > This evidence has led to the now widely accepted prion theory, which states that the cellular protein PrP is the sole causative agent of prion diseases; there is no nucleic acid involved. The theory holds that PrP is normally in a stable shape (pN) that does not cause disease. The protein can be flipped, however, into an abnormal shape (pD) that does cause disease. pD is infectious because it can associate with pN and convert it to pD, in an exponential process--each pD can convert more pN to pD. What is a Prion - Scientific America https://www.scientificamerican.com/article/what-is-a-prion-specifica/ 2. So they officially named this protein (drumroll) prion protein (PrP), and the PrP gene was named PRNP (PRioN Protein). Yep, there is literally a "prion protein". This protein called prion protein is probably like any other highly conserved protein, and performs important every-day cell stuff. So prion protein does not usually display prion-like behavior Not confused yet? Don't worry, there is a 3rd definition that has taken shape... 3. Self-templating. The word "prion" or "prion-like" has come to mean any protein that display self-templating, and is usually talked about in conjunction with epigenetic inheritance. My postdoc buddy contends this 3rd definition is winning the useage war, and so when he hears "prion", he assumes "proteins that can fold into multiple conformations with some being self-propagating." A very clear example of this usage can be found in this article on yeast (and no, it doesn't involve PRNP analogs): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319070/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319070/
    • nonbel 8y ago
      Interesting, thanks for the history.