[HN Gopher] Secret Workings of Smell Receptors Revealed for Firs...
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Secret Workings of Smell Receptors Revealed for First Time
Author : pseudolus
Score : 51 points
Date : 2021-06-22 10:30 UTC (1 days ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| monkeybutton wrote:
| Very interesting! I remember this being an odd gap when I took an
| introduction to neuroscience course many years ago. Visual
| perception was well understood, auditory was fairly complete
| (although I remember there being some mystery around sound
| frequencies that are to fast to be encoded), and then smell was
| "We have some idea but its complex and not like the others. Some
| theories may involve quantum mechanics".
| post_break wrote:
| I wish we knew more on how covid messed them up and how to fix.
| Ever since I had covid my smell sensitivity is very low. I get
| really weird smells and tastes from food that sometimes make me
| sick.
| burnished wrote:
| If I understand correctly[1] covid messes with supporting cells
| and not the sensory neurons themselves and there is hope that
| this means that particular side effect should be temporary.
|
| [1]https://hms.harvard.edu/news/how-covid-19-causes-loss-smell
| UncleOxidant wrote:
| 'Secret' doesn't seem like the right word to use here. It implies
| that it was some sort of government coverup.
| SllX wrote:
| 'Secret' in context here simply refers to a mystery, much like
| "secrets of the Universe" would.
| favoritecolor wrote:
| I love when I see smell research on Hacker News -- and hopefully
| I can provide a bit of context about this paper.
|
| This finding recently made a big splash at AChemS 2021 (the
| annual meeting for the Association for Chemoreception Sciences).
| And it actually is a really big deal. A protein structure is
| extremely information rich, telling you where all of the atoms of
| a given protein are (ish). Before this finding, there were NO
| structures of any olfactory receptor, and historically the
| publication of the first structure of a given biomolecule has
| been a watershed moment for that field (insulin, ribosome, many
| other examples).
|
| What's more, they used the structural information to rationally
| engineer their olfactory receptor, expanding the binding pocket
| and changing how the receptor responds to different odorants.
| That was pretty much impossible to do before this. So, this is a
| pretty huge finding, and will definitely encourage more
| structural work on olfactory receptors in the future.
|
| If I had to poke a hole in this finding, it would be that insect
| olfactory receptors are substantially different from mammalian
| olfactory receptors. But in my opinion, it seems that the buzz
| about this paper is definitely justified. Very cool!
| shoto_io wrote:
| Is this in any way support for the "Vibration theory of
| olfaction"?
|
| https://en.wikipedia.org/wiki/Vibration_theory_of_olfaction
| beebeepka wrote:
| Thanks to your link, I discovered this:
| https://en.m.wikipedia.org/wiki/Docking_theory_of_olfaction
|
| Had no idea it's just a theory. I've lived many years
| "knowing" that we detect smells due to their shapes.
| Duller-Finite wrote:
| This paper is the first structure of any odorant receptor-
| ligand interaction. There's currently no equivalent
| structure for mammalian odorant receptors to validate the
| docking theory, but it's likely correct.
| [deleted]
| jfengel wrote:
| Question: does this put an end to Luca Turin's vibration
| theory?
|
| I realize that this has long been considered crackpottery, and
| there has never been a reasonable sense of a mechanism for it.
| But it did seem to offer at least a stab at a couple of
| questions that didn't have good answers in the ordinary lock-
| and-key model of olfaction, such as why sulfur-containing
| molecules all smell "sulfury" if they all unlock different
| locks.
|
| As far as I can tell the idea sorta just died out. A lot of
| work was done trying to make odor molecules with different
| isotopes, with intriguing but inconclusive results.
|
| Still, I've been kinda curious to see if the theory was finally
| over and done.
| smegcicle wrote:
| about time we start working on the smell-o-vision future
| predicted in the 6G whitepaper from the international telegraph
| union
|
| https://www.itu.int/en/ITU-T/focusgroups/net2030/Documents/W...
| Duller-Finite wrote:
| This is truly a landmark study. This is the first structure of
| any odorant receptor. It is, however, one from an insect, so the
| structure is not homologous to mammalian olfactory receptors,
| which are a large family of G-protein-coupled receptors.
| epmaybe wrote:
| Forgive my ignorance, but I am wondering if this is all that
| different. GPCRs typically downstream towards ion channels,
| right? So even if insect physiology relies on ligand gated ion
| channels, is the end result the same, just more metabolically
| expensive in mammals?
| Duller-Finite wrote:
| Not really. GPCRs amplify signals at each step via their
| second messenger cascade. These channels form homotetramers
| whose structure differs greatly from the canonical seven
| transmembrane domain structure of GPCRs. So this study is
| important since there were no studies indicating how odorants
| bind and activate odorant receptors. However, it is unlikely
| that the mechanisms in insects odorant receptors will
| directly apply to those of mammalian odorant receptors. In
| contrast, mammalian odor receptors will work much more like
| those of other class A GPCRs like the b-adrenergic receptor,
| of which there are numerous structures interacting with
| ligands and in various configurations, and which was the
| basis of the work that won the nobel prize in 2012.
| amelius wrote:
| I'm smelling click-bait.
| Uhhrrr wrote:
| Reasonable, given the title, but as someone who had no idea how
| smell receptors work, I thought it was neat.
|
| The nut:
|
| > [T]he limited repertoire of receptors on its olfactory
| sensory neurons must somehow recognize a vast number of
| compounds. So an individual receptor has to be able to respond
| to many diverse, seemingly unrelated odor molecules.
|
| > That versatility is at odds with the traditional lock-and-key
| model governing how selective chemical interactions tend to
| work. [....]
|
| > Now, new work has taken a crucial and much anticipated step
| forward in elucidating the beginning stages of the olfactory
| process. In a preprint posted online earlier this year, a team
| of researchers at Rockefeller University in New York provided
| the first molecular view of an olfactory receptor as it bound
| to an odor molecule.
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