TEDMED 2016
Jennifer Pluznick: You smell with your body, not just your nose
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Do your kidneys have a sense of smell? Turns out, the same tiny scent detectors found in your nose are also found in some pretty unexpected places -- like your muscles, kidneys and even your lungs. In this quick talk (filled with weird facts), physiologist Jennifer Pluznick explains why they're there and what they do.
Jennifer Pluznick - Physiologist
Jennifer Pluznick is on a mission to find out more about olfactory and other sensory receptors. Full bio
Jennifer Pluznick is on a mission to find out more about olfactory and other sensory receptors. Full bio
Double-click the English transcript below to play the video.
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Here's a question for you:
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how many different scents
do you think you can smell,
do you think you can smell,
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and maybe even identify with accuracy?
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100?
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300?
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1,000?
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One study estimates that humans can
detect up to one trillion different odors.
detect up to one trillion different odors.
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A trillion.
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It's hard to imagine,
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but your nose has the molecular
machinery to make it happen.
machinery to make it happen.
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Olfactory receptors --
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tiny scent detectors --
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are packed into your nose,
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each one patiently waiting
to be activated by the odor,
to be activated by the odor,
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or ligand,
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that it's been assigned to detect.
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It turns out we humans,
like all vertebrates,
like all vertebrates,
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have lots of olfactory receptors.
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In fact, more of our DNA is devoted
to genes for different olfactory receptors
to genes for different olfactory receptors
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than for any other type of protein.
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Why is that?
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Could olfactory receptors
be doing something else
be doing something else
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in addition to allowing us to smell?
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In 1991, Linda Buck and Richard Axel
uncovered the molecular identity
uncovered the molecular identity
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of olfactory receptors --
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work which ultimately
led to a Nobel Prize.
led to a Nobel Prize.
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At the time,
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we all assumed that these receptors
were only found in the nose.
were only found in the nose.
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However, about a year or so later,
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a report emerged of an olfactory
receptor expressed in a tissue
receptor expressed in a tissue
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other than the nose.
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And then another such report emerged,
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and another.
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We now know that these receptors
are found all over the body,
are found all over the body,
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including in some pretty
unexpected places --
unexpected places --
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in muscle,
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in kidneys,
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lungs
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and blood vessels.
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But what are they doing there?
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Well, we know that olfactory receptors
act as sensitive chemical sensors
act as sensitive chemical sensors
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in the nose --
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that's how they mediate
our sense of smell.
our sense of smell.
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It turns out they also act
as sensitive chemical sensors
as sensitive chemical sensors
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in many other parts of the body.
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Now, I'm not saying that your liver can
detect the aroma of your morning coffee
detect the aroma of your morning coffee
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as you walk into the kitchen.
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Rather, after you drink
your morning coffee,
your morning coffee,
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your liver might use an olfactory receptor
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to chemically detect
the change in concentration
the change in concentration
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of a chemical floating
through your bloodstream.
through your bloodstream.
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Many cell types and tissues in the body
use chemical sensors,
use chemical sensors,
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or chemosensors,
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to keep track of the concentration
of hormones, metabolites
of hormones, metabolites
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and other molecules,
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and some of these chemosensors
are olfactory receptors.
are olfactory receptors.
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If you are a pancreas or a kidney
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and you need a specialized chemical sensor
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that will allow you to keep track
of a specific molecule,
of a specific molecule,
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why reinvent the wheel?
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One of the first examples
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of an olfactory receptor
found outside the nose
found outside the nose
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showed that human sperm
express an olfactory receptor,
express an olfactory receptor,
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and that sperm with this receptor
will seek out the chemical
will seek out the chemical
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that the receptor responds to --
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the receptor's ligand.
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That is, the sperm
will swim toward the ligand.
will swim toward the ligand.
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This has intriguing implications.
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Are sperm aided in finding the egg
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by sniffing out the area
with the highest ligand concentration?
with the highest ligand concentration?
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I like this example
because it clearly demonstrates
because it clearly demonstrates
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that an olfactory receptor's primary job
is to be a chemical sensor,
is to be a chemical sensor,
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but depending on the context,
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it can influence how you perceive a smell,
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or in which direction sperm will swim,
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and as it turns out,
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a huge variety of other processes.
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Olfactory receptors have been
implicated in muscle cell migration,
implicated in muscle cell migration,
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in helping the lung to sense
and respond to inhaled chemicals,
and respond to inhaled chemicals,
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hand and wound healing.
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Similarly, taste receptors once thought
to be found only in the tongue,
to be found only in the tongue,
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are now known to be expressed
in cells and tissues throughout the body.
in cells and tissues throughout the body.
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Even more surprisingly,
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a recent study found
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that the light receptors in our eyes
also play a role in our blood vessels.
also play a role in our blood vessels.
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In my lab,
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we work on trying to understand the roles
of olfactory receptors and taste receptors
of olfactory receptors and taste receptors
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in the context of the kidney.
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The kidney is a central
control center for homeostasis.
control center for homeostasis.
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And to us,
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it makes sense that a homeostatic
control center would be a logical place
control center would be a logical place
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to employ chemical sensors.
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We've identified a number
of different olfactory and taste receptors
of different olfactory and taste receptors
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in the kidney,
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one of which, olfactory receptor 78,
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is known to be expressed
in cells and tissues
in cells and tissues
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that are important
in the regulation of blood pressure.
in the regulation of blood pressure.
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When this receptor is deleted in mice,
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their blood pressure is low.
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Surprisingly, this receptor
was found to respond
was found to respond
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to chemicals called
short-chain fatty acids
short-chain fatty acids
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that are produced by the bacteria
that reside in your gut --
that reside in your gut --
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your gut microbiota.
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After being produced
by your gut microbiota,
by your gut microbiota,
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these chemicals are absorbed
into your bloodstream
into your bloodstream
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where they can then
interact with receptors
interact with receptors
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like olfactory receptor 78,
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meaning that the changes
in metabolism of your gut microbiota
in metabolism of your gut microbiota
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may influence your blood pressure.
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Although we've identified a number
of different olfactory and taste receptors
of different olfactory and taste receptors
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in the kidney,
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we've only just begun
to tease out their different functions
to tease out their different functions
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and to figure out which chemicals
each of them responds to.
each of them responds to.
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Similar investigations lie ahead
for many other organs and tissues --
for many other organs and tissues --
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only a small minority of receptors
has been studied to date.
has been studied to date.
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This is exciting stuff.
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It's revolutionizing our understanding
of the scope of influence
of the scope of influence
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for one of the five senses.
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And it has the potential
to change our understanding
to change our understanding
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of some aspects of human physiology.
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It's still early,
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but I think we've picked up on the scent
of something we're following.
of something we're following.
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(Laughter)
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Thank you.
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(Applause)
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ABOUT THE SPEAKER
Jennifer Pluznick - PhysiologistJennifer Pluznick is on a mission to find out more about olfactory and other sensory receptors.
Why you should listen
Jennifer Pluznick's fascination with understanding how interactions at the molecular level affect functions at the organismal level led her to pursue a Ph.D. in renal physiology from the University of Nebraska Medical Center. While researching kidney disease as part of her postdoc at Yale University, Pluznick came across scent receptors in the kidney. She initially wrote off this surprising finding as a fluke, but after taking a second look, she realized how important this discovery could be for understanding kidney function. Since 2010, Pluznick and her lab at the Johns Hopkins School of Medicine have researched the role of the olfactory signaling system. Most recently, they’ve found a possible connection between the bacteria in your gut and how your kidney manages blood pressure.
Jennifer Pluznick | Speaker | TED.com