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The 2012 Nobel Prize in Chemistry – what are G protein-coupled receptors?

Many proteins make up the G protein-coupled receptor family, including the κ-opioid receptor (above). Wikimedia Commons

The 2012 Nobel Prize in Chemistry – what are G protein-coupled receptors?

Two US scientists have been awarded this year’s Nobel Prize in Chemistry for discovering the receptors that transmit signals such as light, taste or smell to cells.

Robert Lefkowitz (of Duke University Medical Centre in Durham, North Carolina) and Brian Kobilka (of Stanford University School of Medicine in Palo Alto, California) received the prize for their work on “cells and sensibility”.

For a long time, it remained a mystery how all the cells in our body could specifically sense and respond to their environment. No-one really knew how these sensors could transmit an external signal across the cell membrane to the inside of the cell, resulting in a broad range of physiological processes.

When Dr Kobilka was introduced to receptors while doing postdoctoral research in Dr Lefkowitz’s lab, their work focused on sensors located in the heart that respond to the hormone adrenaline.

These receptors were found to be located right at the the cell surface and are part of a much bigger family of receptors called G-protein-coupled receptors (GPCRs).

Thanks to the pioneering work of Lefkowitz and Kobilka, it is now known that GPCRs can detect many other internal signals which are relayed via these receptors to the inside of our cells as a message to do something unique.

For instance, when adrenaline binds to receptors in your heart (which the Nobel Prize winners characterised) all the cells may contract harder and faster. You may well have experienced this “internal” sensation when you have become nervous about something.

Indeed GPCRs are responsible for the anxiety you may experience when a spider falls out of your sun visor when you are driving your car!

GPCRs are also used to relay messages from the external environment to provide us information. We now know there are receptors in our nose to detect odours, in our eyes to detect light and in our mouth to detect flavours.

So when you drink your favourite glass of red wine it is your receptors for odour and flavours that give you the taste sensation. And, of course, light receptors allow you to see the nice colour of your shiraz.

There are many different GPCRs located right throughout our bodies involved in everything ranging from fat metabolism to neurotransmission.

In fact most physiological processes depend of GPCRs and approximately half of all medications act on these receptors to help treat many different medical conditions.

The so-called beta blockers are used to treat high blood pressure (hypertension) and antihistamines for allergies. Even honey bees use their GPCRs to find their way to the next flower!

Identifying and understanding how GPCRs work has been crucial to unravelling the complex network of signalling between cells and organs and the environment.

The groundbreaking work of Lefkowitz and Kobilka has opened many paths of discovery at the biology/chemistry interface and has considerable broader impact in our day-to-day lives.

Understanding how these nanoscale molecular machines are intricately built and how they function has been and will continue to be crucial for the field of molecular biology in the future.
Further reading:
The 2012 Nobel Prize in Chemistry, explained
The 2012 Nobel Prize in Physics, explained