The Histamine H1 human membrane protein. |
An
international team of scientists using Diamond Light Source, the UK’s
national synchrotron facility, has successfully solved the complex 3D
structure of the human Histamine H1 receptor protein. Published in the
journal Nature this week, their discovery opens the way for the
development of ‘third generation’ anti-histamines, specific drugs
effective against various allergies without causing adverse
side-effects.
The
team, comprising leading experts from the USA (The Scripps Research
Institute in California), Japan (Kyoto University), and the UK (Imperial
College London and Diamond), worked across three continents for 16
months on the project.
Professor
So Iwata, David Blow Chair of Biophysics at Imperial College London,
BBSRC Fellow and Director of the Membrane Protein Laboratory at Diamond,
said: “It took a considerable team effort but we were finally able to
elucidate the molecular structure of the Histamine H1 receptor protein
and also see how it interacts with anti-histamines. This detailed
structural information is a great starting point for exploring exactly
how histamine triggers allergic reactions and how drugs act to prevent
this reaction.”
H1
receptor protein is found in the cell membranes of various human
tissues including airways, vascular and intestinal muscles, and the
brain. It binds to histamine, an important function of the immune
system, but in susceptible individuals this can cause allergic reactions
such as hay fever, food and pet allergies. Anti-histamine drugs work
because they prevent histamine attaching to H1 receptors.
Dr
Simone Weyand, post-doctoral scientist at Imperial College London, who
conducted much of the experimental work at Diamond, said: “First
generation anti-histamines such as Doxepin are effective, but not very
selective, and because of penetration across the blood-brain barrier,
they can cause side effects including sedation, dry mouth and
arrhythmia. By showing exactly how histamines bind to the H1 receptor at
the molecular level, we can design and develop much more targeted
treatments.”
The
research was technically challenging because membrane proteins are
notoriously difficult to crystallise – a step that is vital in solving
protein structures using a synchrotron. The proteins were grown in cells
at Kyoto University in Japan, then processed cell material was flown to
Professor Raymond Stevens at The Scripps Research Institute in La
Jolla, California, who leads the GPCR Network of the National Institute
of General Medical Sciences’ Protein Structure Initiative funded by the
National Institutes of Health Common Fund, and has developed powerful
techniques to analyse membrane proteins and crystallise G-protein
coupled receptors (GPCRs).
The
crystals took around two months to grow and when each batch of around
100 was ready, they were frozen and flown to the UK. Here, Prof Iwata
and Dr Weyand worked with Diamond’s scientists to analyse a total of
over 700 samples using the Microfocus Macromolecular Crystallography
(MX) beamline I24, a unique instrument capable of studying tiny
micro-crystals using an X-ray beam a few microns wide.
Dr Simone Weyand working on the Microfocus Macromolecular Crystallography beamline at Diamond Light Source. |
Prof
Stevens said: “A key aspect of our program is to collaborate with the
leading researchers in the world so that we can uncover the mysteries of
how GPCRs work. To fully understand this large and important human
protein family will take a global community effort and the study of
multiple receptors with different techniques and approaches. The
collaboration with the Iwata lab is a great example of success made
possible by joining forces; in this case, our work on histamine H1
receptor helps to advance the field as quickly and efficiently as
possible.”
Prof
Iwata added: “The fact that we’ve managed to solve this structure in 16
months starting from pure protein is very exciting as it shows what can
be achieved when a team of experts pool skills and experience in sample
preparation, experimental techniques and data analysis. Having the
Membrane Protein Laboratory situated inside the Diamond synchrotron
itself is a major advantage for projects like this. We’ve benefited
from rapid-access to the beamline and round the clock support for our
experiments and data analysis work.”
Professor
Gerd Materlik, Diamond’s Chief Executive, said: “Solving this
challenging structure so quickly is a significant achievement for Profs
Iwata and Stevens, their groups and the I24 beamline team. I’m
delighted that, in addition to providing access to cutting-edge research
facilities, our scientists and technical experts have played an active
role in this exciting project and I look forward to many future
discoveries from the Membrane Protein Laboratory and the Microfocus MX
beamline.”
This
research was supported by the ERATO Human Receptor Crystallography
Project from the Japan Science and Technology Agency, the Targeted
Proteins Research Program of MEXT in Japan and the National Institutes
of Health in the USA. Funding also came from the UK’s Biotechnology and
Biological Sciences Research Council (BBSRC), Grant-in-Aid for
challenging Exploratory Research, the Mochida Memorial Foundation for
Medical and Pharmaceutical Research, the Takeda Scientific Foundation
and the Sumitomo Foundation.
