Novel Chemical Tools to Study Ion Channel Biology

159 Pages·2015·5.58 MB·English

by  Christopher Ahern

Advances in Experimental Medicine
and Biology
Volume 869
Editorial Board:
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Christopher Ahern • Stephan Pless
Editors
Novel Chemical Tools to
Study Ion Channel Biology
1 3
Editors
Christopher Ahern Stephan Pless
Molecular Physiology and Biophysics Drug Design and Pharmacology
University of Iowa University of Copenhagen
Iowa City, Iowa Copenhagen
USA Denmark
ISSN 0065-2598 ISSN 2214-8019 (electronic)
Advances in Experimental Medicine and Biology
ISBN 978-1-4939-2844-6 ISBN 978-1-4939-2845-3 (eBook)
DOI 10.1007/978-1-4939-2845-3
Library of Congress Control Number: 2015945350
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Contents
Introduction ...................................................................................................... 1
Stephan A. Pless and Christopher A. Ahern
Engineered Ionizable Side Chains .................................................................. 5
Gisela D. Cymes and Claudio Grosman
Cysteine Modification: Probing Channel Structure, Function
and Conformational Change ........................................................................... 25
Myles H. Akabas
Functional Site-Directed Fluorometry ........................................................... 55
Michael Priest and Francisco Bezanilla
Bioreactive Tethers ........................................................................................... 77
Karen Mruk and William R. Kobertz
Flipping the Photoswitch: Ion Channels Under Light Control ................... 101
Catherine K. McKenzie, Inmaculada Sanchez-Romero
and Harald Janovjak
Incorporation of Non-Canonical Amino Acids .............................................. 119
Lilia Leisle, Francis Valiyaveetil, Ryan A. Mehl
and Christopher A. Ahern
Index .................................................................................................................. 153
v
Contributors
Christopher A. Ahern Department of Molecular Physiology and Biophysics,
University of Iowa, Iowa City, IA, USA
Myles H. Akabas Departments of Physiology & Biophysics, Neuroscience and
Medicine, Albert Einstein College of Medicine, Bronx, NY, USA
Francisco Bezanilla Department of Biochemistry and Molecular Biology and
Committee on Neurobiology, University of Chicago, Chicago, IL, USA
Gisela D. Cymes Department of Molecular and Integrative Physiology, Center for
Biophysics and Computational Biology, Program in Neuroscience, University of
Illinois at Urbana-Champaign, Urbana, IL, USA
Claudio Grosman Department of Molecular and Integrative Physiology, Center
for Biophysics and Computational Biology, Program in Neuroscience, University
of Illinois at Urbana-Champaign, Urbana, IL, USA
Harald Janovjak Institute of Science and Technology Austria, Klosterneuburg,
Austria
William R. Kobertz Department of Biochemistry and Molecular Pharmacology,
University of Massachusetts Medical School, Worcester, MA, USA
Lilia Leisle Department of Molecular Physiology and Biophysics, University of
Iowa, Iowa City, IA, USA
Catherine K. McKenzie Institute of Science and Technology Austria, Klosterneu-
burg, Austria
Ryan A. Mehl Department of Biochemistry and Biophysics, Oregon State
University Corvallis, Corvallis, OR, USA
Karen Mruk Department of Chemical and Systems Biology, Stanford, CA, USA
vii
viii Contributors
Stephan A. Pless Department of Drug Design and Pharmacology, Center for
Biopharmaceuticals, University of Copenhagen, Copenhagen, Denmark
Michael Priest Department of Biochemistry and Molecular Biology and
Committee on Neurobiology, University of Chicago, Chicago, IL, USA
Inmaculada Sanchez-Romero Institute of Science and Technology Austria,
Klosterneuburg, Austria
Francis Valiyaveetil Department of Physiology and Pharmacology, Oregon Health
and Sciences University, Portland, OR, USA
Introduction
Applying Chemical Biology to Ion Channels
Stephan A. Pless and Christopher A. Ahern
Abstract Ion channels are membrane-spanning proteins that control the flow of
ions across biological membranes through an aqueous pathway. The opening or
closing of this pore can be controlled by a myriad of physiological inputs (voltage,
ligands, temperature, metabolites, pH), which in turn allow for the controlled flux
of ions across membranes, resulting in the generation of minute electrical signals.
The functional implications of ion channel function on physiological processes
are vast. Electrical impulses, in the form of action potentials or diverse chemo-
electrical signals, coordinate the syncytium of the heart beat, support a myriad of
neuronal communication pathways, insulin secretion, and are central to the immune
response, with more roles being discovered virtually everyday. Thus, ion channel
function is a biophysical process that is central to biological life at many levels. And
with over 500 channel-forming subunits known today in humans, this large class of
proteins is also increasingly recognised as important drug targets, as inherited or
acquired ion channel dysfunction are known causes of disease.
Keywords Ion channels · Chemical biology · Side chain protonation · Cysteine
modifications · Unnatural amino acids
Ion channels are membrane-spanning proteins that control the flow of ions across
biological membranes through an aqueous pathway. The opening or closing of this
pore can be controlled by a myriad of physiological inputs (voltage, ligands, tem-
perature, metabolites, pH)), which in turn allow for the controlled flux of ions across
membranes, resulting in the generation of minute electrical signals. The functional
S. A. Pless ()
Department of Drug Design and Pharmacology, Center for Biopharmaceuticals,
University of Copenhagen, Copenhagen, Denmark
e-mail: [email protected]
C. A. Ahern
Department of Molecular Physiology and Biophysics, University of Iowa,
Iowa City, IA, 52246, USA
e-mail: [email protected]
© Springer Science+Business Media New York 2015 1
C. Ahern, S. Pless (eds.), Novel Chemical Tools to Study Ion Channel Biology,
Advances in Experimental Medicine and Biology 869,
DOI 10.1007/978-1-4939-2845-3_1
2 S. A. Pless and C. A. Ahern
implications of ion channel function on physiological processes are vast. Electri-
cal impulses, in the form of action potentials or diverse chemo-electrical signals,
coordinate the syncytium of the heart beat, support a myriad of neuronal commu-
nication pathways, insulin secretion, and are central to the immune response, with
more roles being discovered virtually everyday. Thus, ion channel function is a
biophysical process that is central to biological life at many levels. And with over
500 channel-forming subunits known today in humans, this large class of proteins is
also increasingly recognised as important drug targets, as inherited or acquired ion
channel dysfunction are known causes of disease.
Many ion channels are ‘selective’, i.e. they display a strong preference (or selec-
tivity) for either a cations or anions, or even for a certain type of cation, e.g. potas-
sium ions. Depending on the type of ion channel the activity of these proteins is
controlled (or gated) by a wide variety of stimuli, including chemical, electrical and
physical: while many ion channels open in response to binding of ligands to (ligand-
gated ion channels), others do so as a result of changes in the membrane (voltage-
gated ion channels) or even mechanical stimuli (mechanosensitive channels). In-
terestingly, it is becoming more and more clear that a number of ion channel types
are responsive to more than one stimuli, resulting in a polymodal gating behaviour.
The study of ion channels has been traditionally challenging and the field re-
quired numerous major technological advances to blossom to its current state of
understanding. Although the idea of bioelectricity had been formulated as early
1786 by Galvani, the molecular and atomic basis for this phenomenon remains
surprisingly elusive. A seminal breakthrough, both conceptual and technical,
came about in the in the mid-twentieth century when Hodgkin and Huxley estab-
lished the ability to record ionic currents from the quid giant axon. Soon after,
this led to the pioneering work of Sakmann and Neher who established the patch
clamp technology, which allows measurement of the unitary ionic currents in the
picoampere range. Later on, the purification and cloning of membrane protein
(complexes) delivered the first protein sequences of ion channels and transmem-
brane receptor proteins. Of crucial importance in this context was the develop-
ment of the polymerase chain reaction (PCR), which facilitated gene cloning, but
also endowed researchers with the capability to change the coding frame of ion
channels. This molecular revolution segued to the high-resolution crystal struc-
tures of channels by the MacKinnon and Agre laboratories, which has harkened
a new era of atomic scale understanding that continues to surprise and illuminate
the ion channel world. Thus at each step in the conceptual, molecular and atomic
understanding of bioelectricity in animals; from the spark of life, to macroscopic
and microscopic ionic recordings, and then molecular expression, site-directed
mutagenesis and structural biology, crucial technological innovations and their
subsequent widespread application has been the common (and essential) driver
in progress.
Indeed, the efforts over the past 25 years through the combination of structural
and functional interrogation of ion channel genes has been an incredibly powerful
means to elucidate the physiology and pharmacology of ion channels. However,