ION CHANNELS, RECEPTORS AND TRANSPORTERS
Impaired glycosylation blocks DPP10 cell surface expression
and alters the electrophysiology of I
to
channel complex
Diego Cotella
&
Susanne Radicke
&
Alessio Bortoluzzi
&
Ursula Ravens
&
Erich Wettwer
&
Claudio Santoro
&
Daniele Sblattero
Received: 27 July 2009 / Revised: 23 February 2010 / Accepted: 10 March 2010 / Published online: 31 March 2010
#
Springer-Verlag 2010
Abstract DPP10 is a transmembrane glycosylated protein
belonging to the family of dipeptidyl aminopeptidase-like
proteins (DPPLs). DPPLs are auxiliary subunits involved in
the regulation of voltage-gated Kv4 channels, key determi-
nants of cardiac and neuronal excitability. Although it is
known that DPPLs are needed to generate native-like
currents in heterologous expression systems, the molecular
basis of this involvement are still poorly defined. In this
study, we investigated the functional relevance of DPP10
glycosylation in modulating Kv4.3 channel activities.
Using transfected Chinese hamster ovary (CHO) cells to
reconstitute Kv4 complex, we show that the pharmacolog-
ical inhibition of DPP10 glycosylation by tunicamycin and
neuraminidase affects transient outward potassium current
(I
to
) kinetics. Tunicamycin completely blocked DPP10
glycosylation and reduced DPP10 cell surface expression.
The accelerating effects of DPP10 on Kv4.3 current
kinetics, i.e. on inactivation and recovery from inactivation,
were abolished. Neuraminidase produced different effects
on current kinetics than tunicamycin, i.e., shifted the
voltage dependence to more negative potentials. The effects
of tunicamycin on the native I
to
currents of human atrial
myocytes expressing DPP10 were similar to those of the
KV4.3/KChIP2/DPP10 complex in CHO cells. Our results
suggest that N-linked glycosylation of DPP10 plays an
important role in modulating Kv4 channel activities.
Keywords Kv4.3 potassium channel
.
Glycosylation
.
Tunicamycin
.
DPP10 protein
.
Electrophysiology
.
KChIP2 protein
Introduction
DPP10 is a member of the dipeptidyl aminopeptidase-like
(DPPLs) protein family. As with the other members of the
family, DPP10 is a single-pass type-II transmembrane
protein, with a large extracellular portion and a short
variable intracellular domain. It shares homology to the
serine protease DPPIV/CD26, but it lacks enzymatic
activity, since the catalytic serine residue is substituted
by aspartic acid [24]. Several DPPL isoforms have been
reported [1, 35], and their expression varies among
distinct neuronal populations as well as different organs
and tissues.
We and others have shown that DPPLs associate with
pore-forming subunits of the voltage-dependent K
+
channel
(Kv4) to form the multi-protein complexes that underlie the
A-type currents in the brain and the transient outward
potassium current (I
to
) in the heart [14, 21, 25, 39]. I
to
plays
a major role in cardiac repolarization, and the delineation of
its molecular basis is essential to understand malfunctioning
D. Cotella and S. Radicke contributed equally to this work.
D. Cotella (*)
:
S. Radicke
:
A. Bortoluzzi
:
C. Santoro
:
D. Sblattero
Department of Medical Sciences and Interdisciplinary Research
Center for Autoimmune Diseases (IRCAD),
University of Eastern Piedmont “A. Avogadro”,
Via Solaroli 17,
Novara 28100, Italy
e-mail: diego.cotella@med.unipmn.it
S. Radicke
:
U. Ravens
:
E. Wettwer
Department of Pharmacology and Toxicology,
Faculty of Medicine “Carl Gustav Carus”,
Dresden University of Technology,
Fiedlerstraße 42,
Dresden 01307, Germany
Pflugers Arch - Eur J Physiol (2010) 460:87–97
DOI 10.1007/s00424-010-0824-2