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