title: SUMOylation regulates Kv2.1 and modulates pancreatic beta-cell excitability.
abstract: The covalent attachment of small ubiquitin-like modifier (SUMO) proteins regulates protein localization and function. SUMOylation has recently been shown to modulate ion-channel function; however, the extent to which this affects native currents and cellular excitability remains to be determined. The voltage-dependent K(+) (Kv) channel Kv2.1 regulates pancreatic beta-cell excitability and insulin secretion. We found that YFP-tagged SUMO1 (SUMO1-YFP) can be immunoprecipitated with Kv2.1 when these two proteins are coexpressed in HEK 293 cells. Furthermore, direct infusion of recombinant SUMO1 peptide or coexpression of SUMO1-YFP inhibited current through cloned Kv2.1 by 80% and 48%, respectively. Insulin-secreting cells express SUMO variants 1 and 3, and expression of the SUMO1-YFP in human beta-cells or insulinoma cells inhibited native Kv currents (by 49% and 33%, respectively). Inhibition of the channel resulted from an acceleration of channel inactivation and an inhibition of recovery from inactivation, resulting in the widening of beta-cell action potentials and a decreased firing frequency. Finally, these effects on channel function and excitability were augmented by the conjugating enzyme Ubc9 and rescued by the SUMO protease SENP1. Thus, protein SUMOylation can exert a strong inhibitory action on the voltage-dependent K(+) channel Kv2.1 and can regulate cellular excitability in native beta-cells.
authors.affiliation: Department of Pharmacology, University of Alberta, Edmonton, Alberta, T6G 2E1 Canada.
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Dai
authors.forename: Jelena
authors.initials: J
authors.lastname: Kolic
authors.forename: Paolo
authors.initials: P
authors.lastname: Marchi
authors.forename: Simonetta
authors.initials: S
authors.lastname: Sipione
authors.forename: Patrick E
authors.initials: PE
authors.lastname: Macdonald
mesh_terms: D004553:Electric Conductivity; D006801:Humans; D050417:Insulin-Secreting Cells / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology; D051669:Shab Potassium Channels / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*
chemical_list: C496988:KCNB1 protein, human; D051669:Shab Potassium Channels; D025841:Small Ubiquitin-Related Modifier Proteins