title: Molecular aspects of adrenergic modulation of the transient outward current.
abstract: Transient outward channels have a different impact on action potential configuration in small mammals compared to large mammals. Small mammals depend primarily on Ito1 for repolarization, while in larger animals Ito1 only indirectly determines action potential duration by setting the level of the plateau. Transient outward channel expression and distribution also differ between animal species. Nevertheless, the primary protein sequence of the underlying Kv1.4, Kv4.2 and Kv4.3 alpha1-subunits displays remarkably high levels of amino acid identity. Transient outward channels are subject to alpha- and beta-adrenergic regulation, mainly decreasing Ito1. However, adrenergic stimulation is also an important determinant of transient outward channel downregulation in cardiac disease. Adrenergic stimulation of PKA as well as PKC leads to an inhibition of Ito1, which has been correlated with phosphorylation of the Kv1.4, Kv4.2 and Kv4.3 alpha1-subunits. Calmodulin-dependent kinase II, on the other hand, has been shown to be involved in an increase of Ito1. Comparison of Kv1.4, Kv4.2 and Kv4.3 primary amino acid sequences demonstrates a strong conservation of (potential) phosphorylation sites between different species, despite the fact that Ito1 has a different effect on action potential configuration in mammalian species.
authors.affiliation: Department of Medical Physiology, University Medical Center Utrecht, The Netherlands. m.a.g.vanderheyden@med.uu.nl
authors.forename: Marcel A G
authors.initials: MA
authors.lastname: van der Heyden
authors.forename: Tessa J M
authors.initials: TJ
authors.lastname: Wijnhoven
authors.forename: Tobias
authors.initials: T
authors.lastname: Opthof
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D018663:Adrenergic Agents / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000818:Animals; D006331:Heart Diseases / Q000503:physiopathology; D051665:Kv1.4 Potassium Channel / Q000187:drug effects* / Q000235:genetics; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology; D016415:Sequence Alignment; D051672:Shal Potassium Channels / Q000187:drug effects* / Q000235:genetics; D013045:Species Specificity
chemical_list: D018663:Adrenergic Agents; D051665:Kv1.4 Potassium Channel; D051672:Shal Potassium Channels; D011494:Protein Kinases