The A-type potassium channel Kv4.2 is a substrate for the mitogen-activated protein kinase ERK

The mitogen-activated protein kinase ERK has recently become a focus of stu dies of synaptic plasticity and learning and memory, Due to the prominent r ole of potassium channels in regulating the electrical properties of membra nes, modulation of these channels by ERK could play an important role in me diating learning-related synaptic plasticity in the CNS, Kv4.2 is a Shal-ty pe potassium channel that passes an A-type current and is localized to dend rites and cell bodies in the hippocampus. The sequence of Kv4.2 contains se veral consensus sites for ERK phosphorylation. In the present studies, we t ested the hypothesis that Kv4.2 is an ERK substrate. We determined that the Kv4.2 C-terminal cytoplasmic domain is an effective ERK2 substrate, and th at it is phosphorylated at three sites: Thr(602), Thr(607), and Ser(616). W e used this information to develop antibodies that recognize Kv4.2 phosphor ylated by ERK2, One of our phospho-site-selective antibodies was generated using a triply phosphorylated peptide as the antigen. We determined that th is antibody recognizes ERK-phosphorylated Kv4.2 in COS-7 cells transfected with Kv4.2 and native ERK-phosphorylated Kv4.2 in the rat hippocampus, Thes e observations indicate that Kv4.2 is a substrate for ERK in vitro and in v ivo, and suggest that ERK may regulate potassium-channel function by direct phosphorylation of the pore-forming alpha subunit.