[Abstract Title]. - Society for Neuroscience

Poster
234. A-Type Potassium Channels
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 234.2/C26
Topic: B.04.f. Channel trafficking
Title: Kv4.2 C-terminal interaction with KChIP4a: effects of phosphorylation on binding and
surface expression
Authors: *L. LIN, A. M. WIKENHEISER, D. A. HOFFMAN;
LCSN, NICHD-NIH, Bethesda, MD
Abstract: Voltage-gated potassium (Kv) channels play important roles in regulating the
excitability of myocytes and neurons. Kv4.2 is a key constituent of the A-type channel in CA1
pyramidal neurons of the hippocampus and is critically involved in the regulation of dendritic
excitability and plasticity. K + channel-interacting proteins, KChIPs (KChIP1-4), have been
shown to associate with the N-terminal of Kv4.2 and modulate its biophysical properties (An et
al., 2000). KChIP4a, which has a unique KIS (K-channel inactivation suppressor) domain
(Holmqvist et al., 2002), abolishes fast inactivation of Kv4 currents in various cell types. In the
present study, we investigated the role of the cytoplasmic C-terminal of Kv4.2 in the interaction
with KChIP4a and the effects of Kv4.2 phosphorylation sites on surface expression regulation by
KChIP4a. We made a series of Kv4.2 C-terminal truncation mutations (560Γ, 490Γ, 417Γ and
406Γ), and CO-IP results show that only 560Γ and 490Γ can interact with KChIP4a.
Immunostaining showed these two proteins co-localize in COS7 cells. These results suggested
C-terminal Kv4.2 plays a critical role in the interaction. We then made site-directed mutations,
changing the phosphosite serine (S) or Threonine (T) to Alanine (A) to remove the
phosphorylation sites on PKA (mPKA), PKC (mPKC), ERK (mERK) and CaMKII (mCaMKII).
We found that the interaction of Kv4.2 and KChIP4a requires the C-terminal of Kv4.2, but not
phosphorylation of Kv4.2 on the C-terminal. Biotinylation experiments showed that cotransfection
of Kv4.2 and KChIP4a in COS7 cells results in a 1.5-fold increase in Kv4.2 surface
expression, compared to Kv4.2 alone. Enhanced surface expression by KChIP4a was abolished
by KChIP4a siRNA, and reduced by mPKA, mERK or mCaMKII Kv4.2 mutations. These data
suggest that PKA, ERK and CaMKII phosphorylation sites of Kv4.2 play an important role in
the trafficking of Kv4.2 through its interaction with KChIP4a.
Disclosures: L. Lin , None; A.M. Wikenheiser, None; D.A. Hoffman, None.
Poster