A VAMP7/Vti1a SNARE complex distinguishes a non-conventional traffic route to the cell surface used by KChIP1 and Kv4 potassium channels.

Sarah E Flowerdew , Robert D Burgoyne (1)

1 The Physiological Laboratory

The K+ channel interacting proteins (KChIPs) are EF hand-containing proteins required for the traffic of channel-forming Kv4 K+ subunits to the plasma membrane. KChIP1 is targeted, through N-terminal myristoylation, to intracellular vesicles that appear to be intermediates in traffic from the ER to the Golgi but differ from those underlying conventional ER-Golgi traffic. To define KChIP1vesicles and the traffic pathway followed by Kv4/KChIP1 traffic, we examined their relationship to potential SNARE proteins mediating the traffic step. To distinguish Kv4/KChIP1 from conventional constitutive traffic we compared it to the traffic of the vesicular stomatitis G-protein (VSVG). Expression of KChIP with single or triple EF hand mutation quantitatively inhibited Kv4/KChIP1 traffic to the cell surface but had no effect on VSVG traffic. KChIP1-expressing vesicles co-localised with the SNARE proteins Vti1a and VAMP7 but not with the components of two other ER-Golgi SNARE complexes. siRNA-mediated knock down of Vti1a or VAMP7 inhibited Kv4/KChIP1traffic to the plasma membrane in HeLa and Neuro2A cells. Vti1a and VAMP7 siRNA had no effect on VSVG traffic or that of Kv4.2 when stimulated by KChIP2, a KChIP with different intrinsic membrane targeting compared to KChIP1. These data suggest that a SNARE complex containing VAMP7 and Vti1a defines a novel traffic pathway to the cell surface in both neuronal and non-neuronal cells.

Mots clés: Life Sciences

Sarah E Flowerdew, Robert D Burgoyne. A VAMP7/Vti1a SNARE complex distinguishes a non-conventional traffic route to the cell surface used by KChIP1 and Kv4 potassium channels.. Biochemical Journal, 2009, 418 (3), pp.529-540. ⟨10.1042/BJ20081736⟩. ⟨hal-00479091⟩